DIY Pre-amp and USB MP3 player (with FM Tuner)

I wanted a Pre-amp to go with my TA2024 chipamp and after seeing the products on offer from various Chinese eBayers I rather fancied having a go
at building my own.

The USB MP3 Player and PSU came from Helder HiFi. Both were well packed in cardboard boxes and were delivered in about 2 weeks.

Adjustable 11- 14V @ 3.5A Switched Mode PSU

The Pre-amp module from Zoe Tsang which came bubble wrapped inside an unpadded buff envelope. Although seemingly inadequate, no damage done.
Delivery took about 10 days.

Four inputs, volume, balance, bass, middle, treble and 3D. The board I received differed slightly from the one shown. The control pot on a separate
board with a ribbon cable has been replaced with one integrated on to an extension of the display board. This made mounting the assembly much more tricky.

During assembly I noticed that the MP3 module had an 'aerial' symbol on the board. Out of curiosity I connected a piece of wire to the marked hole on
the PCB and was quite surprised to hear BBC Radio2 coming through loud and clear. The product description does not mention an FM Tuner. Bonus.

It all works pretty well apart from a problem with the remote controls - they both operate on the same frequency! However the pre-amp remote revealed two more undocumented features of the MP3 module - FM station memory (not sure how many, on autoscan it stored 25 but only about 10 are listenable using a piece of wire as an aerial) and 6 sound 'equalizer' settings ranging from bassy to toppy with something inbetween. Now I can't decide which one gives a 'flat' response!

As for the pre-amp module, no surprises although I haven't discovered how to alter the brightness of the display which apparently can be done using the remote.

All in all I enjoyed this little project but doubt I'll ever master cutting accurate openings in sheet metal.

Update 03-02-2012

I noticed a low level buzz from the speakers when the pre-amp is connected to an amplifier and put this down to the switched mode power supply. This has now been replaced with a linear unit but unfortunately a small amount of noise is still audible.

A bit of a bird's nest. Top left: Rectifier and voltage regulator board. Lower left: 12V 50VA transformer. Bottom left: MP3/FM module. 

Lower right: Input selector board. Bottom right: Display board with integrated function control knob.
Note that the identification marks on the chip have been erased and how the board differs from the one shown at the top of this page.

Update 16-04-2012

Added Tripath TA2024 amplifier board.

2 x 10 Watts doesn't sound much but the tiny board packs a surprising punch