Hi,
I'm working on a tiny PSU to fit into a pedal board that I wanted to power with my USB battery pack (phone charger thing) and also for using all those 5v USB plug in phone chargers around.
I got a couple
Murata MER1S0509SC 5v to 9v DC-DC converters (as that's what I could find locally) and I've tried it out on the breadboard using my phone charger. The charger puts out a steady 5v's under load, the DC converter puts out around 12v with no load and around 9v under load depending on the amount of pedals, seems to drop .1v the more pedals that are daisy chained.
The problem is I'm getting a high pitched whine through the amp. The switching frequency of the DC-DC converter is 62kHz, have I made a mistake here? I thought that'd be fine as it's above 20kHz. Also, the max ripple & noise is stated at 20mVp-p, have I seriously underestimated this? Would putting it in it's enclosure help? as said it's on breadboard with lots of long crocodile clips attached to jumpers and stuff (probs could have clipped straight onto the pins now I think about it). Am I just going to have to accept I need to use some extra filtering? didn't really want to use any components other than the converters.
I've powered a few different pedals with it thinking it could be possible heterodyning with modulating effects but it's happening with simple IC & tranny based drives and fuzzes too.
Any help is appreciated.
Cheers,
Marcus