Tube Amp Archive

I moved the NFB to the 8ohm, added the bright cap on the vol, and made V1 just the one triode.
It's possible that I just can't crank it loud enough to hear what it will do, but it probably all sounds normal.

Thanks for being willing to help, but I think I'm going to having a garage sale.

Peaker over the mixer before stage 2? I hate shared cathode first stages. You do need a bright cap. You are basically playing a Bass circuit with less highend. 150-220p minimum. If you are running the volume wide open you are missing the goodness. Seems like you have 270k mixer setup. Guessing. Byp...

… The amp's overdrive/distortion characteristic seems hard and choked off to me... As you’ve added a master volume, you need to clarify whether you’re referring to preamp or power amp overdrive. Hi, I was referring to preamp drive, but just overall the "distortion" sound I get from the amp. I proba...

Hi, have you halved the value of the anode and kathode resistors and doubled the value of the kathode capacitor at the paralleled V1? No, I left them stock. plate resistor is 100k. cathode is 820r and 250uf I did check other amps that tie in the extra cathode and they didn't have halved values for ...

It’s personal preference, but blending the bright and normal channels is best for me. One channel is too bright and the other too dark, but blended they work great together. Thanks. More info: I don't have a bright cap on the volume pot. The mixer resistor + cap is stock. It's not a frequency/tone ...

Hi all. I just did a Mojotone 45 build, but I only did one input (bright) and tied both triodes of V1. The amp also has a pre-phase MV (1MA pot, in the usual spot (off the treble pot...) Negative feedback is on the 16r tap. The amp's overdrive/distortion characteristic seems hard and choked off to m...

Ten Over wrote: ↑Tue Nov 15, 2022 7:16 pm In an ideal world, you would have 1.275M in parallel with 1M for a total DC resistance of 560k.

Thank you for the info!

No. The tone pots are in parallel with the 1M MV for DC purposes. What are the values of the tone pots? Thanks Ten Over for your reply. The reason I wondered about the pots was that I had the amp built new in 2009, lent it to a friend in 2011 and haven't heard the amp since. It was stored in a damp...

Thanks.
Pots are:
T=250
M=25
B=1M

Hi all. Should an 18w TMB style amp with a 1M Master measure close to 1M resistance on pins 1-3, while in the circuit? I see where the TMB pots affect the resistance of the master, since they are feeding it, but should the outside pins always measure around 1M? I only get around 500k no matter what....

Thanks for the info.

Hey all, This seems like a dumb question but, if my OT speaker taps are right underneath where my negative feedback resistor is on the board, can I just run that tap up through the board to that resistor turret, then run one wire off that turret to the speaker jack with the bundle? or do i have to r...

thanks, everyone, for the info.

thanks. on the liverpool, the hum went away when i pulled the pi tube. and had less hum if i pulled v2... if i follow what i think are best practices from forums, valve wizard, etc and look at other chassis pics for a reality check when i doubt placement of a part or wire, i thought i was doing fine...

Hi all, I've read topics on this subject, with different ways to do it, as well as people saying it's not necessary... Some background: I've had success building Fender circuits, Plexi, and JTM circuits... with no noise problems, but a recent TW Liverpool and JCM 800 had hum issues. JCM was great, b...