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Positive Feedback ISSUE 30
march/april 2007


The Power to Reproduce Music
by Lawrence C. Smith


The electrical current required to power our music reproduction equipment has long been taken for granted. Clark Johnsen makes the point that the people involved with audio, whether as manufacturers, reviewers, or listeners, have ignored the problems or at the very least tried to avoid facing the realities. (But then that can be said about much of life)

The first thing we need to do is take a step back and establish what we perceive to be the problem. I believe most will immediately lay blame at the feet of our local power companies. Well if that were the case how can it be explained that all audio systems, no matter where in the world they are located seem to benefit from various "power line products"? It would appear many problems lay elsewhere.

That leads us to several possibilities; the components we are trying to power are designed wrong, we are using them in an incorrect manner, or the system we have assembled is not functioning properly! Before everyone becomes irate claiming all their equipment works just fine please note I said the system was not functioning as a system!

Time to start at the beginning (or Backstory as they say); Music is fundamentally a human, physical art. The devices we have created to capture this event have developed from purely mechanical (acoustic recording and playback) to electrical (modern Hi-Fi). During this development a reproducer was considered one part of the chain; probably the best example being a phonograph from the 1940's. All in one box, with a turntable, amplifier, and loudspeaker all designed to work as a unit and all powered from the same main power source. The only problem was that it didn't sound like being in Carnegie Hall.

Enter the "tinkerers" (or Audiophiles as we like to be called) who decided they could make the sound better by adding a bigger speaker, which of course required a bigger box, which then caused feedback through the turntable. Then we needed a more powerful amplifier, which also didn't fit in the original box. As can be seen we have created numerous problems by making changes to the system without careful consideration of the secondary effects caused by our actions. We now have pieces and parts' lying all over our living room floor connected by various wires and plugged into whichever AC outlet is the most convenient! Notice we have now added interconnect cables and speaker wires (which based on the example must be adding something to our original reproducer) along with several new line cords.

Audiophiles striving for bigger and better added more and bigger components to our basic reproducer until the lights started to dim on loud passages, that's when, in the early 1970s I realized it was time to have a higher capacity electric service brought into my home. The perceived improvement was instant, greater dynamics, deeper bass; in fact I was even able to rupture a gas main in front of my house! (I was designing some really serious subwoofers at the time) During this same time period, after running downstairs to reset a circuit breaker for the "millionth" time during a particularly loud party (you know the kind of party, the one that required someone to stand over the amplifiers with a CO2 fire extinguisher) I ran a heavy commercial extension cord from an outlet in the dinning room to power part of the system. That solved the problem of falling down the stairs at the party but the next day there was a strange "Buzz" in the system that continued until I put everything back on the same AC line, the way it would have been in our original example.

Now this was not one of those "Eureka" moments but a realization that we really had to look at everything that can affect an audio system. Light dimmers all had to go (discovered that interference while setting up a new lab) and the system always seemed to sound better very late at night with everything in the house turned off, and adjacent houses dark for the night.

In 1980 while working on the original Pro-Reference preamplifier it became apparent that the sound was different when plugged into a Variac (which it was through a great deal of the development) and plugged directly into the wall outlet in my system. The sound when plugged into the wall outlet seemed clearer and faster! The Variac should not have been current limiting with the low draw of a preamplifier and one would think that a transformer in the line would, if anything acts to filter out some garbage.

Around this same time I had the opportunity to listen to many different pieces of equipment connected to high-end GenRad automatic constant voltage Variacs. These were serious laboratory quality units that had the unique ability to make anything connected to them sound closed in and congested! So much for transformers added in the AC line.

This was all taking place in the 1980s and the audiophile community was slowly becoming aware of the influence of the AC line on our elaborate systems. Many people would talk about noise from CB radios, early cell phones, and air conditioners. Everybody wanted to be "isolated" from the outside world. I remember sitting in my lab discussing my transformer experiences with George Tice, who at the time was determined to get rid of the garbage coming into his system. He built and sold a lot of "Power Blocks" so I guess everyone else was looking for an answer. Even my good friend (the late) Sal DiMicco got hooked on the transformer craze. Sal went out and got the biggest isolation transformer he could pick up (which, if you knew Sal was pretty big) hooked it up in his listening room and determined that it did seem to eliminate some AC noise on the line and make the system seem quieter. However under really dynamic conditions it might be current limiting, a little. So in typical "if a little is good, then to much is better" fashion he added two more transformers in parallel. The background noise did seem to get quieter yet, but the dynamics were still what I felt "over damped". This was not the direction to head, particularly because it involved a really ugly big box that weighed around three hundred pounds that really only succeeded in making the system sound "polite".

One day the door bell rings, then a knock, then the bell rings again (must be Sal) he comes charging in, sticks a wire in my hand and runs to the listening room all the way saying "you gotta try this! Plug this in I wanna hear it over here" all the while I'm looking at this wire in my hand trying to figure out what's so special about this line cord. We listened and listened some more. Sal brought some over for me to hard wire into the CD players I was modifying for him. That line cord sounded great! Cleaner, clearer, faster it did it all. Now my mission was to figure out why! (I guess it must be magic)

By the end of the decade I had installed the Distech "Power Bridge" on about every type of equipment available and in most cases the results were very positive. On my own Pro-Reference preamplifier it really didn't seem to help (an extremely isolated highly regulated over designed power supply) and due to the stiffness of the cord it mechanically coupled the chassis to the environment, or on my CPR preamplifier (which was powered by batteries and not connected to AC when in use) but everything else was fair game. This brings me to a "Eureka" moment!

As technical advisor for Chesky Records I was working in my lab on the original over sampling A-D converter (Bob Katz was responsible for the original build) I was working on the layout and grounding in an effort to reduce noise and improve the sound. I had spent all day monitoring the incredibly large amount of RF generated inside the chassis, attempting to shield and isolate the analog section, for some reason I installed a Distech line cord, and went back to my measurements. The noise was suddenly so great inside the converter I had to change the scale on the scope in order to get a measurement! We had known the Distech Power Bridge was highly capacitive, But this was amazing. No RF (that I was able to measure) would pass through that line cord! The noise in the Chesky box wasn't going anywhere, at least until you hooked up an interconnect cable to it. Then the shield of the cable could carry all that digital noise right to the next component in the chain.   

I needed to find a better place for all that digital garbage. The AC mains ground proved to be the ideal place to send it, of course you then have to keep all that "Digital AC Grunge" from getting back into the analog components. The PAC IDOS (Isolated Digital Outlet Strip) was born. The IDOS is still in use in many systems and when the system is properly configured has been found to do the job without adding any colorations of its own.

Over the years I have found many "truths" concerning audio systems. Some of the most important ones relate directly to connecting to the AC power.

  1. Remember the KISS principle (Keep It Simple Stupid)

  2. Three prong AC cords were designed to protect you from shock when the electric drill you are holding in your hand shorts out, while standing in a cast iron bathtub full of water. They can cause problems in a Hi-Fi system in two ways; creating an additional "signal ground" path and coupling the components to a source of RF noise.

  3. A Hi-Fi system will sound better if all the components are plugged into the same AC outlet as long as the components do not draw more current than the single source can supply.

  4. A single 20A dedicated circuit, with shortest direct run to the entrance panel has less chance of picking up interference. Additional switches and outlets in the line create points where RF noise may be rectified and introduced into the system.

  5. When current demands require additional power, a second or third 20A dedicated circuit may be run paying careful attention to the wire lengths. Keeping all lengths equal will tend to minimize ground voltage differentials.

  6. In a system with digital components efforts should be made to keep the noise they generate from entering sensitive analog components. One way to do this is with separate AC lines (of equal length and capacity) for the digital and analog sections.

  7. Wall outlets can affect the sound due to the effects of different materials. Capacitance and resistance that varies with load create a constantly changing tuned circuit. Different materials used in the manufacture of the plugs and socket can cause a "diode" effect much the way it does in speaker cables and interconnect plugs.

  8. AC cords used on digital components have a different sonic effect than when used on analog components. This is due to the fact that all line cords act as filters, some more than others and each system will react to the digital noise being blocked by the cord or not in a different manner.

  9. Special "line filters" should be used only to remedy specific problems. Often these devices can add more to the sound than they remove.

  10. Make sure all the components in the system have their AC plugs properly polarized. This can have a tremendous effect on distortions in the signal "ground" reference.

These few observations and "truths" are really only "the tip of the iceberg" when it comes to correctly powering an audio system. Grounding, both signal and AC power is the key to many audio problems. As an exercise, just think about all the "ground" or zero voltage points that there are in a audio system, and then consider the fact that none of them really are at "zero voltage"! (or maybe I should say "the same zero voltage")