I use the MP1584 to step down 5VDC to 1.5VDC to power an audio equalizer taken from a Panasonic walkman (RQ-P255) from the nineties. However this is working great, sound is great, it introduces a heavy whine and don't know how to avoid this. See also the schematic below of the device I have build. What can I do to remove the whine?
I have build/want to build a Micro Portable Stereo Amplifier With Battery, Equalizer, BlueTooth And Line-In/Line-Out (in a small candy case) so you can connect any speaker you want (nice to use outside in the garden/party) and you can use it as a BlueTooth Walkman. I have added an equalizer taken from an old walkman of the nineties, the Panasonic RQ-P255. This because most bluetooth transmitters don't support an equalizer and, some bluetooth speakers supports only EQ with presets (hate it).
Figure out how the equalizer works and it was very straight forward but requires only 1.5VDC input (the whole device, all other parts, operates on 5VDC). Because of positive reviews of the MP1584, I use this little device to step down 5VDC to 1.5VDC. This is working great except the whine it produces, very annoying. The device has an equalizer on/off switch and when I turn it off, the whine is gone.
What can I do to remove the whine?
The whine i'm talking about
This is recorded with a microphone of a Tascam DR07 nearby speaker. The picture below is the waveform 1600% amplified.
To hear the whine 800% amplified: https://drive.google.com/file/d/0B2l-eQoHefcVaVd3ZVNZMXJYcXM/view?usp=sharing
To hear the whine - whine original: https://drive.google.com/file/d/0B2l-eQoHefcVb2NMS3dINDU3SFU/view?usp=sharing
Notice: I don't have an oscilloscope.
Schematic of the device
Notice: I'm not a hardware designer or schematic professional, so maybe the schematic is not as it should but I think it is very clear what goal I want to achieve. The headphones connection is not in the schematic. EDIT: 200K must be 200 Ohms
Setup of the device
What I got so far
BlueTooth module and switch and headphone jack not implemented yet.
What it should look like when finished ;-)
Used parts/devices in current setup:
Battery charger / DC converter taken from this product: http://www.mrhandsfree.com/en/shop/7318-portable-power-chargers/product/7320-portable-power-charger-2600-mah
Equalizer taken from this product from the past: http://img19.staticclassifieds.com/images_slandokz/91858292_1_644x461_kassetnyy-audiopleyer-panasonic-rq-p255-pavlodar.jpg