Clean to Mean Mod for Peavey Windsor 100W Head

[johnnybgoood]

I completed a mod to my Windsor 100W. With some experimenting and numerous transistor swaps, the head can now go from clean to dirty with a simple turn of the guitar volume knob. The amp voicing is robust and full. This mod was easy to tackle thanks in large part to Doug H freely sharing his schematics for the "Shiva Pre Amp", "Power Amp" and "Power Supply."
DougH's diagrams can be googled.

I posted the details of my mod in three jpegs (see links below) containing a schematic, step-by-step procedure and parts list.

This "Clean to Mean" modification to the Peavey head maintains the single channel construction. Using humbucker pickups with Alnico 2 magnets, the amp's tonality ranges from chimey cleans to raging thick distortion ringing with a full dynamic overtones. After the mod, the amp exhibits plenty of headroom, and sustainable feedback that is simply controlled by the guitar's volume potentiometer. The bass is very big and responsive with the resonance knob unlike the stock setup with all the unecessary compression and fizz.

I've played and tested this amp thoroughly for close to 30 hours. The master volume has been dimed and the speakers are connected through a 200 watt attenuator. The preamp is set at 12 o'clock and the guitar is plugged into the high-gain input. The tubes used are strictly ECC83's and EL34's (JJ's).

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Working on the Windsor head was easy to say the least. It's architecture is highly desirable for modifications and is extremely durable. The PCB boards are very simple to navigate and any parts needed are easy to order.

I kept the R6 resistor at 2.7k because when I plugged in an 820ohm the guitar's sensitivity was too high (i.e. I could hear the travel of the shaft in the guitar's volume knob. R4 and R5 are 820ohms. The C5 and C28 capacitors were changed to 0.68UF axials. For C27 I used a 330UF which was the biggest value cap that I had on hand.

I've had this amp cranked and I've also played it at whisper levels while keeping the MV at full. The notes played are articulate and warm while still retaining some necessary edge and complexity. There are no dissonant harmonics when notes are pinched.

This amp is a definite treasure and a top-notch rock machine.

Keep rockin'!

[novosibir]

Great first post!
I'd like to have more new members like you coming here

Welcome on board, have fun!

Larry

[johnnybgoood]

Thanks for the supportive reply and for MetroAmp forums. A lot of knowledge in all these threads.

[loud and dirty]

So, how do these mods sound compared to the Doug H mods? Did you mod the PI in this one? I only noticed minor changes in that section. But i only looked briefly at the mod. Have you paired this with the phase inverter mod posted by inkomodo.dragon? I'm trying to figure out just how important the PI mod is on this amps.

[loud and dirty]

Wow.. It's been awhile. I did end up modding mine. I didn't totally follow the "Clean to Mean" or the "JCM 800" mods. I looked at what I liked in some older JMP's and what was different between the JMP MV and the JCM 800. Came closer to the JMP in the end. Lower filtering and a little less gain. My choke hasn't got here yet. I still have fixed the PI either. Still it's pretty good improvement.

The really good:
The fuzzies and the volume fluctuations are gone.
It has a clean tone if I want it.
Not mushy like it used to be. A touch loose but in a very different way.

The not so good:
It's a bit harsh still. Not horrible though.
Loose bottom end with fat humbuckers.

I'm thinking of going back to both 100MFD filter caps and dropping the 100 MFD on the screens to the recommended 47 MFD...I have seen people use 32 or lower in Marshalls. I'm hoping that will tighten it in the right places and make it loose in the right places. We'll see.

[demonufo]

I looked at what I liked in some older JMP's and what was different between the JMP MV and the JCM 800. Came closer to the JMP in the end.

There isn't ANY different between the JMP MV's and the JCM800 MV's up to April 1984, though. Afterwards is a slightly different story.
Somebody did offer me a clean one of these for £100 6 months back. I turned it down not only because I was/am broke, but I didn't think it had much going for it.

If you've got loose fat bottom end, lowering the filtering is one of the last things you should be doing. That will loosen further, NOT tighten. You'd probably be better off choosing some smaller value coupling capacitors in the first stages, and perhaps putting a resonance control or fixed resonance cap in the NFB loop if you need to bring the bottom end back in.

[NiLace]

This amp is a definite treasure and a top-notch rock machine.

I know, I know it's been a lot of years since the first post, but I have just registered to thank you for sharing this modification.

I have recently ended mine and I could not be happier with the result. Wonderful sound, very dynamic, flexible with the EQ and a rock machine indeed.

Thanks