SHO before a Crunch Box (There is a weird hum when both are engaged?)

[sevenisthenumber]

I have built the  MarkM layout for the Crunched Box along with a Zvex SHO (Andrew Carrell layout) in one enclosure, two footswitches. They both work great but when they are on together there is a strange hum in the background.....? The SHO is pre crunchbox. What could be causing this?

[sevenisthenumber]

I had been using 9v power supplies like the BOSS and EH one... I just used a fresh battery and it isnt happening???  Anybody know how to fix this?

[Toney]

Sounds like a grounding issue, assuming they both work OK independently.
How's the power? Did you include some filter caps?

[sevenisthenumber]

okay....   i removed the led's positive wire from the 9v jack and it goes away. With a battery this noise isnt an issue??? ONly with the adaptors...

They work great independently with the led's but not together???

[sevenisthenumber]

Should I add more filtering? how?

[MikeH]

What is the value of you current limiting resistor for the LED?  Just curious...

[petemoore]

  Duplicate post fodder 

[sevenisthenumber]

What is the value of you current limiting resistor for the LED?  Just curious...

1k metal film

[petemoore]

  First, have a capacitor across the power rails, a BFC, 100uf should cover it.
  Then you could try reducing the current through the LED by increasing the 1k, this will tell you if increased current = increased ripple.
 

[Toney]

Yeah, like Pete said.
Another thing that could possibly help... having the current limiting resistor on the neg side of the LED if you don't already.
Also... just try another LED!

[frokost]

I had the same issue recently. A 100 R in series with + and a 100uF to ground solved it.