Between 1992 and 2014 Krell used a Plateau Bias described in Patent Number: 5,331,291. Based upon sensed output bias voltage .AND. output transistor temperatures .AND. current driven into the speaker load, control logic set a modestly higher than required output bias to maintain ClassA operation, up to the maximum safe limit, even for a few minutes after the transient power demands dropped. Stable, fully Class-A operation at a uniform transistor temperature and operating point for reasonable periods.
Krell engineers believed that a "tracking bias" design which continuously changed the output bias point created audible artifacts.
I-Bias adds a microprocessor plus improved analog sensors to better control "plateau bias" functions for greater accuracy and efficiency...shorter periods of necessary high bias. I-bias also provides network control which allows the owner to selectively "cap" bias current, thus allowing Class-AB operation during monster music peaks to reduce waste/heat. iBias allowed Krell to significantly reduce both physical size and fan cooling demands for HT rack mounting.
================alternative==========
Study the "dual slope" Class-AB bias threads which use two opamps in the bias circuit plus ThermalTrak output transistors for very low measured distortion. A few watts of Class-A bias, plus precise thermal tracking creates efficient, low distortion home amps.
Once you add +/- 15V power supplies for an opamp DC Servo, it is easy and cheap to add a few quad comparators/opamps, plus NAND/NOR logic gates from MOSFETs, for all-analog protection + management.
Krell engineers believed that a "tracking bias" design which continuously changed the output bias point created audible artifacts.
I-Bias adds a microprocessor plus improved analog sensors to better control "plateau bias" functions for greater accuracy and efficiency...shorter periods of necessary high bias. I-bias also provides network control which allows the owner to selectively "cap" bias current, thus allowing Class-AB operation during monster music peaks to reduce waste/heat. iBias allowed Krell to significantly reduce both physical size and fan cooling demands for HT rack mounting.
================alternative==========
Study the "dual slope" Class-AB bias threads which use two opamps in the bias circuit plus ThermalTrak output transistors for very low measured distortion. A few watts of Class-A bias, plus precise thermal tracking creates efficient, low distortion home amps.
Once you add +/- 15V power supplies for an opamp DC Servo, it is easy and cheap to add a few quad comparators/opamps, plus NAND/NOR logic gates from MOSFETs, for all-analog protection + management.
Some Ideas on Temperature Compensation for Audio Amplifier EF Triples
Andrew C. Russell uses low voltage opamps to establish a high accuracy 2-slope Vbe vs. Temp bias.
"Ideas on Temperature Compensation for Emitter Follower Triples in Class AB Audio Amplifiers"
ThermalTrak output transistors improve accuracy.
Andrew C. Russell uses low voltage opamps to establish a high accuracy 2-slope Vbe vs. Temp bias.
"Ideas on Temperature Compensation for Emitter Follower Triples in Class AB Audio Amplifiers"
ThermalTrak output transistors improve accuracy.
The circuit seems in precise bias control for temperature. The paper hardly speaks about THD.
A friend of mine is an excellent microprocessor/controller programmer so if the bias to be controlled using that how it has to be done?
I just need the bias higher when signal just arrives and the bias to be less when the signal goes out as if like modulating bias. How to do this using micro controller/processor?
A friend of mine is an excellent microprocessor/controller programmer so if the bias to be controlled using that how it has to be done?
I just need the bias higher when signal just arrives and the bias to be less when the signal goes out as if like modulating bias. How to do this using micro controller/processor?
The circuit seems in precise bias control for temperature. The paper hardly speaks about THD.
A friend of mine is an excellent microprocessor/controller programmer so if the bias to be controlled using that how it has to be done?
I just need the bias higher when signal just arrives and the bias to be less when the signal goes out as if like modulating bias. How to do this using micro controller/processor?
A friend of mine is an excellent microprocessor/controller programmer so if the bias to be controlled using that how it has to be done?
I just need the bias higher when signal just arrives and the bias to be less when the signal goes out as if like modulating bias. How to do this using micro controller/processor?
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