audio circuit ,analog fade out on mixer

[rochest126]

I want to realise fade out effect in one channel of mixer,is it works?

 

[ericgibbs]

h 126,

The first OPA on the 'muted' channel has a very poor bandwidth due to the 100nF capacitor across the 100K feedback resistor.

I have attached a couple of images showing the OPA response with and without the 100nF.

This response needs correcting before considering the mute action.

The muting transistor is disconnected for these tests.

Who designed the mixer.?

When mute is switched On or Off you will get a loud 'pop' on your amp output.

E.

 

[audioguru]

A transistor that clamps the input signal causes severe distortion. A Jfet is usually used as a fade circuit instead.
Your transistor is changing the DC voltage of the inverting input of the opamp which causes its output voltage to jump near the positive supply voltage when the transistor turns on causing the POP.

R16, R18 and R20 in your circuit do nothing and can be replaced by a piece of wire.
There are THREE bias networks (R4 and R5, R7 and R10, R12 and R13) when only ONE network is needed that can bias hundreds of opamps. Usually the junction of the bias resistors has a capacitor to ground to attenuate power supply noise.