[Wayne1]

A couple of years ago I started gathering parts to build a DAC.

There have been so many changes in digital technology, it did not seem wise to invest in a single board DAC just to find out it would be obsolete is 6 months.

I decided to build it as a series of modules. I wanted to use very good power supply designs. Most digital sections run off of 5 volts DC and maybe some might need 3.3 volts. I decided to use the Salas Reflektor Shunt regulators for the digital section.

I also wanted separate USB input and separate DAC with a separate analog section. That way if something new comes out, I should be able to change just a single section without getting rid of the entire unit.

The project did not really kick off untill I had a chance to try out ROON and a Raspberry Pi with Kali reclocker and Piano DAC.
I saw what I think the future of home digital audio is going to.

I put away my Logitech Touch, bought an Odroid C2 and subscribed to ROON

I finally got the project onto my bench and ended up with this:



I built is as a proof of concept in an old chassis I had. Lot of holes drilled in it from previous uses.



The digital section starts off with a pair of R core transformers. Each one feed into a Salas Flexy board with a CRC snubber and soft recovery diodes to reduce transformer secondary ringing. From there I have a Jensen four pole cap for some isolation. That is part of the CRC citcuit feeding the Salas Reflektor Shunt regulators.



One of the regulators feeds the JL Sounds I2SoverUSB board:
"I2SoverUSB uses reclock to reduce jitter significantly. I2S, S/PDIF outputs, oscillators and reclock are galvanically isolated from XMOS processor and USB ground. The galvanic isolation eliminates common noise originated by the computer. There is an galvanically isolated external master clock input. The board is equipped with NDK NZ2520SD low jitter oscillators 45.158MHz and 49.152MHz. LP5900 ultra-low noise linear voltage regulators are used."

The other regulator feed a JL Sounds AK4490 DAC boardWhich has Native DSD Support
Supports 2.8MHz (64fs), 5.6MHz (126fs) and 11.2MHz (256fs) DSD
According to AKM, the volume control module and the delta-sigma modulator can be bypassed for DSD resulting in “direct” DSD rendering. The AK4490 contains an integrated low-pass filter specifically for DSD data. It also has 5 separate digital filters



For the analog section of this proof of concept buils I used the JL Sounds LME49710 filter board but with a Sparkos Lab discreet op amp



The analog section gets it's power from a separate toroidal transformer going into a pair of Salas Flexy boards with a different value CRC snubber and soft recovery diodes along with Jensen four pole caps. The regulators are Salas Simple Shunt Low Voltage (Back in Black)






The entire package sounds VERY good. I have no trouble upsampling all my files to DSD256 through ROON and sending them through the Odroid to the DAC. No dropout or glitches.

As time moves on, I  hope to be able to move the Odroid into the same case as the DAC and run I2S direct to the DAC getting rid of the USB section.

Eventually, I hope to build a tube analog section for it.

Cheers,
Wayne

[brj]

Very nice, Wayne!  Flexible build, too.  I remember reading about the Salas boards when they came out, but had forgotten about them... had you used them before?

You might want to try the demo version of HQPlayer (paired with Roon as the front end to hide the somewhat painful HQP user interface) and see how you like it's filters compared to Roon, especially going all the way to DSD since the AK4490 supports it natively.  It looks like that Odroid C2 could handle the processing, though perhaps not with the most aggressive filters.

[Wayne1]

Hello Brian. Thank you for the comments and suggestions.

This is the first project I have used the Salas boards in.

One of the goals for the power supplies was to use the CRC snubber along with the Jensen four pole caps.

Salas recently came out with a newer, smaller design for his shunt regulator that split the board into two pieces. The rectifier section had the CRC snubber and was designed to use Mundorf four pole caps. I bought those boards to use in this project. The layout of the Jensen caps and the Mundorf are slightly different so I had to do a bit of improvising to get the Jensen to fit.

I chose the Salas based on part to an article in Linear Audio comparing multiple regulator designs https://linearaudio.net/sites/linearaudio.net/files/V4%20JW%20F7.pdf That chart shows the very low noise the regulator is capable of. I also liked the fact it is a thru hole design. The boards are very well made and seem like they are able to stand up to repeated soldering and desoldering.

[WC]

Looks like a good build. So why did you use the odroid instead of the Raspberry pi? Was it due to issues with the raspberry pi usb? I am building a DAC/Streamer/preamp/DSP unit in a single box and I have 4 off the Salas shunt boards to assemble.

[Wayne1]

Thanks for your comments on the DAC build.

I used the Odroid C-2 because it uses a faster processor, has more ram, has gigabit ethernet and does not have the conflicts that the Raspberry Pi does between ethernet and USB.

As I am using ROON for software and upsampling, the Odroid is a far better match.

I am using DietPi for OS which does have a specific build for RoonBridge for Odroid.

If you plan on using some other software, the Raspberry Pi may be fine for you.

There is an isolator board that is built for the Odroid that will should allow me to connect the Odroid to the DAC board through I2S.