Mosfet boosts and power supplies

[Rockhorst]

I've built both the Slambox and the Thunderpuss from MB. The circuits work well, but I've noticed that they are both very picky about their power supply, either daisy chained or not. Sometimes I get a whistling noise from one of them when on a power supply, other times it's like a flanging sound. I've only had reliable results with an isolated power supply like the PP2+. Today a friend of mine checked out a slambox with a Godlyke Power All adapter, huge whistling noise. With a Boss adapter, the noise got considerably less, but still there faintly in the background.

I know that simple power supplies can cause noise and adding pedals in a daisy chain makes problems worse...but what strikes me as odd is that its primarily the mosfet boosts that seem to be affected by this. Haven't had these problems with higher gain pedals such as the AMZ Mini Booster, MB Grapevine or Neutrinos.

Anybody recognize this? What's the cause and what's the fix? Does it come with the mosfet territory?

[jonrhee]

I've had the same problem with both the Thunderpuss and the Slambox, both times while building two in one overdrive and boosts. I'd be very interested if there's a solution other than a PP2+. Wondering if it was because I used BS170s from Tayda. What brand mosfets did you use?

[Loztboy]

Same here. I thought it was a problem that I created. But my lavache, thunderpuss and sprout screams and whine with a cheap power supply but works like it should with my pp2+ and boss/ehx wall wart. I have video of the problem in my thinderpuss tech help thread. The cheap power supply works ok with other pedals.
Edit here is the video. Is this what you experience?

[jonrhee]

Mine's more like a high pitched squeal. I have noticed one of my friends was running his a 12v using a TC electronic power supply. Not sure if thats a factor. He is also using a Blues Jr which is like brightness galore. My amp is also very bright but the squeal is less noticable.

[stecykmi]

you could try a small series resistor on the +9v input jack, that may help decouple the power supplies a little more. try something like 100ohm.

[Rockhorst]

@Loztboy:
That's EXACTLY the noise I'm talking about, right there in your video. (sorry, I hadn't checked this thread since Octobre 2011). Since the pedals work just FINE with about any other power supply, it makes you wonder what's different in the Godlyke (supposedly it has some filtering built in). The MOSFET boost that

@Stecykmi:
I built is Brian's version/PCB, which also has some power filtering present. Could it be the two 'bite' each other? Can you over filter? If so, which component in the filtering is most suspect?

[nzCdog]

That video sounds exactly like the intermittent hum I would get from my TC Electronic Nova Delay power supply!    Although from what I noticed it was right through the pedalboard and not reacting with just one pedal in particular. 

The fix was to unplug the power supply and plug it back in again, so I have reason to believe it was some wierd resonance issue related to the switch-mode operation of the wall wart.  Now I have a linear power supply I have no noise issues at all.

I'd be interested to hear if Misha's suggestion of the resistor helps filter things better for you.  Another idea is add a 100n cap from 9V to Ground, that seems to help in some cases too