Gain capacitator values on LM386 and other op amps

[ExpAnonColin]

I've been trying various cap values in between the gain terminals, and I really couldn't hear much of a difference between 10uf and 200uf.  Either it doesnt make much of a difference or it doesnt effect volume or something else..?  Someone want to shed some light for me?

[R.G.]

That cap is used to shunt AC current around an internal resistor. If the capacitor is big enough to shunt the resistor, making it bigger will not make a difference.

Try putting a resistor in series with the cap and varying the resistor.

You should see a gain between 20 and 200 depending on the AC impedance between the two points. You want the capacitor value to NOT matter because that would mean that for some frequencies the gain would be larger than others.

[Joep]

You can find the datasheet here.

From the datasheet:

Application Hints
GAIN CONTROL
To make the LM386 a more versatile amplifier, two pins (1
and 8 ) are provided for gain control. With pins 1 and 8 open
the 1.35 kW resistor sets the gain at 20 (26 dB). If a capacitor
is put from pin 1 to 8, bypassing the 1.35 kW resistor, the
gain will go up to 200 (46 dB). If a resistor is placed in series
with the capacitor, the gain can be set to any value from 20
to 200. Gain control can also be done by capacitively coupling
a resistor (or FET) from pin 1 to ground.

Changing the cap value, will change the frequency response, the lower the cap, the more bass will be cut.

Hope this helps.

Joep

[ExpAnonColin]

You can find the datasheet here.

From the datasheet:

Application Hints
GAIN CONTROL
To make the LM386 a more versatile amplifier, two pins (1
and 8 ) are provided for gain control. With pins 1 and 8 open
the 1.35 kW resistor sets the gain at 20 (26 dB). If a capacitor
is put from pin 1 to 8, bypassing the 1.35 kW resistor, the
gain will go up to 200 (46 dB). If a resistor is placed in series
with the capacitor, the gain can be set to any value from 20
to 200. Gain control can also be done by capacitively coupling
a resistor (or FET) from pin 1 to ground.

Changing the cap value, will change the frequency response, the lower the cap, the more bass will be cut.

Hope this helps.

Joep

Ah, that's perfect, I didn't have the datasheet before.  Thank you!  It all sort of clicks into place..