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CA 3080/LM 3886 tube pwr amp emulation
CA 3080/LM 3886 tube pwr amp emulation
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Old 10th December 2004, 01:19 PM   #1
metalhead is offline metalhead  Finland
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Default CA 3080/LM 3886 tube pwr amp emulation

Has anyone tried operational transconductance amplifier such as CA 3080 or LM 3080 driving audio power IC ( for example LM 3886 or alike). Do you (resident geniuses)have any suggestions how to use amplifier bias input of 3080 to reduce the gain and bias as a means for emulating tube amplifier sag/compression (power supply voltage sag,screen grid voltage sag).Could this be achieved? Im not so much after a hifi audio power stage as im thinking in the lines of electrical music instrument sound production audio power stage(certain behaviour and coloration). Maybe this question could be used as thinktank of how to approach that "tube like" behaviour using these two building blocks.Allso, How to add " soft clip" to the circuitry, add FB etc. Thank you for your time and my appologies(?).
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Old 14th December 2004, 11:37 AM   #2
metalhead is offline metalhead  Finland
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Continuation.... CA 3080 must "read" the load (8 ohm) to behave as descriped. Bias supply(s) connected to pin 5 of CA 3080. .....?LM 3886 saturation point is...?
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Old 3rd February 2018, 04:10 PM   #3
Michael Koster is offline Michael Koster  United States
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Here'a a concept based on another idea I'm working on. The idea is to make a "scaled down" load line for the CA3080 that is a copy of the actual output current.

The scaled load could be provided by another CA3080 with the proportion of load set by the ratio of bias to the CA3080 that is driving the signal.

I think we would need a gyrator to set the quiescent operating voltage...

I didn't show a lot of other required components to focus on the concept at first.

I am currently building this circuit. My version is with a 6V6 pentode and MOSFETs for the feedback load and gyrator, but it's essentially the same concept. I'm using a TDA7293 instead of the LM3886, and driving a virtual ground input to the chipamp (to deal with the pentode voltage swing).

It's described in a little different form here:
A new perspective on current-sharing hybrid amplifiers
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Last edited by Michael Koster; 3rd February 2018 at 04:22 PM.
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