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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@almarg  That’s interesting to hear, Roger. Although to be precise I’m pretty certain that the 8 and 8B were both single-chassis stereo amps.

I’ve never heard an 8 or 8B but during the 1990s I owned a pair of Model 9 monoblocks and a pair of Model 2 monoblocks. And I greatly preferred the sound of the 2s to the 9s, although in fairness I can’t exclude the possibility that condition may have been a factor in that.

The 2 was similar in some respects to the 8 and 8B, which came later of course. Although in addition to being monoblocks the 2 employed tube rectification, while the 8 and 8B used solid state rectification, and the 2 used 12AX7 input tubes while the others used 6BH6s.

I’ve commented here in the past that at least when used in conjunction with speakers having benign impedance characteristics and not requiring more than the 18 or 20 watts or so that the 2s were capable of in triode mode, in that mode the 2s were one of the best sounding amps I’ve ever heard.

 
I never got my hands on a 2 but I studied the 5 (half of an 8) in great detail and I saw how they did the tertiary feedback winding. I had to do a lot of experimenting to make that work out but its a trick I have rarely seen in other amplifiers.

The separate feedback winding makes the amp more stable into reactive loads. Perhaps few know that we made all the transformers for the RM-9. I cut my teeth on the design of that output transformer.

The 9 was quite a departure from the 8, far more complex, perhaps better specs, but when you take specs too seriously (as in too much feedback) things can go downhill. 


RIP Charley
I  was a friend of some small depth on Facebook and a BIG fan of his VXR amp....countless hours of musical enyoyment.
Peace and grace for his family and a lasting legacy of greatness is my prayer...

@ramtubes, oh yeah Roger, now I remember Dick Olsher's review of the RM-9 Mk.2. I found Olsher to be a reviewer from the Gordon Holt school (a school I approve of ;-), and he loved the amp. I believe his closing line was something like "Who needs an MC75 (the classic Mac amp) when we have the RM-9 Mk.2?"

I also remember The RM-5 and the Audible Illusions Modulus 2 were considered THE bargain tube pre-amps to choose between. I found the AI Mod's 30dB of line stage gain unfortunate and ill-advised, as well as it's dual-mono volume controls. The Modulus is still in production (in updated form, of course), so Roger, any thoughts of offering a contemporary RM-5 type pre?

Why would dual mono volume controls  be ill advised?
This is kind of an obtuse question, but why do some amplifier manufactures say to use a preamp between their amplifiers and the streamer when you are only using a streamer and power amp, no vinyl and no other sources.  I understand the need for a volume control and to have the impedance's low for the streamer/DAC and high for the power amp.  My streamer/Dac is <100 ohms and the power amp is 47K.  There is an implication that the preamp does other things that affect the SQ.  Any idea what those are?  An Allegri+ addresses the impedance problem and give a volume control and is extraordinarily transparent on my Ribbon Speakers.   My amp and steamer is very high end.  Is there more?