The Amp Garage

Yeah I think I just can make out Z5U,25M,1kV.
CW

Hey, sorry I missed seeing this. Give me a couple and I’ll take a look at my photos. I think it is a pretty small cap, maybe 25pf but I’ll double check.
CW

Probably should clarify what is going on with the trimmer. B+ rail comes from filter to bottom terminal of 10k trimmer at the 100k and continues on to V1 off the bottom terminal. The 56k is on the wiper. I don’t know if the wiper and top terminal are jumpered but either way a variable resistance 56k...

Actually, the other way around. From what I can see, this is the same circuit as Tweedle Dee #1. So... .02 couplers all around, stock PI resistor values, 10meg/.002uf LNFB, trimmer on plates not cathode and stock 56k/100k plate values, 1k cathode resistors on V1 and the 22uf filter caps. I really th...

Am I going to ruin the fun if I tell you what the component values are?
CW

Edge came out in 2016
CW

So an update on this now that it is wired up. There is a 31mA current draw on the secondaries which is going past the limit on my transformer. The other issue is that the filaments are sagging a bit even though I have a 1A filament winding. Talked to Phil at Heyboer, I really want to use the same cu...

... how much more current draw does the voltage doubler circuit put on the transformer? I'd say at least four times the DC current, but the waveform is spiky and will peak at a much higher value depending upon the DC resistance and reservoir capacitors. For this case I'm getting 65 mA peak and 25mA...

Hey look at that, thanks. The only thing that I wonder about is the 300VDC rating.
CW

Although not a choke question, another interesting thing about this device is the little Triad transformer used as the reverb driver. It is a S-13X which has a primary of 25k and a secondary of 3.2 ohms driven by a 5751 tube. So a mismatch with the 8 ohm input of the reverb pan. Not sure if he was t...

OK, so I am envious of being able to do all those calculations but did you, at some point, simply disconnect the LNFB and listen to the amp turned up? Do you hear a difference with it in and out of the circuit? If you don't hear a difference, then all the calculating may show why but if you do hear ...

Are potentiometer casings referenced to ground?
CW

Thanks Martin.
CW

Martin, the primary is 60 ohms and the secondary is 235.3 ohms. I wanted a transformer that would fit the existing cut out and I needed enough filament wind for 3 preamp tubes, so the 40 mA was as much as we could get for secondaries. Bill at Heyboer said he also beefed up the primary a bit. For a 6...

Thanks guys. I can say that the device is a three tube stand alone reverb that Dumble did in the early eighties. It uses two 12ax7s and one 5751 as the reverb driver tube. The cut out for the power transformer is the venerable Triad R-2C, so 15mA DC. The hole spacing for the choke is 1 3/4", pretty ...