Tweaked 2204

mrbobo · Apr 20, 2009

What started out as a filter cap job ended up allot more (mods). I always disliked the stiffness and sheer icepick factor of my mid 80's Marshall 2204. Yea, I should have just sold it and bought a Metroamps kit...but I didn't. But I now like the amp. Quick homemade backing track...limiting on the master bus, no eq anywhere, some reverb on the lead.
guitar/amp/speaker/sm57

The lead is a bit bright, because I wanted to highlight the sweet treble chirp that I attribute to the Sozo caps.

edit:4/21/09 1000 EDT - mixed the guitars up louder

JTyson · Apr 23, 2009

Nice tone, what did you change besides the caps?

mrbobo · Apr 23, 2009

thanks guys...it would be easier to tell what I didn't change...heh

Icepick reduction: Remove preamp bright cap C5
reduce neg. feedback R22 from 100k to 51k
increase fizz cap c18 from 50pf to 100pf

Voicing/gain:
all audio caps to Sozo, not the vintage but the regular (except C1=Solen fast cap)
all small caps are silver mica (100pf, 470pf caps)
all added/changed resistors are 1 watt carbon film

R3 input R lowered to 10k
C4 increase from 470pf to .0022u (ala SLO-100)
C1 increase from .68uf to 1 uf (solen fast cap)
tone stack slope, R15 increased from 33k to 39K (slight low mids cut)
Preamp Filter cap- lowered from 50+50 to 32+32u

Gain: here's where it gets hairy,, some things do add gain but cause other problems, like lack of guitar volume response, blocking distortion, too much bass, etc.
-V1b increased Plate R from 100 to 150k; lowered cathode R1 to 1.8k.
-added parallel 2m R from preamp wiper to ground
-on V2a: got rid of the voltage divider (again, ala SLO-100 )
-also on V2a: bypassed the cathode R9 with .68u Sozo

Amp is biased; EL-34 power - all tubes are Tung-Sol
Changed some of the coupling caps value to deal with bass, blocking distortion. Not the "proper" thing to do, but it's working. heh I'm just a hack at this. But I can tell you it was fun as hell modding this thing. Now, I love my amp- and it still sounds like a Marshall.