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

@pryso

Roger, really appreciate your efforts with this post. But, a question -

"Over 100 watts is only justified by either high listening levels or insensitive speakers or both together. Excess headroom is a myth."

I and many others find headroom seems to relate to clean (undistorted) dynamics. Would you expand on your myth statement, why you feel that is the case? Maybe the key is "excess"?

Thank you for bringing this up. Ive been waiting for this.

Answer is I cant say what you are hearing. I dont know if you are clipping sometimes or not. If you have a scope or peak reading voltmeter you could find out.

Now here is what i DO know. A 1000 watt amplifier played at 1 watt is likely overkill, though I had one Japanese man express this headroom is necessary. I responded, large amplifiers played at low levels may not be as good as smaller amplifiers. Many people feel small amplifiers sound better when they are enough.

Amplifier designers have to commit certain "sins" when making really big amps. High power tubes amps are enormous with enormous transformers. Take the JA200 for instance. Theres a big sin in that amp. It plays 200 watts cleanly up to 500 hz or so. As you go up the power bandwith is reduced every octave. At 20 KHZ it does just a few watts. I have measured it. Go look at the 4 chassis of that amplifier. Yet this ampifier has good reviews and hardly anyone knows about this problem. Did JA get hold of one? IDK?

Tube amplifiers scale up pretty much pound for pound for watt. 500 watts is 5 times heavier than 100 watts. Again look at the Jadis. BTW that power rolloff is entierly intentional. I could easily modify that amp to have full power to 20KHZ. The transformers are excellent. Why they chose to roll off the power I dont know, I dont speak French. Im happy to fix one up for anyone interested.

So i ask you, how many watts do you have and how many are used at your average listenting level. The headroom on CDs is well defined and easy to measure. The ones that play loud likely have 10 db. Good ones have 20dB not much more or they sound too soft.

There is a lot to this question so lets hear back from you and others.

There is a lot to this question so lets hear back from you and others.

My own philosophy is based on the expectation, generally speaking, that for a given level of quality, and within a given architecture (solid state, tube push-pull, tube SET, etc.) and class of operation (A, AB, D, etc.), there will tend to be at least a loose correlation between amplifier power capability and amplifier cost. And in choosing an amplifier I prefer to direct as high a percentage as possible of the amount I want to spend toward quality, rather than toward watts.

My listening includes a lot of well engineered classical symphonic recordings, which therefore have very wide dynamic range, and not infrequently reach brief dynamic peaks approaching 105 db at the listening position. So I choose an amplifier that in conjunction with my speakers can comfortably support that level, with a few db to spare, and I don’t pay for any more watts than are necessary to accomplish that. Instead, I try to direct whatever $ I choose to invest in an amplifier toward quality, as much as possible and as best as I can determine that based on research and listening.

On another note, happy Thanksgiving to all!

Best regards,
-- Al

@bdp24 

@jcder, everyone is going to recommend his own pre in answer to your question. Here are a couple to consider: There is a Hovland HP-100 listed on Audiogon right now (at an asking price of $2350), a fine line stage (I heard it in Brooks Berdan’s reference system for quite a while). The EAR-Yoshino 868L line stage, another good one, occasionally pops up for around $3,000. The 868 has one true balanced (via transformer) XLR input, if that matters to you. EAR Designer Tim de Paravicini very much strikes me as the UK’s equivalent of Roger Modjeski; old school EE’s with good ears and lots of knowledge and talent.

Happy Thanksgiving. May I remind everyone the purpose of this thread is to ask a technical question, not to discuss whose preamp is better.

This is the only time I will say this and I will ignore future preamp comparisons. 

@ieales A balanced input is no guarantee of better sonics. The devil is in the details.Every audiophile should read Bill Whitlock’s AES paper"An Overview of Audio System Grounding and Interfacing" available here https://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf

Thanks for the link.. Its 212 pages of slides. Power point :( I hope he takes breaks with refreshments. This could take hours. Id need 3 cocktails and a sandwich.

Can you direct us to a few pages with some meat on the bone. Im sure there is some wisdom there.

@terry9  

Thanks for all your help, Roger. You really have opened up a stack of stuff for me to do. Much, much appreciated.

Hate to be pedantic, but I think that the 45uF figure should be 4.5uF, which is less of a problem: (75**2)  *  (800  *  10**-12)  = 4.5  *  10**-6. Your other concerns with the Vanderveen (got it right this time?) transformer remain an area of intense interest (and research!) to me. Thanks again!

You are indeed correct, it is 4.5 uF and still too much.  What raised my flag was that when i measured my speaker was at 80 pF for the 3.5 sq ft panel and I managed to make a transformer with about the same 80 pF capacitance and at 200 to 1 step up. Not much point in going further than that as half the power is in each. However had I used the plitron the numbers would be 90% of the energy absorbed by the transformer and 10% to the speaker. Thats a bad deal. 

Have you measured your drive capacitance? It is simply what you get stator to stator with a cap meter. I knew it when I was Direct Driving my 63's but that was 10 years ago. 

Not sure they still do but the 63's have a big 220 UFelectyrolytic cap in series with the hot speaker terminal to block DC. Do they still have this in some or all models? I could never understand why so large when 10 uf PPN would do.