Power Question

[Kinski]

Okay, I ran into something that I can't get around.

I was building a little noise box for my 1.5 year old son.

Its 2 Atari Punk Consoles running parallel, with a single master volume.

When testing it out of the box, I was powering each APC with its own 9v battery. When It came time to box it up, I used a single 9v battery to power both. This is where I ran into problems.

Longs story short, when powering both APCs separately, they function independent of each other (as I wanted). When powered together with the same 9v battery, adjusting one APC alters the sound of the other APC. Why would this be?

I just ended up putting two 9v batteries in the box, so no big deal, however, I'd really like to know why this is as I have plans for more multiple APCs and I'd ideally just use a single power supply.

Could someone enlighten me as to why this would be and perhaps a way to solve this issue without using multiple power supplies?