#1
Hi. I recently bought a JCA22H, and today I noticed it crackles a bit.
It happens on both channels, though only with gain knobs turned up. It sounds like you're turning a dirty pot, or the kssssh sound of a walkie talkie. I've tried with and without guitar, with a different speaker cable and I've given the valves a whacking with a chopstick.

The sound does not appear on my Peavey Ultra.

Is it just the ghost of cheap amps, or is there anything I should check?
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Last edited by AtaBorMan at Nov 5, 2013,
#2
It is probably either a preamp tube going microphonic or a tube pin arcing with the circuit board. If you have a warranty still - use it. If not, you try swapping some of the tubes around (V1 and V2 for example), or replace some of them. If it still persists I'd inspect the circuit board around the tube sockets.
#3
I do still have warranty, but I can't be arsed with our postage system. I'll have a swap around, got plenty of spare valves, and if that doesn't help, I'll have a look. Was planning on modding it tomorrow anyway. Worst case scenario I'll have to call a mate and have him take a look.

Edit: As I turned it on again, I noticed it's a constant noise for the first second or two, only to be more sporadic after that. It also seems to happen on both amps, with gain turned up, so my first observation was faulty.
Quote by Todd Hart
Shooting your friends with a real gun is a definite faux pas.

Quote by mystical_1
Professor Plum in the Studio with a new Amp

Quote by snipelfritz
If only I were the only one at home right now. I don't need my parents asking who Mr. Wiggles is.
Last edited by AtaBorMan at Nov 5, 2013,
#4
It does react to me knocking on the amp. I'll swap the output valves tomorrow. If that doesn't help, I'm out of my depth when it comes to troubleshooting.
Quote by Todd Hart
Shooting your friends with a real gun is a definite faux pas.

Quote by mystical_1
Professor Plum in the Studio with a new Amp

Quote by snipelfritz
If only I were the only one at home right now. I don't need my parents asking who Mr. Wiggles is.
#5
I hope I'm not being stupid by pointing out that most amps do make some sort of noise when you're not playing, especially if you have OD or the gain up high.

It could also be external (maybe?) is there noise coming from the outside that maybe your pickup is picking up? I know if I have my amp up anywhere past 6 on the volume that you can hear background noise through the amp.
#6
Volume on guitar is 0. And yeah, I'm fine with hissing and humming amps, that's rather normal. It's this sporadic crackle that has me confused.
Quote by Todd Hart
Shooting your friends with a real gun is a definite faux pas.

Quote by mystical_1
Professor Plum in the Studio with a new Amp

Quote by snipelfritz
If only I were the only one at home right now. I don't need my parents asking who Mr. Wiggles is.
#7
Power tubes can go microphonic (I had one do that a few weeks ago) but preamp tubes do it more commonly. Try tapping the tubes gently with a pencil, if it's microphonic you will hear the tapping through the speakers.
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