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Post subject: Bit of 'magic' loss over time
Posted: Mon Apr 30, 2012 12:46 pm
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Professional Musician
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Hey all,

I've noticed that during practice sessions with my AC4 that it seems to lose a bit of oomph over time. Sounds great when I fire it up, but somehow it seems to drift slightly from the sweet sounds I get for the first 10 or 20 minutes.

Could this be tube related? She runs a 12ax7 and an el84, if that helps. Thanks


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Post subject: Re: Bit of 'magic' loss over time
Posted: Mon Apr 30, 2012 2:46 pm
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AC4 is a VOX ? Welcome to the Fender Forum . Does'nt mater , tubes amps are all the same.

Your problem could be many thing , tubes, resistor (s) in power supply ........Is it "old" this amp ?

Do you see EL84 comming very very red after 10 or 20 minutes ? More than the first fifth minutes ?


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Post subject: Re: Bit of 'magic' loss over time
Posted: Mon Apr 30, 2012 3:06 pm
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Foolow Stratele's advice. Also, how old is the 12AX7? Have you tried subbing in a new one?


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Post subject: Re: Bit of 'magic' loss over time
Posted: Tue May 01, 2012 10:42 am
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Thanks guys, I'll keep an eye on the color change over time. It's a (relatively) new AC4TV, likely a couple of years old and the tubes are still stock. Perhaps I should just look at retubing it with JJs or something since going NOS is worth more than the amp is.


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Post subject: Re: Bit of 'magic' loss over time
Posted: Tue May 01, 2012 12:11 pm
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JJ 's tube are fine , don't forget to check bias.


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