LT1166 bias IC

Sebastiaan · 6th June 2011, 09:54 AM

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 · 6th June 2011, 11:19 AM

here an Overview of the threads here arround auto-bias and variable bias - perhaps this helps
Dynamic Bias - Active Bias - Automatic/Self biased - Overview wanted
Variable operating biass output ?
Ultimate ECC for Class B from Thule Audio? Topology also used by Teac
Threshold's optobias - diyAudio (Optobias US4752745)

"An Adjustment-Free Complementary Power Amplifier" by J.Diamond
Any new design sliding bias amps out there ?
Biasing schemes for bipolar transistor circlotrons

ingenieus · 3rd September 2011, 03:21 PM

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

6th June 2011, 09:54 AM	#1
Sebastiaan diyAudio Member Join Date: Jun 2004 Location: the Netherlands	LT1166 bias IC 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

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6th June 2011, 11:19 AM	#2
tiefbassuebertr diyAudio Member Join Date: Jul 2005 Location: D-55629 Schwarzerden	here an Overview of the threads here arround auto-bias and variable bias - perhaps this helps Dynamic Bias - Active Bias - Automatic/Self biased - Overview wanted Variable operating biass output ? Ultimate ECC for Class B from Thule Audio? Topology also used by Teac Threshold's optobias - diyAudio (Optobias US4752745) "An Adjustment-Free Complementary Power Amplifier" by J.Diamond Any new design sliding bias amps out there ? Biasing schemes for bipolar transistor circlotrons

3rd September 2011, 03:21 PM	#3
ingenieus diyAudio Member Join Date: Apr 2011	LTspice IV comes with a model of the LT1166 included. A simulation can provide at least some answers, if not all.

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