could someone please explain how this circuit works

Hi all, im looking at making this circuit for a audio mixer.

I would like to try and understand how it works before i attempt to build it

The main thing im unsure of is the FET's purpose and why do you need a 9v supply?

thanks

Well that's a REALLY poor mixer, barely worthy of the name. Far better to build a proper mixer using a single opamp.

The FET (or opamp) is to provide gain to make up for the losses in the mixing process, the 9V battery powers it.

I think the choice of using FET is just a random choice. An opamp amplifier or a common emitter should work as well.

The fet here is used like an emitter follower. It has no voltage gain, but it supplies a high impedance point for the signals to be mixed together and increases the current so the signals can be sent to another stage. You need a voltage supply because transistors don't work without any voltage or power, and it's 9 volts so several volts of signal can be handled without clipping the peaks off.

thanks for explaining

ok from your comments Nigel I'm going to re-think the idea!