Man am I enjoying my Marshall last couple of days!!!!!!!

[Vrad]

So I changed one resistor on my Super Lead. Put the original stock resistor back in and I've been playing since Thursday of last week. Fuck I love this thing... LOL!

Got Jeff's (grooveHT) USACG strat loaded up with Dimarzio '61s and a 36th anniversary
Into the Reissue '74 Phase 90 -> OD808 -> Line 6 Echo Park

I love it...
1 billion guitar tones with the flick of a switch/volume knob/pedal...

 

[JTyson]

 

[CaseyCor]

Good stuff! I too have been on a Marshall kick, despite the fact I don't have one

Mid 70's Super Lead, a DAR, and a OD100 are on my mind. Thanks a lot Mr. Mark Day for giving me more GAS for Suhr Aldrich pickups for my Les Paul/Upcoming Explorer and a PT-100.

 

[Vrad]

Good stuff! I too have been on a Marshall kick, despite the fact I don't have one

Mid 70's Super Lead, a DAR, and a OD100 are on my mind. Thanks a lot Mr. Mark Day for giving me more GAS for Suhr Aldrich pickups for my Les Paul/Upcoming Explorer and a PT-100.

Had this amp for about 6 years now... fucking thing never gets old. Endless entertainment...

 

[JakeAC5253]

Which resistor did you change?

 

[Vrad]

Which resistor did you change?

Plate resistor on the V1A. It's originally a 100K. I upped it to 220k for more gain. Left it like that for a while. Put it back to 100K (original Iskra resistor). Sounds better.

 

[JakeAC5253]

Oh cool idea. You could probably get a better effect if you do it on a later stage, but you may not need to if you are enjoying it now as is. The Marshalls have three gain stages right? Or is it two gain stages and a phase inverter tube?

 

[Vrad]

Oh cool idea. You could probably get a better effect if you do it on a later stage. The Marshalls have three gain stages right? Or is it two gain stages and a phase inverter tube?

Well here goes:
This is a 1971 Super Lead...
Those amps had no master volume. Basically it had 2 gain stages and 2 channels. Normal and Bright.

The MV Marshalls (JMP 2203 etc..) have 3 gain stages and a Pre-phase inverter master volume.
The circuits are very similar to the older non-mv models like the plexi's etc..

I took my Non-mv Super Lead and converted it to a 2203 because I got sick of attenuators and my PPIMV. The change from plexi circuit to a 2203 is really moving a couple wires around. What happens is instead of having the 2 gain stages + one more in paralell, you end up putting all 3 in series thereby making it truly 3 gain stages. It's like the One Wire mod, but it sounds 'right'. The one-wire mod is sloppy, boomy and farty-sounding, but it gives you an idea of how much gain is there on tap in 3 gain stages.

Anyway... what I ended up with was a 2203 with modified filtering. I lowered the filtering on the preamp and pi. I added Sozo 100uf Royal 67 caps on the screens and grids. Then I changed the V1A gain stage to be like the Jose value which is 2.7k/68uf. On a stock 2203, it's a 10k resistor. If drop down that value, you get more gain. If you put a cap across that resistor, you end up filtering certain freqencies. Constantly kept going back to that configuration, so I guess it works for me.
The other thing I did this time around (I went back and forth with this mod) was I added a .68uf across the V2A resistor. This is very common mod and was actually stock on alot of Marshalls. Seems like Marshall would throw that in there sometimes. This gives a midrange bump and a bit more gain.

The trick with this amp was I really didn't want to change it too much and make it all high-gain. It's largely stock except for the filter caps and the 1st gain stage... which was changed when I got the amp. So yeah... long-winded response... LOL!

 

[Mailman1971]

Sounds like a good time.
All this Marshall talk is making me want another one....

 

[JakeAC5253]

Nice writeup! I'm always down to learn more about amps. It's just confusing because there were so many versions of the same basic circuit idea.

 

[Vrad]

Sounds like a good time.
All this Marshall talk is making me want another one....

Everyone should own a simple 1 channel Marshall... LOL!
It just does nearly everything. So many great recordings were done with those amps.

 

[Vrad]

Nice writeup! I'm always down to learn more about amps. It's just confusing because there were so many versions of the same basic circuit idea.

My pleasure...

Yeah there's alot of ways to arrive at the same thing. I'm limited in what I want to do because I don't want to hack up a vintage Marshall. If it was a Metro or Ceriatone, I'd experiment more. Like take out the Cathode Follower, or add another tube. But I'm not doing any of that with this amp. It's just too killer and mostly original.

 

[Vrad]

Nice. Funny thing is I have been playing my Marshalls more the last few weeks. I keep going back and fourth between my 71 and 74. Both have PPIV masters. The both are basically stock sans a few minor changes like NFB on 8 ohm tap (74 now has EL34's etc). With a pedal they rip. A lot of smooth gain and TONE. I have also been playing my modded 72 SL the most. I too did the Jose specs...2.7k/.68uf, but on the new added preamp tube as well as the original V1. There is something about those that adds to the sound, but still retains the "Marshall" sound. I went back to a 56k NFB resistor (for some reason I would go to 100k for the gain ) I also added a Jose master with a 18v and 20v zeners. Then I added the typical depth mod with a 500k pot and a .0047 cap across it. I usually tinker with the 72 daily, but I have not touched it in a few weeks. I think it is finished. We need to get together and test amps

Yeah I always go back to that 2.7k/.68uf configuration. It sounds like a Marshall, but gainier.
I want to try a 4.7k/.47uf on the V1B just to see what it does. Also want to change the treble peaker circuit to use a silver mica instead of the ceramic. See what that does...should be a bit smoother. Basically little tweaks here and there.
You know what I did? I put a .022 cap in series with the NFB wire. Instead of using a resonance control I just hardwired a value I liked. I think the pot was screwing up the tone. I hated it with the pot, but love it in-line. I think I have it on the 8 ohm tap as well. I have a 47k NFB resistor. Left that stock. I don't need it to be high-gain. I want classic Marshall crunch at manageable volumes. If I need more I'll hit it with a boost.

Did you put the Zener's across the MV? Or you did the whole Jose MV thing? Because I hated the Zener's there for some reason.

I need to find a Ceriatone or Metroamp somewhere I can tinker more freely with. Want to add a tube or remove the CF. Change the tone stack... etc.

Yeah we need to try and hang again.