Vox repeater RF Noise with DC connect

[huggsie66]

Hi All
newcomer here, was wondering if anyone has a solution to my problem. Have made many fuzzes, so thought I would try something different, a Vox Repeater. http://tagboardeffects.blogspot.co.uk/2012/08/vox-repeat-percussion.html

Anyway got this going fine with just battery clip, but a friend asked for one with DC for daisy chaining. Unfortunately I get lots of rf and hiss noise with the dc input, but lovely and quiet with just battery. Things I have ruled out.
Power supply works fine with all other pedals, I recently built a meathead clone just to test, with no problems. Wiring seems simple enough, copied exactly the same as it should be.Checked and rechecked soldering. Have tried with 2 repeater circuits with same problem. Making this one for a friend so I really want to cut out the noise, anyone have a solution? I am stumped! Thanks in advance!

[R.G.]

1. How is the grounding from power to circuit done? Does it include power switching by the input jack?
2. Is there any power supply decoupling from +V to ground?
3. If there is, is one of the decoupling caps a 0.1uF CERAMIC?

[Chugs]

Looking at the layout, the audio part of the circuit has no power supply filtering.

In which case, and following on from 2. and 3. of RG's reply, add power supply decoupling in the form of a 100uf cap from 9V to ground with a 0.1uf cap in parallel. Preferably add a small resistor, say 47-100 ohms in series with the cap too.

[huggsie66]

Hi thanks for the advice. As a relative newbie I can't quite visualise what you mean. Do I need to build a daughter board or can I add these components to the circuit. Also are these caps electrolytic or standard? A rough diagram would really really help my newbie brain. Thanks!

[Chugs]

Ok, let start with something simple then.

Take a 100uf electrolytic cap and solder the positive leg in any of the three holes on the top row next to the 9V input. Solder the negative leg of the cap to the ground row of the vero at the bottom. You might need to do this on the back of the vero.

[huggsie66]

Hi, Ok did that, and it has reduced the high pitched whine, which changes frequency as I turn the pot. It is still noticeable though, could I try a larger value? thanks!

[Chugs]

Yes, try a larger value.

If there is still noise after trying a larger value electro then try placing a 0.1uf ceramic cap in parallel with the electro.

Then, if the noise persists, try adding a small value resistor is series with the caps. The easiest way to do this would be to solder the resistor between the 9V wire and DC socket.

[huggsie66]

Hey Chugs,
want to thank you, the noise has dropped considerably, still there a little, maybe when its boxed up etc, it may be a bit quieter. I had to do all you suggested, gonna maybe buy some better quality hookup wire as well, thanks again!

[Chugs]

No problem. Glad to hear the suggestions helped.