PCM1704 DAC Power Supply Upgrade

This post is the update from my PCM1704 DAC built.

As I always mentioned that a DAC will sound good if it is feed with a good power supply as well. It is all begin with the power transformer, regulator circuitry, the capacitors around it and the components layout. It will bring significant improvement to the DAC sound quality.

In this post, I will upgrade my previous PCM1704 DAC built with better transformer and I will make a small change to the power supply layout as well.

The new components in this upgrade is the power transformer.

I got this toroidal transformer taken from EAD DAC unit. It is a sealed toroidal transformer and has multiple secondary output that very suitable for individual power supply in this PCM1704 DAC.

Because this new transformer has multiple secondary output, then I should reconfigure the rectifier to accommodate this transformer output as well

So I will using 4 bridge diode instead previously only 1 and each diode bridge is for each secondary transformer output.

Previously, I built the PCM1704 DAC with resistor in series for each negative power supply. This method is describe in the PCM1704 Japanese version datasheet as shown bellow schematic on Figure.4.

The resistors will act as additional power supply ripple rejection, but the drawback, it makes the LM337 negative regulator power supply that feed into that IC become very hot. This might be the present of oscillation so I remove it and return back to the original design. It is now the same as Figure.3 on the schematic bellow.

In the sound comparison result, I couldn't tell the sound changed by using both method anyway.

The components upgrade list is just like that.

Now I tidy up the casing for this new transformer placement.

This new components upgrade significantly improve power supply regulator stability.

Right now all IC power supply regulators are slightly warm and the analog output are noise free, If compare to before this upgrade, there was a small hum to the speakers if I turn the amplifier volume up to the maximum.

This PCM1704 DAC after this upgrade sound more revealing simply because the background noise seems more quieter. This makes music more pleasant to hear and every harmonic are more revealing than before.

With this good result, this upgrade is worth to spent.

Cheers.

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