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What the hell is this noise?


Gunsfreddy2003
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Er, dry solder joint,  or,   power supply, thinking smoothing capacitors,  is it valve or s/state, don't stick yer fingers in for a fiddle if it's valve, they run at nutty levels of volts, 1200/1500 volts, doesn't just dissipate after turn off either. Have you tried a different instrument? , different  lead ?

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I sometimes get a similar sound through my studio monitors....then I realise my mobile phone is close by. Move it and its gone :D Could there be anything close by that might affect your amp? (router, home wireless phone, mobiles etc)

Edited by Acebassmusic
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19 hours ago, Acebassmusic said:

I sometimes get a similar sound through my studio monitors....then I realise my mobile phone is close by. Move it and its gone :D Could there be anything close by that might affect your amp? (router, home wireless phone, mobiles etc)

 

19 hours ago, Hellzero said:

Do you have any PLC emitter/receiver nearby ? Unplug it, the noise will disappear.

The amp is in a room with a wireless booster that comes via a power line adapter from downstairs - do you reckon that could be it?

I’ve rehearsed so many times in that room before though with no issue at all - that is what puzzles me.

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Sounds like a dry joint or a faulty connection, fairly common but sometimes difficult to track down. It could also be a phone or both, a common source of noise is that the faulty connection acts as a radio receiver picking up electrical noises. What you do next depends upon your level of knowledge and how much you like fiddling with stuff.

You could start by unplugging guitar and leads and seeing if it happens with nothing connected. If it still happens you know it is the amp (make sure there are no phones switched on nearby) Try the amp in another room. If the noise goes it's your guitar leads or maybe the bass itself. Keep swapping stuff until you are certain.

Assuming it's the amp set the volume to a reasonable level and try wiggling each control one at a time. obviously each volume or tone control will change the sound but you are listening for the noise getting much worse or going away. If it does the poor connection is inside the potentiometer or pot behind that control. You can then either try cleaning it with switch cleaner (Servisol is what I use) or take it in to be serviced/replaced. It's not a bad idea to clean all the pots, Dirt and wear accumulates so if one pot gives trouble the rest are often not far behind. The next thing to check are the jack sockets. a squirt of servisol and wiggling a plug in and out may fix them. Pay special attention to any fx loops. those have switches built in so the signal gets through when you don't use fx. They corrode over time and that switch connection can cause problems, especially if you never use them.

Beyond that you need to delve inside the amp. Beware the voltages can be quite high and the power supply can store considerable power for hours after you unplug everything. DC shocks are more 'interesting' than mains shocks, not to be repeated. Don't open up an amp unless you know at least enough to keep yourself safe. If you aren't sure then you don't have enough knowledge. However if you've managed to narrow down the possibilities you'll often get a better deal from the repair people.

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1 hour ago, Phil Starr said:

 Pay special attention to any fx loops. those have switches built in so the signal gets through when you don't use fx. They corrode over time and that switch connection can cause problems, especially if you never use them.

I’d start here, as I had a similar problem in the past and this was the cause

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3 hours ago, Gunsfreddy2003 said:

 

The amp is in a room with a wireless booster that comes via a power line adapter from downstairs - do you reckon that could be it?

I’ve rehearsed so many times in that room before though with no issue at all - that is what puzzles me.

I used to run my own (amp and electronics) repair shop years ago. When I had that issue on a Glockenklang I bought new and which was dead quiet in the store, I first thought as a repairer that during the car trunk transport a solder had "broken", then I started to think about what could generate such a noise, and knowing that these PLC items and the so called digital power supplies are huge mains polluters, I unplugged the one I had nearby (around one meter away and just on the next socket) : the amp became dead quiet again !

18 minutes ago, JPJ said:

I’d start here, as I had a similar problem in the past and this was the cause

No, an effect loop unused for years will "only" cut the signal alternatively or totally, not making that noise.

 

Go the easy path first and unplug everything nearby and if the noise disappear, plug back each one until the noise comes back, then you'll find the culprit.

If not go the dry solder path, which is an easy but long fix : renew all solders. And beware of humidity which can act the sameway or overheated bakelite which becames conductive... 

Edited by Hellzero
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