Posted by Amp Weenie Bluz Harper on October 30, 2001 at 14:51:29:
In Reply to: Tube amp tip posted by Ron on October 30, 2001 at 09:52:51:
: I use a Blackface Fender Champ amplifier with an Astatic JT-30VC (volume control) mic. The Champ, like most guitar amps, comes with a 12AX7 pre-amp tube.
: I just read a tip that said if you are using a bullet type mic, you should get better results from the tube amp if you replace the 12AX7 pre-amp tube with a 12AU7 pre-amp tube. I'm no amp tech-weenie but the basics are that the 12AU7 produces less gain and cuts higher frequencies.
What youre dealing with is amplification factors 12 AX 7 =100%
12 AU 7 = 17% its that simple, less pre amp gain = less feedback when using a mic.
You might want to try 12 AT 7 =60%
12 AY 7 =44% Enjoy....Bluz
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