Signalyst DSC-1 DSD DAC


(Andrew Cox) #1

Opening this thread as a blog for my intending build of the Signalyst DSC-1 DAC. This is a DSD only DAC with a USB input via an Amenero module and an unbalanced output (although there is a differential version available, not decided yet). I intend to send it 512 DSD through an NAA on an mR.

The first step will be putting together a parts list. There is both a bare board and a kit available on eBay. This ad for a project kit suggests that 8KO6 resistors are reccomended by Signalyst to replace the 15KO parts.

Would be interested in views about best components to use, whether Susumu and Wima, or any other reccomended brands.

Edit: Fixed the link to the eBay kit.


(Andrew Cox) #2

As usual, I got the first step of the project wrong. It’s not putting together a parts list, it’s working out what design to use and whether it will achieve the intended result (playing 512 DSD through an mR NAA).

A few notes to self (and you !) about things I have discovered on further reading:

  • Firstly, the DSC1 design requires a USB module to receive a signal and a power supply (15v +/- DC, +5v each for mute, left and right);

  • Jussi has released his DSC1 design under a CERN Open Hardware Licence. This is the equivalent of the General Public Licence for software and includes the following:

The CERN–OHL is to hardware what the General Public Licence (GPL) is to software. It defines the conditions under which a licensee will be able to use or modify the licensed material. The concept of ‘open-source hardware’ or ‘open hardware’ is not yet as well known or widespread as the free software or open-source software concept. However, it shares the same principles: anyone should be able to see the source (the design documentation in case of hardware), study it, modify it and share it.

In addition, if modifications are made and distributed, it must be under the same licence conditions – this is the ‘persistent’ nature of the licence, which ensures that the whole community will continue benefiting from improvements, in the sense that everyone will in turn be able to make modifications to these improvements.

  • Jussi is continuing to work on his DSC2, a differential design with balanced outputs, but sfaik has not yet released a differential design;

  • Chinese manufacturers have kits available for purchase on eBay based on the DSC1 design. They are allowed (indeed, encouraged) to build and sell Jussi’s design under the OHL provided that any modifications they make are similarly licensed for others to use.

  • The item I described as a bare board above from shenglongsi appears to be a kit including parts as set out in the list on that page. I haven’t verified that, but that is my (current) interpretation of the intriguing passage in the description:

The delivery of goods to the list: All elements + patch bare board (not install any components on the board, without any pin element), a relay pin, a pin (2 * 10P)

** This product was not finished board or a full kit, without the ability to complete the remaining elements alone procurement and installation of the board friends carefully shot, thank you !! Product features are as follows:

  • It was gratifying to read that my friends would be carefully shot; it just won’t do to have a slapdash approach to these things. In any event that price (USD $35.66 in my browser) does seem awfully good value for the kit;

  • The Mshow kit appears to be identical, perhaps with some upgraded parts. It costs USD $134.90 in my browser. Mshow indicate that they can assemble and test the kit for a further charge, but they have not yet responded to a message I sent on eBay asking how much assembly costs;

  • Both the shenglongsi and Mshow kits (which appear to use the same board) appear to have a modified mute circuit from Jussi’s design. The mute circuit is very important in a DSD DAC as there can be pops and artefacts at full volume when rates change or music starts or stops (or for many other reasons such as holding your mouth the wrong way) and the DAC is supposed to mute all that stuff and only let through the music. (There is a good explanation for what causes such things in the diyAudio thread linked below). Unfortunately the Chinese manufacturers don’t appear to have published details of their modifications as required under the OHL. Anyone in a position to remind them to do that is encouraged to do so;

  • Shenglongsi also sell a kit for a differential version of the DSC1. This is not Jussi’s DSC2 design, but a modified DSC1. Unfortunately the modifications have also not been released under the OHL. The modifications include replacement of the op-amp IV (current to voltage) output stage with transformers. I wonder whether the introduction of hysteresis effects isn’t jumping out of the frying pan into the fire;

  • The DSC1 thread on diyAudio has a wealth of information and experience about building DSD DACs generally and the above kits in particular. One builder found low level noise correlated with low signal levels (-36 dB). This is unlikely to be a problem for modern music but could affect some Classical program material. The differential kit from shenglongsi requires extensive surface mount soldering and some tiny ICs that can be heat damaged. It is not a recommended build for beginners (so I have ruled it out for me). One builder completed the differential kit and found it interesting (after burn in to get rid of the new parts sounds) but lacking slightly in detail. Another is yet to complete it following some construction issues (note to self, avoid this kit);

  • The Amenero USB module does not yet support DSD 512 from ALSA (meaning the mR) and a firmware upgrade is being worked on. This thread at CA is monitoring the situation. This github thread sets out posts between the Amenero developer, Jussi, Gianluca and others as they close in on native 512 DSD support for ALSA in the Amenero firmware.

  • These are the instructions for flashing new firmware to the Amenero USB module.

I’ve ordered the shenglongsi unbalanced kit for USD $35.66 ! Let’s see if it arrives and what it contains.


(Andrew Cox) #3

Order already processed and shipped ! Should arrive early January.


(Daniel Beyer) #4

Andy, keep me informed as I have been thinking about trying this as well.


#5

It doesn’t use the off selves manufacturers DACs but a ‘discrete’. Looks like each J-K flip-flop chips output to set of precision matched resistors probably convert PDM(Pulse Density Modulation) to analog signals. I guessed there’s a FPGA chip that does noise shaping algorithm before hand and gentle LPF in the analog stage? Looks interesting though, any reason why it only does DSD128 and above and not DSD64 natively?


(Andrew Cox) #6

The only reason I haven’t responded Guy, is because I don’t know. If I find out I’ll post back here.

Santa bought a soldering station with PCB sized alligator clamps and a third hand, so time to start practising.


(Koen Lensink) #7

I have been researching this dac too, so I will follow your progress with great interest.

In a few weeks I will start with the project, I have chosen to order a batch of Jussi/Signalyst designed pcb’s through allpcb.com(minimum is 5 pieces, so I will have some spare).
The reason I didn’t order the Chinese kit, is that to my understanding Jussi made some changes over time to the pcb and the Chinese kit is still version 1.

On DiyAudio.com i have found this DSC1 BOM but haven’t had the time to check if it still correct for current pcb layout. At mouser the components for the dac board only are about €80 if you use this BOM.

To complete your list of available DSC1 boards for sale online I have found this DSC1 + PSU TaoBao but again haven’t had the time to look for changes/differences with the current design. It is about €15 for boards only.


(Koen Lensink) #8

first, I have to give Mcluxun on diyaudio credits for the bom I posted above.

second, have you already thought about power supply’s @andybob?

It seems that a couple of people have changed the supplied resistors to Susumu RG 0.1% 8.06k SMD resistors with good results, to answer your question regarding components.


(Andrew Cox) #9

Thanks koen, all good info.

Call me crazy, but I was toying with the idea of two UltraCapacitor LPS-1s, one for each 5v channel, and a separate Chinese lps for the 5v mute and 15v lines.


(Koen Lensink) #10

crazy don’t know but expensive yes lol.

maybe you should look at the jlsounds usb to i2s as it has isolation on board and dedicated power for the board(which you can power with a third lps-1:grin:)
looking forward to your progress.


(Andrew Cox) #11

I’ll certainly look at it. So far as I can tell the firmware on the Amenero is still not playing DSD 512 from ALSA.


(Koen Lensink) #12

same with jlsounds board, max 256(except for this board its even for windows max 256)


(Rene Bouwmeester) #13

Guys – I’ll be watching this thread like a hawk for updates, but for now I am glad that I am not either one of you. :wink:


(Koen Lensink) #14

Do you mind if I ventilate some of the things I’m tinkering with on your thread @andybob?


(Andrew Cox) #15

I’d suggest keeping this thread for any DSC-1 projects (happy to have others contribute), and new threads for other non-DSC-1 projects.


(Koen Lensink) #16

fair enough :stuck_out_tongue_winking_eye:

instead of an usb module like amanero or jlsounds a bbb with botic driver could possible be used. that way you could eliminate usb and use ethernet input.

and have DSD512…


(Andrew Cox) #17

Very interesting. I happen to have a spare BBB floating around.

This would effectively be substituting the BBB in place of the microRendu -Amenero. It might be a simpler solution, but the implementation in the mR is really good.

It’s going to take a while to build (kit hasn’t arrived yet), so I’ll keep monitoring developments with Amenero and ALSA.


(Andrew Cox) #18

Kit arrived and appears to consist of the surface mount components only, with a resistor, IC and the l2s pins as well. Remaining through hole components ( and possibly some others, haven’t exhaustively checked) have to be separately sourced.

One of the pins on the through hole IC was broken in transit (padded envelope only) so that will need to be replaced.

Have become distracted from the necessary checking by the minuscule scale of everything. My soldering skills would not be up to it, especially with the ICs.

So after a bit of investigation I found this guide. One of the virtues of the reflow oven technique is that you don’t have to be spot on with the application of the solder paste. The surface tension of the molten solder pulls it onto the pads.

Of course a stencil would be the easiest way to apply solder paste, but it might take longer to make one than to do it by hand with a syringe.

So looks like a toaster oven and thermocouple are going to be useful.

Now to check the parts.


(Koen Lensink) #19

nice to hear you received your kit!
looking forward to some pictures:grin:


(Andrew Cox) #20

Closer inspection revealed that the through hole IC leg was bent flush with the body, not snapped off. So that’s good.

Trying to find a BOM for this board so I can identify the missing parts. The BOM provided with the kit is for surface mount parts only. The BOM linked above from DIYAudio (thanks Koen) appears to include PSU and may not be for this board. Will check and report back. I’ll also make enquiries of the chap who sold a complete kit.