6G6B NFB resistor/circuit

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sliberty
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6G6B NFB resistor/circuit

Post by sliberty »

My 6G6B has a 4/8/16 ohm OT. I am currently using the 16 ohm tap.
A standard 6G6B has a 4 ohm OT and cabinet I assume.

How (if at all) should I adjust the NFB circuit to best match my 16 ohm setup? Does the 56K resistor have to be changed? Changed to what? Any changes needed in the pot/cap/resistor part of the circuit?
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rdjones
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Re: 6G6B NFB resistor/circuit

Post by rdjones »

sliberty wrote:My 6G6B has a 4/8/16 ohm OT. I am currently using the 16 ohm tap.
A standard 6G6B has a 4 ohm OT and cabinet I assume.

How (if at all) should I adjust the NFB circuit to best match my 16 ohm setup? Does the 56K resistor have to be changed? Changed to what? Any changes needed in the pot/cap/resistor part of the circuit?
You shouldn't have to change anything if you take the NFB from the 4 ohm tap.
This is regardless of which tap is being loaded.

reddog
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ToneMerc
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Re: 6G6B NFB resistor/circuit

Post by ToneMerc »

sliberty wrote:My 6G6B has a 4/8/16 ohm OT. I am currently using the 16 ohm tap.
A standard 6G6B has a 4 ohm OT and cabinet I assume.

How (if at all) should I adjust the NFB circuit to best match my 16 ohm setup? Does the 56K resistor have to be changed? Changed to what? Any changes needed in the pot/cap/resistor part of the circuit?


I'm not clear on what you asking asking. When you say " currently using the 16 ohm tap", is that in reference to the negative feedback circuit or speaker load on the OT? If it's speaker load you don't have to do anything.

However, if using the 16 ohm tap to drive your NFB circuit and if you wish to have the same degree of negative feedback as the stock layout which uses the 56KNFB resistor and 4 ohm tap, you need to increase the value of the 56K resistor.

TM
Roe
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Re: 6G6B NFB resistor/circuit

Post by Roe »

sliberty wrote:My 6G6B has a 4/8/16 ohm OT. I am currently using the 16 ohm tap.
A standard 6G6B has a 4 ohm OT and cabinet I assume.

How (if at all) should I adjust the NFB circuit to best match my 16 ohm setup? Does the 56K resistor have to be changed? Changed to what? Any changes needed in the pot/cap/resistor part of the circuit?
just change the resistor
56k@4ohms=112k@16ohms=79k@8ohms
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sliberty
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Re: 6G6B NFB resistor/circuit

Post by sliberty »

Thanks guys.

To clarify, I had connecected the NFB wire to the jack, but I see now thatbthis is a mistake in a multi-tap scenario. based on your responses, I should connect it to the terminal strip where I have terminated my OT secondary wires, on the 4 ohm tab. In this way, i won't need different resistor values depending upon which secondary I am using.

Right?
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ToneMerc
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Re: 6G6B NFB resistor/circuit

Post by ToneMerc »

sliberty wrote:Thanks guys.

To clarify, I had connecected the NFB wire to the jack, but I see now thatbthis is a mistake in a multi-tap scenario. based on your responses, I should connect it to the terminal strip where I have terminated my OT secondary wires, on the 4 ohm tab. In this way, i won't need different resistor values depending upon which secondary I am using.

Right?
Yes

TM
Roe
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Re: 6G6B NFB resistor/circuit

Post by Roe »

you can also use a small resistor with a 100k pot in series for some added flexibility :D
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