DAM Grease Box 88

[anders]

Here is a layout of the latest incarnation of the DAM Grease Box.
An output cap blend has been added so now it's basically a 3 knob bender with capacitor values tuned for modern sounds. This one is verified and has been on my pedalboard  for 4 months and it's gonna stay there since it's one of my favorite dirtboxes ever.It's more like a firm fuzzy distortion with lot's of comlex harmonics underneath the dirt. And the added tone control is perfectly tuned.

I used a couple of soviet MP40B for Q1 and Q2 50Hfe and 70Hfe respectively and a japanese 2SB437 with a Hfe of 150 with quite a bit of leakage, 0,35mA.

[tracer03]

Question: the radial capacitor (col. G, rows G-I) - is that *really* a 10 NF polarized? or should that be 10 UF?

[Dex3887]

Its uf. Probably a typo.
Thanks anders for another great layout

[Mulekicker]

I built this one last night and with the fuzz and tone cranked it sounds ok, but the tone control is acting weird, when I roll it back it sounds farty and misbiased. I tried heaps of trannies and it doesn't make any difference. Hmm...gonna have to dig in and see where I went wrong.

[Dex3887]

That describes every single MKIII type build I've ever built. Try the shoddiest leaky transistor you have in q3, its kinda essential for it to work right. Can you post voltages? Q-1-3 C,B,E

[Travis]

For a while I was going for really leaky stuff for Q3 but found that isn’t necessary and can result in erratic behavior. It is necessary to have some leakage but if it’s over the top that will do more harm than good IMO.

The MKIV that I build sounds exactly the same as my DAM Colorsound reissue and has the same voltages. I use OC76 which are only moderately leaky. They are totally low leakage enough to use in a Fuzz Face or similar circuit with great results.

I’ve tried all kinds of ways to get around it. What works for me is some leakage to get it going but not so much that it’s an unstable transistor (despite the reverse bias diode)

[Mulekicker]

I tried probably 15 different transistor combos, some leaky and some not. I had the same tone control issue no matter what, so I assume I screwed up somewhere. Gonna dig into it later and see what's what. Hopefully it's something glaring that I missed last night. I've had pretty good luck with benders so far. I haven't built a straight up MK III yet but I built and LOVE the Park that Rocket did the layout for.

[Travis]

First thing I’d look for is a missing/bad cut or short