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Hoffman Amps Forum image Author Topic: bias resisto question  (Read 1951 times)

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Offline bakerlite

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bias resisto question
« on: March 16, 2013, 11:46:05 am »
Just wondering if anyone know a good starting point for the bias resistor in a vibrolux reverb (aa270 ) ?
I have no 10k linear pots so i cant use the 10k + 15k resistor as called for in the schematic.
The closest I have is a 25k pot but i am not sure how that affects the range of resistor i should start out with?
I know i could learn by trying out a load of different ones till i get the desired bias voltage and sweep range but if anyone can give a nod as to a good starting point it might save me a few 'attempts'!!!
thanks
Cheers,
Bakerlite

Offline sluckey

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Re: bias resisto question
« Reply #1 on: March 16, 2013, 11:56:49 am »
10K pot and 15K is the same ratio as 25K pot and 37.5K. So, I'd start with the 25K pot and a 39K resistor.
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline bakerlite

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Re: bias resisto question
« Reply #2 on: March 16, 2013, 12:04:34 pm »
such a gent, thank you.
So it seems the function of the size of the pot only affects the range of the voltage sweep.
And the resistor detemines the ratio? - in this case about 1:1.5.
Cheers,
Bakerlite

 


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