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GMC Forum _ GEAR & PRODUCTION _ Classic 30 Hum?

Posted by: bluetag May 16 2010, 05:39 AM

hey guys just posting on here cause i had a question about an issue i've been having with my amp. i got a classic 30 awhile ago and i recently noticed whenever i plug in effects into the loop i get a humming noise. would this means theres something wrong with the preamp tubes i have 12a7's in the preamp and el84's. i know tubes generally can be sometimes noisy and this amp has some history of some hum since it has spring reverb. anyways just wondering what the gearheads thought

thanks

Posted by: MickeM May 16 2010, 10:55 AM

If you run the effects from a wall socket there will most likely be 50 or 60 cycle hum (which one depending on your power net frequency)
With batteries this will be gone.

Posted by: Ivan Milenkovic May 16 2010, 02:30 PM

Try to localize the problem. Is the problem happening when plugging in anything in FX Loop? Try to plug the guitar into return jack, or just try various pedal combinations. As Micke Suggested, it could be that the pedals are the issue, not the amp. Test various combinations and let us know how it went, so we can try to localize the issue.

Posted by: Bogdan Radovic May 16 2010, 07:12 PM

You definitely look more into this as many things can cause this hum. See on the back of the amp if you have the Ground/lift switch, try using it to see if hum stays. You should also try plugging only one by one effect pedal in the loop in order to localize the problem. Try using batteries to power the effects as power adapters are know to cause various humming and buzzing depending on the quality...

Posted by: bluetag May 16 2010, 11:24 PM

ya i went to the guitar store today and talked to a few people about it one guy said it might be the pedals. i use a 9v 1 spot adaptor i dont think its the greatest i will start my experiments now and let you know what i find out thanks for the help guys

Posted by: Ivan Milenkovic May 16 2010, 11:43 PM

Before you buy something else, or take amp to service, try putting pedals in front and see if it hums then. If you get the same hum, it's probably the pedals then. Let us know how it went..

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