Where to put the volume control.

[BeBuLamar]

I build a simple headphones amp using the TL084 op amp. Each channel are 2 stage of inverting op amp. It works fine but I need to put a volume control when use with source that has no variable output. Where should I put the pot? Before the first stage?

[TimFox]

That's the usual place, in order to avoid over-driving any of the stages.
Once the first stage overloads, there is no way to avoid the distortion in the signal.
The only reason not to put it before the first stage is if the signal into the volume control is so low that the noise contributed by that stage would degrade the signal/noise ratio.

[CaptDon]

I would suggest that prior to the first stage would be proper as it would allow you the ability to not overdrive the input stage which could happen if the control was after the first stage. Will a TL084 have enough current drive for your headphones?? You may need something with a bit more 'Moxie'.

[BeBuLamar]

Well the TL084 has enough current. I tested on the breadboard without the pot and it works fine.

[magic]

Isn't it the case that if the negative supply goes missing for any reason, the output jumps to the positive?
Are the headphones AC coupled?