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

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.

@stfoth

RM, thank you for taking the time for this discussion. It's really, really refreshing.Turning back to my prior question about your thoughts on Dennis Had and his legacy Cary gear...sorry to bother if you are not familiar (https://www.caryaudio.com/products/). I suppose items like CAD-805, CAD-211, CAD120S, SLI80 (precursor to the one that was just reviewed), V12r, SLM100, 500MB, CAD1610, etc. Some links, if interested.https://www.stereophile.com/tubepoweramps/1200cary/index.htmlhttps://www.stereophile.com/tubepoweram... asked that I clarify a question about your thoughts on how there can be such glowing subjective professional reviews when the measurements are so objectively bad. For example, the 300SEI I mentioned measured poorly, but many folks, including professionals, love it. I suspect some folks will love the SLI100. I was just curious about your thoughts on how or why something might sound "good" but measure like crap. Not limited to Cary gear...just using that because we have two examples in the thread.

Where to begin, I have to nibble on this, its a lot to digest. 

Dennis is a prolific designer and had good people to get the rest done. I dont see the very first amp with the torroids. Wasn't Cary under another name initially?

This is actually an easy question. An amp that measures badly will sound bad if you get it into the situation in which it measured badly. You have to realize that some of these reviewers listen at 0.1 watts no matter what the amplifier power is. 

Any amp that can pass a signal will likely sound good at 0.1 watt, This can be seen by reading reviews in Stereophile. Have you noticed that when an amp is really bad at full power JA will do the IM and other tests at very low levels? He is kind to do that because otherwise we would all by crying. When an amplifier has low distorion he does the IM at very high power. You have to read the fine print. I read the measurements several times before I can construct a reasonable picture in my mind of what is going on. 

So the reviewer may never play the amp loud enough to get into the distorted region. Lets say its a 100 watt amplifier played all below one watt. The new Cary SLI 100 is a good example. Most reviewers are not loud listeners in my experience. They are not pushing that amplifier but John is goning to take it for a run. Anyone who buys it and actually uses the power is going to be sadly disappointed. The amp is just going to collapse into mush. 

Look at the horrible SQ wave on the cary 1601. Ive never seen one that bad, however it wont change the sound. Note JA fig 3 measured distortion at just 1 watt. That wont show transformer saturation in the low end at full power.There is no spec and no measurement of the power bandwidth. How many watts will this amp do at 20 or 40 Hz. I bet not much.  He is just being kind by not going there. 

Look at fig 8 & 9, up to a watt the amp is ok. BUT IT IS NOT A ONE WATT AMPLIFIER. At full power its like 10%

@rsf507 

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

I would like to know the capacitance of the panel itself, the electrode spacing and the polarizing voltage. 

Direct Drive is the best way to go. I have found many cases where half the power goes into the step up transformer and other EQ components. How does he EQ the speaker these days? I just started reading the speaker description. Sounds like its an entire system. 

Roger, I think you provided this information somewhere, but I can't remember where, and can't find it. So let me ask you: what is a good output impedance number to shoot for in a power amp? How low does it need to be to prevent frequency response peaks and dips due to the speaker impedance/amplifier output impedance interaction? I know the figure will be different for a speaker with a wild impedance curve (the original Quad ESL) than for one with a fairly even curve.