Walk me through the Studio Preamp "C+" mod...

[erickompositör72]

...in layman's terms ;-) ...or, it guitar-player-ism's

Being honest, the Studio Preamp through the power section of my Mark IIb S (60W) is the most incredible lead tone I've ever experience in-person in my life. I'm thrilled.

However, recordings I've heard of the IIC+ have always been my benchmark for the perfect lead tone, richest harmonic content, most liquid sound, etc. Does the "C+" mod to the Studio Preamp actually enhance these things in its lead tone? Or does it just change the voicing/frequency emphasis? I honestly can't imagine it getting better than it is now, but I've never played a C+. I also know that if I prefer the un-mod'd sound, it wouldn't be to difficult to pick up another one.

On a side note, I may have a chance soon to A/B my Studio Preamp and a 60W C+, using the C+'s power section to run the StudPre through. So curious to compare the two and hear for myself.

Tangentially: does anyone know the differences between a 60W Mark IIb's power section and a 60W Mark IIC+'s power section? Wondering how close this will be to "apples to apples".

 

[Markedman]

You'll have to wait for a diffinitive answer but I am fairly sure the power section is the same, or as close as anything there is.

I had a Studio Pre amp and I ran it using the effects send into the front input on my Mark IIB. Stand back!!!! Holy sweetness. I found that much much better than using an out to the return.

 

[erickompositör72]

That's interesting- I actually used to do the same with a Marshall 30th anniversary into a silver jubilee (before I converted to Boogie, of course...)

But you're adding another tone stack to the sound, right? My purist sensibilities are pushing back against this application... but of course I'm going to try it now!

 

[dtrax]

I modded mine a few years back. Off the top of my head:

• V1a cathode bypass cap changed to 0.47u - absolutely necessary for tight high gain, but you sacrifice overall low end for both channels.

• "Lead Fat" capacitor changed to 750pF - not much of a change, just a touch more gain in mid freqs

• Series resistor feeding the Lead Drive pot changed to 680k - increases gain a bit

• Added 150pF shunt cap from V3a grid to ground - smoothed out the top end a little

That's all I can think of atm. For me, the mods were definitely worth the effort. The tone is tighter, more aggressive, but still plenty smooth. The clean channel lacks meat in the low end (due to V1a bypass cap change), so that's the biggest compromise.

Hope that helps.

 

[DaveShred86]

• V1a cathode bypass cap changed to 0.47u - absolutely necessary for tight high gain, but you sacrifice overall low end for both channels.

• "Lead Fat" capacitor changed to 750pF - not much of a change, just a touch more gain in mid freqs

• Series resistor feeding the Lead Drive pot changed to 680k - increases gain a bit

• Added 150pF shunt cap from V3a grid to ground - smoothed out the top end a little

Just these 4 changes? how long did it took you? If I would avoid the Lead Fat capacitor change for example... would it still work without problem?

 

[grimlock]

Bump!

I'm also looking for a step-by-step guide, since I've recently acquired a Studio Preamp and would love to do the mod.