http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=fb4a6ade4f
Above is the link to Mouser electronics project manager with the specified parts loaded. For $1.88, and a bit of soldering skill you too can perform this mod.
It's all for sale as a matter of fact, so if you see anything else you want, make me an offer. Except the GI-20.
About the 20/20. I bought it off this board about 6-8 months ago. I'm only selling to pay rent. I have to say, the deep mod is absolutely crucial. It makes this amp sooo much better...
I added a switch to the deep mod as well. This is also a completely reversible, no drill needed option.
Snoopy, what was the purpose of that pc board? It looks unnecessarily complicated. Or maybe my switch is missing something.