My first exposure to the crazy world of cables was in the very early 1980s, when a friend of mine purchased a DNM preamplifier. Dennis Morecroft told him that to get the best out of it he would need a special (read expensive) Japanese interconnect cable to hook it up to the power amp. My friend duly borrowed said cable (which had a worrisome propensity to fall apart whenever you unplugged it) and we took a listen, and I have to say that there was definitely an improvement, and that blew us away for a while.
Shortly after that, a craze developed in UK audiophile circles for using solid-core loudspeaker cable. This was something else I had to try out, and was quite easy because you could buy solid-core cable of the right gauge by the reel from the local hardware store - it is the same stuff you wire your house with. Using this solid-core cable made a significant improvement to the bass weight of my speakers, and the imaging seemed cleaner too. With most of the reel still unused, I got to work fiddling some more. I replaced all the internal wiring on my speakers with it, and got more improvements of the same nature. Cool!
Next, things got silly. I built myself a set of solid-core RCA interconnects - unshielded of course - and blow me down if these weren’t an improvement also. Today, with the perspective of experience, I now know that all I did was replace the cheapest of cheap crap wiring with something just a little better. But at the time all I knew was that there was a world of gain to be exploited by futzing around with cables.
One of the things I did was recognize that the purpose in life of my reel of solid-core cable was to provide mains wiring. So I opened up all of my amplifiers and hand-soldered a length of solid-core to the appropriate terminals on the power supply’s transformer, and an approved power connector to the other end (in those days there were no IEC sockets - all electronics came with a hard-wired power cord). Voila, my first custom power cord. I’ll be honest with you and admit that my objective here was tinkering for tinkering’s sake, so I really was quite emphatically blown away when the solid-core power cord appeared to sound massively better than the stock power cord.
I scratched my head quite a lot over this finding, and because of all the work involved in soldering and disassembling, it was far from straightforward to do repeated AB comparison tests. My solution was rather typical for a twenty-something. I wired the original mains cord in parallel with the new solid-core one. It was a few seconds work to unplug one and plug in the other (and if you plugged both in simultaneously during the switchover you didn’t need to power down the amp), the only downside being a couple of live 240V terminals lying idly around! I now had a system where I could AB demonstrate the truly massive sonic differences between two different power cords. Quite a few people came to hear the demo, and nobody failed to be convinced. Many of them were not even audiophiles. Interestingly, it strikes me just as I write this, that I never thought to listen seriously to BOTH power cords plugged in at the same time.
Thus it was that I became a power cord believer long before it ever became fashionable, and certainly many years before I ever saw a third-party power cord offered for sale in my local HiFi store.
In 1988 I moved to Canada. My Naim 250 power amp and the solid-core built-in cable that I attached to it did not survive the relocation, and I found myself using a Jolida SJ502A tube-based integrated amplifier (with an IEC socket) and a stock Belden power cord. Since I had the fortunate opportunity to build my own house, I was able to specify a dedicated music room. It had reinforced floors, and a double-layer of gyproc on the walls [I might have done that differently if I was doing it again, but there you go]. Motivated by my experience with my solid-core power cords, I also took the opportunity to install a dedicated wiring spur that would power my music system. It used the same 60A wiring that the electrician brought with him to power my 12kW electric furnace (although the furnace used three strands where my music system used just one). A couple of years later I added some “hospital grade” wall sockets with a seriously beefy internal construction. To this day, I remain quite happy with my audio system’s power infrastructure.
Over the years I continued to experiment with home-built power cords. The trouble was, I never had any design basis to work from. I never had any theory of power cables to guide me. If I was going to build a better power cord, I had no clue what characteristics it would need to have. So for many years I knocked together occasional cords based on scraps of unusual cables I came across from time to time. I still have some of them. None of my experimental power cords ever made any sort of noticeable improvement over the Belden cord. A friend gave me an experimental power cord that he made, and that did sound slightly better, but I never heard anything to approach the magnitude of my original solid-core upgrade. Strangely enough, I never considered building another solid-core power cord.
Not so long ago, I had an e-mail exchange with a fellow with a lot more expertise than me, and he suggested a design approach I had not thought of before. His approach was based on RF. Imagine, he said, that RF interference coming down the power cord is like someone try to soak you with a hosepipe. You can try holding up a dustbin lid, and it will block the worst of it, but eventually you will still find yourself standing in a puddle of water. What you want to do is to direct it back the way it came in a controlled manner. According to my correspondent, most electronics contain a RF filter built into their IEC inputs. These filters don’t actually filter out the RF, rather they function by directing it back the way it came. Most power cords, he reasoned, are not good transmitters of RF, and a lot of the reflected RF ends up being “puddled” inside the equipment. He held firm to the view that a good power cord would actually **TRANSMIT** the RF rather efficiently.
Bearing that in mind, I was able to source a few meters of a special RF cable designed to deliver prodigious amounts of RF power to the antennae of a transmitting tower. As it happens, this cable comprises a single 1mm diameter solid core, beefy enough to be able to carry 15A and more, and so I could see myself using it to construct a power cord. The power cord would comprise two of those cables in parallel, one core for the “live” and one for the “neutral”, with a separate copper line for the ground. The shielding of the RF cables would also be connected to the copper ground at the plug end.
I have since built quite a few of those cables. They are monstrously unwieldy. The RF power cable bends, but only reluctantly. To use, you must very carefully bend it into the right shape before you try to install it. If you take one and straighten it out, and plug it into a high quality wall socket, it will stand there - one meter long - sticking out of the wall! You really need a socket that is man enough to grip it, otherwise it can pop right out. Also, you need to use it with equipment weighing at least 1kg, otherwise the power cord can lift it up into the air! But in the right system they sound tremendous, with weight, power, spatial detail and tonal precision. I have had specialty mains power cords come through my system priced well into 4 figures each, and my own cables are every bit a match for them.
For a while we sold these cables as “BitPerfect Digital Precision” power cords, but they are way too unwieldy for most people, and the market is just too small to make it worthwhile. So we don’t sell them any more. But, for the first time, I now have at least one design approach for power cords that seems able to prove itself out. Without doubt there are many more waiting to be found.
Friday, 25 April 2014
Thursday, 24 April 2014
Power Struggles
My recent post regarding the PS Audio Jewel C7 Power Cord I got for my Mac Mini has prompted a number of comments, emails and PMs. Let’s face it, anything you write on Power Cords is guaranteed to have this effect! More than one of you have inquired as to the effects that I think may be responsible for the audible results, and so I though a post on that broader subject may be of interest. Having said that, if you are looking for answers, this is the wrong place. I don’t have them.
Many people object to the notion of the audibility of power cords almost as a fundamental point of principle. After all, if a power cord is audible, so the argument goes, then so is your house’s wiring, and the power company’s wiring that delivers the power to your house, and so on. But there’s the rub. I have no doubt that these things ARE all audible. It’s just that there are some things that you can easily upgrade, and some things that you can’t. Your country’s Power Utility generally falls into the latter category.
In principle, any audio device which is electrically powered can be viewed as a device that draws an electrical signal from the mains, and shapes it to its own purpose. Take a power amplifier. It doesn’t really amplify the input from its preamplifier. What it does is to take the mains power, and use it to fashion a bigger copy of the input signal. The difference may be arguably semantic, but as someone who spent many years working with Optical Amplifiers I thought the distinction was interesting. Therefore, it maybe helps to think that just about everything that comes out of an electronic device came into it in the first place via its power cord.
So it might be more rational to take the position that a power cord cannot possibly NOT affect the sound. Of course you can then argue that any effects ought to be, for all practical purposes, inaudible. That would be a rational philosophical starting point. It at least forces the skeptics into the position where they have to stipulate the effect, and elaborate upon a rationale for supposing it inaudible.
What sonic effects can a power cord actually exhibit? In principle, the mains voltage waveform is a 50Hz or 60Hz pure sinusoid. However, the current that flows along a power cord is not so simple. Inside the audio apparatus the power cord first connects to a Power Supply. The power supply draws current from the mains, via the power cord. This current does not flow in a nice sinusoid. Rather, it flows as a series of spikes. Imagine being 5 years old again, and blowing though a straw into a glass of water. The air that you blow through the straw - into the water - flows at a more or less constant rate. But once the air gets into the water it forms bubbles. The bubbles rise to the surface where they hang around for a while and then burst. The air is actually released back into the atmosphere in a series of sudden events, as each bubble bursts. A Power Supply is a bit like that in reverse. It consumes the current it needs in a series of very short spikes, like bubbles bursting.
You might choose to design a power cord based on allowing those current spikes to travel more freely along the power cord. But I’m not sure about that, and I have two sets of reservations. The first is that I’m not sure that an everyday Belden power cord (such as is shipped with most high-end audio equipment) is particularly deficient in that regard. The second is that, based on how a power supply works, it is not clear to me how bandwidth limitations imposed upon the current spikes (which is one thing that a power cord might be doing) translates into audible effects in the equipment’s functionality. Of course nothing I’ve said proves that it doesn’t. It’s just that I don’t clearly see clear technical arguments for supposing that it does.
The other way to look at a power cord is to consider things that are transmitted along the power cord that you don’t want to see there. And the biggest bugaboo is Radio-Frequency (RF) interference. RF is pervasive. Unlike ‘ordinary’ electrical signals, it is not constrained to traveling along the wires. If it wants to, it is perfectly capable of jumping out of the wires and traveling through open air. This, after all, is how our Cell Phones, Radios, Wi-Fi, GPS, and Microwave Ovens all works. You wouldn’t believe how many ordinary household appliances generate RF interference. Even those which are not designed to work in the RF. Like your refrigerator, dimmer switches, air conditioning, even the street lights outside your house. Add to these your computers and TV sets, and you can see how your household mains wiring can soon be seriously contaminated by RF interference. If you live in a densely inhabited urban environment, it can be quite serious.
At BitPerfect, we took the concept of RF interference quite seriously. Our Power Cords were designed to transmit all frequencies - including RF - down the cable as cleanly as possible, and to accept the reflected RF reflected from the power supply’s input RF filter, and transmit it effectively back down the power cord and back into the mains wiring where it will eventually dissipate. That’s one design approach, and we don’t make any great claims for it, except that it seems to work rather well.
A lot of focus on power cords seems to be based on the cable construction. But our experience is that the connectors at either end are very significant contributors. The connector has two jobs to do. First it has to connect securely to the internal cabling, and that connection itself is a major aspect of cable design. Second, the connector has to mate satisfactorily with the receptacle into which it is plugged. This latter is not something which is under the designer’s control. And it begs a question that is applicable to all sorts of cabling applications - to what extent does a cable comprising a high-end connector require a matching mating connector to plug it into? My experiments suggest that this is an important consideration. (This is something I struggled with when designing BitPerfect’s own XLR interconnect cables.)
I want to also mention something that is seen regularly in specifications for cables, and most particularly power cords. “Cryogenic Treatment” requires that the metal parts comprising the connectors, and often the cable itself, be exposed to “cryogenic” (i.e. seriously, seriously cold) temperatures for a period of several hours. What this is supposed to do is unclear, but it is known that the crystalline structure of some metals can be altered by such cryogenic treatment. But “can alter” is not the same as “does alter”, and I have yet to see any definitive reports of actual physical transmutation being observed on cryo-treated commercially-sold audio components. I have purchased both cryogenically treated and untreated power connectors, and I’m sure I can’t hear the blindest bit of a difference. I spoke to one of those vendors, and they were happy to tell me in great detail exactly how and where they perform their Cryo treatments (the facility they use is one that I am actually familiar with), so I am quite convinced that they actually do what they claim to be doing.
The bottom line for me is that the effect a power cord will have on your system will depend to a large extent on how “clean” your power source is to begin with. For example, I spent some time with a MIT power conditioner. First in a downtown hotel room at a Hi-Fi show, where it undoubtedly cleaned up the sound quite appreciably. Second, in my listening room at home, where my main power is apparently a lot cleaner to begin with, and the MIT made hardly any audible difference. I have also used an industrial UPS as a power conditioner with mixed results. It gave a smoother sound, but also a notably less dynamic one. I used it for nearly a year, but when it expired I chose not to replace it. If you live in an urban environment, a high quality power conditioner such as those sold by PS Audio, MIT, or Transparent Audio should be considered seriously before you spend a similar amount on power cords.
I think money spent on buying good quality wall sockets is money well spent. Mine cost me about $10 each from my local “Reno Depot” (a big-box hardware store). What you are looking for is a “K-Line Contact”. Peer into a wall socket, and you will see that when the blade of the plug is inserted it slides parallel to one flat surface, and is pressed into contact by an angled blade. In a cheap socket there is one angled blade, which makes point contact, not line contact. What you want to see is two angled blades in a “K” shape, each making line contact. When you insert a plug into this, it is going to take quite a bit of force to pull it back out again. You can spend a lot more, and buy sockets with Rhodium- or Gold-plated connectors, but I don’t see the point unless you will be plugging Rhodium- or Gold-plated plugs into them. Whatever you do, don’t spend hundreds of dollars on power cords without installing decent wall sockets first.
When you finally do buy power cords, be sure to work with a reputable dealer who will let you try before you buy. Don’t, don’t, repeat DON’T buy one on-line because it was favorably reviewed or recommended. Power cords are all about synergy, and finding something that works well in your system is paramount. Transparent Audio in particular, while expensive, are very good about letting you try them out for quite a long time without obligation.
If you go to a HiFi show, Nordost can be relied upon to perform a through, detailed, and quite convincing demonstration of their wares, and their products are of reputable quality.
Finally, another aspect of power cord performance - indeed of almost all after-market cable performance - is the break-in period. This is another place where the skeptics love to roll about the floor laughing. Yes, cables do require a break-in period. Power cords are quite easy - you can leave them plugged into a running CD player or something for an extended period - loudspeaker cables less so. You need to plan for a minimum of 24 hours of continuous running to break in a cable, and some will need up to 300 hours. My experience with power cords is that most of them will be in the 24-100 hour range. My new PS Audio C7 Jewel cable, which was sounding a bit “breathy” straight out of the box is now sounding a lot more composed 48 hours layer.
Good luck :)
Many people object to the notion of the audibility of power cords almost as a fundamental point of principle. After all, if a power cord is audible, so the argument goes, then so is your house’s wiring, and the power company’s wiring that delivers the power to your house, and so on. But there’s the rub. I have no doubt that these things ARE all audible. It’s just that there are some things that you can easily upgrade, and some things that you can’t. Your country’s Power Utility generally falls into the latter category.
In principle, any audio device which is electrically powered can be viewed as a device that draws an electrical signal from the mains, and shapes it to its own purpose. Take a power amplifier. It doesn’t really amplify the input from its preamplifier. What it does is to take the mains power, and use it to fashion a bigger copy of the input signal. The difference may be arguably semantic, but as someone who spent many years working with Optical Amplifiers I thought the distinction was interesting. Therefore, it maybe helps to think that just about everything that comes out of an electronic device came into it in the first place via its power cord.
So it might be more rational to take the position that a power cord cannot possibly NOT affect the sound. Of course you can then argue that any effects ought to be, for all practical purposes, inaudible. That would be a rational philosophical starting point. It at least forces the skeptics into the position where they have to stipulate the effect, and elaborate upon a rationale for supposing it inaudible.
What sonic effects can a power cord actually exhibit? In principle, the mains voltage waveform is a 50Hz or 60Hz pure sinusoid. However, the current that flows along a power cord is not so simple. Inside the audio apparatus the power cord first connects to a Power Supply. The power supply draws current from the mains, via the power cord. This current does not flow in a nice sinusoid. Rather, it flows as a series of spikes. Imagine being 5 years old again, and blowing though a straw into a glass of water. The air that you blow through the straw - into the water - flows at a more or less constant rate. But once the air gets into the water it forms bubbles. The bubbles rise to the surface where they hang around for a while and then burst. The air is actually released back into the atmosphere in a series of sudden events, as each bubble bursts. A Power Supply is a bit like that in reverse. It consumes the current it needs in a series of very short spikes, like bubbles bursting.
You might choose to design a power cord based on allowing those current spikes to travel more freely along the power cord. But I’m not sure about that, and I have two sets of reservations. The first is that I’m not sure that an everyday Belden power cord (such as is shipped with most high-end audio equipment) is particularly deficient in that regard. The second is that, based on how a power supply works, it is not clear to me how bandwidth limitations imposed upon the current spikes (which is one thing that a power cord might be doing) translates into audible effects in the equipment’s functionality. Of course nothing I’ve said proves that it doesn’t. It’s just that I don’t clearly see clear technical arguments for supposing that it does.
The other way to look at a power cord is to consider things that are transmitted along the power cord that you don’t want to see there. And the biggest bugaboo is Radio-Frequency (RF) interference. RF is pervasive. Unlike ‘ordinary’ electrical signals, it is not constrained to traveling along the wires. If it wants to, it is perfectly capable of jumping out of the wires and traveling through open air. This, after all, is how our Cell Phones, Radios, Wi-Fi, GPS, and Microwave Ovens all works. You wouldn’t believe how many ordinary household appliances generate RF interference. Even those which are not designed to work in the RF. Like your refrigerator, dimmer switches, air conditioning, even the street lights outside your house. Add to these your computers and TV sets, and you can see how your household mains wiring can soon be seriously contaminated by RF interference. If you live in a densely inhabited urban environment, it can be quite serious.
At BitPerfect, we took the concept of RF interference quite seriously. Our Power Cords were designed to transmit all frequencies - including RF - down the cable as cleanly as possible, and to accept the reflected RF reflected from the power supply’s input RF filter, and transmit it effectively back down the power cord and back into the mains wiring where it will eventually dissipate. That’s one design approach, and we don’t make any great claims for it, except that it seems to work rather well.
A lot of focus on power cords seems to be based on the cable construction. But our experience is that the connectors at either end are very significant contributors. The connector has two jobs to do. First it has to connect securely to the internal cabling, and that connection itself is a major aspect of cable design. Second, the connector has to mate satisfactorily with the receptacle into which it is plugged. This latter is not something which is under the designer’s control. And it begs a question that is applicable to all sorts of cabling applications - to what extent does a cable comprising a high-end connector require a matching mating connector to plug it into? My experiments suggest that this is an important consideration. (This is something I struggled with when designing BitPerfect’s own XLR interconnect cables.)
I want to also mention something that is seen regularly in specifications for cables, and most particularly power cords. “Cryogenic Treatment” requires that the metal parts comprising the connectors, and often the cable itself, be exposed to “cryogenic” (i.e. seriously, seriously cold) temperatures for a period of several hours. What this is supposed to do is unclear, but it is known that the crystalline structure of some metals can be altered by such cryogenic treatment. But “can alter” is not the same as “does alter”, and I have yet to see any definitive reports of actual physical transmutation being observed on cryo-treated commercially-sold audio components. I have purchased both cryogenically treated and untreated power connectors, and I’m sure I can’t hear the blindest bit of a difference. I spoke to one of those vendors, and they were happy to tell me in great detail exactly how and where they perform their Cryo treatments (the facility they use is one that I am actually familiar with), so I am quite convinced that they actually do what they claim to be doing.
The bottom line for me is that the effect a power cord will have on your system will depend to a large extent on how “clean” your power source is to begin with. For example, I spent some time with a MIT power conditioner. First in a downtown hotel room at a Hi-Fi show, where it undoubtedly cleaned up the sound quite appreciably. Second, in my listening room at home, where my main power is apparently a lot cleaner to begin with, and the MIT made hardly any audible difference. I have also used an industrial UPS as a power conditioner with mixed results. It gave a smoother sound, but also a notably less dynamic one. I used it for nearly a year, but when it expired I chose not to replace it. If you live in an urban environment, a high quality power conditioner such as those sold by PS Audio, MIT, or Transparent Audio should be considered seriously before you spend a similar amount on power cords.
I think money spent on buying good quality wall sockets is money well spent. Mine cost me about $10 each from my local “Reno Depot” (a big-box hardware store). What you are looking for is a “K-Line Contact”. Peer into a wall socket, and you will see that when the blade of the plug is inserted it slides parallel to one flat surface, and is pressed into contact by an angled blade. In a cheap socket there is one angled blade, which makes point contact, not line contact. What you want to see is two angled blades in a “K” shape, each making line contact. When you insert a plug into this, it is going to take quite a bit of force to pull it back out again. You can spend a lot more, and buy sockets with Rhodium- or Gold-plated connectors, but I don’t see the point unless you will be plugging Rhodium- or Gold-plated plugs into them. Whatever you do, don’t spend hundreds of dollars on power cords without installing decent wall sockets first.
When you finally do buy power cords, be sure to work with a reputable dealer who will let you try before you buy. Don’t, don’t, repeat DON’T buy one on-line because it was favorably reviewed or recommended. Power cords are all about synergy, and finding something that works well in your system is paramount. Transparent Audio in particular, while expensive, are very good about letting you try them out for quite a long time without obligation.
If you go to a HiFi show, Nordost can be relied upon to perform a through, detailed, and quite convincing demonstration of their wares, and their products are of reputable quality.
Finally, another aspect of power cord performance - indeed of almost all after-market cable performance - is the break-in period. This is another place where the skeptics love to roll about the floor laughing. Yes, cables do require a break-in period. Power cords are quite easy - you can leave them plugged into a running CD player or something for an extended period - loudspeaker cables less so. You need to plan for a minimum of 24 hours of continuous running to break in a cable, and some will need up to 300 hours. My experience with power cords is that most of them will be in the 24-100 hour range. My new PS Audio C7 Jewel cable, which was sounding a bit “breathy” straight out of the box is now sounding a lot more composed 48 hours layer.
Good luck :)
Tuesday, 22 April 2014
The Little Jewel
Some things should no longer amaze me the way they do.
Paul McGowan of PS Audio recently posted on his blog the story of his new "Portable" music server, based on a Mac Mini, and running BitPerfect. He mentioned that he replaced the stock Mac power cord with one of his own PS Audio Jewel power cords. He said the difference was well worth the effort.
Now I have always been intrigued by the way power cords affect the sound of audio equipment. We even make our own power cords here at BitPerfect, but they are seriously unwieldy affairs, and not well suited to consumer use. Power cords typically make their presence felt in areas of detail, and the subtleties in sonic textures. I would typically see them as "finishing touches", to be applied after all the other choices in cables and interconnects have been made. I would not normally choose my power cords first. Loudspeaker cables, and particularly interconnects, are the "foundational" cables and usually can be relied upon to make the most substantive areas of contribution to the sound of a system. They can change the whole character of the system, whereas power cords tend to tidy up the loose ends.
None of this is definitive. Rather it reflects in very broad-brush terms my expectations - my prejudices if you prefer - regarding the role of cables in high-end audio. So when Paul McGowan made his comment about using a specialist power cord for his Mac Mini, my ears pricked up. I had never paused to consider using an up-market power cord for my Mac Mini. What audible difference - if any - did I imagine it might make? Normally, I would immediately swap in any one of a number of power cords I have at hand, and find out for myself. But all of those come with a standard IEC equipment connector and the Mac uses what is termed a C7 connector.
Cutting a long story short I decided to get a PS Audio C7 Jewel power cord, the same one Paul used, to see what - if anything - I might hear. It arrived today, and I immediately plugged it in, the idea being to let it run for a few days to break in before making any meaningful comparisons.
The Jewel is a very nicely built power cord, with very professional-looking custom-molded connectors at each end. Quite unusual in its price bracket. Our BitPerfect Digital Precision power cords are so stiff that they would very happily suspend the Mac Mini in mid-air if I outfitted one with a C7 connector. In fact, you could probably plug both Mac and Cable into the wall socket and have it stick straight out into the room if you wanted. A cool (if warped) party trick, but not so convenient. The Jewel, thankfully does not, and coils up quite happily among the spaghetti behind my equipment rack.
So why am I bothering to write this? The answer is that, straight out of the box, this Jewel power cord has made a stand-out difference to my reference system. Within a few seconds of starting playback, it became immediately obvious that my system's soundstage has cleaned up very considerably. There was also a lot more air to the tonal presence - a hell of a lot, actually. Maybe even too much. But after as little as an hour's listening it has smoothed out quite a bit. I cannot remember a single cable making as much difference straight out of the box. The Jewel has opened out the soundstage - particularly in terms of soundstage depth. And the ability to locate individual instruments within the soundstage has improved dramatically. Their positioning is much more stable. The texture of those individual instruments also seems that much cleaner.
It is almost all upside. To be fair, while the soundstage has got bigger, the sense of power has somehow subjectively diminished. It is as though I want to keep winding up the volume. Maybe that will ameliorate with break-in. But right now I am listening to Cookie Marenco's DSD recording of Mahler's 5th (Tilson Thomas), which I downloaded from Blue Coast Records, and the volume is at -17.5dB. Normally I would have it at -24dB. It doesn't subjectively sound any louder. I'm really not sure what to make of that. But H@ly Cr@p! It sounds good!
Previously, no single cable had ever made such a profound immediate impact. Perhaps the Transparent Audio Premium USB cable has been my reigning champion in that regard. But not any more. Now that honour goes to the little Jewel. I look forward to giving it a thorough work out once it has fully broken in.
So now I have to think a bit more about what all this means. Inevitably, this is going to lead me down the path towards custom power supplies, which I have seen can cost as much as the Mac itself. Hmmm... In the meantime, the PS Audio C7 Jewel is a fine and keenly-priced upgrade. Actually, a serious bargain, to be quite honest with you.
Paul McGowan of PS Audio recently posted on his blog the story of his new "Portable" music server, based on a Mac Mini, and running BitPerfect. He mentioned that he replaced the stock Mac power cord with one of his own PS Audio Jewel power cords. He said the difference was well worth the effort.
Now I have always been intrigued by the way power cords affect the sound of audio equipment. We even make our own power cords here at BitPerfect, but they are seriously unwieldy affairs, and not well suited to consumer use. Power cords typically make their presence felt in areas of detail, and the subtleties in sonic textures. I would typically see them as "finishing touches", to be applied after all the other choices in cables and interconnects have been made. I would not normally choose my power cords first. Loudspeaker cables, and particularly interconnects, are the "foundational" cables and usually can be relied upon to make the most substantive areas of contribution to the sound of a system. They can change the whole character of the system, whereas power cords tend to tidy up the loose ends.
None of this is definitive. Rather it reflects in very broad-brush terms my expectations - my prejudices if you prefer - regarding the role of cables in high-end audio. So when Paul McGowan made his comment about using a specialist power cord for his Mac Mini, my ears pricked up. I had never paused to consider using an up-market power cord for my Mac Mini. What audible difference - if any - did I imagine it might make? Normally, I would immediately swap in any one of a number of power cords I have at hand, and find out for myself. But all of those come with a standard IEC equipment connector and the Mac uses what is termed a C7 connector.
Cutting a long story short I decided to get a PS Audio C7 Jewel power cord, the same one Paul used, to see what - if anything - I might hear. It arrived today, and I immediately plugged it in, the idea being to let it run for a few days to break in before making any meaningful comparisons.
The Jewel is a very nicely built power cord, with very professional-looking custom-molded connectors at each end. Quite unusual in its price bracket. Our BitPerfect Digital Precision power cords are so stiff that they would very happily suspend the Mac Mini in mid-air if I outfitted one with a C7 connector. In fact, you could probably plug both Mac and Cable into the wall socket and have it stick straight out into the room if you wanted. A cool (if warped) party trick, but not so convenient. The Jewel, thankfully does not, and coils up quite happily among the spaghetti behind my equipment rack.
So why am I bothering to write this? The answer is that, straight out of the box, this Jewel power cord has made a stand-out difference to my reference system. Within a few seconds of starting playback, it became immediately obvious that my system's soundstage has cleaned up very considerably. There was also a lot more air to the tonal presence - a hell of a lot, actually. Maybe even too much. But after as little as an hour's listening it has smoothed out quite a bit. I cannot remember a single cable making as much difference straight out of the box. The Jewel has opened out the soundstage - particularly in terms of soundstage depth. And the ability to locate individual instruments within the soundstage has improved dramatically. Their positioning is much more stable. The texture of those individual instruments also seems that much cleaner.
It is almost all upside. To be fair, while the soundstage has got bigger, the sense of power has somehow subjectively diminished. It is as though I want to keep winding up the volume. Maybe that will ameliorate with break-in. But right now I am listening to Cookie Marenco's DSD recording of Mahler's 5th (Tilson Thomas), which I downloaded from Blue Coast Records, and the volume is at -17.5dB. Normally I would have it at -24dB. It doesn't subjectively sound any louder. I'm really not sure what to make of that. But H@ly Cr@p! It sounds good!
Previously, no single cable had ever made such a profound immediate impact. Perhaps the Transparent Audio Premium USB cable has been my reigning champion in that regard. But not any more. Now that honour goes to the little Jewel. I look forward to giving it a thorough work out once it has fully broken in.
So now I have to think a bit more about what all this means. Inevitably, this is going to lead me down the path towards custom power supplies, which I have seen can cost as much as the Mac itself. Hmmm... In the meantime, the PS Audio C7 Jewel is a fine and keenly-priced upgrade. Actually, a serious bargain, to be quite honest with you.
Friday, 11 April 2014
Sales & Marketing
I overheard a conversation the other day. I know it’s rude to listen in on other people’s conversations but some people talk so loud its like they want to be overheard. Anyway, one fellow was holding forth over the way a certain product was being marketed. He advocated certain solutions to address these concerns, involving, among other things, a brick wall, a party of uniformed gentlemen sporting rifles, and a group of unhappy former Marketing executives.
It is sad that the term “Marketing” engenders a rather negative response these days, and I thought it was worth a comment or two to address the topic. The problem we are seeing is that the term “Marketing” is not really being applied correctly. And the reason for that is the way many large companies - particularly those which serve consumer markets - organize their sales and marketing efforts.
I suppose very few people who have not worked in these areas of business have ever bothered to stop and consider the differences between Sales and Marketing. In most peoples minds the two are conflated into one single entity, “Sales-and-Marketing”. So what exactly is Marketing if it is not the same thing as Sales?
The easiest definition is that Marketing is the activity that stops once the product is designed and put into manufacture. Sales is the activity that starts at that point and seeks to put the product into customers’ hands. To illustrate that distinction, I want to invent an imaginary product and discuss the task facing Umberto, an equally imaginary VP of Marketing. For relevance, my hypothetical product will be an audio product. (And for my sins, I did serve time in the trenches as a Product Marketing Manager, although not in any consumer-oriented field.)
Umberto first heard of the Globular Diaphragm in a meeting with his VP of R&D. The product of fruitless research in an unrelated field, it turned out that a Globular Diaphragm could be used to make a loudspeaker with some remarkable properties. For a start, the loudspeaker would be incredibly efficient - close, in fact, to the maximum theoretical efficiency. In addition, it would exhibit an unusually large auditivity coefficient, and a remarkably low dispersive deflation, qualities which, if I hadn’t made them up, would permit the design of a remarkably good, and unusually small, loudspeaker.
As VP of Marketing, Umberto’s job was to figure out which markets would be best served by this new technology. Small and efficient are two words which immediately crystallized two more words in his mind: Smart and Phone. With Globular Diaphragm technology at his disposal he could own the Smart Phone market! Unfortunately, reviewing this possibility with his VP of Engineering he found that, because the technology relied on a material known as Barely Obtainium (a commercially produced version of Unobtainium), it was extremely expensive. In fact, it would make the loudspeaker so expensive that no Smart Phone manufacturer would be willing to consider it. So that option was discarded.
Umberto next considered the Military market. In general, when something new comes along which offers a great technological advance, but is too expensive to be used in a mainstream consumer product, the natural thing to do is to sell it to the Army. Umberto envisaged a product that could be deployed behind enemy lines. It would be so light it would blow about in the wind, all the while emitting (rather loudly, due to its dispersive deflation) that god-awful tune “I know a song that get’s on everybody’s nerves!”. Such a device could cause massive disruption in enemy morale. As it happened, Umberto met with his local Senator - a powerful member of the Standing Committee on Military Spending. The Senator was wildly enthusiastic, and was sure the Joint Chiefs would all want to be on board. He outlined the road map to making the program work. If all went well, the product could go into service in as little as ten years time! Eventually, Umberto discarded that option.
Next, Umberto decided to investigate the high-end audio market. He soon found, much to his astonishment, that not only was there a market for $1,000 loudspeakers, there was also a market for $10,000 loudspeakers. Even $100,000 loudspeakers. This market was tailor-made for Globular Diaphragm technology. He commissioned a prototype from his VP of Engineering - a cost-no-object design that would blow away every other loudspeaker ever produced. The prototype was about the size and shape of an electric kettle, but sounded for all the world like a pair of Wilson Alexandria XLFs. The incredible quantity of high-quality Barely Obtainium used in that design would mean that such a product, if he ever committed it to manufacture, would have to sell for north of $100,000. But every dealer he met told him the same story. Yes, it was better than the Big Wilsons. And yes, the small size meant that it was much easier to deploy in a real-world installation. But anyone who was willing to blow that kind of cash on a pair of speakers wanted it to look like the Big Wilsons, and not like a pair of kettles. And it needed to weigh 2 tons, not 2 kg.
When he got home, Umberto sat down, somewhat deflated, and poured himself a nice glass of Brunello. Needing to relax, he turned on his Bose Wave radio. Having listened to nothing but incredible audio on his lengthy road trip, it suddenly dawned on him just how god-awful his Bose Wave radio actually sounded. He wondered how good it might sound if he ripped out the tinny speakers and popped in a pair of the smallest and cheapest Globular Diaphragms. Within a week he had a prototype. He knew the chief buyer at Best Buy, where he bought his Bose Wave Radio, and made an appointment to demo his prototype. Unfortunately, the prototype looked pretty strange, due to the fact that it had been cobbled together from the bits and pieces that were lying around. It looked like the love-child of a Retro table-top radio and a futuristic Plasma TV. But it sounded quite amazing. And the Best Buy buyer absolutely loved the bizarre new look.
This turned out to be a killer idea. His Best Buy buddy indicated his strong interest in carrying such a product. Umberto arranged meetings with all the major distribution outlets. They all thought it was a killer product. They all wanted a copy of the prototype to take home - and they all got one. They all reported back that their wives (they were all men, of course) all thought it looked really cool. They all wanted another one for their country cottages - and they all got one. And they all agreed it was the most desirable new lifestyle product they had come across in a long time. They all wanted to carry it.
Umberto’s job was now done, and, per company policy, ownership of the product was handed off to the VP of Sales, Greasy Pete. Greasy Pete’s team opened preliminary sales talks with all of the enthusiastic retailers. Negotiations were tough. While the product looked and sounded amazing, it was still way too expensive. Only Apple can get away with asking that kind of money. Wasn’t there some way of getting the price down?
Greasy Pete met again with Umberto and the VP of Engineering to brainstorm ways of trimming costs. It turned out, of course, that the Globular Diaphragm was pushing the cost through the roof. Greasy Pete suggested they replace the Globular Diaphragm with a cheap parts-bin loudspeaker cone. That way they could realize a massive cost savings. He could push it at retail for one-third of the price originally envisaged, and actually make double the projected revenue. The retailers would love it even more. After all, he assured Umberto, customers won’t care what it sounds like. It would still look way cooler than anything else in the store.
Greasy Pete immediately christened the new product “21st Century Soundscape” and launched it with a slick advertising campaign, which was based on the notion that a newly-married couple’s first priority would be to purchase a new “21st Century Soundscape” portable audio system, whose pounding room-filling beat could be carried up to the bedroom eliciting spectacular, although unspecified, benefits. Sales turned out to be equally spectacular, and the product was a roaring success. As to the Globular Diaphragm technology? It was set aside and forgotten about.
Several months later, two audiophiles passed a shop window with a big display of 21st Century Soundscape products. “So, do you enjoy a 21st Century Performance in your bedroom?”, asked the first, quoting the product’s now ubiquitous catch phrase. “Have you actually heard the thing?”, replied the other, “It sounds awful.” “I know,” said the first, “It’s nothing but marketing hype. Those guys wouldn’t know great sound if it chased them down the street.”
That’s my little story. It is not a morality play. In the end Greasy Pete made what looks like the right call, but who knows? In most modern companies Greasy Pete holds the title VP Sales & Marketing, and he is a senior executive with a lot of clout. Umberto holds the title Product Marketing Manager, and wields a much smaller club. What Greasy Pete wants, Greasy Pete usually gets. A very wise man, the Chairman of the Board of one of my companies, had ten rules of business. One of those was “Never Let The Salesman Set The Price”. That was - and remains - a fine piece of advice. It describes a path that can be a very hard one to follow, and can lead to disaster if you should give in to temptation and stray.
It is sad that the term “Marketing” engenders a rather negative response these days, and I thought it was worth a comment or two to address the topic. The problem we are seeing is that the term “Marketing” is not really being applied correctly. And the reason for that is the way many large companies - particularly those which serve consumer markets - organize their sales and marketing efforts.
I suppose very few people who have not worked in these areas of business have ever bothered to stop and consider the differences between Sales and Marketing. In most peoples minds the two are conflated into one single entity, “Sales-and-Marketing”. So what exactly is Marketing if it is not the same thing as Sales?
The easiest definition is that Marketing is the activity that stops once the product is designed and put into manufacture. Sales is the activity that starts at that point and seeks to put the product into customers’ hands. To illustrate that distinction, I want to invent an imaginary product and discuss the task facing Umberto, an equally imaginary VP of Marketing. For relevance, my hypothetical product will be an audio product. (And for my sins, I did serve time in the trenches as a Product Marketing Manager, although not in any consumer-oriented field.)
Umberto first heard of the Globular Diaphragm in a meeting with his VP of R&D. The product of fruitless research in an unrelated field, it turned out that a Globular Diaphragm could be used to make a loudspeaker with some remarkable properties. For a start, the loudspeaker would be incredibly efficient - close, in fact, to the maximum theoretical efficiency. In addition, it would exhibit an unusually large auditivity coefficient, and a remarkably low dispersive deflation, qualities which, if I hadn’t made them up, would permit the design of a remarkably good, and unusually small, loudspeaker.
As VP of Marketing, Umberto’s job was to figure out which markets would be best served by this new technology. Small and efficient are two words which immediately crystallized two more words in his mind: Smart and Phone. With Globular Diaphragm technology at his disposal he could own the Smart Phone market! Unfortunately, reviewing this possibility with his VP of Engineering he found that, because the technology relied on a material known as Barely Obtainium (a commercially produced version of Unobtainium), it was extremely expensive. In fact, it would make the loudspeaker so expensive that no Smart Phone manufacturer would be willing to consider it. So that option was discarded.
Umberto next considered the Military market. In general, when something new comes along which offers a great technological advance, but is too expensive to be used in a mainstream consumer product, the natural thing to do is to sell it to the Army. Umberto envisaged a product that could be deployed behind enemy lines. It would be so light it would blow about in the wind, all the while emitting (rather loudly, due to its dispersive deflation) that god-awful tune “I know a song that get’s on everybody’s nerves!”. Such a device could cause massive disruption in enemy morale. As it happened, Umberto met with his local Senator - a powerful member of the Standing Committee on Military Spending. The Senator was wildly enthusiastic, and was sure the Joint Chiefs would all want to be on board. He outlined the road map to making the program work. If all went well, the product could go into service in as little as ten years time! Eventually, Umberto discarded that option.
Next, Umberto decided to investigate the high-end audio market. He soon found, much to his astonishment, that not only was there a market for $1,000 loudspeakers, there was also a market for $10,000 loudspeakers. Even $100,000 loudspeakers. This market was tailor-made for Globular Diaphragm technology. He commissioned a prototype from his VP of Engineering - a cost-no-object design that would blow away every other loudspeaker ever produced. The prototype was about the size and shape of an electric kettle, but sounded for all the world like a pair of Wilson Alexandria XLFs. The incredible quantity of high-quality Barely Obtainium used in that design would mean that such a product, if he ever committed it to manufacture, would have to sell for north of $100,000. But every dealer he met told him the same story. Yes, it was better than the Big Wilsons. And yes, the small size meant that it was much easier to deploy in a real-world installation. But anyone who was willing to blow that kind of cash on a pair of speakers wanted it to look like the Big Wilsons, and not like a pair of kettles. And it needed to weigh 2 tons, not 2 kg.
When he got home, Umberto sat down, somewhat deflated, and poured himself a nice glass of Brunello. Needing to relax, he turned on his Bose Wave radio. Having listened to nothing but incredible audio on his lengthy road trip, it suddenly dawned on him just how god-awful his Bose Wave radio actually sounded. He wondered how good it might sound if he ripped out the tinny speakers and popped in a pair of the smallest and cheapest Globular Diaphragms. Within a week he had a prototype. He knew the chief buyer at Best Buy, where he bought his Bose Wave Radio, and made an appointment to demo his prototype. Unfortunately, the prototype looked pretty strange, due to the fact that it had been cobbled together from the bits and pieces that were lying around. It looked like the love-child of a Retro table-top radio and a futuristic Plasma TV. But it sounded quite amazing. And the Best Buy buyer absolutely loved the bizarre new look.
This turned out to be a killer idea. His Best Buy buddy indicated his strong interest in carrying such a product. Umberto arranged meetings with all the major distribution outlets. They all thought it was a killer product. They all wanted a copy of the prototype to take home - and they all got one. They all reported back that their wives (they were all men, of course) all thought it looked really cool. They all wanted another one for their country cottages - and they all got one. And they all agreed it was the most desirable new lifestyle product they had come across in a long time. They all wanted to carry it.
Umberto’s job was now done, and, per company policy, ownership of the product was handed off to the VP of Sales, Greasy Pete. Greasy Pete’s team opened preliminary sales talks with all of the enthusiastic retailers. Negotiations were tough. While the product looked and sounded amazing, it was still way too expensive. Only Apple can get away with asking that kind of money. Wasn’t there some way of getting the price down?
Greasy Pete met again with Umberto and the VP of Engineering to brainstorm ways of trimming costs. It turned out, of course, that the Globular Diaphragm was pushing the cost through the roof. Greasy Pete suggested they replace the Globular Diaphragm with a cheap parts-bin loudspeaker cone. That way they could realize a massive cost savings. He could push it at retail for one-third of the price originally envisaged, and actually make double the projected revenue. The retailers would love it even more. After all, he assured Umberto, customers won’t care what it sounds like. It would still look way cooler than anything else in the store.
Greasy Pete immediately christened the new product “21st Century Soundscape” and launched it with a slick advertising campaign, which was based on the notion that a newly-married couple’s first priority would be to purchase a new “21st Century Soundscape” portable audio system, whose pounding room-filling beat could be carried up to the bedroom eliciting spectacular, although unspecified, benefits. Sales turned out to be equally spectacular, and the product was a roaring success. As to the Globular Diaphragm technology? It was set aside and forgotten about.
Several months later, two audiophiles passed a shop window with a big display of 21st Century Soundscape products. “So, do you enjoy a 21st Century Performance in your bedroom?”, asked the first, quoting the product’s now ubiquitous catch phrase. “Have you actually heard the thing?”, replied the other, “It sounds awful.” “I know,” said the first, “It’s nothing but marketing hype. Those guys wouldn’t know great sound if it chased them down the street.”
That’s my little story. It is not a morality play. In the end Greasy Pete made what looks like the right call, but who knows? In most modern companies Greasy Pete holds the title VP Sales & Marketing, and he is a senior executive with a lot of clout. Umberto holds the title Product Marketing Manager, and wields a much smaller club. What Greasy Pete wants, Greasy Pete usually gets. A very wise man, the Chairman of the Board of one of my companies, had ten rules of business. One of those was “Never Let The Salesman Set The Price”. That was - and remains - a fine piece of advice. It describes a path that can be a very hard one to follow, and can lead to disaster if you should give in to temptation and stray.
Monday, 31 March 2014
Real-Time DSD Conversion
BitPerfect user Eugene Vivino writes: “As you may be aware, PS Audio is releasing the DirectStream - a product that upscales all signals to 2xDSD. They say they do this because all PCM processors mask the sound in some way, while DSD outputs a more realistic and believable signal. And reviewers say that it sounds ‘right’. Now that BitPerfect supports DSD, would it be possible to add real time DSD conversion?”.
Actually, we will soon be taking delivery of a DirectStream. We are getting one of the first batch of production units. We continue to hear great things about this product, from both public and private sources, and as the hype has been quite intentionally built up I feel justified in expecting great things of it. But does DirectStream’s contribution to the state-of-the-art derive from the fact that it upscales to 2xDSD? I have received both private and public communications from Paul McGowan and his team on this subject, and I have no intention of commenting on any aspect of any information communicated privately. But I am prepared to comment on some of the publicly-acknowledged elements of DirectStream’s design.
One of the defining aspects of the DirectStream design lies in the fact that it does not use anything that you would describe as a conventional DAC chip. So I need to recap briefly on what a ‘conventional DAC chip’ actually does. What these devices do is to convert the incoming PCM signal to what is often erroneously described as DSD, primarily for the entirely laudable motive of avoiding customer confusion. This is because DSD is 1-bit 2.88MHz, and nothing else. To create DSD it is necessary to pass an incoming signal - whether analog or digital - through a thing called a Sigma-Delta Modulator. These SDMs can be configured to produce all sorts of different outputs, and 1-bit 2.88MHz (DSD) is just one possibility. More specifically, SDMs can produce a multi-bit output as well, with as many bits as you like. It turns out that there is at least one seriously good reason to use a SDM with a multi-bit output. This is that SDMs can be unstable, and, in particular, a 1-bit SDM can be seriously unstable. SDM design is not for the faint of heart. A typical commercial DAC chip will take the incoming PCM and pass it through a SDM to create a multi-bit, even higher sample rate, version of “DSD”, which it then converts to analog.
What Paul’s team have done is to focus on one of the fundamental benefits of single-bit SDM-based DACs. With a multi-bit output - such as PCM itself - the DAC has to create an output voltage which has a magnitude determined by the bit pattern. The more bits, the more different possible output levels there are. With 1-bit, there are only two levels - encoded as 1 and 0 - and from an electrical perspective, all a DAC has to do is switch its output between two fixed voltage sources represented by those numbers. These voltage sources can be, for example +1V and -1V, and can be controlled and regulated with fantastic precision, and with extremely low noise. The job of the DAC is then simply to switch the output signal line between one voltage source and the other. This is something you don’t need a chip to do, and is furthermore something you can employ a lifetime of audio electronics circuit design experience to realizing in the best possible manner.
Of course, DirectStream has some other quite unique elements to its design, such as its approach to jitter rejection. But all that aside, the only thing that counts is what it sounds like, and I am as intrigued as the next guy on that score, and quite impatient to boot!
So when Eugene Vivino observes that DirectStream upscales all incoming PCM to 2xDSD, the truth is that virtually all DACs do something very similar, except that it isn’t necessarily 2xDSD. And there is nothing particularly special about 2xDSD, other than that it is a bit better than 1xDSD. Unless you are using what is termed a ladder DAC, a vanishing beast with only a few examples still in production, the process of Digital-to-Analog conversion fundamentally involves converting the PCM data to one of the “DSD-like” SDM-produced formats. This in and of itself is unlikely to be the source of any differentiating performance attributes that might emerge from DirectStream.
Now, as I mentioned earlier, SDM design is not for the faint of heart. It is based on some massively complicated signal-processing mathematics. A breakthrough in SDM design will often earn you a PhD. There is also a lot of untapped potential in SDM design waiting patiently in the wings for computing power - always inexorably moving forward - to reach a level necessary for these process-intensive SDM designs to be brought into real-world implementation.
Yes, BitPerfect could implement PCM-to-DSD conversion on-the-fly to enable your PCM content to be delivered to your DAC in DSD form. But simply converting PCM to DSD is no panacea. It will not suddenly release trapped information in your PCM data stream. The only reason you would want to do that is if BitPerfect’s PCM-to-DSD conversion algorithm would produce a significantly better result than the equivalent functionality inside your DAC’s DAC chip. Make no mistake about it, these chips contain algorithms designed by teams of dedicated mathematicians, who know their stuff, and are implemented on silicon designed expressly for signal processing. So, at BitPerfect, we do not have an SDM of that quality, and with all respect to the other fine player Apps out there, some of which offer this capability, none of them do either.
The SDM technology we are working on requires seriously impressive amounts of processing power, so when we reach the point where we are able to implement it, it will not be introduced in a real-time system, but likely as an option in a forthcoming version of DSD Master.
Actually, we will soon be taking delivery of a DirectStream. We are getting one of the first batch of production units. We continue to hear great things about this product, from both public and private sources, and as the hype has been quite intentionally built up I feel justified in expecting great things of it. But does DirectStream’s contribution to the state-of-the-art derive from the fact that it upscales to 2xDSD? I have received both private and public communications from Paul McGowan and his team on this subject, and I have no intention of commenting on any aspect of any information communicated privately. But I am prepared to comment on some of the publicly-acknowledged elements of DirectStream’s design.
One of the defining aspects of the DirectStream design lies in the fact that it does not use anything that you would describe as a conventional DAC chip. So I need to recap briefly on what a ‘conventional DAC chip’ actually does. What these devices do is to convert the incoming PCM signal to what is often erroneously described as DSD, primarily for the entirely laudable motive of avoiding customer confusion. This is because DSD is 1-bit 2.88MHz, and nothing else. To create DSD it is necessary to pass an incoming signal - whether analog or digital - through a thing called a Sigma-Delta Modulator. These SDMs can be configured to produce all sorts of different outputs, and 1-bit 2.88MHz (DSD) is just one possibility. More specifically, SDMs can produce a multi-bit output as well, with as many bits as you like. It turns out that there is at least one seriously good reason to use a SDM with a multi-bit output. This is that SDMs can be unstable, and, in particular, a 1-bit SDM can be seriously unstable. SDM design is not for the faint of heart. A typical commercial DAC chip will take the incoming PCM and pass it through a SDM to create a multi-bit, even higher sample rate, version of “DSD”, which it then converts to analog.
What Paul’s team have done is to focus on one of the fundamental benefits of single-bit SDM-based DACs. With a multi-bit output - such as PCM itself - the DAC has to create an output voltage which has a magnitude determined by the bit pattern. The more bits, the more different possible output levels there are. With 1-bit, there are only two levels - encoded as 1 and 0 - and from an electrical perspective, all a DAC has to do is switch its output between two fixed voltage sources represented by those numbers. These voltage sources can be, for example +1V and -1V, and can be controlled and regulated with fantastic precision, and with extremely low noise. The job of the DAC is then simply to switch the output signal line between one voltage source and the other. This is something you don’t need a chip to do, and is furthermore something you can employ a lifetime of audio electronics circuit design experience to realizing in the best possible manner.
Of course, DirectStream has some other quite unique elements to its design, such as its approach to jitter rejection. But all that aside, the only thing that counts is what it sounds like, and I am as intrigued as the next guy on that score, and quite impatient to boot!
So when Eugene Vivino observes that DirectStream upscales all incoming PCM to 2xDSD, the truth is that virtually all DACs do something very similar, except that it isn’t necessarily 2xDSD. And there is nothing particularly special about 2xDSD, other than that it is a bit better than 1xDSD. Unless you are using what is termed a ladder DAC, a vanishing beast with only a few examples still in production, the process of Digital-to-Analog conversion fundamentally involves converting the PCM data to one of the “DSD-like” SDM-produced formats. This in and of itself is unlikely to be the source of any differentiating performance attributes that might emerge from DirectStream.
Now, as I mentioned earlier, SDM design is not for the faint of heart. It is based on some massively complicated signal-processing mathematics. A breakthrough in SDM design will often earn you a PhD. There is also a lot of untapped potential in SDM design waiting patiently in the wings for computing power - always inexorably moving forward - to reach a level necessary for these process-intensive SDM designs to be brought into real-world implementation.
Yes, BitPerfect could implement PCM-to-DSD conversion on-the-fly to enable your PCM content to be delivered to your DAC in DSD form. But simply converting PCM to DSD is no panacea. It will not suddenly release trapped information in your PCM data stream. The only reason you would want to do that is if BitPerfect’s PCM-to-DSD conversion algorithm would produce a significantly better result than the equivalent functionality inside your DAC’s DAC chip. Make no mistake about it, these chips contain algorithms designed by teams of dedicated mathematicians, who know their stuff, and are implemented on silicon designed expressly for signal processing. So, at BitPerfect, we do not have an SDM of that quality, and with all respect to the other fine player Apps out there, some of which offer this capability, none of them do either.
The SDM technology we are working on requires seriously impressive amounts of processing power, so when we reach the point where we are able to implement it, it will not be introduced in a real-time system, but likely as an option in a forthcoming version of DSD Master.
Sunday, 30 March 2014
Seeing is Believing
They say “seeing is believing”, but nobody ever proposes that “hearing is believing”. Yet how our brains make sense of what we see, and how our brains make sense of what we hear, seem to be accomplished more or less the same way. In each case, the brain starts by trying to figure out what it might be seeing/hearing, and tries to correlate what it actually sees/hears with its pre-determined idea. If the correlation is good, then our brains are able to conclude convincingly what it is that we are seeing/hearing. So, in order to see or hear something accurately, we don’t so much have to actually see it, or actually hear it. Rather what we need is an ensemble of evidence that allows our brains to make the necessary correlation in order for us to feel confident that we know what we are looking at or listening to.
There are many examples of this in action. The most obvious ones are ambiguous images, such as the one that is either a black table lamp against a white background or the white silhouettes of two faces looking at each other against a black background. I’m sure you can think of many other examples. When we look at such a picture, we cannot see both interpretations simultaneously. When we consider it to be a table lamp, we don’t perceive the faces. And when we see the faces, we don’t perceive the table lamp. For us to switch the way we see the image, we must consciously switch from one mode to the other. The more complex the image, the more effort is needed to switch our perception from one perspective to the other.
Over the last couple of weeks this has been illustrated to me in an interesting way. During this time, the hour I have been waking up in the morning has coincided with the time the sun rises, and starts to illuminate by bedroom. I have quite heavy curtains that do a pretty good job of keeping the sun out. But nonetheless the sun works way past the cracks. In doing so, it starts to illuminate the ceiling above my bed, throwing shadows of my curtain rail as it does so, making a pattern of dark lines across the ceiling. My ceiling is a flat white, and has an all-white 5-blade ceiling fan in the middle. At this time of year the fan is turned off. The angle of the fan blades is such that some of the blade faces are in the shadow of the encroaching sunlight, whereas one in particular faces it directly.
OK, you get the idea. Now, as the sun gradually rises, and illumination level rises, the fan blade which faces the sun just happens to take on the exact same shade of white as the ceiling behind it, and I cannot tell the two surfaces apart. I know exactly where that blade should be, because I can see the rest of the fan outlined quite clearly by its shadows. But over the course of about ten minutes, as the light gradually improves, what I see on my ceiling is a five-bladed fan, with one blade clearly missing. It is just invisible, as though it had been removed. My eyes do not detect the difference in tone of the white fan blade and the white ceiling behind it, so my brain tries to interpret the image as best as it can, and the best correlation it can come up with is the one with the missing fan blade. I know it is there, but try as I might I cannot perceive any indication of the presence of the apparently missing blade.
As the sun continues to rise, and the room gets brighter, eventually the optical illusion is replaced with the reality of the five-bladed fan, but at the point of transition an interesting thing happens. At a certain moment, if I concentrate hard enough I can see the emergence of some contrast around the edges of the “missing” fan blade. My brain can lock onto that and suddenly can “see” all five blades. However, like the aforementioned optical illusions, with some effort I can switch between perception modes. The fan can have either four blades or five.
This is where it gets interesting, though. I mentioned at the start that the curtain rail casts a shadow across the ceiling comprising a number of thin dark lines. Bear in mind that this is still a low-light situation, so the thin shadow lines are only just visible, but visible nonetheless. One of those shadow lines happens to run right through the disappearing fan blade. So when my brain sees the five-bladed fan, it sees that the shadow runs across the ceiling behind the fan blade but not across the fan blade itself. In other words, my brain recognizes that the fan blade obscures the shadow, so I see a shadow line interrupted by the 6 inches or so of the fan blade. Am I making myself clear? Good.
So what happens when I switch my perception mode to that of the four-bladed fan? In that case, my brain’s model has constructed no blade to obscure the shadow line, and so it expects to see the shadow line pass uninterrupted across the portion of the ceiling no longer obscured by the apparently missing fan blade. In short, when I visualize the five-bladed version of the fan, I see the shadow line interrupted by the fan, but when I visualize the four-bladed fan, I see the continuous shadow line. This is not a sub-conscious artifact - I can consciously switch my perception between the two versions of the apparent optical illusion. I am fully aware of the apparent contradiction which is that something which is quite obviously visible in one version becomes equally obviously invisible in the other version. Seeing is believing, indeed.
This holds some lessons for us in interpreting how we hear, if we are willing to accept this model of cognitive perception. It tells us that in order to be satisfied that we are hearing a certain thing, it is not sufficient to determine whether that thing is in and of itself audible. What we need is for that thing to make sense in the light of everything else that the brain is hearing at the same time. And I should say perceiving, rather than hearing.
As an example, humans have an uncanny ability to locate sounds in three dimensions. Not only can we locate something from left to right, but we can also locate it in terms of distance, and also in terms of height. How we are able to do this remains a topic of active research. The simple picture of how we hear is that we have two ears, and that our brains can infer the direction from which a sound is coming based on the time delay between the arrival of those sounds at our two ears. But this does not explain, for example, how we can perceive any vertical component to the localization.
This area of research has also shown up some remarkably interesting results. In the right conditions, test subjects can reliably differentiate between sounds originating from two points in space which are remarkably close together. When you crunch the numbers, the time difference between the arrival of the signals from those two locations is absolutely minuscule - of the order of 10 microseconds. This generates some tough problems, since in order to achieve that degree of temporal resolution, it is more or less a requirement that whatever is doing the detecting must have a bandwidth of around 250kHz. Considering that our hearing has a measurable upper limit of the order of 20kHz, this is problematic, and no theories yet exist to physically account for it.
However, some interesting observations do suggest that humans can perceive audio signals at frequencies considerably higher than 20kHz. By connecting a person up to a brain scanning device of some type, researchers have shown that the human brain can show a measurable response to audio signals at frequencies as high as 45kHz, even though the subject reports that they don’t hear a thing.
So if we base our models of audio reproduction theory solely upon simple stereo signals with a bandwidth of 20kHz, we may find ourselves unable to account for everything that practical experience throws at us. There are new things that we need to learn, but the fact that we don't know what they are is not an excuse for assuming they don't exist.
There are many examples of this in action. The most obvious ones are ambiguous images, such as the one that is either a black table lamp against a white background or the white silhouettes of two faces looking at each other against a black background. I’m sure you can think of many other examples. When we look at such a picture, we cannot see both interpretations simultaneously. When we consider it to be a table lamp, we don’t perceive the faces. And when we see the faces, we don’t perceive the table lamp. For us to switch the way we see the image, we must consciously switch from one mode to the other. The more complex the image, the more effort is needed to switch our perception from one perspective to the other.
Over the last couple of weeks this has been illustrated to me in an interesting way. During this time, the hour I have been waking up in the morning has coincided with the time the sun rises, and starts to illuminate by bedroom. I have quite heavy curtains that do a pretty good job of keeping the sun out. But nonetheless the sun works way past the cracks. In doing so, it starts to illuminate the ceiling above my bed, throwing shadows of my curtain rail as it does so, making a pattern of dark lines across the ceiling. My ceiling is a flat white, and has an all-white 5-blade ceiling fan in the middle. At this time of year the fan is turned off. The angle of the fan blades is such that some of the blade faces are in the shadow of the encroaching sunlight, whereas one in particular faces it directly.
OK, you get the idea. Now, as the sun gradually rises, and illumination level rises, the fan blade which faces the sun just happens to take on the exact same shade of white as the ceiling behind it, and I cannot tell the two surfaces apart. I know exactly where that blade should be, because I can see the rest of the fan outlined quite clearly by its shadows. But over the course of about ten minutes, as the light gradually improves, what I see on my ceiling is a five-bladed fan, with one blade clearly missing. It is just invisible, as though it had been removed. My eyes do not detect the difference in tone of the white fan blade and the white ceiling behind it, so my brain tries to interpret the image as best as it can, and the best correlation it can come up with is the one with the missing fan blade. I know it is there, but try as I might I cannot perceive any indication of the presence of the apparently missing blade.
As the sun continues to rise, and the room gets brighter, eventually the optical illusion is replaced with the reality of the five-bladed fan, but at the point of transition an interesting thing happens. At a certain moment, if I concentrate hard enough I can see the emergence of some contrast around the edges of the “missing” fan blade. My brain can lock onto that and suddenly can “see” all five blades. However, like the aforementioned optical illusions, with some effort I can switch between perception modes. The fan can have either four blades or five.
This is where it gets interesting, though. I mentioned at the start that the curtain rail casts a shadow across the ceiling comprising a number of thin dark lines. Bear in mind that this is still a low-light situation, so the thin shadow lines are only just visible, but visible nonetheless. One of those shadow lines happens to run right through the disappearing fan blade. So when my brain sees the five-bladed fan, it sees that the shadow runs across the ceiling behind the fan blade but not across the fan blade itself. In other words, my brain recognizes that the fan blade obscures the shadow, so I see a shadow line interrupted by the 6 inches or so of the fan blade. Am I making myself clear? Good.
So what happens when I switch my perception mode to that of the four-bladed fan? In that case, my brain’s model has constructed no blade to obscure the shadow line, and so it expects to see the shadow line pass uninterrupted across the portion of the ceiling no longer obscured by the apparently missing fan blade. In short, when I visualize the five-bladed version of the fan, I see the shadow line interrupted by the fan, but when I visualize the four-bladed fan, I see the continuous shadow line. This is not a sub-conscious artifact - I can consciously switch my perception between the two versions of the apparent optical illusion. I am fully aware of the apparent contradiction which is that something which is quite obviously visible in one version becomes equally obviously invisible in the other version. Seeing is believing, indeed.
This holds some lessons for us in interpreting how we hear, if we are willing to accept this model of cognitive perception. It tells us that in order to be satisfied that we are hearing a certain thing, it is not sufficient to determine whether that thing is in and of itself audible. What we need is for that thing to make sense in the light of everything else that the brain is hearing at the same time. And I should say perceiving, rather than hearing.
As an example, humans have an uncanny ability to locate sounds in three dimensions. Not only can we locate something from left to right, but we can also locate it in terms of distance, and also in terms of height. How we are able to do this remains a topic of active research. The simple picture of how we hear is that we have two ears, and that our brains can infer the direction from which a sound is coming based on the time delay between the arrival of those sounds at our two ears. But this does not explain, for example, how we can perceive any vertical component to the localization.
This area of research has also shown up some remarkably interesting results. In the right conditions, test subjects can reliably differentiate between sounds originating from two points in space which are remarkably close together. When you crunch the numbers, the time difference between the arrival of the signals from those two locations is absolutely minuscule - of the order of 10 microseconds. This generates some tough problems, since in order to achieve that degree of temporal resolution, it is more or less a requirement that whatever is doing the detecting must have a bandwidth of around 250kHz. Considering that our hearing has a measurable upper limit of the order of 20kHz, this is problematic, and no theories yet exist to physically account for it.
However, some interesting observations do suggest that humans can perceive audio signals at frequencies considerably higher than 20kHz. By connecting a person up to a brain scanning device of some type, researchers have shown that the human brain can show a measurable response to audio signals at frequencies as high as 45kHz, even though the subject reports that they don’t hear a thing.
So if we base our models of audio reproduction theory solely upon simple stereo signals with a bandwidth of 20kHz, we may find ourselves unable to account for everything that practical experience throws at us. There are new things that we need to learn, but the fact that we don't know what they are is not an excuse for assuming they don't exist.
Subscribe to:
Posts (Atom)