# JCM800: Soft crackling sound in background when playing on lower strings



## TubeStack (Jul 16, 2009)

Hey folks - love the forums here!

Just bought a JCM800 2204 head, having a blast with it. Sounds like the power of the gods when cranked wide open. :rockon2:

Was just playing at a lower volume and noticed there's a soft, scratchy, crackling sound in the background when I play on the lower three strings (even higher up the neck). 

It's like a soft vinyl record crackling in the background, underneath the sound of the guitar. If I hit a note, or notes, even gently, the crackling lasts for the duration of the strings ringing. It only lasts for the duration of the notes and does not happen when I'm not playing. When not playing, everything's fine, amp sounds normal. 

I've tried temporarily putting in other power tubes, and also tried swapping the preamp tubes, one by one, but this has made no difference, same sound still happens.

This wasn't happening with my last tube amp, so I don't think it's the guitar.

Any ideas? I'm going to do a full re-tube and have a professional rebias it and give it a once-over, but this won't be for a little while, and I was wondering what the issue might be, or if it's a common occurrence with a known cause. 

Thanks!


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## lbrown1 (Mar 22, 2007)

does the amp have an effects loop (pls excuse me for not already knowing)....if it does - have you placed anything in there?

I get the EXACT same thing with my traynor - a crackling popping sound

I suspected it had something to do with the gain from the device in the loop - but I removed the POD and tossed in a regular chorus pedal - same issue

to fix the problem - I just don' t use the effects loop


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## wayne (Apr 8, 2009)

What are you using for a cab?

Without seeing it, I would suggest checking your speakers (make sure the lugs where the leads join on are good and tight), and check/swap for another speaker cord.

Lots of things can cause crackling - those two in particular can cause damage to your amp.

W


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## mrmatt1972 (Apr 3, 2008)

My guess;

http://www.geofex.com/ampdbug/filter.htm

matt


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## TubeStack (Jul 16, 2009)

wayne said:


> What are you using for a cab?
> 
> Without seeing it, I would suggest checking your speakers (make sure the lugs where the leads join on are good and tight), and check/swap for another speaker cord.
> 
> ...


The same sound happened with two different cabs, although now that I think of it, I was using the same speaker cable with both cabs... will try a different cable and report back.


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## TubeStack (Jul 16, 2009)

Okay, tried the speaker cable switch, crackling/scratchy sound still happening.

Some have said it could be old caps or filters.

Bought it used at a music store - I don't know how closely those guys actually check the gear over before reselling it. The store owner did say their tech found some dirty pots... but I don't if they ever got cleaned, or not.

Do dirty pots only make noise when the knobs are being turned? Or could they cause something like this, when no knobs are being turned?


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## TubeStack (Jul 16, 2009)

lbrown1 said:


> does the amp have an effects loop (pls excuse me for not already knowing)....if it does - have you placed anything in there?
> 
> I get the EXACT same thing with my traynor - a crackling popping sound
> 
> ...


Thanks, but it doesn't have an effects loop.


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## wayne (Apr 8, 2009)

TubeStack said:


> ... Do dirty pots only make noise when the knobs are being turned? Or could they cause something like this, when no knobs are being turned?


If they're really dirty, the slightest vibration could make them make noise. If you've got a can of tuner cleaner (NOT contact cleaner), give 'em all a little squirt and work them around a bit. Last time I checked, it was still available at Radio Shack/The Source.

Another simple thing to check is whether or not the tubes are making good contact in their sockets. Sometimes wiggling them around a bit, or plugging them (carefully!) in and out of their sockets a couple of times will make it stop. Some contact cleaner (or tuner cleaner so you only have to buy one can of "stuff") here can help as well.

W


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## TubeStack (Jul 16, 2009)

Well, it seems to have sorted itself out, for now. Was just jamming for an hour or so, and there was no crackling/scratching at all. Just bought it a few days ago - maybe it just need some dust shaken off... we'll see how it goes.

Thanks for all info and input - much appreciated.


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## wayne (Apr 8, 2009)

Glad it worked out well. Love those amps! Would love to have one but they're getting awful spendy, and I already have enough people telling me to turn it down. There's a certain clockwise motion that goes with adjusting the volume knobs on an '800 that gets the better of me every time 

You've got yourself a classic there. When time and money permits, you should really have someone knowledgeable in electronics/amp repair go over it and make sure it's in top shape. Tube amps need maintenance every so often to ensure reliability and good tone. They can go for years without it, but due to the high voltages inside failure can be quite dramatic and destructive.

Filter capacitors need replacing every 10 or so years. Tubes, particularly output tubes need replacing. How often depends on how much you play. Tube sockets get loose and need tightening. Doing these things will make sure your amp always works good when you need it, and keeps it's resale value in case you don't need it any more.

OK, lecture's over. You can continue playing loudly now! sdsre

W


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## bcmatt (Aug 25, 2007)

wayne said:


> There's a certain clockwise motion that goes with adjusting the volume knobs on an '800 that gets the better of me every time


I hear you on that one. Unfortunately the 2204 is such a loud amp, that I never really play my clone that I built. At one time it was my dream amp, but I forgot that in my dreams, I had a nice, big, empty place to play it in too.
(Well, to be precise my dreams also sometimes included beautiful girls wanting to hear me play; AND I actually COULD play guitar)


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## TubeStack (Jul 16, 2009)

wayne said:


> Glad it worked out well. Love those amps! Would love to have one but they're getting awful spendy, and I already have enough people telling me to turn it down. There's a certain clockwise motion that goes with adjusting the volume knobs on an '800 that gets the better of me every time
> 
> You've got yourself a classic there. When time and money permits, you should really have someone knowledgeable in electronics/amp repair go over it and make sure it's in top shape. Tube amps need maintenance every so often to ensure reliability and good tone. They can go for years without it, but due to the high voltages inside failure can be quite dramatic and destructive.
> 
> ...


Thanks for the advice, and yes, it's certainly a classic! Truly the best rock amp I have ever owned. I can't get over the killer hard rock and blues tones I'm getting, and it pairs especially well with my '74 SG. :food-smiley-004:

I couldn't believe it when I walked into my local music store and saw it sitting there... I was like, _WHOA!!!_ Went back and traded in my old setup that very day.

I'm definitely going to re-tube it and ask our own Wild Bill here to give it a once-over. He's fantastic, a real local treasure for musicians and amp-lovers.


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## TubeStack (Jul 16, 2009)

wayne said:


> ... There's a certain clockwise motion that goes with adjusting the volume knobs on an '800 that gets the better of me every time ...


LOL! So true, it's totally addictive - I can't stop myself from reaching for that volume knob.

Good thing that Ho Attenuator is on its way in the mail... , though I know I'll still have let it rip, nice and pure, every now and then. 

I'm hooked! evilGuitar:


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