Anyone know anything about valve Amps, little crackle sounds
Discussion
Hi all, just bought an old 1983 Marshall jcm800 4104 single channel 2x12 valve combo, oh my God, what a sound! :-)
Anyhow, on certain notes I hit, and I can replicate it hitting whatever note makes the sound, I get a short little crackle sound as soon as I hit the note, it doesn't last for the whole note?
Yesterday I replaced the preamp valves with new matched set of Sovtek 12ax7lps valves, but before t I did this I put the valves in and out the sockets soaking the pins each time in contact cleaner, amp sounds even better, tighter than it did but rarely still get this short little crackle, usually at higher volumes?
I've ordered a new pair of JJ el34, s for the output valves as well to rule this out.
I've also cleaned the pots and jack inputs, although they didn't crackle anyway. Thanks!
Anyhow, on certain notes I hit, and I can replicate it hitting whatever note makes the sound, I get a short little crackle sound as soon as I hit the note, it doesn't last for the whole note?
Yesterday I replaced the preamp valves with new matched set of Sovtek 12ax7lps valves, but before t I did this I put the valves in and out the sockets soaking the pins each time in contact cleaner, amp sounds even better, tighter than it did but rarely still get this short little crackle, usually at higher volumes?
I've ordered a new pair of JJ el34, s for the output valves as well to rule this out.
I've also cleaned the pots and jack inputs, although they didn't crackle anyway. Thanks!
Thing with valves, you can get resonance of the metal bits inside the valve (microphony) that does affect the sound output, but it's not normally a crackle, but it might have been.
We used to get some noise problems with defective valves and instrumentation amps.
Been many a year since I've had to repair a valve amp
Normally though, on old valve amps, it's the capacitors that age and need replacing, or the contacts in the switches or potentiometers. Might be worth giving them a clean as well.
We used to get some noise problems with defective valves and instrumentation amps.
Been many a year since I've had to repair a valve amp
Normally though, on old valve amps, it's the capacitors that age and need replacing, or the contacts in the switches or potentiometers. Might be worth giving them a clean as well.
sw67 said:
Had this before with my valve amps - normally a combo rather than head. Changing the power amp valves fixed it for me but check everything is tight. Its a fairly common problem and you can also buy rubber rings to put on the valves.
Yes I,ve seen those rubber rings, might give them a try. The standard valve covers are all present and attached securely.More I play it I think one of the new preamp valves I got is a bit dodgy, light rustling sound I never had before, dammit.
robbocop33 said:
Hi all, just bought an old 1983 Marshall jcm800 4104 single channel 2x12 valve combo, oh my God, what a sound! :-)
Nice 
robbocop33 said:
I've ordered a new pair of JJ el34, s for the output valves as well to rule this out.
Went for Reflector Corp EL84 output valves in my 1974X when I replaced all the valves, Harma Retros for rectifier and pre/trem stages.Gary C said:
Normally though, on old valve amps, it's the capacitors that age and need replacing, or the contacts in the switches or potentiometers. Might be worth giving them a clean as well.
Had this on the 1974X - the trem didn't work at all when I picked it up, which was all down to the three caps in the trem circuit. Replaced them (with some decent orange drops) and all good again.sw67 said:
Had this before with my valve amps - normally a combo rather than head. Changing the power amp valves fixed it for me but check everything is tight. Its a fairly common problem and you can also buy rubber rings to put on the valves.
This would be where I'd heading too for intermittent cracking, backed up a bit by this and this. Probably worth cleaning up the speaker connection jack and socket too.My problem doesn't seem to be that major, none of the knobs crackle when turning them, no crackling from the power and standby buttons etc, no sound drop outs, just this short little crackle when I hit certain notes, it's just niggling me. New output valves should be here tomorrow.
Incidentally there were some weird valves in this amp, preamps were ecc83, s and one output valve was an ITT one, probably out an old telly lol, and a Siemens one??
Incidentally there were some weird valves in this amp, preamps were ecc83, s and one output valve was an ITT one, probably out an old telly lol, and a Siemens one??
Just an update, cleaned all valve sockets, pots, jacks etc, fitted brand new JJ el34, s and matched set of Sovtek 12ax7lps preamp valves, still this crackle.
Don't think I really explained this the same before, but now I've noticed the crackle sound I get is only on one note??? The first F up the A string(fifth string).
Only amp tech in my area is over at Namm till middle of February.
Don't think I really explained this the same before, but now I've noticed the crackle sound I get is only on one note??? The first F up the A string(fifth string).
Only amp tech in my area is over at Namm till middle of February.
Edited by robbocop33 on Wednesday 31st January 19:08
robbocop33 said:
Just an update, cleaned all valve sockets, pots, jacks etc, fitted brand new JJ el34, s and matched set of Sovtek 12ax7lps preamp valves, still this crackle.
Don't think I really explained this the same before, but now I've noticed the crackle sound I get is only on one note??? The first F up the A string(fifth string).
Only amp tech in my area is over at Namm till middle of February.
Somewhere on the board is a component or solder joint that is damaged. You've found the resonant frequency that best exposes the damage. It could be anywhere, it's going to be a complete bugger to find.Don't think I really explained this the same before, but now I've noticed the crackle sound I get is only on one note??? The first F up the A string(fifth string).
Only amp tech in my area is over at Namm till middle of February.
Edited by robbocop33 on Wednesday 31st January 19:08
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