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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I feel one of the great benefits of tube products is the limited bandwidth eliminates susceptibility to much of the higher frequency ac noise. Comments?
Some products allow the music to communicate to you, some don’t, and a combination of components may speak to me, but not to you. I know this isn’t a technical question, but I felt compelled to write it nevertheless.
Dr Herbert Melcher showed that there are tipping points in the brain. Normally music is processed by the limbic system. But when things audio go amiss, the processing is unconsciously transferred to the cerebral cortex. At that point the music 'subjectively' loses its 'soul'. For this reason, its really important to know how the ear/brain system perceives sound, so as not to violate its perceptual rules (if you want the gear to be emotionally involving). Once you know that, it becomes and engineering task that is fairly mundane.
He made excellent equipment and I can see from JAs measurements he did a good job on the three major characteristics of a good amplifier, one that would drive a wide variety of speakers well. On this I am in complete agreement with Charley. Im not sure why I need to listen to his amps, I am confident they sound find. Charley and I are on the same page with what is important.
Charles made **zero feedback** amps and IMO his are some of the best solid state amps made. What I like about his approach is that he solved the issue of an amp that acts as a voltage source while also lacking the usual coloration of brightness caused by the distortion of added feedback. The industry needs this sort of diversity and he is missed.

I feel one of the great benefits of tube products is the limited bandwidth eliminates susceptibility to much of the higher frequency ac noise. Comments?
You can have plenty of bandwidth and not have noise problems. Noise is best handled by proper power supply design and good grounding technique. I find also that fully balanced differential circuits are handy for noise rejection as well. This means that you can have a wide bandwidth tube amplifier and have it be very quiet, even though it may not be shielded by a chassis.
@krelldreams  I’d like to add this: I appreciate the fact that there are two professionals contributing here, despite the fact that there is tension that’s been created by disagreement. I’m trying to read through the commentary to the points being made, the examples being given, and the facts. The reality is, there are many ways to arrive at the same destination. I’ve listened to, and owned A LOT of gear in my life, though none, so far, by either of these designers. Some products allow the music to communicate to you, some don’t, and a combination of components may speak to me, but not to you. I know this isn’t a technical question, but I felt compelled to write it nevertheless.


I appreciate your balanced view on two designers, with very different viewpoints, airing their design thoughts in public. Im fine with it and I hope readers understand that sometimes a statement is so shocking to me that I get a little worked up about it.

I have experienced and previously stated where cartridge loading makes large difference. I love to do things on the fly with minimum time between evaluations. Therefore I built a 6 position load box for my Denon 103 from 10 to 200 ohms, including no load. I can just dial through and listen. The Denon is a cartridge that needs loading otherwise it is bright and harsh. Around 100 ohms it sounds good to me. Below that it gets kinda dead sounding. On the other hand we did the same with the Lyra and no load sounded the best. We had a switch of 12 loads from 3 ohms to no load. From 10 ohms up we heard no difference. The audience was 40 people who generally agreed and were surprised at what they heard. 

I fully agree and have stated before that each of us have a system that is "his sound". It can be fun to visit and listen to others sound. Now what does one do when (and this is a horribly delicate situation which I have encountered too many times) one visits a friend and while the owner thinks things are fine the system is actually broken. When I found the bad 6SN7 in the Oppo the owner said it had probably been like that for a month. When we find a speaker out of phase it might have been that way for half a year. When I hear a distorted amplifier and I put it on the bench and find it way out of spec what has the listener been doing? 

I visited another audiophile who had $100,000 of good gear in a cubic room about 14x14x14 feet with all hard surfaces and no treatment at all. The room was so live I couldn't even carry on a conversation. I politely said.. "Hey its nice outside can we go sit in the sun and chat" When we came back in to listen he asked me what I though of his system. I told him, Sorry I cant hear the system I can only hear the room. Once again he though because he had good equipment that it had to sound good. 

Of course we should trust our ears but where is our reference? How many high end systems are being listened to with something out of wack. 

I am likely one of a very few designers that actually will repair others equipment. I do this because I like to see others work, how they make things, how their things perform. I have tested over 400 amps and preamps and can tell you all about what is going on in them. 

 
@ptss  @ OP. How do you feel about Spectral Audio designing amps with extreme bandwidth? Are there benefits for solid state amps?

When I went to Vegas in 1978 Spectral was playing B&W video through their line stage. The volume control thus because the contrast control which they encouraged everyone to play with. The picture was ok so it was at least a few MHz of bandwidth. I guess they liked bandwith. Their designs were, in my opinion, excellent.

I dont see how it makes a difference to go that far and it is an invitation for RFI to be passed on to the power amp. 

After a certain point slew rate and bandwidth are just for bragging rights.

In output transformer tube amps wide bandwidth, maintaining stability and getting the big 3 parameters reasonable, is the greatest challenge