Here are the mods I did to my JCA20

[psychodave]

UPDATED preamp schematic

I havne't double-checked the photos, but are you sure that 68k/68k divider is in the right order? Shouldn't the 68k and cap to ground be before the 68k going to the grid and not after it?

No that would be an incorrectly implemented voltage divider and equate to and and act as a grid stopper.

Yeah I realize that. I was curious because in other Jose-style mods I typically see it done the other way (Cameron Jose, Fortin KK, Meshuggah, Ceriatone, etc.).

the Cameron’s, real Jose’s and Friedman’s are almost always before. As for Ceriatone he copies Fortin and.....Fortin, I’ll leave that alone

This was stock from when it was a Friedman mod. I added the cap based on Marks advice.

 

[FourT6and2]

UPDATED preamp schematic

I havne't double-checked the photos, but are you sure that 68k/68k divider is in the right order? Shouldn't the 68k and cap to ground be before the 68k going to the grid and not after it?

No that would be an incorrectly implemented voltage divider and equate to and and act as a grid stopper.

Yeah I realize that. I was curious because in other Jose-style mods I typically see it done the other way (Cameron Jose, Fortin KK, Meshuggah, Ceriatone, etc.).

the Cameron’s, real Jose’s and Friedman’s are almost always before. As for Ceriatone he copies Fortin and.....Fortin, I’ll leave that alone

I'm sure either way has its appropriate application. For what it's worth, Cameron showed me a few amps and it was done the way I'm talking about and that's the way he even suggested I do the ones I've built. But maybe because it was implemented as fusedbrain describes with dual gains.

 

[nico22]

usually ccv is 68K then 68k//1n to ground
saw cameron marshall mod with coupling cap then 1n to ground, then gain pot with 82k from wiper to ground, then grid stopper... chupacabra/cali style

 

[FourT6and2]

usually ccv is 68K then 68k//1n to ground
saw cameron marshall mod with coupling cap then 1n to ground, then gain pot with 82k from wiper to ground, then grid stopper... chupacabra/cali style

Yeah that's the "feel" control. Just dumps signal to ground to reduce gain. The cap can go in a number of different places and just bleeds some high end. For example, the Meshuggah has a 68k grid stopper and a 68k resistor from gain to ground. Ceriatone chupa/yeti has a 150k grid stopper and 82k "feel" resistor on a push/pull. You can use a pot as well and just make it a variable control The higher the value, the less effect it has. But it serves to reduce gain and tighten up the low-end a bit. Putting this resistor after the grid stopper, from the tube's grid to ground, does something slightly different. With a cap there, on the grid to ground, it creates a filter.

 

[311splawndude]

Sounds awesome Dave

FYI - your updated modern vid is not working. I'd be interested in that.

 

[psychodave]

Sounds awesome Dave

FYI - your updated modern vid is not working. I'd be interested in that.

I deleted a bunch of videos. The modern and Aldrich are Marks work, so it’s not my place to take pics or share. The JCA20 is my work based on lots of help from Mark.

 

[acev]

Here is my JCA BE mod crappy quick clip:

 

[psychodave]

Here is my JCA BE mod crappy quick clip:

Sounds good!!

 

[apophis]

Ended up buying one already modded. Has epic mods capn' crunch, capacitor upgrade, loop upgrade, external bias pots, mid shift and depth knobs, hi cut control, negative feedback control, saturation switch. Also has a head cover. Got it for 350 plus shipping so it seems a great deal to me? anybody have experience with epic mods?

 

[psychodave]

Ended up buying one already modded. Has epic mods capn' crunch, capacitor upgrade, loop upgrade, external bias pots, mid shift and depth knobs, hi cut control, negative feedback control, saturation switch. Also has a head cover. Got it for 350 plus shipping so it seems a great deal to me? anybody have experience with epic mods?

I’ve seen his stuff on some FB sites. Don’t really know anything about them though.

 

[Econ]

Ended up buying one already modded. Has epic mods capn' crunch, capacitor upgrade, loop upgrade, external bias pots, mid shift and depth knobs, hi cut control, negative feedback control, saturation switch. Also has a head cover. Got it for 350 plus shipping so it seems a great deal to me? anybody have experience with epic mods?

Where can you get them with all these mods?

 

[apophis]

Got it from Reverb man

 

[psychodave]

Ended up buying one already modded. Has epic mods capn' crunch, capacitor upgrade, loop upgrade, external bias pots, mid shift and depth knobs, hi cut control, negative feedback control, saturation switch. Also has a head cover. Got it for 350 plus shipping so it seems a great deal to me? anybody have experience with epic mods?

Where can you get them with all these mods?

I wouldn't be surprised if epic (or others) has already taken my mods and started to incorporate or sell them...

 

[Fret-Shredder]

Here is my JCA BE mod crappy quick clip:

Nothing crappy about that at all. Sounds freaking awesome man.

 

[acev]

Here is my JCA BE mod crappy quick clip:

Nothing crappy about that at all. Sounds freaking awesome man.

Thanks! I actually prefer EVH 5150, so I will be selling the JCA.

 

[riffermadness]

So here are the mods I did to my JCA20. Have fun modding and don’t be a bozo by saying the mods are your own or selling them. Tone stack is 560pf, V1 snubbers are 47pf. Diodes are 5 volt and MPSA20. Caps on the gain pot are 2000pf and 4700 pf. Depth caps are .0433 (two caps .0033 and .001. I mixed caps on purpose since they have a very audible effect here). Choke is a Mojo 778. Presence is .1uf. Everything you need to know is in the pictures.

https://imgur.com/a/1uBmo9q


Here is the amp:

Sounds great...I did some mods on a Custom 22 and all the tracers on the PCB wanted to peel up even at the lowest temps..the pcb is not as thick as some other amps I have modded/ repaired.
I wanted to try it again but those damn tracers have me not wanted to deal with it again.

I see you got the newer front grill as well..I can't remember his name but the main Jet City guy is super cool,we emailed a few times then he wanted to call me and he did..he sent me a spare Custom 22 pcb that somebody did some work on..I still have it if you or anybody else wants it..also the grill like yours I have as well.

I did manage to get the Custom 22 up and running but the mods I purchased were blah at best..sold amp.

I like how your JCA 20 sounds,Great Job !

 

[CornNutz]

Dave, quick question. I think I recall you saying in a different thread a while back that you changed the the output transformer to a classictone, am I recalling this correctly?

If so that would be the 40-18037 http://www.classictone.net/40-18037.html ?

 

[psychodave]

Dave, quick question. I think I recall you saying in a different thread a while back that you changed the the output transformer to a classictone, am I recalling this correctly?

If so that would be the 40-18037 http://www.classictone.net/40-18037.html ?

Here is what I have. I don’t think they offer it anymore? I don’t even know the specs on it.

 

[Fret-Shredder]

Dave... I've listened to this a few times and damn it sounds good.

 

[CornNutz]

Dave, quick question. I think I recall you saying in a different thread a while back that you changed the the output transformer to a classictone, am I recalling this correctly?

If so that would be the 40-18037 http://www.classictone.net/40-18037.html ?

Here is what I have. I don’t think they offer it anymore? I don’t even know the specs on it.

I emailed classictone, and here is the reply:

That part was custom made for Jet City and is no longer available.

Thank you for your interest in our products. Please contact me if you have any more questions.

Mark Sacketti
V.P. of Engineering
Magnetic Components, Inc.
9520 Ainslie Street
Schiller Park, IL 60176
Tel# 847-671-0633
Fax# 847-671-9419