Guitar Gear Forum

Hi all,

Finally got around to modding my JCA22h on the weekend and have run into a little issue. The mods I made were the SLO mod (changes to VR1, VR2, R5, R9, C5 and C6), the front panel channel switch mod (SPDT switch from the backline.tk blog) and also a DPDT switch with both a 33k and 47k on it for the slope resistor at R26.

The mods are working but I appear to have introduced a "POP" in to the amp when switching channels. I think it may have something to do with the channel switch mod (http://toboy-diy.blogspot.co.uk/2013/09 ... witch.html). I can't find anyone online having had the same issue as myself after doing this mod. Could this issue have something to do with the other mods I made? I'm wondering if the cap changes at the crunch and OD gain pots could be causing any issues?

Any help with this would be greatly appreciated! When I have some time tomorrow night I think my first port of call will be to reverse the channel switch mod and see if that gets rid of the "POP". If not then at least it will narrow the search down.

Thanks

No pop on my JCA50H after adding a channel switch, but I may have wired mine differently - I soldered wires from the switch in parallel with the jack on the back panel. Pretty sure I put a link to my mod in the references section of the main JCA thread (see first page).

Thanks for responding. I am starting to think that it isn't actually the switch mod that's causing the pop but actually either the slope resister mod or the two cap changes for the SLO mod. I've read that if the caps leak any DC voltage to the pots then that can result in a pop so I might need to make sure isn't happening.

I've done slope resistor mod (also referenced in JCA thread), and had no issues.

I haven't done the SLO mod, so can't speak to that one - sorry.

to the board, and best of luck!