Pro-Ject Pre Box S2 Digital preamp and DSD DAC witht MQA - Mods!

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Pro-Ject Pre Box S2 Digitial preamp and DSD DAC with MQA!

OK, so I have a unit in house. I have listened to this VERY small and capable DAC and am very impressed! Retail is $400, but it can be had for $350 most places.

The design uses the latest set of SABRE 32-bit DAC, filter and headphone chipset, featuring multiple digital filters, user selectable.
I have used it via Coax and USB input with DSD files and color me impressed! Are there better DACs? Yes, but for a LOT more money!

I have opened it up and even knowing that it was small inside, I was STILL amazed at HOW much they have packed into this 4"x4"x1.4" enclosure and what they have achieved!

I also listened with headphones via HiFi Man HE1000's and Lazuli Reference cable and the sound was also very good! The HP amp is not High Power, but will drive most moderately efficient modern headphones and certainly ANY IEMs!

"So Dan, how are you going to mod this LITTLE DAC?"  Well, the answer, is that I am not actually going to do any work TO the DAC itself, but rather plan to build an external box to provide a MUCH cleaner and better DC supply and an improved analog stage, possibly unity gain, to add some body to the sound. It is VERY resolving, but perhaps a bit forward. I believe that a cleaner supply and the following analog stage I have in mind will treat this nicely.

I am envisioning a box that will be similar in size to the DAC, or possibly large enough for the Pro-Ject box to sit on top of the external box. Either way, the total combination will still have a small footprint.

I have an idea that I am going to pursue and we will see how it goes.

Please post here with levels of interest, ideas, suggestions and what you are looking for in terms of a total solution.  I know that some have asked about balanced XLR outs and that is also possible.




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So AC in to the external box, signal in to Project box and signal out from the external box with one or two umbilical between the two boxes?


AC into external box, DC into Project box.
Audio signal from Project box to external box, audio out from audio box.

Umbilical will just be a very short cable with the appropriate micro-usb connector at the DAC.
Signal connections between boxes will just be short RCA cables.



I have become quite enamored with the Project S2 DAC/preamp! Retail is $400 ($350 street price) and it features SABRE Reference DACs, Digital filter, volume control and HP amp out.

It is physically TINY at 4"x4"x1.4".  The stock power supply is a 5VDC wall wart and I have measured it...noisy!
The DAC puts out 2Vrms and features full DSD as well as MQA playback! It also allows for a range of user adjustable digital filters!

My plan is to provide a separate box to include a VERY GOOD 5V DC supply and tube output stage.

The S2 will actually  not be touched at all.  Because it is so small inside, I have decided to simply provided it a clean external power supply and a tube follower circuit to add some missing body and weight.

The intent is to build a small box that is sized to allow for two S2 family devices to sit on top. The box will have at least two 5V DC supplies and RCA analog inputs and outputs for the tube follower circuit. The mod box can be used simply as a supply for the S2 devices, simply as a tube follower for the S2 devices or other digital source. Or, as it was intended is to provide both clean 5VDC supply and tube follower for the S2 DAC.

The goal is to provide a solution, including the S2 DAC for < $1K.

The mod box will include the tube supply, tube circuit and DAC supplies.

I am listening to the S2 DAC right now fed DSD files, into the tube buffer, directly into a 150SE to Maggie 1.7i's in my office and it sounds CRAZY GOOD!  I have not even evaluated it with the upgraded supply yet and I expect that will REALLY improve things!  I have the circuit designed and tested, but I need to purchase a USB - USB micro cable.

Because the S2 devices have a Micro USB input for power, I intend to put a pair of standard USB power outs on the back of the mod box and an additional USB power out on the front, for charging a phone or powering any other USB device, of appropriate current rating.

I see this being an ideal setup for a simple audio system, desktop system, office, den, etc.

Please let me know the level of interest and I will share more as I get further along.


Dan Wright


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I agree that it sounds like an ideal source for a desktop solution.  Have you used the headphone amp yet?  If so, how is it?  Not needing a separate dedicated headphone amp (unless you are really picky or spoiled  :wink:) would help a lot with system matching.


I did hook it up to a pair of HiFi Man HE1000's and it was surprisingly good! It drove them well, but WOULD run out of power if pushed. For all but the more power hungry headphones, I would say it is great!

I tested it with the tube follower in place today and then without. The tube follower circuit DEFINITELY adds body weight and a much bigger soundstage that is very welcome in my opinion.  When I bypassed the tubes stage, I found that while very detailed and resolving, the presentation was a bit bright and forward.

I measured the tube follower stage today, at < .05% THD at 2Vrms in and frequency response of Flat from 20Hz - 200Khz where it was about 1dB down! So no, this is not a distortion adding or BW limiting tube follower stage!

I have the regulated, super clean 5VDC supply tested and ready to implement in place of the stock wall wart supply, which produces over 200mV of noise at the input to the DAC!  I expect great things once our OWN 5VDC linear supply is introduced!