#1
Posted this in GG&A, and figured I'd post it in the electronic guru's section of the forum, too. Hopefully you guys can help me...

I thought I'd solved my reverb rumble issues by changing my tubes (one of the power tubes was REALLY microphonic...). But, apparently I haven't.

After my amp has been on for a while, and I turn up the reverb, this really low, staticky rumble comes out of the amp. Turn the reverb off, it goes away. It's not my amp's proximity to elctronic devices; I had band practice today, and we practice in my mate's shed which is in a field about 200 feet from his house. There's no electronic devices in there aside from our amps.

The only thing is, the actual reverb unit is on the bottom of the amp. Any help would be way appreciated. I have no ****ing clue what the problem is...
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#3
What do you mean by 'rumbling'? I have this problem where if the reverb in my amp is turned up past 6 it slowly fades into a harmonic-like- feedback sound.

All I can say is that maybe something has the same resonant freq as the springs, making them slightly vibrate like a string. Or something.
#4
Quote by Invader Jim
What do you mean by 'rumbling'? I have this problem where if the reverb in my amp is turned up past 6 it slowly fades into a harmonic-like- feedback sound.

All I can say is that maybe something has the same resonant freq as the springs, making them slightly vibrate like a string. Or something.

I mean.... hmmm.

It only starts to "rumble" (by rumble i mean it's almost like radio static, but more of a roll.... kinda like static "thunder" if you will) when the amp has been on for a while. If you use the reverb for the first ten minutes of playing, it's perfectly fine. Any length past it, and the "rumble" starts. It goes away completely when the reverb knob is on 0.

I can't see how it would be frequency related, unless the frequency is from the amp's cabinet vibrating while on.. But I can't see how it'd be that, because it happens even when the guitar's volume is on 0.

OH! I should also add that the rumbling is still audible while playing with the reverb on. Jim, or anybody else, if you have any other links to forums I could check out and post my problem in, I'd much appreciate it.

Thanks for your help so far, man. I really appreciate it.
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Last edited by stratman_13 at Jan 26, 2009,
#5
I dunno of any forumes. Maybe you could search for a tube amp or amp electronics forum.

Mine's a bit different. When I turn up the reverb fairly high, it'll be fine for a few seconds and will slowly fade in. Since mine's a musical tone, I'm thinking it was because of a mutual resonance.

I'm telling you this to try to help you debug the problem. I have no experience with amps, so I can't help much. Maybe Losenger, SomeoneYouKnew, or kurtlives91 can help? They are the resident gurus.
#6
Alright thanks man. That'll definitely help.
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#7
Is the reverb in a reverb bag? How is it mounted in the bottom of the cab? Are all screws tight? Have you moved the tank? Having the tank in "wrong" place can add serious amount of hum and noise.

Could be slightly faulty or failing connections leading to the RCA jacks. I would give them with a light spray of compressed air/contact cleaner.
#8
It's a reverb tank, and it's mounted on four screws with four rubber bushings. I have a pic somewhere. I haven't move the tank; and the screws are tight. Let me find that pic....



Got it. I'll blast them with some compressed air today, see what happens then. I think we have some contact cleaner in the shed too......

Thanks man. I'll bump again if I have any more problems.
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#9
Is this your Palomino V32? I'd have to stick a 'scope on it, but my first guess is that perhaps one of the op-amps in the reverb circuit is faulty, maybe oscillating. Op-amps can behave erratically depending on ambient temperature. I don't think it's the reverb tank itself. One step beyond cleaning connections would be to ensure that the connections to and from the reverb tank are intact using an ohm meter.

All in all, I'm suspicious of those op-amps.
#11
I doubt it. My V18's chips aren't socketed. Almost nobody sockets chips. It adds cost, and isn't generally advantageous to a manufacturer. Break out the solder wick!
#14
^ a lot of these cheap production amps use huge PCBs though. That means loosening a lot of chassis mounted stuff usually to be able to flip over the PCB. Makes things a major pain.
#15
Yeah, but the you can socket the chips.

Hell, I don't even like working with my FM25R because of that. At least if you do it right the first time, you'll only have to do it once.