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 Post subject: Amp Hum
PostPosted: Mon Mar 22, 2010 11:57 am 
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Recently (about a week ago) my amp started humming whenever I play it. It's a Fender Deluxe VM, and it never used to do that. I know it's not my guitar because I turned it down and it made no difference. It's not the single coils of my Strat either, because it hums with my Les Paul too.

The people in my band and the people I jam with have started noticing and it's a little embarrassing. It's a tube amp, so it's supposed to buzz to a certain extent but not this much. Does anyone have any idea what could be wrong?

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PostPosted: Mon Mar 22, 2010 12:01 pm 
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You might have a bad tube or one of them might not be seated properly. I would check there first.

If one of your jam buds says anything, just reply, "hum, what hum?"

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PostPosted: Mon Mar 22, 2010 1:25 pm 
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I was thinking it could be something along those lines. How can I tell if a tube is bad?

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PostPosted: Mon Mar 22, 2010 1:31 pm 
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if anybody calls attention to a strange humming noise, just act dumb and start humming a tune. then act like you've suddenly been brought back to earth and raise your hand.

anywho, i had a similar problem with a 12ax7. after a few minutes' warming up, this loud hum would start up. its obvious that it isn't normal. to answer your question, i found out it was one of my preamp tubes by pulling/substituting tubes one by one until it didn't happen. i hate that method btw.


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PostPosted: Mon Mar 22, 2010 5:43 pm 
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If it is not the tubes, maybe the filter capacitors? I experienced this a while back.


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PostPosted: Mon Mar 22, 2010 8:36 pm 
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same hum with either guitar and just a cable vs. through all of your pedals?

If you have power for your pedals, is it and the amp plugged into the same outlet/power strip?

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PostPosted: Mon Mar 22, 2010 9:07 pm 
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Different guitars, different cables, it doesn't make a difference. Sometimes the pedals and amp are plugged into the same power strip, but last night they weren't and it still hummed.

I haven't checked the tubes yet, but I will tomorrow. I have a gig coming Saturday with a new band and it's really important that my first impression is a good one. Nothing like a little pressure. :lol:

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PostPosted: Mon Mar 22, 2010 11:56 pm 
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My understanding (from a technically astute poster elsewhere) is that the two 12AX7s are in the gain channel so you get pre-amp tube distortion. If true, you might turn the gain channel all the way down and try the clean channel.

If that eliminates the problem, it's probably one of the 12AX7s ... just a quick test. However, I'm not 100% sure the poster was right so if the quick test doesn't eliminate the hum, you'll need to pull the pre- tubes anyway.

If one of the power tubes, remember that you should replace both as a set even if only one is bad. If one of the originals is still good, keep it with you as an emergency spare. The amp will work with a mismatched pair (unless they're absurdly mismatched), it just won't be optimal.


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PostPosted: Tue Mar 23, 2010 6:33 am 
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hey~
i went thru a lil of the same experience recently.
i heard a wierd low hum, sounded kinda like someone was outside
mowing their yard.
it got worse and louder as days went by.
turned out to be be a power tube - when i bought a matched quad 6L6
(the power tubes were 2 yrs. old- but don't let time be the only factor in changing tubes)
and changed them, PRESTO, i haven't heard that hum since !!!

ALSO, same experience, but with a "crackle sound" (sounded like a guitar instrument cable shorting out) turned out to be a bad 12ax7
when i changed them all - problem solved. Then I sub'd out them til i found the one and discarded and kept the good ones for backup

my pref on decent Affordable tubes (my twin~amp has 12!) are Electro-Harmonix btw

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PostPosted: Wed Mar 24, 2010 9:36 pm 
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I played it at practice today and the unusual hum was gone. I guess that's a good thing, but that was really weird.

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 Post subject:
PostPosted: Thu Mar 25, 2010 3:42 am 
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It could be one of your power tube( 6L6) have dirty socket contacts.

Amp power off, remove an plug tubes few time. It's remove "dirt" from contact on the socket.

If your output tubes are not matched ( It could change when old) or a bad contact ( the amp see like not matched, or different). You could have hum.

In your case it look like bad contact.
Be careful when removing output tube, do not break pins guide. Pull tubes
very staight.

If your hum comming back, be sure to unplug every thing from your amp to be sure is not your guitar or pedals, or wires the problem

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PostPosted: Thu Mar 25, 2010 5:00 am 
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sometimes you get a hum from a bad power source. Flourescent, neon lights on the same circuit as the outlet. A bad ground may also contribute to excessive hum. good luck, hope its a simple fix.

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 Post subject: Re: Amp Hum
PostPosted: Sun Jun 10, 2012 7:51 am 
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This may not have anything to do with the hum, but switch to another cable ... & make sure your not using the footswitch cable as a guitar to amp cable. My M3 hum'd like crazy as soon as I turned it on the 1st time. Nothing seen to help except adjusting the master to 0. My heart was hurting...new amp & it hum'd like an Ole Sailor. But I just switched cables & WOW....crystal clear & what an Amp it has turned out to be!
This amp is very sensitive. Any defect in the cable is picked up by this amp. So spend a few more bucks & get a new cable for your M3 if your having any noise problems.
Hope this helps at least one person out there. My 64 concert amp is the same way. That's what made me think to change cables...old lessons learned!


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