Pro-Ject Pre Box S2 Digital

(Magnus) #847

New review:

(Fernando) #848

New driver available, an updated Thesycon driver 4.47

The link will change when they update the S2D page, but this link will work for some days.


I decided to try a Schiit Magni 3 and connected it to the Pro-ject’s pre-outs. I was surprised how much better everything sounds compared to the built-in headphone amp.

Might be a stupid question, but how does one handle volume when having a separate headphone amp? It seems to work well setting Roon to “fixed volume”, turn the knob on the Pro-ject to full (0 dB) and handle volume on the Schiit. Transport is a microRendu.

Very happy with this setup for now, only gripe is the noise when switching from a PCM track to DSD.

(Sean) #850

This is a great way to do it.

I use a THX 789 headphone amp connected to my S2 DAC. Much better than when I was using the S2 DAC’s built in amp, with my headphones anyway.

(Wim) #851

I set the volume to fixed 100% in Roon device settings and use the volume knob of my headphone amp.
In another setup I have the amp on fixed volume and use the remote of the S2 Digital to adjust volume.

(Fernando) #852

I’m sharing all my findings regarding power supply and softwares that I use with the S2D. Long post :slight_smile:

Power supply. I’ve tested: Included switching power supply, 5v powerbank, USB port from computer (additional port, not the USB data cable), iFi iPower 5v, grounded iFi iPower 5v, Chinese Linear Power Supply.

Based on my listening, the best ones are (in the following order): 1- grounded iFi 5v; 2- chinese LPSU; 3- ungrounded iFi 5v.

I already had an iFi iPower for the S2D and was happy with that (significantly better than the included PS or 5v powerbank). But I finally found a Chinese LPS that has a 5v USB output + 12v output and also a 115v/230v switch. I have a 12v mini PC that I will use as an audio endpoint for Roon/HQPlayer. So a single linear power supply with 12v + 5v is what I wanted. This is the one I found:…-linear-thermal-power-supply/32923450663.html

I ordered one, and while it was on the way, I decided to try the JSGT (John Swenson’s Ground Technique) on my iFi iPower. Bottomline is: all switching power supplies suffers from leakage current. Linear power supply blocks most of leakage current. iPower has a ultra low noise output across the audio bandwidth. But iPower is still a switching power supply and suffers from leakage current.

The technique is basically connect the negative pole of the power supply to the ground pin of the same power outlet (or power strip) where the power supply is connected.
More details here:

I made my mod a little different (aesthetically better) than the original idea of using additional female connector + male connector. Mind that these 2 socket male plugs must be connected to the same power outlet (or power strip).



This grounding made a great improvement. The Chinese LPS arrived later and it sounds good, it’s sturdy and well-built. However the grounded iPower still sounds better.

Software and configuration. I find DSD128 better than DSD256 or DSD512 on the S2D. I thought it strange and looked for explanations. I found out this:

It’s an article from an engineer involved in the creation of SACD at Sony. The article is from 2015 and now we have DSD256 or DSD512 capable hardware, like our Pro-Ject S2D. But capable doesn’t mean optimized. Rough analogy: it’s like a video-game capable of running a 4K game, but at 15 fps. I think DSD256 (at least on the S2D) still introduces some kind of distortion or artifact, because it doesn’t sound as natural as DSD128. But again, this is all based on my listening impressions. One fact is that DSD128 already solves the problem of audio bandwidth noise that DSD64 presents.

Source material: I mainly use Qobuz and Tidal, both on Roon. HiRes from Qobuz is great! MQA from Tidal is nice, as long as we decode only the 1st stage on Roon and then upsample on Roon or HQPlayer. Then I upsample to DSD128 on HQPlayer, using poly-sinc-short filter and DSD5v2 modulator. The filter is a matter of choice, but it seems that DSDv2 is the “correct” modulator for this DAC. I came to this conclusion only after having such a clean power supply. Roon upsampling instead of HQPlayer does a good job. HQPlayer upsamples better, but Roon using DSD128 “Precise, Linear Phase” filter and “5TH order (CLANS)” modulator comes close. I also use parametric EQ on Roon, and it squeezes the best out of my Shure SE846 IEMs.

And the final piece after upsampling is JPlay Classic (only the driver, not JPLAY femto). I use Ultrastream engine, 500 Hz DAC Link and Kernel Streaming. 1000Hz DAC Link sounds even better, but it needs a dedicated audio computer so it doesn’t have dropouts, but currently I’m using my work PC to everything. I also use Fidelizer software. I bought Audiophile Optimizer but still haven’t tested because it also needs a dedicated audio computer. Using my mini PC for that is the next step.

And finally on the Pro-Ject Control Panel, the lowest available ASIO Buffer Size, and Safe Mode unchecked.


Nice info, thanks. Question I use Roon to upsample then straight to the dac it goes using RAAT; at the control panel for the s2 would you set lowest buffering as well as uncheck safe mode? Is so, why would I do this? Thanks

(Fernando) #854

Yes, I always do that. It assures minimum latency on the driver. For me, it gives the best sound. You can try different settings of the buffer and chose your favorite. It’s effective only if you use ASIO, not WASAPI.


Hi and thanks. I just switched my settings and giving it a try. Still can’t decide if I like DSD upsampled to 128 or just straight up pcm. Alot of choices on this DAC!

(Fernando) #856

That’s the thing with out hobby. Try and try, play with settings. My main recommendation is to invest on a power supply. Grounded iPower or a Linear PS.


Absolutely is huh! As far as the power supply goes I haven’t gone beyond using the supplied one. Ive seen alot of mixed feelings on this. I will have to explore this to satisfy my curiosity. As far as I know there’s nothing measurable in this but there are many out there claiming a pretty substantial gain in sound quality in upgrading the psu as you are saying, including the designer…

(Costas) #858

I’ve got an Allo USBridge with separate iFi iPower for just the USB board (Sparky gets its own wall wart and J28 is open). Do you folks think it’s a good idea to power the S2 over USB? Or would you run another iPower to the S2 as well?

(Gerald Richardson) #859

John Darko at Digital Audio Review had commented that Sparky/USBridge is not enough to drive the S2, so I use a separate power supply for the unit.

(Costas) #860

Thank you Gerald. I certainly agree with that.

But I’m suggesting powering the Sparky board separately, and the USB board with the iFi iPower supply. From
Please note that you can feed the Sparky separately with one PSU (5V / 2.0A) and USbridge HAT (5V / 100ma + whatever your DAC needs).

Do you folks think it would be a good idea to use another iFi iPower supply just to power the S2? (That would be 3 separate power supplies total; 2 for the USBridge and one for the S2). Or is that overkill?

(Gerald Richardson) #861

I use this inexpensive power supply.

(Wim) #862

I’m using an Audiophonics Linear Regulated Low Noise Power Supply that is powering the RPi3B, the RPi 7" display and the Pre Box S2 Digital.

(Ralph Pantuso) #863

I love it! But be prepared for lots of fallout. :fearful:

(Sean) #864

I had some discussion with the designer (John Westlake) further up in this thread and he was not a fan of the iFi iPower. Neither is John Swenson. Leakage isn’t the only thing Swenson has commented about with the iPower but also it’s waveform when he’s measured it…

Not sure the Swenson grounding trick is enough to save it, even if it helps a little (shunting some leakage to ground).

I linked the Jameco linear power wall wart way up in the thread and it got John Westlake’s thumbs up.

@fgribas can you share (describe) the differences in SQ that you heard between stock SMPS vs USB powerbank (5Vdc battery) vs grounded iFi iPower?

I know you already mentioned which you prefer but can you describe the differences? If possible.


(Fernando) #865

I can do further testings when I get back home, I’m travelling this week.

As far as I remember: quieter background, deeper and stronger bass, better instrument positioning. All of these gets better comparing the different PS. For me, even the stock SMPS sounded better than powerbank. But it depends on the power circuit where you are. And my powerbank is a cheap one, it must have poor voltage regulators: Pineng PN-968 10000 mAh

Besides me, other users stated that the grounding trick worked nicely with the iPower.

I must say that the Chinese LPS that I bought is very nice! Much better than the stock SMPS, powerbank and ungrounded iPower. But the grounded iPower is a little bit better.

One thing that anyone can try is to do the grounding trick on the stock SMPS.

(Sean) #866

This is stricky as the stock SMPS has a microUSB plug.

Thanks for sharing your comments and observations also.