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

I spent close to $20k on a pair of brand name monoblocks, plugged them into my dedicated 20 amp outlets and they had a loud line level hum, hired electricians, changed out grounding rods etc to the tune of $3k in costs. Took all my other equipment and cables to my dealer to make sure they weren’t the issue and they weren’t. Finally I paid $10k and bought a used amplifier and bingo the problem went away. My system is silent and absolutely glorious sounding again. The monoblocks worked at my dealer without issue but had an issue in my house. How can a designer build a product like this and what could the problem be. I am out 000’s of dollars and lots of my own time researching the issues. I borrowed isolation transformers etc as the manufacturer said it was my house that was the problem and not their amps... they were a joke to deal with and basically blew me off. The only thing they offered was to pass a name along to me if they heard of anyone wanting to buy a pair. FYI, this company has a 20 year warranty... your thoughts are appreciated. Thank you for listening to my rant...

@mapman

I use the receivers only as a simple demonstration of the benefits of more clean power in a line that otherwise is mostly similar in design.

Just my gut feel but I suspect there are many who have underpowered systems that clip perhaps in often subtle ways and then blame the results on a bad recording and never know it. Been there, done that myself in the past for sure as well.

Whereas not taking chances with clipping even in its most subtle form is perhaps the single biggest key to getting the best possible results. That and keeping noise to a minimum which is much harder to do in any high power integrated amp or receiver with more circuit and components in closer proximity to each other compared to separate devices

Sorry but this is not consistant with my experience. 

I find from conversations with customers that they are actually using only a fraction of the power they think they are using. In otherwords they have tons of headroom they did not think they have. Once again we do have tools to measure these things and guessing is just not good. Happy to hear any numbers you care to share in your system.

I studied clipping in many classic amplifiers and in my own of course. When tube amplifiers clip they often take a long time to recover. The highly respected HK Citation tube amps are horrible clippers with very slow recovery, the ST-70 is not so good either but recovers faster. A few amps that handle clipping softly with virtually no recovery time are the Marantz and so few others I cannot even recall them. I have measured over 100  power amps in 400 pages of notes. Before I embarked on the RM-9 I had the opportunity to play with a Marantz 5 which is a mono 8. It blew me away comparet to the Dynaco and other amps I had measured. When I designed the RM-9 I was very interested in doing as well as Marantz (SId Smith) and I feel I did. Sid Smith set a standard that might just be unbeatable for clipping and recovery. I would say if you amp never never clips you have too much amp.

So to sum it up. Good amps can clip a bit, Most people don't here clipping if it is gentle and recovers fast. Extreme headroom means nothing and may acually be a detriment due to making an amplifier far larger than it need be. I have never found a good argument for excess in anything. Thats just philosophical. I like to live lightly on this Earth. Over powered systems impress me not.

@btp24

Roger, why is damping such an outdated term? ;-) I have heard you speak of how even a low output impedance amp doesn't, contrary to common believe, "damp" a woofer. You have quoted Paul Klipsch on the subject, as I recall.

As Paul said, What does it matter if you have some ohm or so of external resistance in series with 6 ohms of voice coil resistance?   

Its how output impedance affects and modifies the frequency response that we need look at. Its so obvious. That happens to be the first thing in every Stereophile test report. JA knows and he tells. Its fun to read the manufacturers response to high output impedance. They have no excuse but to make something up. 

Low damping amplifiers will bump up the bass at the resonant frequency of the speaker by providing extra voltage that is undesirable. One bump for sealed, two for ported. 

So we really aren't damping anything, are we?

@stfoth... where do these forum name  come from?

Hello, RM! You mentioned the recent measurements of the Cary SLI100. Reminds me a bit of one a few years back on the 300SEI.

https://www.stereophile.com/content/cary-audio-design-cad-300sei-integrated-amplifier-page-3

That's something of a sort of classic amp with quite a few fans.
Compound question.
Your thoughts on Dennis Had and legacy Cary gear?
Your thoughts on the disparity between the measurements and folks who say things like that in the subjective review?

I believe Dennis was a RF engineer that switched to audio. His first amp with the torroid output transformers was a quickly discontinued disaster. He should have know torroids are good for RF but no good for audio ouput. He learned though. I dont know anything about the legacy gear. Got a link?

Anyone who thinks a gapless torroid is good for an audio output transformer is kidding himself. Luckily few exist. 

Not sure i understand the second question. Can u clarify and expand?

I read a report by JA measuring a Prima Luna tube amp (some years ago). He found an output impedance of 8 ohms! This means a DF of 1 ohm or less! Combined with the typical varying impedance of most speakers this is way too high! How can supposedly competent engineers get away with something like this? Because the result is far from neutral, accurate SQ! No matter how pleasing the "golden ear" crowd claims!