Peavey Ultra Plus - crunch mod

[Twangmaster]

Hi,

I would like to know if somebody in the forum would have suggestions how to mod a Peavey Ultra Plus (120) so that the clean channel goes into crunch territory. At the moment (with singlecoil pu's) it is clean all the way to 10.
Does anybody have a clear picture of resistors and/or capacitors to change?
I do have a schematic available, but I'm unsure how to mod it.

Thanks,
Olav

[Enzo]

Well, doesn't the crunch function on the amp work? You have to use the footswitch to get to it, you know.

[Paleo Pete]

I'm with Enzo here, that's a 3 channel amp, the clean channel is supposed to be clean, crunch channel and high gain (apparently "Ultra" ) both accessed by footswitch. There should be no reason or need to mod it, the crunch channel should do what you want quite nicely.

[Enzo]

And in fact the crunch channel is the clean channel with some gain things switched it.

[Twangmaster]

....I do use both the chrunh and gain channels as is - and they are great - but I just want a slight tube distortion (compression) on the clean channel - it is too clean as is - any sugestions?

Regards,
Olav

[Amp Kat]

Use a slight boost pedal when you use that channel. Just leave the box on so that when you change channels it's there.

[Twangmaster]

...making a mod to the first or second gain stage, by increasing the gain of one of these stages - does anyone have suggestion for resistor values here - otherwise I'll have to just try.

[Enzo]

Since clean and crunch/ultra are the same channel through the first two stages, anything you do to the stages to make clean crunchier will make the existing crunch even more crunchy. Be aware of that.

One thing they do is to switch in C15 in stage 2 for the gainier channels. If you ground the bottom end of C15 it will stay there and add a little gain to the clean. Since it is switched in for the crunch/ultra already, this mod would only affect the clean. And whe doing that, since C15 is a mere 0.47uf, you might raise its value to 1uf, 10uf or 22uf and see what you get. Instead of changing htem out, tack the larger caps in parallel with C15. That way you can easily remove it, and if you are careful, the board needn't come out. And if you go to 10uf, that 0.47 in parallel adding to it makes little difference. Increasing this cap ONLY works if you ground the end of it as mentioned above.

EVerything after the first two stages up until the effects loop is crunch/ultra only.

I don't know how much difference it would make, but increasing R5 from 220k to 470k might get you a little more.

[Twangmaster]

Thanks for the suggestions - I will give it a go - and report back when I have results.

Regards,
Olav

[Twangmaster]

...and it didn't give much gain (if any at all) - but it did change the whole frequency responce of the amp. After inserting a 22mF cap where you suggested, I now have a bell clear Fender amp - no Peavey anymore. I actually like it a lot - soft mids and bell clear treble - both in the clean and distorted channels. The tonecontrol in the clean channel have quite limited response after this mod.
So I am thinking of keeping it in, but would still like some distortion in the clean channel - should I lower the cathode resistor fro 1,5k to 1k?

Regards,
Olav

[Enzo]

Clip a 10k or something pot across that resistor, and dial it up and down - mindful not to go to low. See what it does. I am not the guy to recommend resistor values here. Other members mess with that all the time.

Sorry those ideas didn't pay off, it was just what came to mind looking at the drawings.

[Twangmaster]

I put a 1.9k accross R14, and kept the 22mf cap accross also - it gave a slightly more gritty sound in the crunch and od channels - but the only effect on the clean channel was a bit of compression - which I also like a lot - so I will keep it. So the two small changes have mainly given a much more ballanced sound in all channel - so I can recommend the.
The only drawback: Does any of you know why the mid, and to some extent the low tonecontrols in the clean channel now have very little effect when turned from 1-10?
It would still be nice to have suggestions on how the get some slight crunch in the clean channel - do I need to post in the mods forum - or any suggestions here?

Best regards,
Olav