mdXS - the source is everything

Hi there,
Here are the doings and wrong doings of a group of complete laymen in Vienna trying to built good digital audio players. We have put together a little site with our findings.

Our main goal is to improve the sound quality by

  1. going thru a bunch of off the shelf DACs + trying to find the best available
  2. built/adding the best power supplies for as many stages in the circuit as accessible (following what we see in Naim Audio equipment since the 70’)

Comments are welcomed here.

One of the final unit see below.

Straight to the questions:

  1. Is clean power the most effective way to upgrade the SQ according to you?
  2. What software were you using for testing?
  3. In general what would you recommend in order to get most of Pi and Pidac?

Thanks and looking forward since I’m going that way as well:)

  1. Of the shelf hardware is limited (we like the PCM5122 chip), we trust Volumio (we are just able to put an image on a SD) so all we can do is to create a perfect environment for the given parts. Looking at high end products like Naim Audio one obvious thing they do up the chain is adding designated power. So that’s what we tried and we like the result.
  2. We trust our ears (4 pairs).
  3. It’s a budget question. The SuperTeddyReg costs as much as the DAC. We don’t want to miss it for the DACs analog circuit (best alternative would be the tracking preregulator). For the other regulators single stages are a good start. If you don’t want to get too much into soldering you can get them without the LED reference on ebay. The PSU section and the star ground layout should not be ignored.

Very interessting !
What is the target of the USB hack ?
Could you show the back of your board - or a scheme ?

The USB port deals with the wifi dongle & a power hungry hard drive. So separating this from the CPU won’t hurt.

Separating USB from main PSU is a very good practice…
As for the rest, great work! Love it!

Looks very nice! I’m so jaleous of people who can do this stuff. I’m better with software :wink:.

Question. You are using a DAC. If there is only a i2s => spdif out, is there any value in powering that one trough a separate PSU/decoupled from RPi?

AK4399 works and puts all the other DACs in the shadow despite the fact that you need an USB to I2S board.

For a project description go here:

You can use the player software as described or you can use Volumio.

The reference equipment used are the Linn streamers and the Linn software is used to control the player.

You can also use the dual AK4399 which is slightly but noticeably better.

The only two drawbacks are:

  1. you need an USB 2 I2S board
  2. you need a dual voltage transformer

Well, we get nervous when looking at a command line.
A good audio player needs multiple talents - a trust in one’s ears to make decisions, hardware and software skills. We partly cover 1 & 2 and want to try to share our findings plainly.

Obviously the quality of the regulator for the DAC’s analog section had the most noticeable effect. We did test regulators for the three digital sections (USB, CPU, DAC) ranging from one cell phone charger to 3 SuperTeddyRegs. Here the difference is more subtil. ± we settled for the 3 cheap single regulators. Any power demand (or fluctuation of such) propagates thru the entire system so we want to separate as much as possible. Looking at a possible reference (Naim NDX) one can see already plenty of designated regulators. This is only a mid range streamer in it’s basic config. - the knob on the upper left perimeter allows you to add 6 external regulators to the circuits.

That might be because of it’s multiple onboard PSUs and that’s what we are talking about. Building a dual DAC system (that’s what you can see in the Naim DAC - again with lots of designated regulators which we use as our reference) would be great but we totally miss software skills for that.
Thanks for your website, one of us is already interested in recreating such a player. We don’t want to waste the AK4399. What’s about an ODROID C1+ with its i2s MKLC. Maybe one could spare the USB interface then.

Sorry for the OT guys… guussie I see you know quite well Squeeze lite, what about creating a plugin for Volumio2 ?

That’s an interesting idea. I will investigate the data. It seems to work with their own Hifi Shield.

I won’t have time to try this out until well into next year, so I would be interested to know in case you make progress with this.

The sound of the AK4399 does not only seem to be due to the PSU’s. It’s a very high end chip. I have also tried the dual AK4399 board and it improves on the single board. But the board sees to be faulty and one channel fails regularly. I have also had a lot of problems with the Chinese supplier.

I included Squeeze lite in order to add Tidal, Qobuz and other services support to Pete’s Java mediaplayer because a friend was asking for it. I don’t really use it myself and the integration works but is not really user friendly, so it would need a lot of work both on the server side as well as on the player and the Control side.

I don’t have the programming skills to develop an integration with Volumio2, nor do I have the time available for the moment, sorry about that.

Capedory, do you have a BOM and circuit diagram to your latest build the X8 s I’ve just got the IQ DAC and I’d like to try it out.

Hello guussie, did you investigate odroid master clock. I bought a ak4495 board and i would like to use it without the usb board.

Enviado do meu HUAWEI P2-6011 através de Tapatalk

Hello smallangryboy,
do you want to rebuild the copperplate or just make a nice sounding dac in a box?

We did not produce a kit or description so far, but it all starts with bending away (or cutting) all power supplying und ground pins of the 40 pin connector of the pi. (bending away makes a gap of about 1mm which is not a problem, you just have to do the spacing between pi and dac right)

And then at least support the pi +5v, the dac digital +3v3 and the dac analog +5v with a “better power supply” and please leave the switching handy charger power supply away. Don’t forget that the pi and the dac will also need ground, and the leads should meet at one point (star ground).
“Better power supply” is the key to better sound and it starts with a good transformer, rectifier, crc cap array and power regulators using lm317 or even a superteddyreg for the analog side of the dac.

Look at the circuit of the “acoustica 5v LED” lm317 reg on our site for a simple and good reg: … regulators

We sometimes leave a lot of stuff away, such as the diodes on the original Texas Instruments proposal for the lm317 or the in or out caps, but we can not guarantee for proper and safe function in different than our setups. We have lots of links to people who have something to say about these things on our site.

All in all these improvements of the pi-dac combo are not really complicated, and if you are really keen to build something we’ll support you.

Have a nice day and sorry for answering late - haven’t been here for a while…

Hi everyone, an update from our mdXS project: X-7 series mark II - our new reference!
(I’m selling my Naim DAC - it’s still a tiny bit better at very low frequencies but it’s missing something essential - it’s not a source)

So by now we have a volumio/raspberry/iqaudio music player with 5 designated power supplies - e.g. one 3V3 superteddyreg directly to the PCM chip’s AVDD pin 8 analog power (I removed the IQaudIO DAC’s on board LDO). Soon I will add another superteddyreg for the DAC’s digital section (we visited Teddy Pardo in Tel Aviv and were listening to some amazing electronics - his DAC has more that 10 regs!).
Also a standard implementation by now is a CRC configuration (e.g. 2 caps with a 2 ohm @ 3W resistor in between) at the PSU - simple, cheap but effective, it reduces the ripple dramatically before it even gets to the regulators.
PS: Hi Michelangelo, thanks for volumio 2 - the ui response and steady connectivity is great! Again, whenever you want to visit Vienna, be my guest.

Hi !

i just have seen your website and as Naim enthousiast i really would like to build the same construction you did !

i have a pi 2 (might buy a pi 3 for that), an hifiberry dac + Pro which now works with volumio 2 .

do you have a complete list of required elements and a tuto for that ?

thanks a lot !

Hi troubadour,
I’m going to put together a resource page
for the “naim style shoe box” mdxs over the holidays.
My next one will have the hifiberry DAC+ Pro as well. I will not hesitate to add a separate power regulator to the clocks!!
So far I have some components listed + there is a sketchup 3D model attached. Wiring diagrams will follow…
The pi + the usb need a lot of power - single LM317 will do but a tracking pre-reg ist not much more work.
The DACs digital part (3V3 for chip and clocks) seem to be critical - for us a minimum requ. is a single LM317 + the VBR filter (I will test the dismissed TPS7A4700 for that as well)
We always stick to the TeddyReg for the DACs 5V AVDD (best sound IOO).
PS: Pi 3’s WiFi might have a weak performance inside the metal case. I use a 2 with an edimax USB dongle

Hi !

Many thanks for your answer and the weblink!

i see you prefer having a usb HDD inside your box. Why not using LAN or Wireless LAN to connect to a NAS ?
do you find it better with a usb HDD ?

how about native DSD support ? Are you investigating on it ? by adding a card or something else ?

have a nice sunday!