SuperBAF Cheap Tube Amp Guide ~$1200 or less

Since the Elise review unit wasn't my own, I didn't want to hold on to it for too long. Maybe a bigger output cap could have helped bass extension. I opened it up, took photos, but didn't trace the circuit. The cultists were so mad at me that I even took photos, but I did it to show the well laid out internals. Based on measurements, I assumed it was a SET OTL. Also taking a guess that it's a cathode follower as with most OTLs. The output impedance was rather high at about 45 ohms. I am appreciative that someone wanted a ZD for cheap, but this is not realistic. The sound of these amps is dictated by circuit topology, not by tubes (or you can let the tubes dictate topology.)

What makes the ZDS interesting for an OTL is that the output is taken from the plate, something can be done with those MIG-25 radar tubes because of their super low plate resistance. Normally cathode followers are used because they have lower resistance, but in this case it wasn't necessary. Finally, feedback is applied to reduce the output Z to about 20 ohms. This is why the ZD has less of that "wet OTL" type sound. A good amount of feedback, plate follower, low plate resistance. Finally, the ZDS uses stiff 6D22S rectifiers into a CLCLC circuit. All caps except the first are poly foil caps, BIG poly caps. The big electrolytic has a small film cap in parallel (one of the Super tweaks).

Any of you guys who have built maxed out TIIIs or Cracks will know that chokes and good caps are not cheap. Not saying that more money spent necessarily means better sound, but these things do make a difference. I guess what I am trying to say that you are better off building a ZDS than trying to make a completely different amp into a ZDS by X-mas tree tube rolling. And that building your own ZDS is possible. None of this stuff is secret or proprietary intellectual property as the Elise cultists would have you believe*. One day when Craig retires, which could be soon, I'd love to see the ZDS in the public domain as a kit. Maybe SuperBAF can sell it and we can give Craig a small royalty, just to make things right.

* Everything and anything was already invented by the 1950s. It's just a matter of how you put it together.

 

having owned/own 4 of these amps listed, glad to see them compared all in one thread!
kudos to @Hands and @Marvey for this sticky post to the world of amp researchers.

that being said, didn't buy my EC Uber Super7 amp for under $1200, nor would I sell it for under $1200!

 

Blame @MisterRogers and @Hands! At one point, no one wanted a Super 7. But really, @Hands did the heavy lifting. I totally trust his opinion on this stuff. I just added a few notes, lightened up some personal biases, and scrubbed phrases like "total rip off" (or something like that) and other comments that weren't necessary to the discussion. I left the EC amp in there as reference since it's OOP, otherwise I would have removed it.

 

As soon as I heard MisterRogers's modded S7, I had to have one. I even let a used listing or two slip by before giving in. And then with bad influences like MisterRogers (and CS S7 mod/cap rolling thread), you mod it for a really fantastic sound like a true audiophool. I can't believe anyone would pass up on a good condition S7 or sell theirs unless they had a Studio or ZDS, maybe a whiz bang edition T3. Been singing its praises since that day and will continue to do so.

 

Different tubes will work better depending on if it's the Mk1 or Mk2. I have the latter.

One pair CBS/Hyton, one pair Sylvania bad boy, one pair short bottle/chrome splash Sylvania (very common). Front tube is a RCA 6BX7 but that is NOT to be used unless you have the same regulator upgrade mod that MisterRogers did to his and mine.

 

what headphones do you have?

I just went through a lot of 6SN7 rolling upon EC Uber 7 purchase for HE1K.
would rather not turn this into a tube rolling thread tho, so please send me a PM.