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Choke for biasing driver tube

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Posted on August 29, 2016 at 10:21:49
DAK
Audiophile

Posts: 2712
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Joined: August 8, 2010
I was wondering if this might be an improvement? My 6sl7 driver tubes are biased with 390 ohm 1w resistors. It occurred to me that chokes of about that value are around. Would this be worthwhile? If i tie both cathodes to one choke it would need to be double the value correct? cheers, Dak

 

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Half the value. (nt), posted on August 29, 2016 at 11:41:20
Tre'
Industry Professional

Posts: 17263
Location: So. Cal.
Joined: February 9, 2002
.
Have Fun and Enjoy the Music
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RE: Choke for biasing driver tube, posted on August 29, 2016 at 11:47:55
Tre'
Industry Professional

Posts: 17263
Location: So. Cal.
Joined: February 9, 2002
"I was wondering if this might be an improvement?"

Depends on the circuit and what you're trying to accomplish.

If it's a differential amp relying on a non-bypassed common cathode resistor for corrective feedback then a choke (with it's much higher impedance while still providing the proper DCR for bias purpose) will give more feedback.

But in that case a SS CCS might be even better.

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

 

RE: Choke for biasing driver tube, posted on August 29, 2016 at 12:29:13
DAK
Audiophile

Posts: 2712
Location: PACIFIC
Joined: August 8, 2010
Thanks for the reply.
If it's a differential amp relying on a non-bypassed common cathode resistor for corrective feedback then a choke (with it's much higher impedance while still providing the proper DCR for bias purpose) will give more feedback. But in that case a SS CCS might be even better.

Can you define differential amp? i am not sure about that term. But in my amp i have a single side of a 6sl7 driving a 6550. Each section of the 6sl7 has its own bias resistor. The signal is split before the 6sl7 and each section handles half of the signal. If that is a differential amp then i got one. cheers

 

RE: Choke for biasing driver tube, posted on August 29, 2016 at 17:01:54
Tre'
Industry Professional

Posts: 17263
Location: So. Cal.
Joined: February 9, 2002

The driver stage in a Williamson circuit (V2) is one example of a differential amplifier.

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

 

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