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

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modwright

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.

Thanks!

Dan

woodsyi

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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?

modwright

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.

Dan

modwright

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.

Thanks,

Dan Wright

PicknPop

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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.

modwright

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!

Dan

NavyDoc

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This looks very promising, I am putting together a digital only system and need a great (but not horribly expensive) DAC/Preamp to feed my McIntosh amp.

Will this mod keep - and hopefully improve - the preamp function?

Thanks

modwright

The 'mod' is actually a box that would be added to the Pro-Ject S2 DAC/preamp.  It is too small inside to do anything to it, by itself.  The mod box would add a tube follower and provide a very clean 5VDC supply for the S2 DAC/Preamp as well as another S2 product with the same micro USB connector and 5V supply needs.

Because of this, the preamp function of the unit would not be limited in any way of course.

Dan

NavyDoc

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I re-read the thread. Looks like a good project to provide a high quality sound from a pretty low cost DAC.

modwright

Absolutely.  Once I get freed up from a few things that I am finalizing, I will build a prototype and send it out for key customers to evaluate and give me feedback (that means you D. Meyers!).

Thanks,

Dan

modwright

I will have a concept piece of our Unity Gain Tube analog stage and power supply for the Pro-Ject S2 DAC.

While this will provide power for the Pro-Ject S2 DAC, it will also provide a superior power supply to the Chord MoJo DAC and any other product that accepts a 5VDC supply via micro USB connector.

The Unity Gain Tube Analog stage will use (2)6dj8/6922/7308 tubes and can be used as a tube analog stage upgrade for ANY digital source.  Simply connect the analog outs from your digital source to the analog inputs of our tube stage. The tube stage then connects to preamp, amp or integrated.

We are showing with Studio Electric this year at RMAF.

I hope to see you there!

Dan

PicknPop

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This feeding the new Elac Argo would probably be a nice small room system for just streaming Tidal and the like.   :D

modwright

Great idea, thanks!

Dan

modwright

OK, so I have a prototype for the Pro-Ject DAC Unity Gain Tube Analog Stage and linear 5V PS 'Mod Box' for lack of a better name yet!

First of all, the Pro-Ject DAC itself is actually not altered in any way! Its stock supply is a wall wart with micro USB connector, 5VDC.

The 'Mod Box' contains a tightly regulated, completely linear 5V DC supply, rated for 2A current.
The 'Mod Box' contains a 6922 based Unity Gain Tube Analog stage and RCA inputs and outputs.

The 'Mod Box' can be used between ANY digital source and preamp/amp.  It has no volume control and is Unity Gain, i.e. no gain added.  If offers a WIDE frequency response from 20Hz - 100Khz flat. It also measures less than .02% THD. So, it is not adding distortion, nor is it limiting frequency response. It does however offer an EXTREMELY low output impedance, allowing for excellent matching with any preamp/amp of even the lowest input impedance and will drive any cable easily.

I have always felt that tubes add 'Magic' to the music, for lack of a better word. Many attribute it to even order distortion, which is also true. Tubes impart their own sonic character to the signal that IS additive and in my mind makes things sound more natural and musical.

Many reading this will say that we are simply adding 'TONS' of tube distortion (note the < .02" THD of the device itself) and that we are adding a 'band-pass' box, that is lobbing off the highs and lows to accentuate the mid-range (note the BW of 20Hz - 100Kz flat!).

Today's listening tests were done by myself, Kristin and Julia.  Kristin and Julia work for ModWright and while not Audiophiles, both LOVE music! Julia attends a lot of live music and both ladies are young and have excellent hearing. I would often ask my wife to listen in the early years, because women, who are not audiophiles in particular, simply have great hearing and will give their impressions, free of 'audiophile' adjectives and expectations.

The digital filter settings were more subtle and both Julia and Kristin found a couple that they preferred, the differences were not huge. I personally found that some of the digital filters make the music more aggressive while others are more musical.  Your tastes will vary here.

I played a track for both Julia and Kristin on the Oppo and then on the Pro-Ject with the Mod Box in line. They both agreed that it was very close. Julia said that if she had to pick between the two, she preferred the 205 with tube mods. We all pretty much felt that in many ways, the Oppo had a slight edge, but we also all agreed that the difference was SMALL! Considering the cost difference: $~$3800 for 205 with mods and ~$1K for Pro-Ject DAC and Mod Box, this speaks volumes.

When I took the Mod Box out of the loop and just played the Pro-Ject DAC by itself compared to the 205, both Kristin and Julia said that the DAC sounded thin and 2-dimensional compared to the modiifed 205. Kristin said it sounded more like her car radio and Julia said that it just sounded very thin. Keep in mind, there are no mods to the Pro-Ject DAC, were are simply adding the Unity Gain Tube analog stage to the stock outputs of the DAC.

Lastly, keep in mind that both Pro-Ject S2 DAC and Oppo 205 are both feeding a SWL 9.0 Anniversary Edition tube preamp, into a KWA 150SE SS amp. I mention this because many people ask, "why not just add a tube preamp?".

So in short, based on my listening and that of my employees today, I am very pleased with the level of performance that we are able to achieve with the Pro-Ject DAC and 'Mod Box' with Unity Gain Tube Analog stage.

The strengths of the Pro-Ject DAC are:
Extreme flexibility with regards to formats (DSD, MQA, all hi-rez inputs) and multiple selectable digital filters.
It also acts as a preamp allowing for direct connection to the amp.
It has a built in headphone amp that drove even my HE1000's well! They would have liked a bit more power, but the S2 DAC will drive most modern headphones well!
It is inexpensive! It can be had for $350-$400 new!


The 'Mod Box' offers both upgraded power supply - 5VDC - and Unity Gain Tube Analog stage, which elevate its performance to an entirely different level, making it a VERY high value solution for DAC, HP amp and preamp!

I am going to do further experimentation with the 'Mod Box' - and find a better name! - including tube-rectification and pass through RCA to allow for comparison of the stock source with and without the Unity Gain Tube Analog stage. I may make allowances for different types of tubes also. I like the 6dj8 family very much however for its low plate impedance, high transconductance and ultimately its sound! I will test with 6CG7 at least, as this tube has EXACTLY the same tube curves and sound of the 6SN7.

Please let me know if you are interested in this and if so, what options you would like to see.  I plan for this to be a product that can be used with any number of different digital sources, in-line with their RCA outs. Additionally, I may make the power supply option modular such that it could accommodate different power supply voltages and connections. Certainly we could provide 5V, 9V, 12V DC and could offer different connectors to suit a group of different products. We could also simply have a USBA connector on the back and make umbilicals that were terminated with the connector suited to different products.

Thanks and I look forward to your feedback!

Dan

witchdoctor

I used to own a tube buffer from Musical Fidelity that you could place in the analog signal path or in the tape loop of your pre-amp.
I like that you are making this unit interchangeable not dependent on any one dac.
I changed buffers recently because I wanted one with a HDMI port and found one that really adds value in my system for 2 channel music. Do you think it would be possible to add an HDMI port to your new product in addition to RCA jacks? thanks

modwright

HDMI is interesting. I always assumed that HDMI carried digital signal content only?  How does the buffer you are referring to work via HDMI? Is there a DAC in the buffer also?

Thanks,

Dan

witchdoctor

The buffer I am using is not a DAC, it "remasters" the signal using technology developed by Aftermaster Studios in LA:

http://aftermaster.com/studios/

I use the buffer strictly for 2 channel music, it will not pass a dolby/dts signal. I have 2 HDMI ports on my blue ray player so I can switch when listening to movies or music. Here is a review:

https://www.youtube.com/watch?v=bOCRyrPRIdM

It costs less than $200 and comes with a 30 day money back. They are marketing it as a device to improve TV audio (which it does) but I use it strictly for music. I'll bet they would be happy to license the chip to you if you like it :).


modwright

I wanted to share the results of listening tests that we did here, comparing a fully modified Oppo UDP-205 with our tube mods, to a stock Pro-Ject S2 DSD/MQA DAC feeding our Unity Gain Tube analog stage, with linear 5V PS for the Pro-Ject DAC.

With two of my employees, Julia and Kristin, ladies with good ears and no audiophile prejudice.  Both ladies enjoy music and Julia goes to a lot of live music and knows what it should sound like.

Both agreed they were very close! Both also picked the Oppo in a blind test, but agreed that the differences were small.

Interestingly enough, they both agreed that the stock Pro-Ject was nowhere close, but once I added the Unity Gain Tube Analog stage, they became very close.

The fact that the Oppo mod edged the Pro-Ject DAC out should also not surprise, when we consider the cost difference of about $1K for the Pro-Ject DAC and mod, vs. $3800+ for the Oppo 205 with mods.

I believe that the Pro-Ject DAC with the Unity Gain tube analog stage represents a very good value!  The same Unity Gain tube analog stage could also be used with any digital source, that is good, but benefits from the body, impedance matching and tube character that the mod circuit adds.  For the record, THD is < .02% and BW is flat to 100Khz. So, the tube stage is not adding distortion or reducing bandwidth to make digital sound better.

Your comments and feedback are welcome.



SFDude

I might be in one of those "hazy" states of mind but, the S2 analog outs would go into the Unity Gain Tube stage, then out to a preamp/amp?

-dave

modwright

Yes, to preamp or amp.  Because the S2 DAC has a built in preamp, it could go direct to an amp, using the preamp stage in the S2 DAC. Or even directly to powered speakers!

Thanks,

Dan