I hate to say it, but now I think maybe I like my amp in ultralinear mode versus triode

@dogearedaudio "Zero" feedback? Really? I’ve looked at the CAD-280SA V12 manual online and it doesn’t mention feedback, but perhaps that’s a different model. Hard to imagine they use NO feedback. Maybe not global feedback, which encompasses the output transformer. Internal feedback can be used to good effect, but no feedback at all is hard to imagine.

Re-checking my own prior Cary amps on this and there are several I can account for that followed Dennis’ vision for "absolute zero-feedback designs", and talk some here about "low- and zero-negative-feedback triode circuitry " and how it "tended to generate the sound he preferred—to his ears" unquote.

Some of the older Steroephile articles in the early to mid 2000s challenge and mention this too;

 https://www.stereophile.com/tubepoweramps/1098cary/index.html

On some search engines you can look for these words and hyphenated phrase +Cary +"zero-feedback" and different amps will pop up references this about some times.

To @xenolith, agree, yes, you are fortunate to own those very unique and interesting big blue amplifiers from Gary and Charlie. I love one-off boutique custom builds like this with audio, cars, and motorcycles. Great story how they got finished. Very cool, and Thank You for sharing the info and photos. Happy listening. 

@decooney 

A single-ended amp like the 805 or his Inspires, sure, I can see no global feedback.  But a 100wpc push-pull ultralinear amp without feedback seems like a stretch, in terms of achieving good bandwidth and a decent damping factor.  But anything's possible.  He's a very clever designer.

A single-ended amp like the 805 or his Inspires, sure, I can see no global feedback.  But a 100wpc push-pull ultralinear amp without feedback seems like a stretch, in terms of achieving good bandwidth and a decent damping factor.  But anything's possible.  He's a very clever designer.

As far as the CAD-805RS, what Cary lists on their site under specs for feedback is "0 to 10 dB continuously variable control."

Ralph makes a very good point about the percentage of screen taps and their relationship to the effectiveness of UL operation.  In an earlier post I referred to the original "Musician's Amplifier," the first iteration of the the British Williamson amplifier proposed by Sarser and Sprinkle.  It employed tubes and transformers more readily available on the American market.  In 1952, when Hafler and Keroes published the first "ultralinear" Williamson, Sarser and Sprinkle noticed that the output transformer they chose for the "Musician's Amplifier," the Peerless S-265-Q, had primary taps that could act as 50% loads for the screens.  They urged hobbyists to convert their "Musician's Amplifiers" to "ultralinear" operation by some simple changes to the circuit.

In fact, while the 50% taps of the Peerless transformer are not *ideal*, they actually brought the output tubes just a hair closer to true triode operation while doubling the power output.  Having built this amp myself, I can tell you that the result, despite its flaws, is quite beautiful.