advertisement


Pro-Ject Pre Box S2 digital DAC

Anyhow, i did take a look at Bryston 4B-SST2 schematics ... if i can still read schematics partially well it does show 68microfarads that input signal is going through ... not sure if that one is supposed to block DC but my guess is yes ...

I agree - there does seem to be an input capacitor. Hmm... Puts us back in square one in sorting out the issue :(
 
my experience with "Pro-Ject Pre Box S2 digital DAC"

Am using odroidxu4 (running Armbian builds of Ubuntu) as endpoint for Roon as well as LMS/squeezelite.
Worked immediately with no issues.
I also have a benchmark dac2 hgc (which i used both as preamp for pro-ject s2 and to compare).
Love - all resolutions worked out of the box. PCM all the way to 768khz and DSD via DOP all the way to DSD256 with Roon.
Sounds very good. Haven’t done a lot of critical listening - but i hear nothing worse compared to Benchmark DAC2. Remote (one that comes with it) is cheapo plastic bit bigger then credit card but works great for volume control and switching filters or on the fly or sources etc.
sounds GREAT to me.
things i love compared to Benchmark:

switching between various sampling rate sources is practically instant. i.e. from 44.1khz CD to 192khz hires source or dsd is instant. on benchmark there was 0.4sec delay or you missed bit from start of the song. if all upsampled obviously none of the dac’s have issue with changing sampling rates but it makes me happy. i still use LMS from time to time so that comes in handy
over 24+ hours no issues, clicks, losing sync etc … i think digital piece/USB is well implemented and has no obvious bugs …in spite of changing, reseting, roon and squeezelite - not once i had to reboot due to sw bug. that is great!!!. e.g. SMSL M9 DAC i also have works fine sounds good but when you reboot the pc or endpoint it starts with hiss until music app (roon or squeezelite) actually starts sending sometjhing (or even silence) … no big deal but bit annoying. as i am planning to replace benchmark dac2 with it and going directly to poweramp can not do that with SMSL m9 but think i ll have no issues with Pro-Ject S2
it remembers volume setting upon power off … which is good if going to power amp directly
MQA support - seems to work very well. 48 all the way to 192khz abd blue light works (tested with Roon/Tidal).
downsides compared to benchmark:

does not have balanced out’s that my amp has (Bryston) … can use RCAs but would be nice if it was balanced
don’t care about headphones so did not compare at all
it can not be powered off (if powered or connected via USB only and source is powered its always powered). not a big . deal … just would be nice if you could power it off
has mute on remote just like benchmark … what benchmark also did is ‘Dim’ which takes volume 20 or 30db down so if you get a phone call can still hear the music but at much lower volume instantly … just cool
i miss ability to power up amp via preamp/dac. it requires 12V output and i guess it did fit in benchmark and pro-ject bing 2-4 smaller box it kinda didn’t fit. if i switch to pro-ject and eliminate benchmark as a preamp ill have to turn on/off amplifier manually and cant do it via remote no more :frowning:
i wish pro-ject would display sample rate and depth. behcmark does it with LEDs … and smsl has info screen. not that it matters cause it DOES work whatever you send to it (16/24/32 bit and any sample rate) …
but benchmark is 2000EUR and Pro-ject 350. makes you wonder if its worth it.

However, last step was to try S2 directly powering poweramp (Bryston SST2). All of the above still holds true however, there might be a problem for me to use it in that way unless you guys have some idea:
Issue: when sample rate changes between the tracks very often i hear a farily loud click/pop between the tracks. I rebooted, powered off … changed settings in the DAC (filters and ‘distortion settings’ on or off) but that did not make any difference. i even inserted Intona isolater between by USB source computer and S2 just to be sure it’s not due to some ‘ground’ connection issues.

My guess is that it could be fixed in the firmware of the S2 (whenever input sample rate changes drive output to 0 in few ms and that i think could do it) … it happens when going from 44.1 to 192 and any other mix … some combo’s almost every time some not so often. Of course if I upsample all the content from Roon to 352 or 384 kHZ it is a non issue but then MQA support is gone etc.

I have no clue why i did not hear those clicks/pops when S2 was connected to Benchmark DAC2 which acted as pre-amplifier.

Any thoughts/ideas ?

Thanks !!!

Gahabana,

I suspect the click is related to change of sample rate (When we need to select different Base master clock frequencies) - not DC offset.

You should not hear clicks between 48KHz and 96KHz etc.

We will look into it and see if we can reduce the level of the click - although we dont experience the clicks on our lab units.

It would require a user installable firmware update.
 
I suspect the click is related to change of sample rate (When we need to select different Base master clock frequencies) - not DC offset.

That was of course my first thought too, but how would that manifest itself with one amp but not with another?
 
That was of course my first thought too, but how would that manifest itself with one amp but not with another?

No idea, if it was DC then the "transient change" would still be heard irrespective if the AMP's DC or AC coupled.
 
hi JohnW,
yes that is correct and you are spot-on. 44.1 to 88.2 to 176.4 is fine. same with 48, 96, 192 ... DSD (DOP) is in the 1st buckett (88.2/176.4) - so yes - that is when the pop happens. ... from user standpoint - if pop is less loud then music (when one presses the 'next song' during 1st one) - one could live with that .... but it kinda happens as well when one songs finishes (silently or even with silence) and another one starts.

Hope you do manage to check that. My FW version that it says on the device is 2.1 - hope this helps ?

thank you a million !
 
Julf - i have only one amp (Bryston)... the difference between 2 setups (given that bryston has effefctively 2 inputs - balanced and rca and with jumpers at the back you decide which is the 'active' input) is that initially i used Benchmark DAC2 as preamp (as it has analog input as well) for output from S2. then i connected S2 directly to the amp and realised clicks are really really loud even when music is playing at fairly low volumes (e.g. -35 or -40dB).
tx
 
Julf - i have only one amp (Bryston)... the difference between 2 setups (given that bryston has effefctively 2 inputs - balanced and rca and with jumpers at the back you decide which is the 'active' input) is that initially i used Benchmark DAC2 as preamp (as it has analog input as well) for output from S2. then i connected S2 directly to the amp and realised clicks are really really loud even when music is playing at fairly low volumes (e.g. -35 or -40dB).
tx

So just to check that i understand you correctly - when you ran the S2 output via the DAC2, you didn't have any pops, but when you run it directly to the amp, you have the pops?
 
but it kinda happens as well when one songs finishes (silently or even with silence) and another one starts.

Just for clarification, the click only occurs between tracks with sample rate change?

So with no sample rate change then no clicks between tracks?
 
Is the gain lower on this than the mdac? I get a very low hum through the mdac into my power amp. Maybe this is a better match for my power amp.
 
hi JohnW - yes - pops/clicks are happening ONLY when samplerate changes and then only when it changes from 44/88/176/352 and 48/96/192/384 (and vice versa).
If master frequency does not change there are no pops/clicks. Tried many times by now.
When it does change, then it does not click/pop every time but more then half times it does.
 
Julf - i have only one amp (Bryston)... the difference between 2 setups (given that bryston has effefctively 2 inputs - balanced and rca and with jumpers at the back you decide which is the 'active' input) is that initially i used Benchmark DAC2 as preamp (as it has analog input as well) for output from S2. then i connected S2 directly to the amp and realised clicks are really really loud even when music is playing at fairly low volumes (e.g. -35 or -40dB).
tx

I suspect that he clicks are present with the pre-amplifier but you have there level attenuated by -35dB to -40dB, with digital pre mode the clicks are not attenuated.

It sounds like the root cause as to why the click is so audible in your setup is excessive system gain. -35dB to -40dB is way too much attenuation for normal listening levels.

Typically we listen anywhere from -30dB to -10dB (really loud).

We will see if we can mitigate the level of the click, but having so much excess system gain is sonically not great (due to much attenuation and wasted gain).
 
Is the gain lower on this than the mdac? I get a very low hum through the mdac into my power amp. Maybe this is a better match for my power amp.

hi Hayche,
no hum whatsoever. neither when S2 goes directly to poweramp nor when it goes 1st into another preamp (at least not in my setup with Bryston amp and with benchmark dac as a pre-amp).
 
So just to check that i understand you correctly - when you ran the S2 output via the DAC2, you didn't have any pops, but when you run it directly to the amp, you have the pops?

Julf, when i ran S2 into Benchmmark acting as a preamp, i heard lot less clicks as i was at the sametime testing roon upsampling to 768 and/or DSD so sampling frequency did not change that often.

Secondly , i've just replugged it back - pops/clicks can be still heard in that setup - S2 runs at 0db (or -3db) but they are lot less loud. I guess the only explanation is - benchmark dac might have DC elimination or capacitors at input or output or both so it makes it less loud.

When connected to power-amp directly - and even at -30dB i get fairly loud pops. i would normally listen at -15 to -10db (medium loud to farily loud) ... but pops would be loud and i was worried over damaging speakers.
 
I suspect that he clicks are present with the pre-amplifier but you have there level attenuated by -35dB to -40dB, with digital pre mode the clicks are not attenuated.

It sounds like the root cause as to why the click is so audible in your setup is excessive system gain. -35dB to -40dB is way too much attenuation for normal listening levels.

Typically we listen anywhere from -30dB to -10dB (really loud).

We will see if we can mitigate the level of the click, but having so much excess system gain is sonically not great (due to much attenuation and wasted gain).

JohnW, yes i would normally listen in that range (-25 to -10db) which is from 'i guess people talking volume to loud music volume) ... the only reason why i mentioned -30db or -35db (below that is too low to hear music really - at -50dB it is like very quiet music and at -60db you can barely hear it and at -70db ear must be on the speaker) is cause at -15db pops are really loud through speakers. louder then music (which usually is silent in between songs).
Now i have just tested via Benchmark DAC2 as a pre and S2 playing at -70dB (cant hear music from 3m) ... it popped relatively loud (volume on benchmark used as a pre is almost at max (3pm)) - which is about the same what i get when S2 connect to poweramp directly.

I think there is no mismatch - Bryston delivers full power at about the same level where benchmark as dac delivers full volume and its about the same where Pro-ject DAC S2 does - about 2V rms according to specs. I realised same volume when going through Benchmark as pre for DAC which means it's all good.

Maybe it is my unit doing something specifically wrong ... as i mentioned earlier - pop click does not happen every time when master freq. gets changed but on average half of the time or more i can hear it.
 
JohnW, yes i would normally listen in that range (-25 to -10db) which is from 'i guess people talking volume to loud music volume) ... the only reason why i mentioned -30db or -35db (below that is too low to hear music really - at -50dB it is like very quiet music and at -60db you can barely hear it and at -70db ear must be on the speaker) is cause at -15db pops are really loud through speakers. louder then music (which usually is silent in between songs).
Now i have just tested via Benchmark DAC2 as a pre and S2 playing at -70dB (cant hear music from 3m) ... it popped relatively loud (volume on benchmark used as a pre is almost at max (3pm)) - which is about the same what i get when S2 connect to poweramp directly.

I think there is no mismatch - Bryston delivers full power at about the same level where benchmark as dac delivers full volume and its about the same where Pro-ject DAC S2 does - about 2V rms according to specs. I realised same volume when going through Benchmark as pre for DAC which means it's all good.

Maybe it is my unit doing something specifically wrong ... as i mentioned earlier - pop click does not happen every time when master freq. gets changed but on average half of the time or more i can hear it.

We will try to reduce with a firmware update - basically increasing the time before the DAC comes out of Mute after sample rate change.

We have a whole load of work ATM, so it will take us a week or two as we want to add other features (Balance control, USB volume control option and Fixed level / Digital Pre-Amp mode) etc.
 
JohnW, yes i would normally listen in that range (-25 to -10db) which is from 'i guess people talking volume to loud music volume) ... the only reason why i mentioned -30db or -35db (below that is too low to hear music really - at -50dB it is like very quiet music and at -60db you can barely hear it and at -70db ear must be on the speaker) is cause at -15db pops are really loud through speakers. louder then music (which usually is silent in between songs).
Now i have just tested via Benchmark DAC2 as a pre and S2 playing at -70dB (cant hear music from 3m) ... it popped relatively loud (volume on benchmark used as a pre is almost at max (3pm)) - which is about the same what i get when S2 connect to poweramp directly.

I think there is no mismatch - Bryston delivers full power at about the same level where benchmark as dac delivers full volume and its about the same where Pro-ject DAC S2 does - about 2V rms according to specs. I realised same volume when going through Benchmark as pre for DAC which means it's all good.

Maybe it is my unit doing something specifically wrong ... as i mentioned earlier - pop click does not happen every time when master freq. gets changed but on average half of the time or more i can hear it.

Hi, I've connected S2 back via Benchmark DAC acting as a pre-amp (volume on Benchmark close to max -about 4pm, and volume on S2 on -20dB) - level volumes are to my ears the same when i connect S2 direct to the amp, but pops/click are wee little easier on the ear when going via Benchmark as a pre (or I am imagining).

I set with my iphone flat in my hand 3 meters from the speakers and played 4-5 songs and am including recording here (should be visible to everyone though you might need gmail account - am not certain) here is the link:
https://drive.google.com/file/d/0B_dPoeqDKpbvTV9OcTdDR3RWUjg/view?usp=sharing
If playback does not work from the browser, download the file - it should have . .m4a extension and play more or less in most of players.

Songs played are (each for about 3-4 to 10 seconds)
1. Radiohead/Just, 44.1khz
2. Killing me softly with his song/Robert Flack, 192khz
3. Feel it (in the air tonight)/Naturaly 7, 44.1khz
4. Imagine/John Lennon, 96kHz
5. Avalon/Roxy Music, DSD64, played as DOP/DSD64
6. Liberian Girl/Michael Jackson, 96kHz
7. Madonna something, 44.1khz

... order played 1-2-3-4-5-6-7 and then back each song for few seconds.
In most of the changes you can hear click/pop - some of them very loud some just annoying. The worst one is between 3 and 4 about 18seconds in a sample - it is really loud.

Hope this helps a bit.
 
We will try to reduce with a firmware update - basically increasing the time before the DAC comes out of Mute after sample rate change.

We have a whole load of work ATM, so it will take us a week or two as we want to add other features (Balance control, USB volume control option and Fixed level / Digital Pre-Amp mode) etc.

hi JohnW - sorry for cross-posting - i didn't see your response before posting my recording of 'pops'. Very happy you are aware of the issues - and YES - i can confirm i am thrilled with the 'speed' of DAC handling FS changes ... my feeling is if you mute it for few milliseconds just prior to doing the change it might work great and still be very fast. even 10ms is hard for people to spot between the songs. Benchmark was bad at that ... took in some cases over half a second and i complained to them 2 years ago but their engineering said it's all good and something must be wrong on my side and then when they came out with DAC3 apart from chip change biggest improvement was taking FS change down to 6ms :)

Balance could be cool (maybe i'd try to use it but i have decent listening space so probably no need) ... USB Volume Control could be handy (Roon can leverage that)... though i will order metal/aluminium remote for S2 as soon as it is available) ... anyhow, i am happy with the feature set and sound. if you get rid of the pops and i think you will :) Pro-ject DAC S2 is a keeper for a long time. :)

Thank you !!!

PS. One other point - i think firmware at the moment (sans pops) is really working well. Like awesome well. Didnt really listen to a lot of music just testing a lot over last 2 days and not once did something get locked up ... was not the case with benchmark (e.g. if Benchmark was playing at frequency not at 44.1khz and i rebooted the player - it would not lock though it would think its all ok - only solution was to power it off and on OR via remote switch to usb 1.0 mode and then back to 2.0 effectively resetting it).
so please please - as you ADD features - try not to screw it up :) cause it is really awesome and i think of high quality !!!

Lastly, as there is no 'driver' for linux ... i did make a patch for kernel (same one as used for Oppo Sonica DAC, just changing the USB ID of the device to the one that S2 has). Roon figured out it can used 'native' DSD and all the way to DSD512. I did discover an issue when switching from PCM to DSD playback (native DSD64 and DSD128 without any Roon resampling/volume changes etc) that song would start as hiss and then over one or two seconds it began to sound well. As I said - this is probably not complete 'tweak' to native USB support in Linux - some DACs need additional commands to be issued when switching from PCM to DSD so that may be the case with S2 but net is - that also sounds great and i tried upsampling to dsd512 which worked flawlessly :) There are no issues at all when using DOP format (DSD64/128/256) - it was locking immediately... really fantastic little product and i would need to have some god-given ears to hear how/why much more expensive DAC sounds better :)

PPS. If you guys want me to try to help on linux kernel patch for native DSD support - glad to try to help if i can - feel free to PM me. LOVE your product !!!
 
@JohnW I can confirm I'm getting the same pop sounds as @gahabana. Thanks for planning to release a firmware update so quickly.

I've also discovered an issue with Qobuz. When streaming from the Qobuz app for Windows, the Pre Box S2 Digital does not sense or display the sample rate. (I've experienced no such problem when streaming from Qobuz via UAPP on Android, nor for that matter Tidal via UAPP/Android nor on Windows, nor downloads on either platform.)

Hope that's helpful. And thanks for designing such an amazingly feature-packed little Box!
 
I've also discovered an issue with Qobuz. When streaming from the Qobuz app for Windows, the Pre Box S2 Digital does not sense or display the sample rate. (I've experienced no such problem when streaming from Qobuz via UAPP on Android, nor for that matter Tidal via UAPP/Android nor on Windows, nor downloads on either platform.)

Hey???? really really Odd! the sample rate is calculated internally by the DAC, I'm at a lost as to understand how the Qobuz app for Windows can effect this - we will have to look into it.

Really odd! :confused: :rolleyes: :)

We are currently really overloaded with work, but looking at the S2 software is on our pending list - the XMOS interface used on the S2 is a development for our MDAC2 project so this early feedback helps debug the software before its release.
 


advertisement


Back
Top