Power Supply Weirdness! Need help...

[Paul Marossy]

This is really strange. I am hoping someone can explain this one...

I have an Arion SAD-1 analog delay that I want to use on a stripped-down pedal board. Since it eats batteries very quickly, I am using a 9V 450mA wall wart with it. It puts out about 12V with this pedal attached to it, and it apparently doesn't have a problem with that. I also want to run a couple of things off of the same power supply, so I made a parallel power cord. Everything is center negative, so I know that is not the problem. Now, here's where the problem comes in: if I try to put anything else on the same power supply as the SAD-1, it will not work! The LED indicator lights up when I step on the switch, but there is no delay. If I remove the other things from the power supply, it works. I know that everything on the board doesn't come anywhere close to 450mA of power usage.

So, does anyone have any idea why the heck the SAD-1 would behave like this? I am baffled on this one...

[niftydog]

Have you measured the voltage of the wall wart with the SAD-1 and another pedal attached?

I know that everything on the board doesn't come anywhere close to 450mA of power usage.

does that include the SAD-1? Maybe it's close to maxing out the wall wart on it's own?

[Fret Wire]

Sounds similar to the old Boss ACA type power supply problems with several pedals.

[Paul Marossy]

niftydog-

I also tried an 9V 800mA adapter, same thing. That's what makes this so weird...

[jrc4558]

I'm thinking outloud, but try to decouple it. 47ohm/47µF cap to ground.
maybe?..

[niftydog]

ah, well then it's easy. It's possessed!  :twisted:

[Ge_Whiz]

The reason is probably that the Arion splits the supply voltage internally and has a ground at the mid-point, to provide virtual +/- supplies, so the signal ground is not the same as the supply -ve. When you add a conventional DC pedal, the earth connection through the jack shorts out the virtual -ve supply in the Arion, preventing it from working. The LED is only connected between signal ground and +ve, so it still works.

Sorry, the only solution is to keep the PSU for the Arion separate.

[Paul Marossy]

Ge_Whiz-

I think you hit the nail on the head! That's gotta be what's going on here. I remember the last time I wanted to use that pedal on my other pedalboard (about 1 year ago), that is what I ended up doing. I couldn't think about it clearly because I was up till midnight working on the "problem" and it was making me mad...

Anyhow, thanks everyone.