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Reverb Hum [message #5040]

Mon, 08 November 2004 11:46

miscreantorgan
Messages: 1
Registered: November 2004

Junior Member

My Kustom 150 combo (pretty sure it's 4X10) gets a real hum going whenever I use the reverb. It's especially apparent when I *really* crank the reverb. It (quickly) gets to the point where the hum is more than you can take. Now, theoretically, I could just turn the reverb off and use an external box, but I'd prefer to use the built-in reverb.

I do know that the reverb does something 'cuz I can jar the amp and get the thunder sound. Fairly sure some signal is going both in and out, too, 'cuz I hear some reverb when I play through it.

I also noticed that if I shift the "head" of the combo (when I've got things all unscrewed) so that it's got the back part tilted up, the hum lessens. The hum also lessens with the back of the amp off. To me, this means that something's feeding back inside, bouncing all over.

One thought I had is that the rubber mat on top of the reverb tank may be old. I've tried to reseat it, though, and it still bends OK.

Thoughts/ideas?

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Re: Reverb Hum [message #5041 is a reply to message #5040]

Mon, 08 November 2004 12:08

rodak
Messages: 516
Registered: October 2001
Location: Georgia

Senior Member

Speaking of reverb, I have two, possibly related problems (one I've brought up here before, but can't remember what the advice was). figured maybe someone could address them all in this one thread.

Kombo organ: Reverb works, but as I turn up the depth, there's a lot of noise, sort of like a hiss, but with more emphasis on the low frequencies, more of a "whoosh". The reverb is definitely working, although not as pronounced as I'd expect, but the noise makes it pretty unuseable.

K150 combo: Similar problem to the Kombo. The tank is mounted upside down in the amp chassis - is that normal? The rubber tank cover has sagged down and may be touching the springs. Any problem relocating the tank to the bottom of the amp, right-side up?

www.combo-organ.com

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Re: Reverb Hum [message #5060 is a reply to message #5040]

Sat, 13 November 2004 19:38

stevem
Messages: 4775
Registered: June 2004
Location: NY

Senior Member

Hi. Reverb pans can pick up A/C hum from the input side of the pan just like when you get to close to the transformer side of a amp with the pickups of your guitar. when manufactures mount their pans the always try to put it as far away from the power transformer and the power cord and the amps inernal A/C wiring as possible. Make sure your pan is mounted with the side marked input on the side of the amp oposite the power trany. Get a pair of good RCA audio cables from raido, and also as a last resort, unwind all the a/c cord off the back of the amp when you use it. Or if your 150 is a combo amp get long RCA cords and mount it on bottom in the speaker section, thats what fender all ways did in fact in 68 when fender made their fist piggie back head with built in reverb they made the head 4 inches taller just to get the pan away from the A/C. Hope some of this may help!

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Re: Reverb Hum [message #5068 is a reply to message #5060]

Sat, 13 November 2004 22:55

rodak
Messages: 516
Registered: October 2001
Location: Georgia

Senior Member

Thanks, Steve. My K150 is an SC combo amp. Did those normally have the pan mounted in the bottom(what I would expect), or hanging upside down inside the amp chassis (a bit odd, I thought)?

www.combo-organ.com

[Updated on: Mon, 15 November 2004 23:01]

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Re: Reverb Hum [message #5093 is a reply to message #5040]

Thu, 18 November 2004 02:06

voided3
Messages: 200
Registered: July 2004

Senior Member

Hello. I've heard of some people putting their reverb pans in vynil bags to reduce noise; my old Ampeg guitar head has one I noticed. Would this work on a K200-A5? Thanks!

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Re: Reverb Hum [message #5094 is a reply to message #5093]

Thu, 18 November 2004 08:59

rodak
Messages: 516
Registered: October 2001
Location: Georgia

Senior Member

I think many reverb tanks were in those bags. I remember seeing them in the bottom of Fender amps, and I have one with "Traynor" on it. It's more of a heavy canvas bag with a smooth vinyl outer layer. I've never known what those were for, but noise reduction certainly makes sense. I'll have to dig up that bag - the tank that was in it was shot; hope I didn't throw the whole thing out!

www.combo-organ.com

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Re: Reverb Hum [message #5103 is a reply to message #5040]

Fri, 19 November 2004 17:17

stevem
Messages: 4775
Registered: June 2004
Location: NY

Senior Member

Hi. The bags are just to keep crap from fall into the holes that some pans have on the top of them.If you unplug both cables from the circuit board and you still have a hum or wind noise that is to the point of being a pain when you turn up the reverb, then you may have a problem. There will be some hum and noise, thats normal, but it should not make the amp unuseable.

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Re: Reverb Hum [message #5118 is a reply to message #5040]

Tue, 23 November 2004 16:39

teleman
Messages: 38
Registered: June 2004

Member

So many problems with reverb in frank head I'm about ready to forget it and play dry or get an outboard unit, long story is in comment section under Kustom A3 schematics------------teleman

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Re: Reverb Hum [message #5119 is a reply to message #5040]

Wed, 24 November 2004 06:37

shadow
Messages: 21
Registered: October 2004

Junior Member

No Message Body

[Updated on: Tue, 04 January 2005 12:35]

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Re: Reverb Hum [message #5127 is a reply to message #5040]

Tue, 30 November 2004 20:32

voided3
Messages: 200
Registered: July 2004

Senior Member

Hello. I wonder if guitar cavity copper sheilding would do the trick. The idea with insulation seems to be the best route though since it also isolates the tank, but then again it would make the reverb pretty hot I bet from absorbing the heat (if that matters). Maybe if you set your amp on some of those gel filled computer keyboard arm rests, some of the noise would be absorbed. Or of course, you could also get a reverb pedal... Cool

Cool

I use a footswitch on my K200-A5's reverb anyway. Just a thought. Good luck!

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Re: Reverb Hum [message #5128 is a reply to message #5127]

Wed, 01 December 2004 08:15

shadow
Messages: 21
Registered: October 2004

Junior Member

you may be right on the heat voided .

[Updated on: Tue, 04 January 2005 12:37]

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Re: Reverb Hum [message #5151 is a reply to message #5128]

Tue, 14 December 2004 11:31

C4ster
Messages: 686
Registered: June 2001
Location: Mukwonago, WI (Milwaukee...

Senior Member

Don't worry about the heat. The reverb does not generate any heat on it's own. Fender never vented their reverb pans and they were in a naughyde bag.
Conrad

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Re: Reverb Hum [message #5153 is a reply to message #5040]

Thu, 16 December 2004 12:52

stevem
Messages: 4775
Registered: June 2004
Location: NY

Senior Member

Sorry, but I printed a mistake in one of my early post. Its the output side of the pan that should be kept from being near the power transformer.

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Re: Reverb Hum [message #5158 is a reply to message #5040]

Thu, 16 December 2004 20:49

voided3
Messages: 200
Registered: July 2004

Senior Member

Hello. I know that the reverb doesn't generate heat, but I thought that if it was wrapped up in insulation it would absorb the amp's heat, which I feared would cause problems of sorts (though I doubt it, just curios/cautious). Thanks!

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Re: Reverb Hum [message #5329 is a reply to message #5040]

Tue, 11 January 2005 20:38

chacuff
Messages: 11
Registered: January 2005
Location: Gulf Coast

Junior Member

Hey Folks,

I am new at the Kustom amps but not to electronics work. (30+yrs) My recently acquired 795 Frankie head has a ground wire going from the reverb pan over to the amp chassis. When I ran the amp with this wire disconnected the reverb hummed like a big dog. I reached in and touched the wire to the pan and it quit. You might check and make sure yours is not missing the ground wire. I would expect the shielded cables to tie the pan back to chassis ground but it obviously is not doing the job.

Give it a try with an alligator clip lead and see if it makes any difference.

Good Luck!

Cecil...

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Re: Reverb Hum [message #5332 is a reply to message #5040]

Wed, 12 January 2005 08:40

stevem
Messages: 4775
Registered: June 2004
Location: NY

Senior Member

The frankie heads use a black wire to ground the pan, all the latter heads get the ground to the pan thru the shielded conductor RCA cables so a seperate ground conductor is not needed.

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