My "Secret" DAC Reveal

Few month ago, I post my DAC project called "the secret" DAC and the first project is post in here.

The term of "secret" is actually the components are hidden inside the copper shield, so it cannot be seen from the outside. It is not only for aesthetic layout but the copper shield helps the DAC inside to immune to any noise interfere.

The second project is post in here. This is a fully remake DAC, using the same chassis but the components inside are all changed. This is because most of my friends that become the reviewer of this DAC doesn't really like the sound from the first one.

The second version of this DAC is become a better sounding DAC than the first one and I think I better reveal what inside those secret DAC.

I start from the first one.

This DAC module is actually using parallels PCM56 P-K, 2 DAC IC per channel. So in total there are 4 IC PCM56 P-K inside the cooper shield.

The receiver is using CS8412 for the SPDIF digital input.

It is configure in non-oversampling and using a resistor per channel for the passive IV converter.

The resistor value is 220 ohm, with parallels PCM56 P-K, the I out is 2 mA or about 0.4 volt after the conversion.

The preamp section is act as headphone amplifier. It is using OPA1622 op-amp. This is the modern op-amp from TI/Burr-brown that deliver high current output and intended to drive low impedance load such as headphone. This preamp/ headphone amplifier circuit is a basic non-inverting amplifier with the 5 times of gain.

As my expectation, mostly the sound from the non-oversampling DAC will more focus on the midrange and more center. They are hardly to become an expansive sound-stage. More over, the parallels DAC will also boost the mid-range presentation to become more forward. Sometimes this makes the music weak in the micro details presentation.

The passive IV using resistor with op-amp gain stage also contributing to the slower sound and narrow dynamic sound. It is like a mellow and boring sound.

Although during the review, one of my friend are like it, but I made a change to become the second "secret" DAC anyway.

If you see the photo above, will you notice what DAC is using on that circuit?

This is not new since I made this DAC several times.

This second project of the "secret" DAC is using PCM63 DAC IC.

The same digital receiver using CS8412 but the input is now using optical Toslink.

The configuration is in over-sampling using SM5813APT digital filter.

The IV stages and the LPF stages are using op-amps deliver the signal output to 3 volt.

For the pre-amp/ headphone amplifier section is the same as previous circuitry built using OPA1622 op-amp. The only difference is on the gain level which is now reduce to 3 times of gain, so the total output is maintain at 9 volt at the maximum volume level.

No wonder everyone happy with the sound quality from this DAC. It is PCM63 anyway.

The PCM63 DAC is more modern than the PCM56. This PCM63 become everyone favorite DAC simply because of the dynamic, the detail, and the sound-stage deliver from this DAC are very good. Even when it compete with today modern DAC, when the PCM63 DAC are designed carefully, it will blown every audiophile away.

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