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

@csontos

Hey Roger. What are your thoughts on designing a ss amp to drive ESLs directly? I'm currently listening to Acoustat Monitor 3 with direct drive servo charge OTL monos. It seems the ultimate comparison between ss and tubes would be a shootout with such. I find directly driven ESLs to be the ultimate in transparency and so the ultimate test bed between the two major topologies.

Many thoughts, mostly of replacing lots of fused silicon.

5,000 volts is a dangerous environment for SS devices. There are no devices over 1,500 volts and they are mostly switches or horizontal output transistors. 

I dont think that is the application to have a shootout. At high voltages tubes make more sense and are more reliable.

Horizontal output tubes are plentiful, inexpensive and very reliable. They lend themselves to a much simpler circuit. 

I have worked on many of the original Servo amps. There are many improvements that can be made to their design. I once offered a drop in board with all tube driver. Perhaps I will again.

@toddcowles

Wondering what your thoughts are on the most significant transition/design element that has improved overall sound quality in today’s amplifiers.

WOW what a question. I cant think of just one. There are so many ampifier designs out there now. Many of them are just horrible.

However I can tell you what has not been significant. Heres a list: premium capacitors, nude resistors, torroid transformers, most cable claims, premium fuses, fancy metal work, purposely colored amplifiers......

I read every amplifier review I can get my hands on. I work on a lot of amplifiers. I rarely see one that hits me on all 8 cylinders.

I think people are looking at the wrong reasons to buy a particular amplifier. John Atkinson has measured some really bad ones lately. Why does a manufacturer send him an amplifier they know will fail his tests?

EVERYONE. Read the review of the Cary SLI-100 pg 91, Dec, 2018, Stereophile. What a disaster, what an embarassment, what foolishness. Then go read the manufacturers comment. They did a great marketing turnaround, or attempted to, making it appear they want it to be that way.  They believe that "specs do not tell the whole story:. Well, when the specs are this bad who cares about the story. So I guess the most significant transition is putting lipstick on a pig.

Marketing rules, appearance rules, internet chatter rules. I caution people about amps with poor specs, amps that if they fail will be difficult to repair. They dont care. The Benchmark that was widely discussed a few weeks ago is impossible for a non factory tech to repair.

Sorry to be the bearer of bad news, but things are not looking good. I posted a thread about the MCIntosh 2300 that the Grateful Dead used. No one cares,they think it cant possibly be good, its too old. Well its damn good. Its clever, its relaible, its rugged. I dont think you can break it. Im not even a Mac guy, but I know a good design when I see one.

When I got into highend design in the 1970s we were making some great advances. Smart engineers were solving problems. I had the opportunity to work with Harold Beveridge for 2 years. There were great leaps of progress. Nakamichi was perfecting cassette decks. Sumiko and others brought us MC cartridges, GAS was making good amps and preamps, We were making great ESL speakers with direct drive amplifiers. Those were days of progress.

Sadly I see little progress now. Perhaps thats why this is so hard to answer. Its all about the looks, the review, the story these days, isn’t it?

I will continue to give this some thought.

Great, great, great thread! Ramtubes can you tell us what amps would be good to drive the Sanders 10e electrostatic speakers? 

Hey, look at this. I just went to Stereophile to look for the Cary and they are running this review of the amp I did for Counterpoint 32 years ago. This was going to be the RM-6.  I almost merged Music Reference with them. Glad I didn't. Im still here and they are not. What a pack of thieves. Never got my royalties. I had the misfortune of hiring Michael Elliott when I worked at Beveridge. What was I thinking. 

https://www.stereophile.com/category/tube-power-amp-reviews

And same time, same reviewer..

https://www.stereophile.com/content/new-york-audio-laboratories-futterman-otl-1-power-amplifier

Two versions of the Futterman circuit. East coast/West coast. Harvey was a hoot. I visited him and his gang around this time. Sadly or not, he folded too. Is there a Futterman curse?

My latest OTL is one with a built in Autoformer. Ive built a few and have another one in process.