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.


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utrak
20 posts
 
I've got another question for the tube amp designers.  Does it matter whether the filament supply is AC or DC?  I've heard arguments both ways.  I think that it would be great if one could get away with an AC filament supply because it requires less current from the power transformer and reduces cost to build.

Thanks  
grannyring's avatar
grannyring
6,441 posts
 
I asked the same question a little back here. Roger said AC is good as long as it is quiet.....😊 Perhaps he has more to add.....

I am upgrading and reassembling an amp with AC fils. Dead quiet.

I also wonder about rectification. My amp has an 5U4 that I am thinking of converting over to a full bridge SS rectifier. I seem to prefer the sound of tube amps and preamps that are SS rectified. My amp is only 13 watts channel/EL86 based and may be low enough power to like tube rectification just fine. I prefer SS rectification in more powerful tube amps, but am not totally sold on their value in lower wattage tube amps ..... say under 10-15 watts. I think I may like SS rectification more in these low power amps, but need to experiment more. I find SS rectification to be more dynamic while delivering much better bass. One can also beef up the supply with more capacitance and very robust Pi filters.
utrak
20 posts
 
Thanks grannyring.  
atmasphere's avatar
atmasphere
11,640 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?
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