Tube version of aleph-x. Is it possible?

[rvrazvan]

Im a tube fan, but i like the work of mister nelson pass. is it possible to build an amp similar to aleph-x, but using tubes?

[lineup]

excuse, but what does aleph-x look like??

[JPeitzman]

I've thought a bit on this exact question, but thought is about as far as it went unfortunately. I don't know much about Nelson's Susy topology, but the input uses P-Channel FETs. Can the whole input be flipped on it's head to accommodate N-Channel FETs instead to more easily translate to tubes?

excuse, but what does aleph-x look like??

attached!

[rvrazvan]

Up! Some help from the professionals maybe ?

[smoking-amp]

The P channel input stage could be replaced with a standard differential tube stage with cap coupling to the output stages. The N channel output stages are acting like SRPP stages. The bottom N channel becomes a conventional grounded cathode pentode stage. The top totem pole N channel is acting like a counter modulated current source, driven by the current and voltage sensed output of the lower N stage. An SRPP stage does similar (just voltage sensing though). An impedance matching output transformer would then be needed between the SRPP output and speaker, unless trying to do an OTL.

Also, an "anti-triode" top totem stage would work similarly (voltage and current sensing, the final output comes off the mid-point of two series current sensing resistors, instead of just the bottom of the current sense resistor, as for SRPP. So the sum of the top and bottom output stage currents is held constant for "anti-triode").

Kenpeters modeled an anti-triode totem pole version once that kept the Q3, Q8 bipolars in the anti-triode tops (tube/hybrid anti-triodes) for more accurate control of current summing. Ken is a fan of the Pass Aleph amps, so may have picked up the idea there.

Also, Wavebourn has built some similar acting type tube/hybrid amplifiers.

[smoking-amp]

The global feedbacks used in the Aleph are replaced by internal plate feedbacks in either SRPP or "anti-triode" output stage models, if the bottom N device(s) is a triode instead of a pentode. The "anti-triode" version then further dispenses with half of the Aleph, with just one side driving the OT. This made the whole design emulate a single triode "SET".

So to answer the original title question: "Tube version of aleph-x. Is it possible?"
Been there, done that.

[kevinkr]

Is there really any reason at all to attempt to translate this into a tube design? While ideal in the solid state plane, I suspect an inverted Futterman or circlotron would make more sense in the tube world, and there is plenty of precedent to help implement one of these designs successfully.

[mashaffer]

I was thinking the same thing. Solid and Hollow States really have totally different requirements.

[smoking-amp]

The totem pole / SRPP output like stages are not the most user friendly outputs with their excessive HV requirements. A more practical tube implementation would be to use a conventional P-P output stage, self split at the cathodes (if you want to strictly follow the Aleph approach, otherwise put a conventional type splitter/driver in front of the output tubes), with a triode on one side and a pentode on the other side of the P-P OT (voltage output versus current output P-P stage).

[DavesNotHere]

Differential Gomes Amplifier


OUTPUT STAGE DESIGN