Strange Problem

[Kinski]

Okay, so I've run into a strange problem. One I've never had before.

I built an amp for a family member for the holidays. Its a chime amp with a Woodrow for dirt that is switchable. Okay, sounds great.

Powered with a OneSpot adaptor, everything is fine. When powered with a battery, it still works, but I also get a massive oscillation that changes in pitch as I turn knobs. All the batteries i've tried are new and very close in voltage to the OneSpot. I have no idea what could be the problem.

Ive been staring at this thing for too long...

Any ideas?

[Kinski]

Oh, and the oscillation from the battery only appears when I engage the Woodrow. When in clean mode, its fine.

[Neil mcNasty]

I've had similar stuff happening on small amp build, and my conclusion has been that maybe I haven't shielded it good enough, just sticking the circuits in a wooden box.
But also if the amp draws a lot of current, then maybe a higher mA battery would help...?

At the moment I'm going to try out a 12v chargeable battery intended for 50cc bikes, going into 9v regulators, to battery power amps (with effects) like these.

I guess that power filtering, shielding between amp section and effects, and similar stuff becomes an issue when building things like these.
I also suspect (guessing actually) that battery powered amps will be more prone to oscillations and interference, since we are dealing with a high degree of amplification with a virtual ground.
Something tells me that this would be more "antenna"-like, compared to when you are hooked up to "real" ground...
Anyone out there with knowledge about stuff like this?

Anyway!
I have a feeling that, when pushing these little amps to the extreme with effects slamming the front end, the total current consumption seem to rise quite a bit over what is suspected/specified.
So the whole amp sags, because the battery does not handle the "realtime" current draw (my language). and it does this in a very, non-charming way, so to speak...
The oscillation issue reminds me of how some of these amps behave when they are running low on the battery. But it only happens when you push the front end with a pedal...

Using several batteries in parallel to increase the battery juice is one thing that comes to mind.
At least that is what I'm going to try for these amps.
+ better shielding/boxes and separation between the amp section and high gain circuits.

[Kinski]

Thanks. I'm built another one and it had the same issue. I'm ditching the idea and just gonna make a RUBY amp. Those are always easy. Thanks again Neil for your input. Much appreciated!