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Old 11th April 2009, 04:16 PM   #1
jetbat is offline jetbat  United States
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Default 6V6GT push pull NFB resistor value

Hi, I am switching my guitar amp from 4 6L6GCs to 2 6V6GTs. I'm using the Fender Princeton AA964 as a referance. I've switched the transformer to a Mercury Magnetics Princeton. My question is about negitive feedback resistor. The original value was 100k. The value on the Princeton schematic seems kind of low at 2.7k. I was planning on installing a pot to see what value sounded good, but the 2.7k would be very close to the pot being wide open.

Any ideas on this?
Thanks
Scott
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Old 11th April 2009, 06:22 PM   #2
jjman is offline jjman  United States
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That Princeton feeds the NFB to a less common location than most guitar amps. And it's a point that is only 47ohms from ground.

My guess is that your 4-6L6 setup was not using that Princeton's phase inverter type.

Have you changed the entire setup to match that Princeton, or just the output-tubes' setup?
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Old 11th April 2009, 07:06 PM   #3
jetbat is offline jetbat  United States
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I've changed just the output tubes and the transformer to match the tubes resistance and give me 8 ohms to the speaker.

So I'll stay away from anything that low and work in the 47k to 100k range.
Thanks
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