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


I closed the cable and fuse thread because the trolls were making a mess of things. I hope they dont find me here.

I design Tube and Solid State power amps and preamps for Music Reference. I have a degree in Electrical Engineering, have trained my ears keenly to hear frequency response differences, distortion and pretty good at guessing SPL. Ive spent 40 years doing that as a tech, store owner, and designer.
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Perhaps someone would like to ask a question about how one designs a successfull amplifier? What determines damping factor and what damping factor does besides damping the woofer. There is an entirely different, I feel better way to look at damping and call it Regulation , which is 1/damping.

I like to tell true stories of my experience with others in this industry.

I have started a school which you can visit at http://berkeleyhifischool.com/ There you can see some of my presentations.

On YouTube go to the Music Reference channel to see how to design and build your own tube linestage. The series has over 200,000 views. You have to hit the video tab to see all.

I am not here to advertise for MR. Soon I will be making and posting more videos on YouTube. I don’t make any money off the videos, I just want to share knowledge and I hope others will share knowledge. Asking a good question is actually a display of your knowledge because you know enough to formulate a decent question.

Starting in January I plan to make these videos and post them on the HiFi school site and hosted on a new YouTube channel belonging to the school.


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@mrdecibel 

Roger, thank you for the response. I have to disagree with you as to warm up time of a component ( which is relative to break in time ). For me, 5-10 minutes is never enough. " Don't sound bad when they come up slowly ". For me it takes much more time. I am not talking measurements, I am talking " listening ". I would like to leave it at that, as this, too, could wind up being a very controversial discussion, and not new to Audiogon. Enjoy ! MrD.


Was that MY amp that took hours? Not all tube amps are the same. However you are welcome to warm up as long as you like. There is no controversy. 

To help solve the warm up problem I put a forming switch on the RM-200 MK II at the suggestion of Richard Vandersteen. This switch keeps the caps formed beyond operating voltage. We both feel that cap forming is the most obvious reason for long warmups.  

One might also consider warm up time on their ears and other senses. When we first sit down we are not in the same state as some time later when we have relaxed and shut out the noise of the outside world.




Thank you Roger. You are a true asset to the audiophile community. Very generous.  
Thank you for your kind offer, Roger.

I build solid state amplifiers, and like to match output transistors. At first I matched for HFE, then VBE at constant current similar to operating spec. Only later did I realize how much this parameter drifts over the first hour of warmup.

However, my latest amps are Class A, and I suspect that a more realistic match is obtained by culling outliers by HFE, then match from VBE using the bias at constant potential and sufficient to generate the operating current. Finally, instead of using matched emitter resistors, I use emitter resistors tailored to the output devices, so that each emitter resistor sees the same potential drop.

Your thoughts? Any advice appreciated.
I wonder, how many have actually heard a Music Reference amp? Not a "trendy" brand, conservatively and timelessly styled (I happen to find the RM-200 minimalistily elegant, in a Scandinavian sort of way), few dealers, fewer reviews. I have found MR owners to be independent-minded, and secure in their own opinions, needing no validation from others. My kinda people.