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east electronics 29th June 2015 07:35 PM

3886 gain
working with 3386 power stage and for the specific application gain resistor R for XY PCB is 22K

Since my preamp is passive i would like more gain 47K sounds fine but i dont know if has any stability restrictions

Can anybody help ?

Arty 29th June 2015 07:40 PM

i think it has a minimum gain for stability.
infinate gain is not possible naturally.

so i think you can got with a higher gain to account losses of a passive preamp.

there are 2 resistors setting the gain, not just one.
refer to the chip datasheet on information regarding how to calculate the desired gain setting resistor values.

abraxalito 2nd July 2015 12:26 AM

Increasing the feedback resistor makes your amp more stable, not less. Nothing to be worried about with 47k other than possibly increased noise.

east electronics 2nd July 2015 08:40 AM

Thanks abraxalito

AndrewT 4th July 2015 01:11 PM

look at the datasheet.

The phase margin changes as the closed loop gain changes.

As you increase from gain = +20dB to gain = +30dB, the phase margin increases significantly. Above +30dB the improvement in phase margin is pretty low.

@ gain = +28dB, the phase margin is probably optimum for audio.
I believe that the many reports we see of Members saying that the 3886 sounds "right" when gain is around 27times is related to this "optimum audio phase margin".

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