Warmer Guv'nor mod,

[LivingDeadPunk]

This is a great an easy mod for the Marshall Guv'nor, The author is François Paillard, I'm just the translator.

The goal is to get a sound closer to the tube sound by changing the opamp and enhancing the power filtering

Schematic: http://optimisetonampli.chez.tiscali.fr/Download/Guvnor_modif.gif

Explanation in French:
http://optimisetonampli.chez.tiscali.fr/exemple.htm#guv


I didn't translated everything, only the useful sections.


Unsolder the OPA and replace it by a socket

Solder side:

- Solder between pin 4 and 8 of the socket a MKP 10nF/63vmin cap
- Solder on R5 legs a MKP 22nf/63vmin cap




Component side:

-Replace C7=10uf with a 100uF cap

- Solder a 10uf/16vmin electro cap to R5 legs
- Solder between - of C7 and R4 a 1000uF/16vmin electro cap


Instead of a TL072 use a OPA2134AP or a OPA2064AP, Both give a larger and more present sound, the 2064 is brighter and faster, the 2134 is "rounder" and closer to the tube sound.


Options:

- Replace C5=8n6 with a Styroflex 10nF/63Vmin cap
- Replace C3=220nF with a MKC 220nF/63Vmin cap
- Replace C4=220nF with a MKP 220nF/63Vmin cap
- Replace C9=220nF with a MKP 220nF/63Vmin cap
- Replace C13=4nF with a Styroflex 4.7nF/63Vmin cap






Notes:

I personnally prefer the OPA2134AP, because it sounds pretty close to my JMP-1 OD1,  a kind of Pete Townsend's overdrive on steroids.

I couldn't find styroflex caps so I used MKP and MKC caps instead.

The only "problem" I've had was with the MKP caps because they are quite large as you can see on the pic.


I hope you'll enjoy it!