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umcoo

Amp making a loud rumbling noise...could it be my house sockets?

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Hi all,

Please excuse the odd thread title.  I have a Peavey T-Max from around 2000.  Just before the first lockdown, the amp made a low rumbling sound when switched on, kind of like static-y thunder noises.  No signal would pass through and preamp/volume settings didn't make any difference.  After switching off and on over a period of time, it never worked right and always made the same noise.

Fast forward a few weeks, I had a tech look at it who said he could find nothing wrong with it, and he had kept it running for 6 hours a day for 3 days with no issues.  As soon as I got it back and plugged into the wall, I had exactly the same issue again.  Tech suggested it could be an issue with my house electrics.  I've run a valve amp on the same socket with no issue, and a small combo with no issue.  Sometimes the Peavey works fine, but I've never got more than 20 minutes through before it suddenly (and loudly) pops and goes back to the rumbling sound.  Again, no signal can pass through at that point and I switch it off almost immediately due to the noise.

Just throwing it out there if anyone has ever experienced an amp doing something like this, or any issues with their house sockets causing significant amp noise.  I'm tempted to take it to another tech after lockdown for a second opinion.

For info, the Peavey has a solid state and/or valve preamp, and a solid state power section.

Thanks all

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As an electrician, my first thoughts would be that the issue was with the kit, not the electrical installation.  

Mains in the UK is dirty but its not that dirty.  The 'cleanest' socket you would have in your house is one with nothing else plugged into that particular circuit.  Try plugging it into different sockets on different circuits, assuming you have more than just one ring final socket circuit in your home, and unplug other stuff from sockets in the same circuit.

if the socket itself has reversed polarity, i.e. the neutral conductor is connected to the line terminal in the socket and line to neutral, then this could well cause issues.

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I was playing through a high end amp at home and it was making a similar noise to the one you describe. I went to all sorts of lengths to eliminate this noise, without success, including putting in a spare pcb. No success and I put it down to the house mains. At the next gig it was fine. If you could try your amp out somewhere else I’d recommend it.

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Agree with all the above advice, and unless you have particularly high or low voltage (which I'd expect to manifest itself in other things in your house), or a fault on that ring main which can be tested by both suggestions above, I reckon it's more likely an amp issue. For peace of mind a plugin socket tester like a Martindale or similar will rule out faulty wiring on your outlets for about £15.

Crude as it sounds, give it a good old thump on the top or shake when it misbehaves, it could be that there is something loose inside which resolved itself by way of the journey to the tech, and has since come back again.

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In my old house I had a plug in WiFi extender. I found whenever I used my amp it was quite noisy unless I unplugged the extender plug. So if you have one of those see if it’s making noise. 

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It's really hard to diagnose a fault from a distance particularly an intermittent one. However when it happens you say it is unaffected by the controls. This means it is happening after the pre amp stages or possibly in the power supply. Thunder implies a loud and changing sound so my guess would be to look at the power supply capacitors first. On an old Peavey they may have leaked and this can be obvious sometimes. However the power supply caps can provide a nasty, potentially lethal shock, even when the amp is unplugged. Probably one for a tech if you don't know what you are doing.

Edited by Phil Starr
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Welcome to the T-Max world. I had one bought brand new in the very early 2000 that had exactly the same problem. After several months of back and forth to Peavey, it was declared as faulty, in fact a design fault !

You have the answer now.

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3 hours ago, wateroftyne said:

Powerline WiFi extenders will do this.

Yes particularly the valve ones 😁

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My ancient Marshall JMP 100 head used to make the same soundfor a short while when it was first switched on and then be ok until next time.  I took it to my tech, I think I remember him saying it was mains capacitors.  It's been ok since.

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On 07/02/2021 at 11:55, umcoo said:

... the amp made a low rumbling sound when switched on

Which is kinda what i what my bass amps to do :)

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Thanks for all the comments, guys.

No WiFi powerline adaptors in the house so that's ticked off.

I've got one of those plug socket testers already actually, and all was fine with the sockets.

Worrying to hear this could be a T-Max issue. There's another thread on here where a guy has an old peavey head making similar noises, and that was a power cap issue. I'll try a different tech after lockdown and see if they can find anything. Ideally could do with booking out a practice place and keep it running for a few hours. 

Many thanks all

 

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Please don't try running it if the fault is present, you could go on and damage the amp further. I've had to repair a couple of amps with similar faults and it is no fun at all getting the contents of a large capacitor off the circuit board and other components. You could write off the amp as an economic repair.

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Slightly unrelated,  but when I recently resurrected an old active subwoofer, it was picking up and amplifying a 50hz buzz.

Couldn't work it out, so I tried it with different cables providing signal to soundbar and thence the sub, to no avail, so I tried every combination of cable and equipment available to me.

Upshot- it was a loose and rattling fuse in the (IEC1) mains cable. Swapped it out. 50hz buzz? Gone.

Moral- check everything. Even the most obscure items can cause their own little issues. Then contact the manufacturers if you can't resolve it.

(I had another issue with a Trace Head. Blew an internal fuse every time I powered it up. A phone call revealed that they'd uprated the transformer, and that it had a greater current draw upon start up than the original. 

Slow- blow fuses of the same value fixed it. Manufacturers don't always get it right,  either.)

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