A couple of things come to mind:

If you have to ask which resistors to change, I'm guessing that you haven't worked on a lot of amps. The Windsor is a 100 watt amp with high voltages present inside. That amp can kill you dead in a hurry if you don't know what you're doing.

The other thing is that being a guitar amp, the OT is probably not suitable for bass. It probably is only spec'd down to 80 Hz or so. A four string bass goes down to what, 40 Hz? So it may overdrive even if you do put in different tubes and rebias.

I would take the amp to a tech and discuss it with him/her. If all that needs to be done is to change out a few resistors, it shouldn't be too expensive, if you already have the power tubes.

From the schematic it looks like you'd need to change out one or two resistors in the bias supply and the grid leak resistors on the power tubes. Not complicated, but dangerous.

I don't mean this to insult you as I don't know your background.

Quote Originally Posted by ttenroc View Post
Does anyone know what modifications I need to perform on my Peavey Windsor 100 watt amplifier to make it operate on 6550/kt88 power tubes. I am using the amp as a bass amp and need more headroom to power my Ampeg 2X15 cabinet .

I understand that the Windsor was designed to be a high gain amp, but I have already performed a clean mod and changed the tone stack to get the amp voiced the way I like it as per these threads(http://www.thefret.net/showthread.ph...Peavey-Windsor , http://www.talkbass.com/forum/f15/pe...s-bass-522387/ ). Please note that I did not do the power section mod that Bill did on his amp.

After the preamp mods I can get some great clean tones up to around 2 o’clock the pre amp. Now I need more from the power section to combat the power tube distortion that I get when I turn my master volume up. It gets dirty around 1 o’clock… Is the 6550 mod as easy as changing the tubes and adjusting the bias pot or do I need to change some capacitor/resistor values to make it work? If so, which caps/resistors and what will values be? Will I need to change my power transformer?
Here is a link to the schematic:
https://rs312l3.rapidshare.com/#!dow...r.pdf|3257|R~0