I built this too (modded version from scratch) and I have the same issue - very low volume, although the controls seem to work except the Level pot, which doesn't do anything. I built this twice, cause I was not able to figure out what is wrong, but same issue. The Bypass out works fine, only the effect out is problematic.
I have another question: I see this (VB) at some of pot labels - what does this mean?
if you're asking those questions then i'm pretty sure that you've got an error in your build.
the blue dot means two links join in that hole.
VB is very important. you might start taking some voltage measurements to troubleshoot your build.
Ok, so I'm only writing because I had the same volume issue and I figured out the problem (at least on my board), the 10k resistor next to the left IC.. I broke it when I soldered it in. Maybe you should take a look at it too.
Assuming that my caps are rated at an appropriate level, will this run at 18v using TL074 ICs? That would mean that I could put john K’s equally awesome active DI in the same box without a charge pump.