Hey I need some help developing a mod. The fx loop for this amp is designed to accomadate rack syatens and not pedals so i need to change it to a standard loop. Any help wwould be appreciated.
Its the jca100 the problem is the loop is at a line level making it horrible for pedals lol and sorry couldn't find one either
I found a schematic for the JCA50H. I'm going to assume that they have the same effects loop.

You could simply add a send level knob that would allow you to adjust the signal coming out of the effects loop.

Without the JCA100H schematic you'd have to take some good pictures, but it wouldn't be hard to modify.
From what I understand the 50 and 100 are the same mi us the power section and that's what I figured I was hoping that I could just adjust the overall level once that way it is still serial
From the schematic I have for the JCA50H, C33 (A 47uF 50v electrolytic capacitor) C15 (A 1uF film capacitor) is the coupling capacitor for the "Send" jack of the effects loop. You'll need to break the connection between C15 (or whatever the correct capacitor number for the JCA100H may be) and the "Send" jack.

Run a wire from the side of the this capacitor that is connected to the "Send" jack to Lug 1 of a 1M audio tapered potentiometer.

Run a wire from Pin 2 of this potentiometer to the tip of the "Send" jack (where the capacitor was connected before).

Run a wire from Pin 3 of this potentiometer to ground.
Last edited by end_citizen at Apr 9, 2012,
Alright man I'll try it out I'm glad their are still tech ppl on ug I thought they all went extinct lol
I was gone for about 2 years, but thanks to the miracle of neurology I'm back on my feet.

Always glad to help. Please do be careful when working on your amp. The schematic I have shows there are bleeder resistors to drain the filter capacitors. Check to see if there is voltage before doing anything. Also, make sure the amp is not plugged into the wall.
Ya man I no people who have almost fried themselves in their amps from not draining the caps and good for u