Pro-Ject Pre Box S2 Digital: MQA HW decoding at reasonable cost

[mansr]

I believe, based on PCB photos, that the Mytek Brooklyn routes all inputs through an XMOS processor which is powerful enough to run the MQA decoder. Some other DACs, and I would guess this includes the S2, use an XMOS processor on the USB input but route S/PDIF through an I2S formatter and then directly to the DAC chip. Such a configuration would make MQA decoding of other inputs than USB impossible. Does anyone have high-resolution photos of the S2 internals?

[rickca]

2 minutes ago, mansr said:

I believe, based on PCB photos, that the Mytek Brooklyn routes all inputs through an XMOS processor which is powerful enough to run the MQA decoder. Some other DACs, and I would guess this includes the S2, use an XMOS processor on the USB input but route S/PDIF through an I2S formatter and then directly to the DAC chip. Such a configuration would make MQA decoding of other inputs than USB impossible. Does anyone have high-resolution photos of the S2 internals?

Yeah, this is exactly what I had in mind when I suggested that SPDIF needs a different implementation of the same decoder used with USB.

[left channel]

11 minutes ago, mansr said:

I believe, based on PCB photos, that the Mytek Brooklyn routes all inputs through an XMOS processor which is powerful enough to run the MQA decoder. Some other DACs, and I would guess this includes the S2, use an XMOS processor on the USB input but route S/PDIF through an I2S formatter and then directly to the DAC chip. Such a configuration would make MQA decoding of other inputs than USB impossible. Does anyone have high-resolution photos of the S2 internals?

 

The lead developer has posted exactly that: S/PDIF is not decoded via the XMOS, so a separate S/PDIF decoder would have been necessary but did not fit, and also caused both technical and pricing problems. (On the other hand, he says they are working on a matching streamer. I wonder if they can do the decoding on that end.) 

 

Anyway, comparing the S2 to Mytek products is putting it in "the wrong ballpark", as we say. It compares very well against SMSL products and other sub-$500 boxes that fit in the palm of your hand.

[mansr]

1 minute ago, left channel said:

The lead developer has posted exactly that: S/PDIF is not decoded via the XMOS, so a separate S/PDIF decoder would have been necessary but did not fit, and also caused both technical and pricing problems. (On the other hand, he says they are working on a matching streamer. I wonder if they can do the decoding on that end.) 

 

Anyway, comparing the S2 to Mytek products is putting it in "the wrong ballpark", as we say. It compares very well against SMSL products and other sub-$500 boxes that fit in the palm of your hand.

I didn't mean to criticise the S2. I just wanted to make it clear that decoding MQA carried over S/PDIF isn't inherently different from any other input. The Mytek already had, for other reasons, a DSP in the common signal path, and this allowed to them to easily add MQA decoding for all inputs.

[arcman]

1 hour ago, left channel said:

 

The lead developer has posted exactly that: S/PDIF is not decoded via the XMOS, so a separate S/PDIF decoder would have been necessary but did not fit, and also caused both technical and pricing problems. (On the other hand, he says they are working on a matching streamer. I wonder if they can do the decoding on that end.) 

 

Anyway, comparing the S2 to Mytek products is putting it in "the wrong ballpark", as we say. It compares very well against SMSL products and other sub-$500 boxes that fit in the palm of your hand.

I don't think anyone is comparing a $300 dac with a $1900 one. My deal is, Much like DSD, Pro-ject somewhere should be saying MQA over usb or MQA not available over Tolink/coax. Most would assume, since the Myteks decode MQA over NON usb inputs that the S2 would do the same. Even all the back and forth with John over on Pinkfish. John could have straight out said (unless he does not know himself) that MQA ONLY works over USB. Especially, aftere I specifically asked him

[arcman]

I got my response from John "

I can only guess that it slipped the manual writers attention - also that the almost all users will use MQA via Tidal / Roon etc. which will be USB sources.

SPDIF is really a sub optimal audio interface - if you have the choice then Async. USB is the preferred option."

 

So hopefully all literature gets updated

[left channel]

@arcman John was hired to design it, but it's not actually his product. Nor is he a support person who is paid to give his full attention to us, be a good listener, and make use of a database of email/post templates to use when responding to your questions. And even then, the rep might have misunderstood how the Bluesound product works. It was only after one of my last messages that John understood the heart of the question, because I poked his sleep-deprived dev mind with the letters "S/PDIF".

Pro-Ject certainly could have managed this better. But see my rant over on pinkfish on how manuals and other details fall through the cracks when something is made in three or more countries (or multiple offices in the same country, for that matter). Welcome to my past life, and to what it takes to make a North American or European product that competes on price with SMSL and other Chinese products.

I am just now responding to the tech support manager at their Austria HQ, and will reemphasize that this too should be clarified in the manual.

 

User manual malfunctions aside, it turns out the lack of MQA S/PDIF decoding was a conscious decision to hit a desired product size and price-point. I hope you'll update the folks on the Bluesound support forum with this information. Want MQA streaming via coax? Buy a more expensive product or add in a Meridian accessory worth almost two of these.

[GUTB]

Great info, thanks guys for exposing the truth on this "hardware MQA" DAC.

[mansr]

3 minutes ago, GUTB said:

Great info, thanks guys for exposing the truth on this "hardware MQA" DAC.

There is no such thing as hardware decoding for something as complex as MQA. It's always a DSP of some kind, although the program may be fully or partially hard-wired.

[MagnusH]

1 hour ago, mansr said:

There is no such thing as hardware decoding for something as complex as MQA. It's always a DSP of some kind, although the program may be fully or partially hard-wired.

Correct, I think in this case the MQA unfolds are done by the XMOS by code supplied by MQA.

[asdf1000]

Hi @Miska

 

I saw you mentioned in another post you have this DAC. Does it measure better than the iFi iDSD DAC with up-sampling to DSD512 (in your opinion)?

 

[left channel]

On 10/30/2017 at 9:14 AM, MagnusH said:

I could not hear any difference if I used the same improved power with the USB signal or into the separate micro USB. But if I for example used USB direct from computer, and supplied clean power on the micro USB, then the difference was quite big compared to only computer USB.

 

The iFi nano iUSB3 I have is nice for experimenting, since it has 2 USB outs, one with improved power only, and one with improved power and re-clocked/regenerated USB signal. For now I use a UpTone USBA>B adapter to get both improved power and improved USB signal from the iFi nano iUSB3.

 

OK, I've finally done a full comparison of external power vs. USB power, with and without the USB REGEN.

Connecting the external power adapter makes the largest difference, with and without the USB REGEN inserted. The music sounds so much better, I am wondering if further improvement could be achieved by replacing the switching power supply with a linear power supply. No need for anything fancy, just a linear "wall-wart" like Schiit supplies with their products. Looking for anything prefabricated with that micro USB connector may be annoying though.

 

The USB REGEN adds further improvement, but not enough when external power is disconnected (which is surprising, as the USB REGEN replaces the USB power). This improvement comes only from the USB REGEN's reclocking, which is apparently better than the design in the Pro-Ject box, about which the Pro-Ject data sheet says "with our new proprietary clock design we have managed jitter rates of unrivalled 100 Femtoseconds, this easily outperforms many renowned and respected audiophile clock generators!"  I can't find specs on the USB REGEN other than it has a "low-jitter clock". There is more published about the ISO REGEN. Anyone? I know circuit design is more important than the bill of materials alone, but this would be interesting.

This is now comparing very well with my Magni/Modi 2U. For this test I played Louis Armstrong's Blueberry Hill in DSD256 with foobar2000, and listened with Beyerdynamic DT770 cans. Final configuration was: external 5v power adapter connected, UBS signal routed via a USB REGEN. The REGEN is externally powered but is not powering the DAC, because the DAC auto-switches to external power. After connecting the REGEN the Pro-Ject box looked like a new device to Windows, and I had to configure buffer settings in the Pro-Ject control panel for DSD256 again. Then all was well. Nice little box.

[lmitche]

11 minutes ago, left channel said:

 

OK, I've finally done a full comparison of external power vs. USB power, with and without the USB REGEN.

Connecting the external power adapter makes the largest difference, with and without the USB REGEN inserted. The music sounds so much better, I am wondering if further improvement could be achieved by replacing the switching power supply with a linear power supply. No need for anything fancy, just a linear "wall-wart" like Schiit supplies with their products. Looking for anything prefabricated with that micro USB connector may be annoying though.

 

The USB REGEN adds further improvement, but not enough when external power is disconnected (which is surprising, as the USB REGEN replaces the USB power). This improvement comes only from the USB REGEN's reclocking, which is apparently better than the design in the Pro-Ject box, about which the Pro-Ject data sheet says "with our new proprietary clock design we have managed jitter rates of unrivalled 100 Femtoseconds, this easily outperforms many renowned and respected audiophile clock generators!"  I can't find specs on the USB REGEN other than it has a "low-jitter clock". There is more published about the ISO REGEN. Anyone? I know circuit design is more important than the bill of materials alone, but this would be interesting.

This is now comparing very well with my Magni/Modi 2U. For this test I played Louis Armstrong's Blueberry Hill in DSD256 with foobar2000, and listened with Beyerdynamic DT770 cans. Final configuration was: external 5v power adapter connected, UBS signal routed via a USB REGEN. The REGEN is externally powered but is not powering the DAC, because the DAC auto-switches to external power. After connecting the REGEN the Pro-Ject box looked like a new device to Windows, and I had to configure buffer settings in the Pro-Ject control panel for DSD256 again. Then all was well. Nice little box.

What kind of power supplies are you using with the REGEN and Project DAC? If they are SMPSes you should try John Swenson's ground shunt tweak with both boxes.

[left channel]

20 minutes ago, lmitche said:

What kind of power supplies are you using with the REGEN and Project DAC? If they are SMPSes you should try John Swenson's ground shunt tweak with both boxes.

 

I'm using the stock power supplies. The Pro-Ject comes with a hopeless little switching wall-wart. The REGEN comes with a small power brick, which the website says is "the best spec'ed and sounding 22 watt/7.5V/2.93A (overkill) tabletop (93 x 54 x 36mm) world-voltage-compatible SMPS we could find".  My main goal would be to replace the Pro-Ject adapter, not modify or replace the REGEN's...at least not yet.

[lmitche]

For less then $15 it is highly likely you can greatly increase the SQ quality of your system by using the technique described here:

 

 

[left channel]

Thanks @lmitche, that looks like a fun experiment. I'd just have to add a micro USB adapter to the end.

[lmitche]

Yep, 

7 minutes ago, left channel said:

Thanks @lmitche, that looks like a fun experiment. I'd just have to add a micro USB adapter to the end.

Yep, or just splice into your existing cable.

[lmitche]

17 minutes ago, left channel said:

Thanks @lmitche, that looks like a fun experiment. I'd just have to add a micro USB adapter to the end.

I look forward to hearing your description of the impact on SQ there.  John Swenson knows what he is doing.

[MagnusH]

Try the iFi iPower, its cheap ($50) and claim to have extremely low jitter, lower than battery. Probably not as good as "real" linear powers, but they tend to be pretty expensive.

 

Btw, the reclocking in the DAC and the reclocking on the USB signal is two different things as far as I have heard. Both helps. That's why a cheap tweak like UpTone Regen and iFi nano iUSB3 can (and often does) improve very expensive DACs. But I am not an tech guru, so someone else have to explain this better :-)

 

But your finding is quite similar to mine: better power gives a quite big improvement, USB reclocking a smaller improvement. Pro-Ject should do like some others and offer an upgrade to iFi iPower at their website, its definitely worth it even on a cheap DAC like the S2.

[left channel]

Agreed @MagnusH. I wouldn't want anything thinking a REGEN is necessary, as that is almost half the price of this product. The iFi is a good option, and the more I think about it the more I'm certain even an upgrade to a cheap non-switching wall-wart would do wonders here. (Or the grounding fix mentioned above, which speaks to my inner child. The 12 year-old ham radio maker inner child, that is! :-)

[Knight Rider]

Hi everyone! I have this DAC and I only use it with Tidal desktop app in Windows 10. I also noticed that it makes a big improvement if I use external power supply with micro usb adapter. Now I'm looking for alternatives to replace that included tiny PSU. Ifi's iPower is maybe one simple and cheap solution. But what you think about this one, could it work?: http://www.aqvox.de/usb-power_en.html

[left channel]

9 hours ago, Knight Rider said:

Hi everyone! I have this DAC and I only use it with Tidal desktop app in Windows 10. I also noticed that it makes a big improvement if I use external power supply with micro usb adapter. Now I'm looking for alternatives to replace that included tiny PSU. Ifi's iPower is maybe one simple and cheap solution. But what you think about this one, could it work?: http://www.aqvox.de/usb-power_en.html

 

Based on my experiment above, improving the USB power does not help as much as plugging the external wall-wart into the separate power input jack. The AQVOX improves the USB power only. My recommendation for further improvement is to upgrade the wall-wart (or try the grounding fix suggested above) instead.

 

Jitter on the USB line is a separate topic. The AQVOX power product does not fix jitter. Anti-jitter products include the AudioQuest Jitterbug and the UpTone USB REGEN. The REGEN also cleans up the USB power, but did not help anywhere near as much as the stock external power supply. I see AQVOX has a Windows AISO driver that may help jitter and other aspects of the USB signal: http://www.aqvox.de/tech.html#matrix

[gahabana]

2 hours ago, left channel said:

 

Based on my experiment above, improving the USB power does not help as much as plugging the external wall-wart into the separate power input jack. The AQVOX improves the USB power only. My recommendation for further improvement is to upgrade the wall-wart (or try the grounding fix suggested above) instead.

 

Jitter on the USB line is a separate topic. The AQVOX power product does not fix jitter. Anti-jitter products include the AudioQuest Jitterbug and the UpTone USB REGEN. The REGEN also cleans up the USB power, but did not help anywhere near as much as the stock external power supply. I see AQVOX has a Windows AISO driver that may help jitter and other aspects of the USB signal: http://www.aqvox.de/tech.html#matrix

i agree with previous posters. Have been powering my S2 DAC with iFi iPower as soon as i figured that it uses external power rather then one coming from player via USB cable (if connected)... it is a modest investment but at 15-20% of the price of the DAC - i think it is worthwhile. Maybe it can sound even better with more expensive supply, but i think that would be the area of very diminishing returns.

 

[left channel]

2 hours ago, gahabana said:

i agree with previous posters. Have been powering my S2 DAC with iFi iPower as soon as i figured that it uses external power rather then one coming from player via USB cable (if connected)... it is a modest investment but at 15-20% of the price of the DAC - i think it is worthwhile. Maybe it can sound even better with more expensive supply, but i think that would be the area of very diminishing returns.

 

 

That looks like a great upgrade for most people, and all the reviews on Amazon say it improves the quality of audio devices. However 2 of the 8 are bad reviews, because the product may introduce a hum via power lines and also produces RF interference over the air. One of them specifically says it interferes with shortwave radios. I am a ham radio operator so I'll have to skip it. The grounding technique suggested above might remove the hum, but I doubt it would do enough about the RFI.

 

This is likely because it is a switching power supply (120/240 volts in), and not well-shielded or designed to avoid such problems. A good choice for cleaner power and airwaves would be any wall-wart that is a linear power supply (only 120 volts or only 240 volts in).  For example the Xing Yuan adapters Schiit includes with some of their products...except we'd need to buy 1,000 of those. :-) But I can try this one from Jameco along with a 2.1 mm to micro USB adapter.

 

Or, I could do the grounding project suggested above. Just thinking out loud.

[semente]

14 hours ago, Knight Rider said:

Hi everyone! I have this DAC and I only use it with Tidal desktop app in Windows 10. I also noticed that it makes a big improvement if I use external power supply with micro usb adapter. Now I'm looking for alternatives to replace that included tiny PSU. Ifi's iPower is maybe one simple and cheap solution. But what you think about this one, could it work?: http://www.aqvox.de/usb-power_en.html

 

I use one to power my R-Pi.

Make sure one Ampere is enough for your needs.

 

R