Tube Amp Hum

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LesterH
Junior tube assistant
Posts: 1
(4/21/04 8:12 am)
 Tube Amp Hum
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 I'm working on a Vibro-Champ. I replaced the tag board with a new one with good grade components (Orange drops and metal films, etc) made by a gentleman in Malaysia (www.ceriatone.com, excellent boards at reasonable prices). No component value changes, no circuit mods. Now I am trying to get the hum down to the lowest level practical. It's no worse than a stock Champ, I just want it quieter. What's the best place to start?

Thanks,

LesterH
 
Voxbox
Junior tube assistant
Posts: 71
(4/21/04 2:13 pm)
 Re: Tube Amp Hum
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 Hi,

try the tech info on grounding at
www.aikenamps.com

You can get away without star grounding as proposed there, but its a good place to start.
BTW, you can go mad trying to get the hum down. gibbergibber.
FYI I found that the steel mounting bolts that held down my mains TF in my 5E3 Deluxe were causing hum to be induced into the chassis. I reduced the hum by using insulated brass studs.
Best of luck.

Cheers

Voxbox
 
PHATamps
I only work on tube amps
Posts: 439
(4/22/04 5:27 am)
 Re: Tube Amp Hum
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 The best place to start with Champs is the heater wiring. You'll notice that one leg of the PT heater winding (green wire) is grounded, as is pin 7 of the 6V6, pin 9 of the 12AX7s, and one terminal of the lamp socket.

Hum can usually be decreased by lifting all these grounds and wiring the heater string the way the big amps are done. Just make sure you reference the winding using 100 ohm resistors, one from each terminal of the lamp socket to ground.
 
 
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