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Replacing vc with a resistor

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Posted on September 10, 2014 at 22:56:42
Ron944
Audiophile

Posts: 48
Joined: July 3, 2000
 Hi, I am building a version of the JE labs 300b stereo amp and would like to use a resistor instead of a volume control. It calls for a 100k pot, what value resistor should I replace it with. Thanks,
Ron

 

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100K resistor (nt), posted on September 11, 2014 at 00:39:45
danlaudionut
Audiophile

Posts: 5480
Location: Schenectady
Joined: June 6, 2002
 DanL



 

RE: Replacing vc with a resistor, posted on September 11, 2014 at 07:56:26
Hornlover
Manufacturer

Posts: 2529
Joined: March 8, 2002
 Are you talking about a stepped attenuator, using discreet resistors?

 

RE: Replacing vc with a resistor, posted on September 11, 2014 at 08:49:55
Tre'
Industry Professional

Posts: 17292
Location: So. Cal.
Joined: February 9, 2002
 If you're using a 76 as the input tube you can use anything up to 1meg ohm for the grid resistor.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: Replacing vc with a resistor, posted on September 11, 2014 at 14:05:49
Ron944
Audiophile

Posts: 48
Joined: July 3, 2000
 I am using 76 for the input tubes. Is there a minimum value that you would recommend.

Thanks,
Ron

 

RE: Replacing vc with a resistor, posted on September 11, 2014 at 14:44:08
Tre'
Industry Professional

Posts: 17292
Location: So. Cal.
Joined: February 9, 2002
 What is the output impedance of the source (preamp)?

My rule of thumb would be 10 to 20 times the output impedance.

Above that and there's really no advantage, below that and you will be loading down the preamp and the harmonic distortion of the preamp's last stage goes up.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

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