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

@prof 

I still love to "visit" electrostatics (the Quad ESL 57s being my favorite), for their unique qualities. But every time I listen to an electrostatic, of any make, I come away happy to have moved on to cone speakers.That includes every hybrid I’ve ever heard: The cones seem to add some body, but only within their frequency range. As the frequencies climb up to where they are handled by the panel, the sound character changes to my ears to that ghostly quality, so I am always aware of this discontinuity.

The term "visit electrostats", the 57 in particular is apt as I "visited" mine today. I am in the process of modifying a OTL amp to improve its "specs", cure offset drift and increase reliability and life of the tubes. I am using the 57 in that test because of its widely variant impedance and revealing nature. The differences are palpable. 

I do not like all ESLs. Beveridge made a great one but it is very hard to place. The 57 as it was called. is truly "Walker's little wonder".
I owned 63's and do not miss them. I like line sources. I like the wide dispersion and center fill that line sources produce. So perhaps its the line source I like the most. I have heard some large cone line sources and I would say they approach ESLs. But the drivers will never do what ESL drivers do. 

I have been around ESLs all my life and sometimes when I hear cone speakers I just want to run out of the room. As far as moving air a 12 inch cone has to go a lot farther than a 4-8 sq ft piece of 1/2 mill mylar that has virtually no mass. Be aware, a cone speaker is a "mass loaded driver" by its vary nature. This cannot be disputed. An ESL is an "air loaded driver" Id rather have air than mass to move around.

In closing, and not to be a tall poppy, but it takes knowledge of both acoustics and electronics to make an ESL. One has to make his own drivers, step up transformers, polarizing supplies and at voltages that scare most people. Cone drivers are bought off the shelf, the good ones have already published curves that you can count on, no high voltage and not much knowledge to hook them up. Red wire, Black wire, cap, choke nothing dangerous, nothing EXCITING. 

@mapman 

I figured it out by listening and trial and error over time and based essentially on those parameters as a guide. However specifications alone seldom tell the whole story. The devil is always in the details much of which is never specified. Detailed measurements like those in Stereophile help a lot but I have found there may still be surprises playing real music even with very comprehensive test measurements at ones finger tips, though if done correctly, measurements certainly help with the decision making process of what to try next or not.

Today I compared two identical amplifiers, level matched, A/B switch in hand. I played Willy Nelson (raspy male voices are very telling), I played Bach Organ works, piano, lots of things. Sometimes listeners bring in music to these tests that they like, but will not expose differences. 

All I had done is add 12 dB of feedback to one amp and left the other stock. i didnt change any caps, didnt replace resistors with naked ones, didnt put in premium wire or fuses.

Both had been measured and were in proper operating condition. 12 dB of feedback will reduce distortion by a factor of 4 and increase damping by a factor of 4. It was not hard to hear the clairty, dynamics, and defined (rather than one note) bass. 

This is the story that the specs told and the listening confirmed. Come on over and have a listen. Lets not worry about comprehensive measurements when even the basic ones arent even good. The stock amp has a damping factor of less than 1 and 4% distortion at full power and I played it at full power. 

These tests are not easy to do even for me. It can take a whole day to set it up, and ive only been doing it for 40 years. Very few people set up these tests.

Why do audiophiles try so hard to ignore, object to, claim that measurements are irrelevent? Why is one reviewers impression more important? Many readers of Stereophile dislike measurements so much they say its a waste of space?

I don't design by measurement but I know what minimum performance is required to make a good amplifier. Of course some designers loose sight of balance in design and drive one spec to the limit. That often results in a bad sounding amplifier. 

What are you going to say to the poor lad who buys the Cary SLI-100 hooks it up to a pair of Maggies, turns it up loud and smiles. If you have a good sense of clean sound you will not enjoy 10% distortion, compression, muddy bass. Without JA's measurements there would be no warning. His reviewer did not use more than a few watts of a 100 watt amplifier, what happens when someone does?

@unreceivedogma

 By “more power” I’m just going by where I set the volume control before and after. It was a surprise, as I thought there would be less, and I was pleased because in my layman’s view it meant less stress on the tubes and circuitry.

This is a popular thought, however where you set the volume control has nothing to do with power or stress on the tubes and circuitry. A volume control controls gain, not power. You an be at full power anywhere on the control setting depending on the gain of other parts of the system. 

Also, I’m not sure what you mean by better technology than cone speakers. First off, the Altec is a horn/cone hybrid. That aside, while electrostatics have their virtues, they don’t move air the way a cone does, as someone here also observed. That’s what I mean by the dynamic punch of the Altecs. I’ve heard some great horn speakers, with prices in the stratosphere.

The Altecs were designed to get a lot of SPL with not a lot of power. When they were designed 20 watts was a lot of power, now its not. I have not heard any good horn speakers, though one of my students has the Avantgarde 3 way. We are having a demo this coming week. Horn speakers tend to have peaks in the response. They are very efficient, however I am not running a movie theater.

Actually ESls couple better to the are and are virtually massless. A cone speaker is a "mass loaded driver" whose motion is totally controlled by the mass. The problem with mass, as we well know is how to start and stop it. 

Rather than defend cone speakers, lets open our thoughts to why they are so popular and do they belong in the home? Fine for cars and portable radios, but that is not HiFi.

There was a time when the best and most expensive speakers were ESLs. But then came along Wilson and the world changed. We made a $4,000 ESL with DD amplifier at Beveridge when wilson was still working in his garage. He won, we lost. What happened?

Speaking of Maggies... I would like use a quality, lower powered tube amplifier to drive mine. What is your idea of an appropriate amount of “tube” power for them? I sit about 9 1/2 feet from the speakers in a 14’ x 21’ x 8’ room, and typically listen at 80-85 dB (measured with a RS meter; C weighting/slow response). They’re rated for 86 dB/ 2.83v/ 500 hz. My preamp volume control is almost always around to 9:00. I really appreciate the idea of simple circuit design for both the amplifier and the preamp. I just feel like I’m not using the power in my amp (200w/ch), and also that I’m not using the gain in my preamp (12 dB). Power is expensive, and I’d rather put the money into the quality of the amp if I don’t “need” the hundreds of watts. 

@fsonicsmith

you can’t possibly mean that preamps are easier in general and I am unaware of any accolades for your preamps (whereas you are lauded for your amps). Obviously you mean that for your tastes and purposes, preamps are easier than amps.

I mean precisely that. You might want to do a little more reading on the RM-1 and RM-5. Perhaps you are new to this hobby.

This has nothing to do with my tastes and purposes. The RM-1 (1976) was lauded for its RIAA EQ accuracy, was the first popular preamp to use the 6DJ8/6922, has the lowest noise possible for that tube. Has 5 fully regulated, short circuit proof power supplies. Built in two chassis and weighs 55 pounds ! It is the only tube preamp to my knowledge that id DC coupled throughout with servos, relay protection and no output coupling capacitor.

That was a lot of work, But once you make a good preamp what is there left to do?

Power amps, on the other hand are a world of variety. Circuit topoligies, output transformers, protection, tube life. These are really difficult things to do.

Granted most people who dont design preamps will agree with you, but they dont design preamps, now do they?

A great preamp does more than attenuate a signal. It breathes life into music. A great preamp is quietly powerful, while a great amp simply provides grunt.

A preamp does not attenuate a signal, it amplifiers a signal, provides selection of sources and control of volume, accurate phono EQ. But these are easy to obtain. There are only about 3 ways to make a preamp gain stage. There are an unlimited distinct ways of making a power amp and a good one is a challenge.

I will say that many preamps fail because of poor power supplies. My power supplies are among the finest and they dont break like ARC power supplies. You can short my power supply, go to lunch, come back, remove the short and all is well, doesn’t even get hot. One millisecond short on an ARC power supply and you wont have time for lunch or dinner. Ask any tech.

A power amp is the finess in a system, certainly not the grunt.

May I remind you this is a thread to ask a technical question.