advertisement


Pro-Ject Pre Box S2 digital DAC

I suspect DSD is not in S/PDIF for the same reason MQA is not there: separate processing would have been required, resulting in a larger box and a higher cost. Some are now looking at the Mytek Liberty as an alternative, though it's a bit over 2x the price and has its own limitations.
 
I suspect DSD is not in S/PDIF for the same reason MQA is not there: separate processing would have been required, resulting in a larger box and a higher cost. Some are now looking at the Mytek Liberty as an alternative, though it's a bit over 2x the price and has its own limitations.

In the case of DSD, the DAC chip usually processes DSD, not the SPDIF interface. This is why I mentioned it's strange that DoP (DSD over PCM) doesn't work with SPDIF. My $50 HiFiBerry Digi+ SPDIF transport has no issues 'passing through' DoP (won't work with Native DSD) to a DAC that can process DSD.

In the case of MQA, it's the USB interface (XMOS) that is doing the MQA decoding, not the DAC chip - with this DAC.

But there is something different about the routing/path of SPDIF in this DAC. I would love to find out, especially how ESS's famous jitter elimination works with this dual DAC chip configuration.
 
...
I would love to find out, especially how ESS's famous jitter elimination works with this dual DAC chip configuration.
John Westlake (along with many designers I guess) has put a lot of work into jitter control in the last couple of years. He designed (but has never developed into a product) a stand-alone jitter-reduction box, called "Detox". He has said that the technology in Detox was trickled-down into the PBS2D, and that it is that technology which is one of the key design facets which contributes to the PBS2D's unexpectedly high performance (for the price).

So, perhaps there is as much jitter control going on outside the ESS chip as inside it?
 
o, perhaps there is as much jitter control going on outside the ESS chip as inside it?

Yes, I suggested the same earlier, that this must be happening before the DAC chips. Otherwise I can't see how the dual DAC chips (with ESS's famous jitter reduction tech) would be used without a complicated solution.

I have read about Detox but do you know where he said this S2 will use similar tech for jitter reduction? Maybe it's this mini-Detox solution that won't allow DSD over PCM 'pass through' also.

Not a big deal at my end. Just interested, that's all.

Btw, the optical input sounds really good.
 
I received the pro-ject a few days ago and last weekend I could test it carefully listening to Tidal. I state that I have an AM Audio system which, despite its excellent quality / price ratio, cost me several thousand euros. I used it with cd players Merdian, sacd Marantz and dac Arcam rdac 2.
Well, listening to the Masters MQA albums is something incredible, never hearing anything like it on my system. The focus of singers and instruments is incredible, as is their "physicality", so realistic that they penetrate your bowels. Excluding the Masters with a limited resolution of 44 or 48 khz, all the others, regardless of the format, have an exceptional performance (obviously if the recording is up to), never harsh and pleasantly analog.
I would say that for less than three hundred euros you can not expect anything more. The italian Audioreview is right to write that this dac sounds like 10 times more expensive appliances.
 
The italian Audioreview is right to write that this dac sounds like 10 times more expensive appliances.

Hi gio, can you share a link to this review? I don't read/speak Italian but maybe I can use Google Translate to help me read their review.
 
... do you know where he said this S2 will use similar tech for jitter reduction? Maybe it's this mini-Detox solution ...

Sorry s, it's buried in a post somewhere. It would have been the MDAC First Listen thread here at pinkfishmedia. I reckon more than 6 months ago, less than 18 months ago. John referred to the PBS2D and its siblings as the "miniDAC". (There is no such thing as a mini-Detox.)

I reckon if you ask about this on the MDAC First Listen thread you'll get some ideas - there is still much interest in the Detox
 
Can anybody compare one of these to the original Mdac sound quality wise? Using the pre in to a power amp also? I use a mdac into a croft series 7. Would love to know if this sounds better.
 
Power supply conflicts solved. I built a linear power supply for my PBS2D and had set the supply to exactly 5.00V When I used the DAC with a USB connection to a PC it was fine initially then might judder the sound until I disconnected the linear supply. I used a PC Probe utility to find the PCs 5v rail was running at 5.04 V So I set the linear supply to 5.07V Result problem solved. I guess the PB2SD was confused over which supply to use.
 
Power supply conflicts solved. I built a linear power supply for my PBS2D and had set the supply to exactly 5.00V When I used the DAC with a USB connection to a PC it was fine initially then might judder the sound until I disconnected the linear supply. I used a PC Probe utility to find the PCs 5v rail was running at 5.04 V So I set the linear supply to 5.07V Result problem solved. I guess the PB2SD was confused over which supply to use.

Hello,

How do you find out which supply is in use?
The S2 has a green icon on the top left corner of the display. I presume that if the icon is present, then the S2 is supplied by the external power.
My question is, it is possible that even if the external power is present (plugged) the S2 uses the usb port power? Which could be the condition for S2 to switch from usb power to external power?
As you noted the condition could be the higher voltage.

I'm using the S2 powered by an iFi power supply and a Mac Mini as source, but I can hear no difference with or without the external power supply. I'm using the iFi power only because I already owned it and some people have found that improves the sound. :)

It's an interesting thing...if I pull the iFi out of the wall socket, while S2 is playing, the S2 restarts and uses the Mac Mini usb power...if I play the same setup, but unplug the micro usb from S2 side (iFi plugged in the wall socket), the S2 keeps playing with no interruption.

As I already noted in another post, the Mac Mini delivers power through the usb even when is shutted down, so the S2 is always powered on.
 
You are right it's difficult to know which power supply is in use. The Green power icon was always present. Before changing the voltage the S2 would play normally for a while (1 to 3 minutes) then go into a juddering mode that I put down to switching back and forth between 2 power supplies. It was only resolved by pulling the power lead to the linear supply. After increasing the linear supply voltage to 5.07v I could play a whole album with no onset of juddering.
 
It's an interesting thing...if I pull the iFi out of the wall socket, while S2 is playing, the S2 restarts and uses the Mac Mini usb power...if I play the same setup, but unplug the micro usb from S2 side (iFi plugged in the wall socket), the S2 keeps playing with no interruption.
Interesting indeed! I made the same observation at Computer Audiophile, in which I said:

"If I switch off the external PSU at the wall socket, the DAC resets itself. I imagined that this is design-intent. But - I noticed that when I switch off an external battery pack, the DAC does not reset. And if I simply pull out the wall wart's microUSB plug, the DAC does not reset. But if I switch off the external PSU at the wall socket, the DAC resets itself."

In my experience, resets when things are unplugged are because of the generation of a power surge. So I was a little anxious about this. However I guess there could easily be other innocuous explanations. For example, when we pull out the PSU's microUSB's plug, voltage disappears instantaneously. Whereas when we pull out at the wall socket, voltage (possibly) decays (relatively) slowly as the PSU's capacitors discharge. And we have heard from others that the PBS2D may behave unexpectedly depending upon the relative voltages at the USB and external PSU sockets. It could be that when voltage disappears instantaneously, the PBS2D switches asap to the USB power, with the PBS2D's internal capacitors providing a very brief reservoir. But when the voltage disappears (relatively) slowly, maybe the control logic/electronics hangs on and hangs on until the internal capacitors are too depleted.

But I am just speculating. And meanwhile am very glad to hear that the iFi iPower? has the same effect as the stock wall wart, which suggests that this is something other than a power surge from the stock wall wart. So thanks for your report.
 
Can anybody compare one of these to the original Mdac sound quality wise?
I reckon the PBS2D sounds pretty identical to the MDAC. Resolution, timing, bass, soundstage, tonal balance. The sound is certainly very similar - so similar that I am not sure I can hear a difference at all. Possibly the PBS2D removes the hardness on a "difficult" piano recording I use*. But the sound is so similar that I suspect I am hearing my confirmation bias. I listened to sources from Tidal on LCD3 headphones through unbalanced connections - which suggests that both the DACs and amplifiers are similar between PBS2D and MDAC.

*"Vingt regard sur 'enfant Jesus" by Messiaen played by Joanna MacGregor, 2nd movement, from Tidal.
 
Hello, one question on the green dot MQA. I was listening to an album from tidal that light up the green dot instead of the blue one and the project's display shows 44.1KHz. But, listening to the same track with another dac without MQA and therefore with the passthrough disabled makes the dac sync at 88.2KHz so highther than the MQA version. Does it means that the green one MQA doesn't even make the hardware unfolding resulting in a worse version of the software unfolded one? This is the album: https://tidal.com/album/81175674
 
And I too noticed this with some Holst, from Tidal.

With PBS2D, dot is blue, rate is 44.1k. "Passthrough MQA" is set.

With Audiolab's MDAC, which does not do any MQA unfolding, "Passthrough MQA" cleared, rate is 88.2k. (You may need to close and re-open the Tidal program after changing "Passthrough MQA" from enabled to disabled.)

(Edit: When I first posted this last week I made a mistake, and reported that I had discovered this in a recording by Messiaen. Wrong. I have corrected above.)
 
Last edited:
You fellows may have discovered something odd about the Tidal/MQA software decoder. That album is listed as 44.1 in the unofficial MQA_list [link]. 44.1 MQA files are supposed to be 24-bit, so they are within the definition of "Hi-Res". But why the software decoder would "unfold" it to 88.2, I have no idea. It may just be handing the DAC an 88.2 "container" with no additional music content at all. I haven't tried to listen to this. Does it sound different?
 
This despite reviewing one of the units with pink capacitors that should have been recalled

Hopefully this is a case of him using an internet image of the inside (or Pro-Ject provided marketing) so that we didn't have to open up his review unit.

Hopefully these (pink caps) are not out in the wild...
 


advertisement


Back
Top