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Author Topic: Amp Feedback/ heat question  (Read 1683 times)

mikey5

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Amp Feedback/ heat question
« on: October 12, 2011, 05:36:37 PM »
Hi guys,

Last night I was playing my Ceriatone Chupacabra through a new guitar (humbuckers), and I was getting a lot of feedback. My amp gain was cranked really high and I was getting a bit of feedback. Also I noticed a faint smell. Not a burning smell, just a smell of heat.

Any thoughts?

Telerocker

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Re: Amp Feedback/ heat question
« Reply #1 on: October 12, 2011, 10:45:27 PM »
Output tubes can produce a lot of heat, especially when the amp is cranked. A bit of feedback on these volumelevels could easily happen. When you hear disharmonics, maybe a tube failes.
Mules, VHII, Crawler, MM's, IT's, BG50's.

Frank

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Re: Amp Feedback/ heat question
« Reply #2 on: October 13, 2011, 09:41:09 AM »
Take a quick look round the back of the amp, see if any of the tubes are red plating. You should see just the internal heaters glowing, if you see any glow on the grey metal plates in the tube then switch off and get the bias checked.

Also see if the transformers are getting hot, transformers sometimes cook a bit and give off a burny electrical smell.

darkbluemurder

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Re: Amp Feedback/ heat question
« Reply #3 on: October 13, 2011, 10:17:51 AM »
Last night I was playing my Ceriatone Chupacabra through a new guitar (humbuckers), and I was getting a lot of feedback. My amp gain was cranked really high and I was getting a bit of feedback.

When you say "feedback" do you mean note feedback, i.e. when you stop playing does it stop? Or is the feedback unrelated to the notes played, i.e. does it continue when you mute the strings? Does it continue when you turn down the guitar volume?

The Chupacabra is an amp with relatively high gain. Feedback may have a lot of reasons:
- it may be the pickups being microphonic - do they have covers? Try another guitar at the same volume and see if it persists.
- a tube may be microphonic. The most likely suspect is the tube in the V1 position because any noise generated in the first stage of the amp will be amplified many times, especially in a high gain amp.

Also I noticed a faint smell. Not a burning smell, just a smell of heat.

Tubes do get hot, especially when they have to work hard in a cranked amp. A faint smell is not necessarily a problem sign. One of my homebuilt amps does that, too. I have played it on several gigs without any problems. Watch out however for

- redplating tubes
- loud hum
- the faceplate getting too hot to touch.

Cheers Stephan