How to eliminate clock noise travelling on shared power lines

[Mark Hammer]

As has been reported here on various occasions, some digital pedals that are nice and quiet when using a single unique power source turn noisy when having to share that power source with another digital pedal.

Now, if one was using a power source where every individual output had RF/EMI protection, and each output powered only one pedal, you'd be in great shape.  But what happens when you havea single "normal" power supply, and you attempt to daisy-chain that power across multiple pedals?

Is there a simple way to stick something in-line, between the outputs of a daisy-chain cable, that would eliminate, or at least reduce significantly, clock noise travelling back and forth and creating heterodyning?  Is it as simple as a cap and choke?

[R.G.]

Oddly enough, I've encountered this problem before. 
In some cases, it's as simple as a choke and a cap. In some cases, it's impossible. In some cases the wrong choke/cap will have a resonance close enough to one of the frequencies there that it's unbearable. In this last case what you need is a damping resistance either in series with the setup or in parallel with the choke to damp the filter's resonance. The value of the damping resistor is a compromise between zero ohms, which damps it fully but prevents the inductor from doing anything and a high value which lets the inductor work great, but doesn't damp. Perfect is a resistor which is close to the impedance of both the inductor and cap at resonance, which varies with inductor and cap.

Doing a general interference suppressor is frustrated by the broad frequency range of switching power supplies inside pedals and the variable amount of suppression of noise coming out of the pedals/power supplies. Staggered filters, each properly damped and tuned are great - but complicated.

Maybe the best simple thing is a parallel-capacitor setup with a small series resistor. 100uF in parallel with 0.1uF monolithic ceramic in parallel with 0.01 mono ceramic in parallel with 0.001uF mono ceramic is a good way to start. Each of the caps picks up being capacitive when the previous one has turned inductive.

[jrc4558]

You can use a voltage regulator. I had a Digitech delay (one generation old silver one) and its spread it's clock noise over into my chorus when powered from a daisy chain DC PS. installed a voltage regulator in the chorus and the problem is solved!

[Mark Hammer]

Hi Constantin!  Nice to see yuo here after what seems like a long absence.  I finally visited the "new" Active upstairs last week.  I missed seeing the gorilla for the last 5 years!  Nice to see it again.