LT1166 bias IC

[Sebastiaan]

Dear All,

Who can tell me more about this "auto bias" IC. I used the search function and read the different opinions. Also I Purchased the awesome book "Designing Audio Power Amplifiers" from Mr. Bob Cordell where he went deeper on this chip.

I fear I don't really understand this IC yet.

As far as I understand (and please correct me if I am wrong), The IC forms an integrator by sensing the voltage drop over the emitter resistors. The servo keeps the DC voltage at 20mV. by adjusting the VBE multiplier transistor inside the chip. Am I correct so far?

Then I wonder what does the chip when the musical signal exceeds the bias current. Will it slides with the music, or does the amplifier switch into class B?

I read about concerns of added distortion mostly in the HF frequencies, since the VBE multiplier modulate with the music signal. Bob Cordell provided solutions for this.

I was wondering, why not only use the servo/integrator part of the chip, and let the chip drive an LDR or an optocoupler in the bias string? A resistor and capacitor can slow down the fluctuation.

Maybe I am all off here, but I hope for some share of thoughts.

Thanks in advance.

With kind regards,
Bas

 

[tiefbassuebertr]

here an Overview of the threads here arround auto-bias and variable bias - perhaps this helps
http://www.diyaudio.com/forums/pass...as-automatic-self-biased-overview-wanted.html
http://www.diyaudio.com/forums/solid-state/145013-variable-operating-biass-output.html
http://www.diyaudio.com/forums/soli...ss-b-thule-audio-topology-also-used-teac.html
Threshold's optobias - diyAudio (Optobias US4752745)

http://www.diyaudio.com/forums/soli...-complementary-power-amplifier-j-diamond.html
http://www.diyaudio.com/forums/soli...-sliding-bias-amps-out-there.html#post2326257
http://www.diyaudio.com/forums/soli...g-schemes-bipolar-transistor-circlotrons.html

 

[ingenieus]

LTspice IV comes with a model of the LT1166 included. A simulation can provide at least some answers, if not all.