Hardware Teardown of Pro-Ject Pre Box S2 Digital DAC

[DonH56]

Technically polymer films contain carbon so are chemically organic compounds... Gotta' love marketing.

 

[captain paranoia]

Gotta' love marketing.

It's not marketing; it's an accurate description of the type of capacitor. Organic polymer capacitors are a group of electrolytics, named after the conductive organic polymers used to create the electrolyte (replacing the inorganic MnO2). The first in production was Sanyo's OS-CON series.

https://en.wikipedia.org/wiki/Polymer_capacitor

'Organic', as in 'organic chemistry', the branch of chemistry featuring carbon and its vast array of compounds. As opposed to inorganic chemistry, one other branch, that deals with everything other than carbon...

 

[DonH56]

It's not marketing; it's an accurate description of the type of capacitor. Organic polymer capacitors are a group of electrolytics, named after the conductive organic polymers used to create the electrolyte (replacing the inorganic MnO2). The first in production was Sanyo's OS-CON series.

https://en.wikipedia.org/wiki/Polymer_capacitor

That I did not know, or had forgotten, can't remember which. Thanks!

Polymer films have been around a long time but have been tweaked much in recent times to reduce their ESR and such. I know high ESR was a problem with many of the earlier organic films but that is generally not true today. For decoupling GHz ASICs we still use MLCC's everywhere (cheaper) but they are not usually in the signal path, or have enough DC bias across them that the piezo effect is minimized.

'Organic', as in 'organic chemistry', the branch of chemistry featuring carbon and its vast array of compounds. As opposed to inorganic chemistry, one other branch, that deals with everything other than carbon...

That's what I meant by "chemically organic"... One of the few things I remember from chemistry classes (many, since I was pre-med at the time).

Anyway, thanks, proof that I am not a capacitor expert. - Don

 

[hifinut]

I did mean that. It seems you are not convinced. Anyway following your review I have ordered a Project Pre Box S2 Digital and it should arrive today. The real test is the sound quality and that is largely personal. I will keep the unit as cool as possible. I am very intrigued to compare the sound with my Audiolab M-DAC+ which cost more than twice the price of the Project unit.

 

[Xyrium]

Since this one is old as dirt, but we're still posting, I have to ask: Was this ever remeasured under the current dashboard? I see the ESS hump was there....guess they didn't quite get that figured out like some other manufacturers did.

 

[Music1969]

I see the ESS hump was there....guess they didn't quite get that figured out like some other manufacturers did.

No ESS IMD hump:

https://www.audiosciencereview.com/...ct-pre-box-s2-dac-headphone-amp-review.10085/

 

[Xyrium]

Thank you, not sure why that follow up didn't show in my search results while the teardown did. Indeed, no hump, interesting since it was there in the first round of tests. I had high hopes for this box, but those distortion specs were, meh. THat headphone performance....ugh

 

[druihle]

Best replacement would be : United Chemi-Con APSG160ELL122MH20S but they are 20 mm height an i don't know if.... They are 16v...
It is probably a multi-layered pcb. Changing the capacitors must be risky enough for people. If someone with skills and professional equipment agrees to do so for a reasonable price then there ....

 

[Anatman]

This hardware teardown is a follow up to my review of the Pro-Ject Pre Box S2 DAC. The DAC performed well in objective measurements. Let's see how it does from overall design point of view.

Here is the high level diagram/major integrated circuits:

View attachment 10922

We see one of the nicest layouts given the small box constraints. Digital side is fully isolated on the left with a moat between it, and the right side analog/mixed signal. The asynchronous interface is implemented using ubiquitous Xmos.

Extracted digital audio samples from USB or other inputs is then routed on top across an isolation moat and board to a pair of ESS Sabre ES9038Q2M parts. ESS is secretive with its specs so I don't have a link to provide for it or the rest of the ESS parts used here.

Precision reference voltage for the DACs is provided by ES9311. http://www.marketwired.com/press-re...h-to-simplify-audio-system-design-2085996.htm

View attachment 10921

Measurements showed absence of typical power supply noise so seems like ESS has done a good job here as has the designer by selecting this part.

Headphone output is provided by Sabre 9802Q: https://www.businesswire.com/news/home/20150108005016/en/ESS-Technology-Introduces-SABRE9602-CES-2015-World’s

View attachment 10923

Alas with no heatsink and no higher than 5 volt supply, it does not provide much drive capability as noted in my review of Pro-Ject S2 Pre DAC.

Another not so good news is use of Lelon electrolytic capacitors indicated by the "OCRZ" notation on top of them. Lelon is a fourth grade brand of capacitors and is known to fail in power supply circuits. Fortunately the analog side of this board runs cool and parts are not under stress so that choice to save money is probably OK. Not so good is the same choice for the switchmode power supply on the digital side to drive the XMOS. Keep this unit cool and away from other hot running products for better longevity.

Interestingly they did use much higher quality WIMA caps elsewhere.

Here are the "clean" pictures of digital and analog sections:

View attachment 10926

View attachment 10927

Notice the nice board providing isolation between the two sides:

View attachment 10928

Mechanical design is quite sturdy for such a small unit. Notice the hefty bolt here to hold the PCB with the front panel switch:

View attachment 10929

There is no flex as a result and the switch feels solid when pushed in and out.

Same routine is followed in the back with connectors feeling very sturdy:

View attachment 10930

The external power supply is a typical switchmode unit:

View attachment 10925

Summary
The Pro-Ject Pre S2 Digital is a well-built, and well-thought out DAC. Excellent attention is paid to isolation of digital and analog. Layout is very good for such a small unit. Mechanical construction is also quite solid and overbuilt compared to much lessor designs (I am looking at you Schiit).

The only thing that raises the eyebrow is use of cheap electrolytic caps from Lelon. For this price range, spending another $10 on better caps would have been nice to see.

So this is a competently designed DAC both in measurements and electrical/mechanical design.

Note: I should say that this tear down was very difficult due to very tiny footprint of the surface mount parts, and lack of documentation from ESS. I think I got all the part numbers right but I am open to being corrected.

Much thanks to forum member who loaned me this unit for measurement and allowing me to get my sticky fingers inside for this teardown.

Hi – and thank you for the review! The first time I read your review, I realized i had to add amplifiers to my rigs. So:
I now have two different rigs with based on each almost identical Lenovo ThinkPad L390 set up. I am mainly listening using Tidal via Audirvana.

Both rigs have each Pre Box S2 Digital, and one of them has the older Pro-Ject Head Box S (2011), and the other a new Pro-Ject Head Box S2. See pictures.

I have read a lot of confusingly – and thoroughly explained WHY - things about where the volume should be controlled from, find no agreement ore consensus. To put it short:

Do you think I should max out the amplifier, and control all the volume from the dac? Or should I max out the dac, and control all the volume from the amplifier? Or – a combination of both at different levels?

 

[helom]

Hi – and thank you for the review! The first time I read your review, I realized i had to add amplifiers to my rigs. So:
I now have two different rigs with based on each almost identical Lenovo ThinkPad L390 set up. I am mainly listening using Tidal via Audirvana.

Both rigs have each Pre Box S2 Digital, and one of them has the older Pro-Ject Head Box S (2011), and the other a new Pro-Ject Head Box S2. See pictures.

I have read a lot of confusingly – and thoroughly explained WHY - things about where the volume should be controlled from, find no agreement ore consensus. To put it short:

Do you think I should max out the amplifier, and control all the volume from the dac? Or should I max out the dac, and control all the volume from the amplifier? Or – a combination of both at different levels?
View attachment 111007View attachment 111008

Lowest intermodulation distortion was just a few db below the DAC’s full output. This should still provide plenty of resolution, so I suppose it could be the ideal level in theory. Shouldn’t make an audible difference however, so I’d just run the DAC at full output.

 

[AnalogSteph]

Since ESS DACs have a habit of hard-clipping at 0 dBFS, I'd leave 2-3 dB of headroom just in case. That's a little over 80% or so in Windows.

Since the Pre-Box is no slouch in terms of dynamic range (~119 dB(A)), you could afford going down to about -9 dB even (and arguably even lower here, where you could turn down the volume in the Head-Box). If you are already making use of playback volume normalization (e.g. ReplayGain), this is probably not going to be necessary though, given that average digital levels would remain well under -10 dBFS most of the time anyway. Something like -90 dBr of distortion worst-case should still fall under inaudible to begin with, and you'd only be hitting that on the peaks at best.

In any amplifier with an analog volume control, you generally want to be avoiding the -6 dB region, which will tend to give increased noise and distortion. Either wide open or <-20 dB tends to be best. That's more of a rule of thumb than set in stone though.

Accurately determining the best settings for a combintion of two such devices actually isn't a trivial task and would require a whole slew of measurements, particularly noise and distortion over a whole range of volume pot positions in the amplifier. Nobody ever does that. In practice, you'll have a whole range of setting combinations available that'll work perfectly fine.