here are some marshall mod schematics!!

The XR1 mod is a stripped down (3 gain stage with a cathode follower) version. Almost identical to XLO Mod Version 2 but the 4th gain stage is a cathode follower instead and Stage 3's cathode resistor is changed to 1k with a 100k nfb resistor connected to the 4ohm tap. (Running N.O.S. RCA 6550 tubes in that green one) Basically a hot-rodded JCM-800 2203 layout with improved gain architecture for a nice warm pissed off tone with great controllable feedback. You can still roll off and get nice vintage tones as well. The grind switch and depth control was not installed on the amp you see in that demo video above.
 
xenrelic":y2f3nfrg said:
The XR1 mod is a stripped down (3 gain stage with a cathode follower) version. Basically a hot rodded JCM-800 2203 layout with improved gain architecture for a nice warm pissed off tone with great controllable feedback. You can still roll off and get nice vintage tones as well.
Click to expand...
I'm looking for clips of the version 3.
 
No clips up of XLO Version 3 yet. The amps with that mod are on their way to Ecuador right now and won't arrive for a couple more weeks. I'll see if Jim can take some video and post a demo of his modified '74 JMP when he's done unpacking it.
 
Hey xenrelic, that is really great that you share your mods by the way. There looks like there is a lot packed into that amp. Helps give ideas as well for those of us who like to tinker. You are squeezing an awful lot into three preamp stages!
 
Kapo_Polenton":33j00cd8 said:
Hey xenrelic, that is really great that you share your mods by the way. There looks like there is a lot packed into that amp. Helps give ideas as well for those of us who like to tinker. You are squeezing an awful lot into three preamp stages!
Click to expand...

Thanks, Kapo. It's actually 4 gain stages, you should see the two channel version... The way I fit everything into a 50watt chassis looks pretty neat. Standoffs and cable ties are our friends! :]
 
xenrelic":23lvbite said:
Kapo_Polenton":23lvbite said:
Hey xenrelic, that is really great that you share your mods by the way. There looks like there is a lot packed into that amp. Helps give ideas as well for those of us who like to tinker. You are squeezing an awful lot into three preamp stages!
Click to expand...

Thanks, Kapo. It's actually 4 gain stages, you should see the two channel version... The way I fit everything into a 50watt chassis looks pretty neat. Standoffs and cable ties are our friends! :]
Click to expand...
Pics. :thumbsup:
 
The Langer mod is 3 consecutive stages of the 2k7/470n cathode arrangement. .47uF, not 4.7uF. Devil is in the decimal. May also benefit from a plate bypass at some point due to the treble peaking. Oscillation isn't as much a concern with this circuit due to the incredible amount of gain that is being dumped between stages due to the 68k grid leak resistors.
 
Hey bmf5150,

Your schematic shows two resistors in parallel across the transformer but your parts list states 330 ohm resistors. How can this be? Two 330 ohm resistors in parallel would equal 165 ohms. Am i missing something? Could you shed some light on exactly how the transformer leads are connected?

Thanks

16-OhmReactiveAttenuatorRevCLight.jpg
 
syncrodude007":12t2yzk3 said:
randall /xenrelic modded some of my fx pedals...top shelf work...good dude :thumbsup:
Click to expand...

Thanks, Andy!

Those pedals were fun to modify.

Here's an old '77 JMP Master Volume head that was owned by Vicious Rumors. My friend Mike (the guitarist from Michael Cosyn Group) had me remove the rat-nest modification disaster and restore it with a point to point board. I had to plug up a few holes in the back and redo the post phase inverter master volume so it doesn't affect the tone at all. We didn't go all out artistic with the wiring on this one, but man, it still came out pretty nice.

Probably the best 2204 I've played through. Those SoZo caps rock!

Here's a gut shot:
1459052_10200658999066618_163099107_n.jpg
 
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