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Autobiasing output tubes (6L6)?
Autobiasing output tubes (6L6)?
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Old 14th August 2019, 02:16 PM   #51
JMFahey is offline JMFahey  Argentina
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I also read "auto bias" as Cathode bias, not considering grid leak bias here which is also "auto" because we are talking power tubes.

Label might be applied to more complex Servo or even Microprocessor based solutions but if so IŽd make it clear what are we talking about.
Design/make/service musical stuff in Buenos Aires, Argentina, since 1969.
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Old 14th August 2019, 06:04 PM   #52
mesherm is offline mesherm  United States
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I have used TL783 voltage regulators as cathode constant current sinks in my SE and PP tube amps with excellent results. Simple, cheap and effective if you don't mind a bit of sand in your amp.
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Old 15th August 2019, 03:42 PM   #53
Ketje is offline Ketje  Belgium
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Originally Posted by Wavebourn View Post
The only adaptive autobias I found worth using long time ago, was based on S/H and envelope sensing. It was an integrator in servo, using very low input current opamp and a teflon capacitor, with MOSFET switch before it that got closed when music level was above pretty low threshold.
That has to be the Sony patent !
Here is another one, if you like a puzzle
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File Type: png Autobias&balance.png (35.6 KB, 149 views)
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Old 15th August 2019, 06:58 PM   #54
Wavebourn is offline Wavebourn  United States
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Autobiasing output tubes (6L6)?
Originally Posted by Ketje View Post
That has to be the Sony patent !
And they patented it 20 years before I started considering tubes worth using, re-inventing the wheel!
Single Ended Class-A-Holism is addictive!!!
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Old 22nd August 2019, 10:45 PM   #55
buffstereo1 is offline buffstereo1
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Default Thank you!!

Thank you all for your thoughtful and courteous responses to my question about auto-biasing 6L6 tubes. I really appreciate it!!
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Old 17th September 2019, 02:13 AM   #56
opcom is offline opcom  United States
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Originally Posted by kodabmx View Post
True, but you get the benefit of self adjustment along with the lack of wasted power in a resistor
A customer so liked the benefit that he had me make him a panel with a meter and 10 position switch by which to set bias on each of his 4 PP amps, with two positions left for future.
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