2. amps-preamps
  3. 140029-80294

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.


128x128ramtubes
atmasphere's avatar
atmasphere
11,896 posts
 
I am comparing a 5ch and 7ch amp. Same brand and specs exactly the same except for one difference -- one is a 5ch and the other a 7ch. Same rating of Tor power supply ( 2 total valued at 1,230VA and 1,025VA)

All things being equal - will sound quality be relatively the same? Dynamics? ... or is one better than the other?

Also -- ideally how big of a power supply is best suited for an amp rated at 200wpc at 8ohms driving speakers that dip to low 3ohms?


It *might* be that the amp with 5 channels could sound a little better, solely based on your comments above, due to 5 channels sharing a common power supply instead of 7. IME probably not a very big difference in any event!
With regards to the latter question, the power supply for one channel should be capable of sustaining 14 amps continuous to sustain the output section of the amplifier (assuming that the amp is doubling power as the load is halved); a bit dependent on the class of operation (for example, a class D amp won't need any more than that, while a class A amp will need a bit more to sustain its driver section.   Generally though its a good idea to have some reserve available in the power supply so that it runs more reliably. I prefer to have the power supply to have considerably more energy than the amp is going to need to make so that it won't limit current when things get complex.


jdechamp
33 posts
 
Roger, let me add my thanks. We spoke years ago when I had a Beveridge RM-1 and you were very helpful at that time. You mentioned a few posts earier that you produce some DD amps for electrostats. I have a pair of Acoustat Xs in need of amplification. Can you provider some information?
georgehifi's avatar
georgehifi
10,312 posts
 
I have a pair of Acoustat Xs in need of amplification. Can you provider some information?
This would be a dangerous amp to own if not made by someone who knows their stuff.
I’m sure from what I’ve seen, Roger will be an ideal choice for this if he wants to take it on, as it’s not part of his line, and would be a special build.
Who knows maybe it could be part of his future line, as there are many Acoustat X’s out there in need of HV direct drive amps. Not to mention other ESL’s that could sound better if they were converted to take HV direct drive amps.

Cheers George
robertrs
17 posts
 
Roger,

Thank you and the other SME's (Subject Matter Experts) for this wonderful thread, although much of it is over my head it is still a great read.
Stereophile just reviewed online yesterday the Cary Audio SLI-100 integrated, I only read JA's measurement section. Are the measurements results a function of the circuit design, layout-topography, or part quality?
georgehifi's avatar
georgehifi
10,312 posts
 
robertrs
Stereophile just reviewed online yesterday the Cary Audio SLI-100 integrated, I only read JA’s measurement section. Are the measurements results a function of the circuit design, layout-topography, or part quality?
The way is it is made, it’s performance (8ohm) tap into a simulated easy speaker load (black wavy trace)
https://www.stereophile.com/content/real-life-measurements-page-2
https://www.stereophile.com/images/1218Cary100fig02.jpg
it does becomes a bit of a tone control, varying it’s frequency response up to +/- 4.5db!!! A good amp should be almost flat.

This is probably as a result of it’s 4.4ohm!! output resistance, that’s a damping factor of under 2 !!! From the 4 ohm tap, it’s 2.3 ohms!!, still to high in my books.

Not good to me, unless you purposely want to change the way a recording is meant to be listened to by the recording engineers, into today's semi demanding speaker loads, it will be fine into very easy to drive speakers, but they usually have their own set of problems   

Cheers George
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