Does anyone care to ask an amplifier designer a technical question? My door is open.

Well ramtubes, we have 100% opposite opinions concerning the necessity for well designed power cords.  I am a beta tester for a boutique manufacturer.  I've sampled at least 50 designs and tested them against all types of high end cables.  When substituted at audio shows, they were the equal of or blew away the comparable high end and expensive cables.  The worst power cables were from High Fidelity with their patented magnet design.  (I've have 8 friends and two high end homeowners who did testing on their equipment as well and the latter two dumped their HF cables).  Two posters have thought HF cables are supreme.  We (10 of us), have found them to be hard, bright, forward sounding and harmonically thin on a wide range of tube Class A, A/B SE and SS amps, pre-amps and phono pre-amps.  

I don't have any electrical engineering degree or knowledge concerning transformer design or household current.  Basically, after auditioning so many PCs on so many high end systems, it appears that you could conclude that all the auditioned equipment was faulty do to poor transformer or power supply designs or implementation.    I disagree.  My own various custom made Class A/B tube equipment are greatly altered based on the power cables and I do not believe they are poorly designed.  They sound magnificent.  The chassis and transformers remain cool to the touch (maybe 80 degrees) after hours of use at sound levels averaging 90 db with challenging impedance speakers (Legacy Focus) with 6 - 12" woofers in a 5,000 cuft room.  The EAR 890 amps Class A chassis and transformers are burning up trying to drive those speakers (no problem with the Signature IIIs at 1 ohm higher impedance and 6-10" woofers).  

Hello Roger,

Years and years ago I re-tubed my ARC SP-10 with your RAM tubes and the phono stage quieted down mighty well.  And then a year or so later I heard your RM200 amp at a dealer in Phoenix and that was a very nice sound as well.  Thirty years later, I have a question that I imagine you or some of the other techie gurus might be able to answer.

I swap between amps with some that only have single-ended inputs and others with only balanced inputs and others with both.  My preamp has outputs for both.  I recently acquired a very nice 4m balanced IC.  For the cases when I want to use the single-ended input only amp, the CAT JL-3 monos, I will need to use an XLR to RCA adapter into the amp.  The adapter I bought has the neg line tied to ground.  But this results in the preamp's neg output line being shorted to ground which does not seem to be a good thing.  Would it make more sense to put a 10k, 50k, 100k, etc., resistor inside the adapter from the the neg pin to ground to more accurately simulate what the cable would otherwise see as the amp's input impedance?

Any thoughts here would be greatly appreciated.

John

I swap between amps with some that only have single-ended inputs and others with only balanced inputs and others with both.  My preamp has outputs for both.  I recently acquired a very nice 4m balanced IC.  For the cases when I want to use the single-ended input only amp, the CAT JL-3 monos, I will need to use an XLR to RCA adapter into the amp.  The adapter I bought has the neg line tied to ground.  But this results in the preamp's neg output line being shorted to ground which does not seem to be a good thing.

Its probably not- check with the manufacturer of the preamp. If the output is transformer coupled, then this is required. So it really depends on the preamp!

But if I were you, I would simply use the RCA output if using an amplifier with a single-ended input. There is no advantage of using the really nice balanced cable if you are going single-ended- the single-ended requirement actually results in the **entire** connection being single-ended so the cable is not operating as designed and intended.

Ralph, couldn't he use a Jensen transformer to make he XLR to RCA change? Would it still offer the proper grounding?
Bob

ramtubes you stated " My stand on power cords is entirely intellectual from an amplifier designer and transformer makers point of view. I know what is inside a transformer and how it works. When you know
about transformers, house wiring etc. we can further discuss this interesting topic."

 Caelin Gabriel of Shunyata Research Inc. knows much more than I do and he is an electrical engineer with a high pedigree in the audio industry. Whether his cables and noise suppression equipment are correct or not, I don’t know. However here are three of his quotes concerning power cables and sonic degredation due to faulty power supplies in equipment.

" Misconception #3: There is up to a hundred feet of wire in the walls, so the last 6 feet of power cord can’t possibly make any difference.

Answer: “The power cord is not the last 6 feet, it is the first 6 feet from the perspective of the component. As stated in #1 the local current and electromagnetic effects directly affect the sonic performance of the component.”

So, he feels that the upstream house wiring all the way the transmission towers are not as relevant as the Power Cables leading to the equipment.

Misconception #4: There is a tremendous amount of electrical interference and EMI coming from outside the home that we need to protect our equipment from. This implies that we need some sort of power conditioner or filter to protect the equipment.

Answer: “Most of the EMI that affects the audio quality of a system is generated by the audio components themselves. Electromagnetic waves that traveling through space dissipate in power at the square of the distance from the source. Further, very high frequencies that propagate through the power circuit do not survive for long. Power lines present a high impedance to MHz and GHz signals due to the relatively high inductance of power lines.

"A primary source of audible sonic degradation is caused by the power supplies in our audio/video components. Most components use FWBR (full wave bridge rectifier) power supplies that generate an incredible amount of transient noise when the rectifiers switch off. The design of a power cable can significantly affect the reactance of these signals within the power supply. The power cable is effectively part of the primary winding of the power transformer. The transition between the various metals used in a power cable and its connectors can cause electromagnetic reflections and diode-like rectification of the noise impulses as they propagate away from the power supply. If the power cable presents a high impedance to these signals they will be reflected back into the power supply where they will intermodulate, thus increasing the high frequency noise levels of the component. Most power supply filters are ineffective at blocking very high frequency noise components and much of it is passed through to the DC rails. The sonic effects of this include: high background noise levels, blurred or slurred transients and a general lack of clarity and purity of the sound or visual image.”

Here he is stating that the equipment power supply creates the sonic degradation.

Misconception #5: There is some sort of conspiracy among audio designers that keeps them from producing a "proper" power supply that is not affect by power cable quality.

Answer: “This concept is like saying that if a speaker where properly designed, you wouldn’t need to use a good quality speaker cable. PowerSnakes have been tested with the most modest of mid-fi equipment and the most exotic state of the art components. We have yet to find a component that cannot be improved by replacing the power cord.

"As long as power supply design is based upon FWBRs or switching supplies, the power cord will always be significant.”

Basically, he is stating that power supply design generally is at fault resulting in power cords making a significant difference.

Are your RM series amps and pre-amps designed to prevent all of these problems? Are most equipment designers not designing their equipment correctly? You would know as I don’t.