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Auto-Biasing Circuits for Complementary Followers
Auto-Biasing Circuits for Complementary Followers
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Old 12th January 2018, 05:56 PM   #21
cbdb is offline cbdb  Canada
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Dosnt matter how high the bias starts or how big the caps are. If the signal stays on long enough, a full cd for example, the caps will increase there voltage and increase the bias. The louder it plays the higher the bias goes. What other tricks?
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Old 12th January 2018, 08:10 PM   #22
indra1 is offline indra1  Indonesia
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Go to the Official M2 thread and try to learn from the first few pages.
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Old 12th January 2018, 08:48 PM   #23
Nelson Pass is offline Nelson Pass  United States
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Auto-Biasing Circuits for Complementary Followers
Quote:
Originally Posted by cbdb View Post
Dosnt matter how high the bias starts or how big the caps are. If the signal stays on long enough, a full cd for example, the caps will increase there voltage and increase the bias. The louder it plays the higher the bias goes. What other tricks?
What circuit does that?
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Old 12th January 2018, 08:59 PM   #24
Zen Mod is offline Zen Mod  Serbia
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Auto-Biasing Circuits for Complementary Followers
aha

that's why I'm enjoying just first side of CD , with my N2

second side is almost unlistenable

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Old 12th January 2018, 10:55 PM   #25
Mark Johnson is online now Mark Johnson  United States
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Auto-Biasing Circuits for Complementary Followers
And let's not forget that the nice people at Linear Technology sell an integrated circuit called LT1166, which auto-biases the output stage of an audio power amplifier. (link to document). It can be used with BJT output transistors, or MOSFET output transistors.
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Old 13th January 2018, 05:04 AM   #26
indra1 is offline indra1  Indonesia
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Thank you Mark, great tip! Affordable and available in easier to see DIP8. Specified for class AB bias but I see no reason why it can not be used for class A. Typical PassDiy bias of 1.3A will need R sense of 15.38 mΩ which can be 6 parallel of 0.1 Ω resistors or a 0.5 inch length of AWG#26 magnet wire.
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Old 13th January 2018, 05:30 AM   #27
Zen Mod is offline Zen Mod  Serbia
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naah

far from elegance and wit , we are having with opto and hall chips
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Old 13th January 2018, 06:59 AM   #28
indra1 is offline indra1  Indonesia
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Totally agree, but a tip on other method is always great nonetheless.
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Old 13th January 2018, 09:01 AM   #29
EUVL is offline EUVL  Europe
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In terms of circuitry the LT1166 is more complex.
But it has one big advantage, namely the sense voltage is +/-20mV, instead of ~1.2V for the opto.
Once can argue this is not important for certain designs, such as those with sufficient NFB.
But if one chooses to design an amp with no NFB, then even a bias of 2A would mean Zout > 0.15R, or damping factor < 48.

If we accept +/-0.6V as sense voltage, then the JLH biasing circuit is IMHO just as effective.
It essentially operates on a similar principle.


My personal opinion, of course,
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Old 13th January 2018, 09:19 AM   #30
indra1 is offline indra1  Indonesia
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Originally Posted by EUVL View Post
In terms of circuitry the LT1166 is more complex.
But it has one big advantage, namely the sense voltage is +/-20mV, ...
Not against 1.3mV sense at 2A bias required by the ACS723 hall chip.
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