Simple Single Supply AC to Dual DC Supply For PCM56 DAC

My latest DAC built is based on PCM56P here. This DAC built is intended to become my experimental project about how good the simple non-oversampling R2R DAC would sounds like. The overall size of this DAC is only 10 cm x 7 cm, very compact in size, slightly bigger than the Chord Mojo here but this PCM56 is far better in sound quality because it is multibit R2R resistor ladder network compare to the simple delta sigma DAC like in Chord Mojo.

Right now I mostly listen the music from this DAC PCM56 in my home audio system. Sometimes I also using this DAC on my headphones setups. This PCM56 DAC is powered by the battery pack. This is naturally has more cleaner power supply compares when using the transformer. This will impact to the smoother sound quality.

But using the batteries is more hassle than using typical wall adapter. I should recharge the batteries when the voltage drop and this is very annoying especially when forget that but I want listen to the music right away.

So in this post, I will share how I change from the dual rail batteries power supply to single supply using typical AC wall adaptor.

The photo above is the final result of this DAC by using power adaptor plug instead of previously  multi pins connector.

This power input require is AC 9 volt. This can be use typical transformer with 15 VA or above.

The detail schematic of the previous batteries connection is on the photo bellow. It using 3 pin connector to accommodate the dual rail power supply from the batteries to DAC power supply module.

This is the new schematic when using AC 9 volt input.

I just need to convert the AC to dual rail DC using 2 pieces 1N4001 diodes. Each diode connect to one AC output then it will converting to one polarity of DC. The other AC output will act as the common ground.

The voltage after the diodes are dual rail +12 volt and -12 volt to the ground respectively. The voltage are increase from AC to DC because of this rectifier process and this is completely normal.

Here is the actual implementation on the DAC board.

As you can see I don't make any changes to the current DAC module. I only add 2 diodes and extra 100nF capacitors for smoothing the ripples as shown in the schematic above.

You can see the space inside is very limited since all the boards are sandwiched together.

This is all finished and the rest of the steps is only installing the power plug.

The power adaptor is actually very simple to build.

I am using used EI transformer rated 20VA taken from old radio. I put it inside plastic box for the power adaptor.

So how this new power supply modification perform? My biggest worry is the noise from using this simple transformer power supply compare to the batteries.

I power up this DAC and connect to my audio system, surprisingly no audible noise occurs at all. It is still quiet just like when using the batteries.

Then comes to the sound quality after this modification, I think this DAC sound more forward, at the same time a little bit noisy on the high frequency. It so much different when using batteries which is more smoother in all frequency band.

At this point, I have no complaining at all since this new power adapter offering more simple and reliable DAC by using a wall power adaptor.

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