PCM1704 DAC Build

I still have several PCM1704 U-J DAC IC taken from the Pioneer unit here, so I think I will use a pair of it to make another DAC again.

As usual, this DAC build will never be the same like my previous built.

Lately I prefer the sound from the non-oversampling DAC and this will be in my first list when making a new DAC. The input will using the SPDIF because this is the only input that I feel more convenience since all my digital source support this input as well. The schematic will be the same like my previous PCM1704 DAC built here which is the same as the schematic on pavouk.org website.

The key difference is only on the analog stages after the current output from PCM1704 DAC.

Let's get started.

First things first, I start to assembly all components in the universal board with size 9 cm by 15 cm. I arrange the most simple and effective components placement that minimize the length of the parts connection points.

This first board is the main board that handle everything in this DAC, from the SPDIF digital receiver using CS8412, then the 32 bit shift register I2S to 24 bit using 5 pieces of 74HCT164 and PCM1704 DAC IC for each channel.

The components around this DAC are quite similar from my previous built. I always using reputable components with the most rationale price for the first build. The film capacitors using Wima, the electrolytic capacitors using Elna Silmic ARS and for the resistors are all Vishay.

I put copper shield to covering the analog stages components. This copper shield is previously taken from the old Marantz CD player. The result is this DAC become so attractive. 

Specifically for the analog stages, I put the Zen IV on it. The schematic and design is published by Nelson Pass on his website at firstwatt.com.

This Zen IV is the update from the original Nelson Pass IV design in his Pass Lab DAC D1 product, which is now only using a pair of 2SK170 and 2SJ74 JFET for each channel.

Then I continue to put the components in the board.

Finished with the DAC main board, now I can continue to build the power supply which is quite straight forward. I using the traditional LM317 and LM337 regulated power supply IC in this build. In my opinion this simple regulator still good to go with it regulator performance and reliability. It is far from the complicated components.

Once I finished with the regulator power supply circuitry, I see a lot of space left in this board, so I put the rectifier and filter capacitors in the same power supply board.

For the power transformer, I using Holden & Fischer toroidal transformer taken from the Kinergetic Research DAC. The secondary output have several voltage and I only using the 22 volt CT for this DAC.

After all connection are done, then I start the initial test for all connection and check the voltage reading on each IC pins.

Especially for the Zen IV circuitry, I set the voltage regulator to 22 volt +/- for each rail voltage. This bellow the recommendation of the original Zen IV in their manual which is require at least 30 volt. Later on I found this is not an issue anyway since the working voltage for this Zen IV can be use as low as 20 volt.

Confirm that all value are set, then it is time to put all components in one nice casing.

I imported this casing directly from China, it is arrived around 3 weeks after I completed the transaction.

The casing is beautiful finished with all material are built from solid aluminum.

I wish I could buy this casing at my local seller, but they don't have any stock left. Since buying directly from China is far easier right now, so I take this opportunity.

Then the last steps are only connecting all input and output cables, then put all IC into the sockets.

This PCM1704 DAC build is now finished.

I put a potentiometer as an output signal volume control just in case I want to connect this DAC directly to a power amplifier. So I don't need another pre-amplifier between them.

This casing design is actually a copy from the Goldmund audio. The left knob is for power turn-on and the right knob is for volume control. The center line is acrylic display which at this moment, I left it blank because I have no idea what kind of display that I will put on it.

The initial test for this PCM1704 DAC is works like a charm. No any issue or whatsoever. Everything works perfect.

This DAC analog output is about 1 volt and it is not loud enough if compare to standard CD player output which around 2 volt. This is exactly the same as Nelson Pass wrote on the Zen IV manual for each 1000 ohm gate resistor will generate 500 mV on each 1 mA current input. So the calculation is correct for 1.2 mA PCM1704 DAC.

I can increase the voltage output anyway, but at this moment I will use as it is first.

This PCM1704 DAC sound signature using the Zen IV as the analog stage is very neutral, just like using a simple resistor for the IV stages except this Zen IV has a voltage gain.

If I compare this DAC to my previous PCM1704 DAC built using a pair of 6DJ8 vacuum tube at the analog stage, they are actually so much different in the sound signature. While the vacuum tube has sound coloration that create more warm sounding, in contrast, the Zen IV using JFET sound more neutral.

I will continue for the sound characteristic detail review on the next post. Since then, I will enjoy this DAC on my audio system first.

Until the next updates.

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