NEED HELP WITH A UNIVOX 1221

[onestepaway06]

Ok first off hello I'm new here, second I need a little help I have autism and its hard for me to understand schematics(had a few problems on another forum so I gtta throw that out there) I have a univox 1221 I want to mod it, I'm not a Newbie I've modded smaller amps before, my problem is as far as I can tell I'm the only person who's ever tried this with this amp, I like a high gain so I want to put a master volume in for sure, post or pre phase opinions? And somebody that can tell me how to wire it up, and id like to be able to make the 2 channels footswitchable if that's possible, and any other mods that could make this amp a monster throw them out there, I just need to know how and where to wire or change the circuit around, thanks in advance and my personal email is onestepaway06@hotmail.com

[sliberty]

Welcome.

I am not an expert, but, my experience with the blue (or black) Univox line is that they are generally rather clean amps, even cranked. When you get your amp cranked up to 10, would you call it high gain? Probably not. So with that in mind, master volumes will not really get you where you want to be. All they do is throw away some of the volume, but they won't make the amp do something it doesn't already do. If you really want high gain from that amp, you will have to make more extensive mods than just adding master volume controls. Perhaps there would be a way to cascade the channels so that the preamp develops more gain before passing the signal off to the phase inverter. But since the 1221 is built on a PCB, extensive changes will be more difficult, and could result in a sloppy amp (which is bad for maintenance).

Alternatively, you could push the amp hard with a good boost pedal - this should get you a high"er" gain tone. without lots of changes to the amp.

Now, having said that, if you are going to put in a MV, I'd recommend a post PI type - this will allow you to push the PI as hard as the amp is able to. You can look in the Trainwreck Files section for the Trainwreck papers, and in those PDFs you will find a few different post PI MV options to chose from.

BTW, I completely rebuilt a Univox U1086 once into a Trainwreck Express. Great chassis and cabinet I called it the Uniwreck. I recently sold it to a close friend.

Good luck.

[onestepaway06]

If I run the volume dimed and adjust the volume low enough using my mxr distortion I can almost get the amp sounding exactly to what I want, almost, it'll start to break up around 8-9, channel 2 seems to break up more due to not having the tremelo and reverb on it so I was thinking on changing channel 2 around to my "dirty" side and having channel one as the clean side and maybe throw a way to make them switchable in there, but like I said I'm autistic so the schematic is just numbers and shapes to me so id need to know what values would need to be changed on caps and resistors to get what ibwant and I can do it, I have no problem changing any of it around even on a PCB is easy for me as long as I know what it is I need to change

[onestepaway06]

If I run the volume dimed and adjust the volume low enough using my mxr distortion I can almost get the amp sounding exactly to what I want, almost, it'll start to break up around 8-9, channel 2 seems to break up more due to not having the tremelo and reverb on it so I was thinking on changing channel 2 around to my "dirty" side and having channel one as the clean side and maybe throw a way to make them switchable in there, but like I said I'm autistic so the schematic is just numbers and shapes to me so id need to know what values would need to be changed on caps and resistors to get what ibwant and I can do it, I have no problem changing any of it around even on a PCB is easy for me as long as I know what it is I need to change

[Stevem]

That's a loud clean amp and it needs another 12ax7 and two complete tone stacks to do the high gain thing well, and as posted the circuit board issue makes it very hard to get where you want to go!
I would plan on striping the amp out, set it up for tag board and unpowered two of the output tubes and cut down to a 40 watt amp.

[cbass]

Sell it and get another amp
These are cool amps Let it be what it is

[sliberty]

The best way to make the amp foot switchable in my opinion would be with an outboard foot switch like this one:

http://www.musiciansfriend.com/amplifie ... ctor-pedal

Its a cheap solution, and won't require you to mod anything.

As for the master volume, the simplest type to try would be Type 3 from the Trainwrack Pages. it uses a single linear pot, and connects from one side of the power amp to the other. You would make the connection at the point where the 100K bias resistors meet the 1K grid resistors. Use the wiper and one leg of the pot. a 500K should do the job.

The theory behind this MV is that enables signal cancelation to occur since it is connecting the two out of phase sides of the power amp together.

This type of MV sounds different than the others, so if you don't like it, you can advance to another type. But since it is the easiest to implement, it makes sense to try it first.

[onestepaway06]

Ok I'll try that for a master volume, to sell the amp and get a different one isn't feasible the amp isn't worth enough to grab another 50 watt head

[ubxf]

Can something like this work
http://kashaamplifiers.com/index.php?ma ... ucts_id=86
It's like adding a tube stage

[onestepaway06]

I built a tube powered distortion pedal which is basically the same concept as that but its not the same as getting the crunch from the amp itself, I dunno maybe I'm just on a pipe dream with this one and I should tear it all down and build it differently, I dont use the vibrato effect so that gives me 2 extra tubes to work with if I do, only hang up I have on that would be if I was going to rebuild it I'd go with like a ceriatone afd #35 circuit but id need to figure out how to build/adjust it for the 6l6 power tubes and the 6an8 pre amp tubes since the 6an8's have a higher gain rating and can be pushed harder plus id want to keep my reverb, which If I went that way I guess id have to find someone who can build me a drop in board for this amp in my affordability range which is pretty low ��

[onestepaway06]

And the other thing is have to worry about would be if my transformers would work the same

[wyatt]

Not too familiar with the 1221, but I had a blue 1011 (100w four input with trem and 'verb) for years. When it blew out (spectacularly, I might add...the OT and two tubes ruined), an amp tech ran off with it when he split town. That was decades ago.

The best I can describe the 1011 amps is cool looking and function with a clean, bland tone.

I occasionally ponder on it, but if I still owned mine, I would gut it and reuse the chassis and iron and build a Marshall circuit into it. I wouldn't bother trying to tweak the stock circuit at all.

[ampfab]

I think i would add a 1 Meg pot after the .005uf coupling cap, followed by a larger value coupling cap before the 6AN8 PI triode.
I've done this with an old Ampeg, worked well.

[onestepaway06]

What did that work as like a gain control ampfab? And how exactly would I wire that up, like which pin on the tube etc? Cuz I have a few 1 meg pots laying around

[sliberty]

Placing a pot where that .005uF cap is will reduce the drive going into the PI. This means that the only place that you can develop any gain is in the preamp tube. The problem is that the preamp is a single stage, and not very hot, so you really won't develop much gain there. This is why I suggested putting the MV after the PI instead of in front of it.

But, it is an easy mod, so go ahead and try it and see what happens. I could be wrong.