JCM Build - Hum and Crackle

shunt94 · 23rd January 2012, 06:13 PM

Hey,

I've had my JCM 800 2204 build up and running for a while now! - However, The Amp has a low frequency hum which you can really hear when you turn up the volume! - But more annoyingly, every now and then it crackles... It also crackles when I tap (Not particularly hard but not soft) on the top of the amp! :S

The Hum could be because I haven't grounded the C.T of the heater windings... I wasn't too sure about grounding them as I'm using the C.T of the heaters to make up 6.3VAC across the valve (One tap is 6.3, so I had to use the C.T otherwise I would have 12.6VAC to the valve heater pins!).
Will grounding the C.T have any affect on anything other than getting rid of the hum?

I have no idea of what could cause the crackle so any ideas on that would be great!

Many Thanks in advance!

23rd January 2012, 06:13 PM	#1
shunt94 diyAudio Member Join Date: Apr 2011	JCM Build - Hum and Crackle Hey, I've had my JCM 800 2204 build up and running for a while now! - However, The Amp has a low frequency hum which you can really hear when you turn up the volume! - But more annoyingly, every now and then it crackles... It also crackles when I tap (Not particularly hard but not soft) on the top of the amp! :S The Hum could be because I haven't grounded the C.T of the heater windings... I wasn't too sure about grounding them as I'm using the C.T of the heaters to make up 6.3VAC across the valve (One tap is 6.3, so I had to use the C.T otherwise I would have 12.6VAC to the valve heater pins!). Will grounding the C.T have any affect on anything other than getting rid of the hum? I have no idea of what could cause the crackle so any ideas on that would be great! Many Thanks in advance!

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