6V6GT push pull NFB resistor value

jetbat · 11th April 2009, 04:16 PM

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

jjman · 11th April 2009, 06:22 PM

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?

jetbat · 11th April 2009, 07:06 PM

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

11th April 2009, 04:16 PM	#1
jetbat diyAudio Member Join Date: Nov 2008 Location: Maryland	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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11th April 2009, 06:22 PM	#2
jjman diyAudio Member Join Date: Jan 2009	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?

11th April 2009, 07:06 PM	#3
jetbat diyAudio Member Join Date: Nov 2008 Location: Maryland	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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