HELP -- LEDs in my A/B box are causing hum . . .

[msb69]

I built the A/B box that is shown on the Fulltone site.  It works great.  However, when I use a 9v adapter so I can have alternating LEDs, there is a hum.  When I remove the 9v adapter, the hum is gone.

Any thoughts? 

[msb69]

Think I just solved it -- the LEDs weren't getting grounded properly.  That's strange, because I originally wired everything exactly as shown on the Fulltone site . . .

[R.G.]

Hmmm... you hook up the adapter, it hums, you remove the adapter and it quits humming, but the LEDs are causing the hum???

I think you have a hummmm-y adapter, not humming LEDs. Filter and/or regulate the voltage out of your adapter, or get an adapter that does not hum.

[msb69]

Hmmm... you hook up the adapter, it hums, you remove the adapter and it quits humming, but the LEDs are causing the hum???

I think you have a hummmm-y adapter, not humming LEDs. Filter and/or regulate the voltage out of your adapter, or get an adapter that does not hum.

Hey RG -- thanks for chiming in.  Actually, I was using a Voodoo Lab Pedal Power 2, and I also tried a Dunlop regulated supply.  The same hum was present with either.

I ended up connecting a wire from ground to the footswitch lug that connects to the negative pole of the 9v adapter jack.  Now alll is well!

[LyleCaldwell]

Yeah, I've found that you have to tie the DC ground to audio ground to keep from getting hum.  Doesn't always make sense, but it's real.