Power filtering distortion plus

rhdwave · January 15, 2009, 12:12:21 AM

I have a distortion plus that is a bit noisy...a hum when engaged. I was thinking it might benefit from a 100uf cap from the power to ground. My question is: can i simply attach this cap directly to the dc jack from the hot tab to the ground tab or will i run into some unforeseen issues with this method?

Much thanks for any responses...

Timebutt · January 15, 2009, 04:02:30 AM

I don't see any problem in doing so, it's the way I usually do it too.
Just this: if you are getting a hum when using the pedal I believe you will have much better results removing the hum by using a regulated power supply. Fun little build or you could simply buy one of the Boss PSA wallwarts, never had any hum problems using those. Just my 2 cents ...

oskar · January 15, 2009, 09:23:43 AM

http://www.muzique.com/lab/hum.htm
It could work...
But chances are your wallwart is having a big cap allready at the output. So then you'ld only put say a 100u in parallel with perhaps a 1000u and you wouldn't notice any difference. A series resistor and then a cap... way to go man!

Mark Hammer · January 15, 2009, 10:48:22 AM

The Distortion+ is designed to roll off the bass as the gain is turned up. My hunch is that this was done (or perhaps only accidentally done, but preserved once the perk was discovered) in order to avoid cranking up the gain for the hum too.

Just exactly how well-filtered is your power supply to start with? It is hard for me to imagine it producing hum with the Dist+ but NOT with other devices.

rhdwave · January 15, 2009, 10:51:52 AM

Thanks for the replies! I have been looking at a lot of different options in terms of power supplies and such. I would like to actually build the Spyder from Geo, however i don't really have any experience wiring mains and i don't want to fry myself. I was thinking of trying to get a deal on a voodoo labs pedal power 2 plus from ebay to eliminate any issues on the power side. I guess i'll try the cap

Quote from: oskar on January 15, 2009, 09:23:43 AM
http://www.muzique.com/lab/hum.htm
It could work...
But chances are your wallwart is having a big cap allready at the output. So then you'ld only put say a 100u in parallel with perhaps a 1000u and you wouldn't notice any difference. A series resistor and then a cap... way to go man!

Just a quick question off this: about what value on the series resistor would you use? Is this something that's dependent on the circuit and will have an effect on the sound?

Again, much thanks!!!

rhdwave · January 15, 2009, 10:55:42 AM

Ahh, just noticed your reply Mark...

Currently i've been getting hum with other pedals as well, as you surmised correctly...my Big Muff with the volume cranked is very loud with it as one example. I've been using the one spot daisy chain to power most of my stuff. i actually have two in operation right now as it seemed that whenever i use the fifth section of the daisy chain, it causes all kinds of strangeness in that particular pedal. So, as i said in the previous post before i saw this, i would like to build the spyder but have some trepidation and was thus thinking of going with the pedal power 2 plus from voodoo labs...expensive, but if it solves many issues i figure it will be worth it in headache savings...

any thoughts are welcome!

Mark Hammer · January 15, 2009, 02:25:04 PM

I often recommend what I like to call a "power distribution box". Certainly not a replacement for things like the One-spot and similar, in terms of current and footprint, but it can address hum and distribution issues nicely and at reasonable cost.

Not complicated, either. Get yourself one of those little black plastic project boxes. This will let you use the cheaper barrel jacks because the box is nonconductive. Install a 2.1mm barrel jack on one side. This will be your wallwart input jack, and requires no modification of the wallwart itself. Get a half-watt 10ohm resistor, a 3k3 1/4w resistor, an LED, and a 470uf-1000uf cap. The 3k3 and LED become the power indicator for the distribution box (nice to know when the wallwart is not supplying power to the board!). The 10R resistor goes in series with the hot lead of the input jack. The 470-1000uf (1000uf preferred) cap goes from V+ to ground. Now run leads from your new, more filtered V+, to as many output jacks as you want, and make yourself some power patch cables to length. That's it.

rhdwave · January 15, 2009, 10:46:22 PM

Thanks Mark! Just to summarize for my own edification:

The difference between something like this and say the spyder or the voodoo labs pedal power 2 plus besides the price (in the case of the voodoo labs unit

)...is that this filters the power coming from the wall wart whereas the spyder and such take the place as a wall wart completely, step down the power from the mains, rectify, filter, regulate, and isolate. Is that about right? Just trying to get things straight in my head...

thanks again Mark!

Mark Hammer · January 16, 2009, 09:05:44 AM

Yeah. You pretty much nailed it. Some wallwarts aim for virtually ripple-free output, while others seem to proclaim "Hey, whaddya want! At least it's NOT AC anymore!", and are content with a couple of diodes and maybe a 220uf cap in that little sealed black plastic gourd. What I described is something intended to a) take a wallwart that went 75% of the way and make it behave like it went 85-90% of the way, and b) make it possible to have a more convenient layout of power cables on a pedalboard.

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Power filtering distortion plus