• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required as is 20 years of participation in forums (not all true). Come here to have fun, be ready to be teased and not take online life too seriously. We now measure and review equipment for free! Click here for details.

Review and Measurements of Pro-Ject Pre Box S2 Digital

SIY

Major Contributor
Technical Expert
Joined
Apr 6, 2018
Messages
2,449
Likes
4,024
Location
Phoenix, AZ
Anti-aliasing or anti-imaging (reconstruction) filter? I suspect you mean the latter.

/pedant
 

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
19,478
Likes
20,554
Location
Seattle Area
I noticed one interesting thing, Amir measurement show the amp have 1.9 ohm impedance while the Russisn site shows 0.1 ohm and then rise to 0.5 ohm at 20 KHz but this is probably becose of the 19 KHz low pass filter.

I think it is becose Amir powered it only through USB and didnt use powerbrick. Maybe with powersupply connected it will have 0.1 ohm output impedance?
My measurements show "high" because of the length of cable and connectors used in my setup. Classic way is to measure it right at the terminal with no wires which is what the above is. I can do that but it is not realistic relative to what people do (i.e. wear headphones with wires).
 

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
19,478
Likes
20,554
Location
Seattle Area
Weak? It will drive HD800 to 108db, thats not weak in my opinion.
It is weak. :) I like to see 100 milliwatts at 300 ohm and S2 only outputs 10% of that.
 

Graph Feppar

Active Member
Joined
Nov 19, 2018
Messages
195
Likes
153
Anti-aliasing or anti-imaging (reconstruction) filter? I suspect you mean the latter.

/pedant
Anti aliasing, anti imaging and reconstruction filter are all the same thing, its just a low pass filter.

Anti aliasing filter is a term used for lowpass in ADC design becose frequencies above the half samplerate get "aliased" into the passband.

Anti imaging filter is term used for lowpass in DAC design becose frequencies above half samplerate are cancerous crap that doesnt belong there, its artefact of sample and hold "stairstep" output of pulse code modulation.


Anti aliasing, anti imaging, reconstruction... and its all the same thing done for the same reason. Its a lowpass filter and its there becose samplerate isnt high enough. Well anyway, since this is DAC, the correct term is anti imaging/reconstruction filter but like I said before, its the all the same thing so there is no reason to be pedant about it.
 

SIY

Major Contributor
Technical Expert
Joined
Apr 6, 2018
Messages
2,449
Likes
4,024
Location
Phoenix, AZ
They're all low pass filters, but have different functions in different parts of the signal chain. That's why engineers gave them different names. I'm admittedly being pedantic, but precision in technical communication prevents a lot of confusion.
 

Graph Feppar

Active Member
Joined
Nov 19, 2018
Messages
195
Likes
153
My measurements show "high" because of the length of cable and connectors used in my setup. Classic way is to measure it right at the terminal with no wires which is what the above is. I can do that but it is not realistic relative to what people do (i.e. wear headphones with wires).
But you measured other amps that show sub ohm impedance. If this S2 is really 0.1 ohm and your cable adds 1.8 ohm, then you must used different shorter/lower resistance cable to get those 0.4 ohm results that Burson Play got.

I think you should measure the cable impedance and subtract it from result becose showing 0.1ohm amp as 1.9 ohm in graph with no warning to take the data with grain of salt is not ideal. For example there might be person who wants to buy amp for Andromeda IEM and is looking for low impedance amp, that graph might make them think the S2 isnt good when in fact its great pairing.
 
Last edited:

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
19,478
Likes
20,554
Location
Seattle Area
But you measured other amps that show sub ohm impedance. If this S2 is really 0.1 ohm and your cable adds 1.8 ohm, then you must used different shorter/lower resistance cable to get those 0.4 ohm results that Burson Play got.
It is not just the cables but the connectors. They can fit loose or tight and as a result easily add or subtract few tenth of ohms. 1/4 inch versus 3.5mm makes a difference too.
 

Music57

New Member
Joined
Dec 21, 2018
Messages
2
Likes
0
Surprised this is not listed with the other DAC in the SINAD comparison chart. Was this test not available or did I miss it in the review? I would love to know where this unit fall in with the other DAC's.
 

Veri

Major Contributor
Patreon Donor
Joined
Feb 6, 2018
Messages
1,891
Likes
1,693
Surprised this is not listed with the other DAC in the SINAD comparison chart
This was measured with the previous measurement set-up, previous dashboard.. amir does not own the unit so it can no longer be added/measured with the new machine.
 
Joined
Feb 25, 2019
Messages
16
Likes
0
In the meantime, I bought it.
Unfortunately, cannot lend it to Amir because I am in Italy, but someone living in the US should do it
 
Joined
Feb 25, 2019
Messages
16
Likes
0
I would like to know, how the pre-amplification has been implemented.
I am curious to know which IC, op-amp, circuit topology (Class A or similar), feedback strategy has been used
 

Music1969

Senior Member
Joined
Feb 19, 2018
Messages
377
Likes
103
Someone has offered one for second review....
Fantastic. I was hoping this could be re-measured with your new measurement rig.

Please remember to enable 'distortion compensation' and use the 'linear phase, fast rolloff' filter for measurements...

Jussi of HQPlayer has said this is the best settings for measurements, for this DAC specifically.
 
Last edited:

Music1969

Senior Member
Joined
Feb 19, 2018
Messages
377
Likes
103
I saw the latest Stereophile mag has reviewed and measured the Pro-Ject S2 DAC and they've now added it to Class A recommended DACs:

https://www.stereophile.com/content/recommended-components-2019-edition

The measurements conclusion: "I was pleasantly surprised by the Pro-Ject Pre Box S2 Digital. This tiny inexpensive box offers almost state-of-the-art measured digital performance"

Not bad for ~USD400
 

Music1969

Senior Member
Joined
Feb 19, 2018
Messages
377
Likes
103
Hello,
To be recommended in "Stereophile" is really good?
I think not always ...
I agree. I'm moreso interested in JA's measurements... very good for this DAC.

Not sure why I even linked the 'recommended components' thing because I don't care for it.
 

FTBoomer

New Member
Joined
Mar 22, 2019
Messages
1
Likes
0
I'm thinking about grabbing the S2 an feeding it from my CCA (needed for wi-fi Roon receiver). Would that combination work or do I need something else as a "front-end" wifi receiver to feed the S2?
 

Music1969

Senior Member
Joined
Feb 19, 2018
Messages
377
Likes
103
I'm thinking about grabbing the S2 an feeding it from my CCA (needed for wi-fi Roon receiver). Would that combination work or do I need something else as a "front-end" wifi receiver to feed the S2?
Get the latest RPi3 Model B+ which features dual-band 802.11ac Wi-Fi. WiFi and USB don’t share same bus power in the latest Pi.

Just load RoPiiie OS on the SD card and setup WiFi via web GUI and you have a great Roon endpoint.
 

maty

Addicted to Fun and Learning
Joined
Dec 12, 2017
Messages
843
Likes
344
Location
Tarragona (Spain)
Pro-Ject Pre Box S2 Digital D/A headphone amplifier Measurements

https://www.stereophile.com/content/pro-ject-pre-box-s2-digital-da-headphone-amplifier-measurements



Fig.19 Pro-Ject Pre Box S2 Digital, Optimal Transient filter, HF intermodulation spectrum, DC–30kHz, 19+20kHz at –3dBFS into 100k ohms, 44.1kHz data (left channel blue, right red; linear frequency scale).
...I was pleasantly surprised by the Pro-Ject Pre Box S2 Digital. This tiny, inexpensive box offers almost state-of-the-art measured digital performance. I note that KM didn't say definitively which of the eight reconstruction filters he preferred, mainly using the Optimal Transient filter. However, I suspect from the measurements that the Hybrid filter offers the best balance between time-domain and frequency-domain performance.—John Atkinson
 
Top Bottom