Univox bass head project done

[Bob-I]

I posted on this amp before but I'm done with the mods now.

I had some challenges early but got past them. I found an external short in the OT that I was able to fix with some heatshrink. I also learned that this amp uses the same PT as the guitar amp with reverb and one more 12AX7, so armed with that information I added another tube. The chassis was even punched for it.

The amp has 2 channels, one for bass and one for guitar. Each use one gain stage, then mix into a cascode stage before the PI. I decided to add a preamp tube, cascade the 2 stages then run into the single bass amp stage. I modded the bright cap to voice it more like a guitar amp. Then I found that this was simply too much gain pushing into the cascode stage so I bypassed that stage and went directly into the PI. There's a gain control between stages 1-2, and a trim between 2-3 as well as a voltage divider with a small cap bypass.

Here's a pic and a clip of the mods.

http://www.patmedia.net/bob-ingram/OD.mp3

[stoo]

Geez.. What was the model number and vintage of that amp?? I have a 70's U1511 that has a painted black chassis (inside and out) and the PC board is mounted trace side out!
Stew

[Bob-I]

Geez.. What was the model number and vintage of that amp?? I have a 70's U1511 that has a painted black chassis (inside and out) and the PC board is mounted trace side out!
Stew

The amp is completley unlabeled, but my best guess is that it's a U-1050 bass head. It's all PTP on that tagboard, check my other thread on this amp for more pics.

This thing's built like a tank, and sounds awesome.