adafruit industries

Has anyone had experience using the POWERBOOST 500 + CHARGER to power a 5v amplifier. I am the proud owner of two PB 500s and love there simplicity. However, when i use them to power a 5v amplifier with just the battery attached, or battery and usb power supply i get a high pitch noise coming through the speakers.

Ive checked it is not the amp by using a different step up buck converter. This only seems to happen when using either PB 500.

Lastly, when I gently pressed a plastic tool against the inductor it seems to change the pitch of the noise. Is there anything i can do to reduce/ eliminate this noise. The amplifier is a PAM 8403.

Boost controllers often have some residual switching noise in the output. Apparently, the noise from the PowerBoost is at a frequency not filtered by your amplifier. Adding some capacitance across the outputs of the PowerBoost should smooth it somewhat. If you have access to an oscilloscope to analyze the frequency, you could design a filter specifically targeted to that noise.

Hi thanks for the advice, and speedy responce. So in short if I use a low pass RF filter using the +ve output as Vin and the -ve output as Grnd this should solve the problem. As this is a high pitched noise i was going to use a cutoff frequency of 234 using 680ohm resister and a 1uf capacitor, does this sound ok? I'm asking as i don't want to blow anything up !!!!

Since this is a power supply, you want to minimize the resistance. An LC filter would be a better way to go.