ActionArnie
So I just got my amp back from it being repaired, previously it had an issue where it produced no sound at all which turned out to be a dry joint on the pcb somewhere in the pre-amp stage.
Having got it back from repair I tried it at home and at bedroom levels it sounded absolutely perfect.
There was a thing tonight I was playing at and when I cranked it up I immediately noticed some unwanted distortion on the clean channel. Not nice distortion, the kind of distortion I've experienced previously with my Sansamp triac with a dying battery. Almost sounds like overdriven hifi speakers. I immediately thought one of my battery-powered pedals was to blame but I plugged straight into the amp and got the same thing.
A bit difficult to google for, so I thought I'd ask, any ideas?
djpauw
The only solution would definitely be to send it to me.... forever.
LOL... Nice amp.
On a serious note; I expect where are talking about a combo amp and not just a head, right? Could it be a damaged speaker driver? Did you test with an external speaker?
Could you perhaps describe the distortion in a little more detail? What does it react to? What affects it? Or is it just a constant noise?
Lemme know, maybe I can think of something.
ActionArnie
Yip combo, didn't have a chance to test other speakers. It reacts to input, the harder I hit the strings the more it would distort. With low volumes it didn't distort. Not sure how better to describe than when I pump my pc speakers too hard, sounds like speaker distortion. Not sure why it would start this all of a sudden ... maybe cos the amp was in my car the whole day?
djpauw
A little early and not enough info for me to make a definite judgment, but it does sound possible that you have a damaged speaker driver....
I would hook up an external speaker and see if you still get the distortion. If yes, remove the driver(s) and do visual inspection. If no we need to scratch our heads a little more....
ActionArnie
Thanks, will try. Its actually a 2x12" so I'm wondering if I could try the speakers individually. I wouldn't expect an 8 ohm load to be a problem as I think that's what the jcm600 1x12" does.
ActionArnie
Weird, so I tried the amp today, and LOUD, much louder than I normally use it live and it seems ok. I'm putting it down to moisture maybe in the speakers.
FenderBender
It is possible that the tubes have rattled loose in their sockets. Wait for them to cool down and check that each one is firmly in place.
Also check that the spade connectors on the speakers fit tightly. If they wiggle, carefully pull them off the speaker terminals, squeeze them together gently with pliers and push them back on. Be careful and support the speaker terminal board with one hand when removing or replacing the connectors and don't snag the pigtail wires that are soldered to the speaker terminals.
Another possibility is that a small foreign body has found it's way into one of the speakers and is/was sitting in the airgap, rubbing between the magnet and the voicecoil. This often happens when amps are laid flat, or upside down for transport and the stuff that collects in the bottom of the cab, "cab lint" as I call it, gets a chance to shift around inside the cab. Often the lint will find it's way out of the speaker again when the speakers are pushed a bit. Let's hope this is what has happened in your case.
Regarding "cab lint", I have recovered a wonderful collection over the last 2 years, including matches, nails, 10mm bolts, chassis screws, a comb, coins and a pair of scissors ?
ActionArnie
Thanks Graeme, I'll check for all the things you mention.
