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On second thought. . . this is about 1" x 1". Probably could fit in-line with the HV PSU on the same side of the 125B box and give more clearance for the tube.

OK. . .OK. . .OK. . . then how about this? . . . . 2" x .4" Use the Sushi HV PSU to heat up the tube? No plate resistors? The caps don't need to be HV? Or do the 680n's need to be HV?

Why the "dual" 47K's & 680n's? Could those just as easily been single components? Or perhaps there was a necessity to obtain fairly exact values (like 23.5K) that couldn't be had in a single component?

I guess that puts us waist deep in the big muddy (obscurity test) . . . not sure where we are at this point . . . not sure where we're goin' . . . too far to turn back. But I'm guessing Phi1's right. Just plug the SOB in and see what happens. And it appears that it's been workin' for a lot of...

According to the Amp Book Impedance Calculator a single stage 12AX7, 100K plate resistor, cathode bypass cap = 38.46K ohms. This is certainly minuscule compared to the output impedance of the pickup (1M +/- ?). I don't know if a second identical gain stage would reduce that further or not...

BnB. . . noted. BTW, I like Steely Dan

Hmm? . . could it be that the preamp's output impedance is low enough such that it is somewhat analogous to buffer? Guitars with active (lo z) pickups or passive guitars with on-board buffer ahead of the volume control don't experience this loss of highs or need for treble bleed circuits. They...

I built a blackface Fender tube preamp pedal using Sushi's HV PSU and I want to run it into a Class D amp (Ducan PowerStage) to play through a conventional speaker cab. I note that Sushi (as well as Kingsley, et. al.) report running their pedals directly into such animals without undue concern...

I read that resistance disproportionately blocks high frequencies so I can understand that #1 would knock off high end. #2 is what we typically use for a volume control on guitars so we've all had first-hand experience with loss of high end as you turn down volume (hence, treble bypass...

What are the differences in the following approaches to attenuating a signal? What's the best way to preserve the "integrity" of the signal?

Do you require both sides of the triode to make this work properly? The cathode followers I've seen in the past only involve one side of the tube. These are in parallel so I wonder if you used both sides simply because you had both available or is there something more substantive going on?

Simple is good. ;) Thanks!

Luv to see the schematic.

Just completed my own blackface Fender preamp as well as one of Sushi's DIY'ers. Want to pair them with the Class D amp when/if PPCB ever gets one put together. I noticed the Finally in your pedal offerings. For those of us wanting to optimally condition the output of our tube preamps to play...

Hmmm? . . . sorry. . . . I must have fallen asleep. Did you guys say something?!?!?!

FWIW, I just built a tube preamp with Mallory 150's / 630v in the tone stack. Before installing them I turned my amp up all the way with a high gain pedal and tried reversing the leads back an forth across a live cable end (see YT clip above) to see if one orientation was louder than the...

Replacing the 220K with a 4K7+220K "Teepee" and the 5K trimmer with a 1K makes things MUCH easier to dial in.

THX! MERRY CHRISTMAS!!!!!

Got the parts in to modify the trimmer for the HV board. It appears that the "top" side of the 220K (next to the word DAUGHTER) connects to the 5K trimmer. Correct?

It's easy enough to determine. . . . But you may be right in that it only becomes apparent in higher voltage situations.