Tube Amp Archive

Still haven’t done it yet. Maybe today.

r21 r22 go to ground power tube pins 3 connect to ground via cathode resistor (130-150R is pretty standard, may take some trial and error) and bypass cap (the higher you go, the closer it'll "sound" to fixed bias... i used something like 3300uf for an 18w jcm800 build and it's my go to amp for trac...

This is pretty embarrassing but I’m glad I asked. At this point there’s no way I’m putting that thing in. My guitar cable was probably laying right on top of my pedal chain. I corrected the bias and it made a noticeable difference, for the better. I also removed the NFB loop and I’m pretty sure it’s...

3. I just plugged a cable in, no guitar, and I was moving the instrument end of the cable around in air while listening. At one point it got much louder. Further inspection showed that when the cable end got close to my pedals the noise went nuts. And worse when right next to the power supply cable...

Let's get clear about where the hum originates: amp or guitar. With nothing plugged into the Pro Jr, how is the hum, at any position on the Volume control? If there is no hum to complain about with no guitar plugged in, you're not going to improve anything by modding the amp. Thank you for the repl...

with strat it is likely mains hum picked up by one of the three antennas in the strat but yes, more than enough heater current to run two 12ax7 at 12v. might as well run it through a bridge rectifier, throw a big ol electro cap on it, and have dc heaters Thanks for the reply. Yeah, the thing is it ...

Okay. I love this amp. The four series came out in 2018 I think. They improved it a lot. Great little amps. I want to be clear that the hum I’m getting is only at loud volumes and it’s very usable except maybe for recording it loud. I don’t want to discourage anyone from getting one of these. With m...

Okay, I have a schematic. I also started to make some clips. I’ll stop hijacking your thread though. I’ll start my own.

Is there a particular place to post non-real Dumble-style clips? Thanks all.

I wouldn’t have posted if the 1 meg before trim pot wasn’t such a big step for me. I’m sure you guys could figure out why it’s needed there but I couldn’t. If you were to post the schematic of your current configuration I suspect that you would get some valuable input regarding what your 1 meg resi...

Wow. My posts are too long. Just noticed that.

So I’m back to 220k without the buzzing. Not sure what fixed it. Carry on.

Glad to hear that you were inspired by this thread and found some success. Looking forward to your clips. You mentioned that you are working with a modified Princeton Reverb. Is it modded with ODS-like circuitry? Yes. I’m chasing Dumble tone. It was actually started by someone else a few years ago....

(Amp is an overhauled Princeton Reverb II.) Well, well, well. Novice/new guy here. This thread helped a ton. I didn’t like the .0047uf and 4.7 meg. My only guitar right now is an Epi 335 (nice guitar I’ve had for 15 years) but the Sheptone pickups are incredibly bright. It amazes me how bright it ca...

Well, sounds like the microcontroller is the way to go. I’m only running two relays in one amp. It’s working so I’m leaving it at that. That’s a cool analog idea though. I might revisit later.

Awesome. Seems like this would be worth developing for sale.

Thanks. I don’t need one yet. I’ve got it going with clean/dirty switch and PAB. I guess my EQ is the “classic” and I find it kind of odd. Unless my circuit’s wrong but I’ve checked it. I only have one guitar right now - Epiphone Dot with Sheptone pickups (very bright). Right now, I like the EQ set ...