Problem with Gretch Controfuzz (GGG)

[Pancra85]

I've done a PCB for this schematic: http://www.generalguitargadgets.com/pdf/ggg_controfuzz.pdf
And is not quite working, I've made sure everything was correctly connected and also that there are not any missconections made with solder.

On the output it sounds as what I think is a booster, when you turn on the potentiometer the volume gets higher and there is distortion when going too far (I am using a 25K pot instead of 10K) but the GAIN pot doesn't do anything.
When probing pin 1 of the TL072 I can only hear a high pitched noise, I think the problem is coming from there. Is the same noise I get from DC, which I can see that is connected to the input and then to pin 3 and don't understand why.
Why to send DC to the TL072 input???

This circuit is supposed to mix a fuzz signal with the dry signal, so I think that GAIN is more like MIX.

Any ideas??? Thanks!