Pro-Ject Pre Box S2 Digital

(Magnus) #868

I run my S2 DAC with toslink now, prefer the sound over the USB from Allo USBridge and through ethernet/fiber. Previously I preferred Allo USBridge and USB, but I think since I started running my DAC on battery that changed. The disadvantage is less sample rate and no DSD.

I use a 6V 12Ah sealed lead acid battery connected directly to the DAC (I have heard that LiFePo4 batteries should be even better due to less internal resistance). Fully charged its 6.7V so a little over the 5V but worked for several months so seems fine (the DAC gets a little warmer though).

100% galvanic isolation from everything except the battery is nice though, no more “sounds better at night” :slight_smile:

For MQA I let Roon do first unfold, then I upsample everything (including non-MQA) to 192khz

(Sean) #869

Another thing is the Swenson grounding trick was specifically advised for use with grounding specific network switches (like Netgear GS105/108 for example).

It appears a lot of people have gone grounding every SMPS in their system, to reduce leakage currents.

However if you ground the DAC’s PSU and you have a grounded USB source, you can now created a nice groundloop and create groundloop hum (depending the rest of the system connection to the DAC).

John’s recommendation is still to have only one component grounded but I think this has been missed by some.

Not a comment at you but just a general comment for those maybe getting carried away with the Swenson grounding trick…

(Fernando) #870

You are right @Sean2016 I completely forgot that the stock SMPS is micro USB wired :frowning:

(Magnus) #871

While I do like the S2 DAC, the lack of support from Pro-Ject means I won’t buy any more DACs from them (or anything else for that matter).

I have ordered the RME ADI-2 DAC as an upgrade to my S2, those guys seems very serious about firmware updates and support, just check their forum:

(Fernando) #872

I’ve been flerting with this DAC since november :heart_eyes:


So my micro usb snapped off the the board.
I thought they had fixed that problem.
Bought from AAdvisor in late June.
Contacting them tomorrow.

(Sean) #874

This nice little DAC has just made Stereophile’s Class A list.

(Magnus) #875

Yea, its a nice DAC, but it needs a proper LPS/battery for power and a good USB input. With stock switched power and USB directly from the computer it’s far below what it can sound.

(Sean) #876

JA’s measurements conclusion:


It’s always nice when our ears agree :grin:

(Ralph Pantuso) #877

Could you please explain in detail how the sound of the Pre Box S2 digital is improved by using a “proper” power supply and USB input. I ask because I have a pre Box S2 digital which I use with the stock poer supply and the coax input and it sounds fantastic!

Specially do you actually hear “noise” from the stock power supply and how does the sound improve using USB input instead of coax input. Again I ask because the fully functioning human ear/hearing that I was born with cannot hear picosecond jitter.

(Sean) #878

This is a great problem to have - for the wallet!

The designer of this DAC himself has mentioned performance is improved with a good quality linear PSU (you’ll need to read at the top of the thread).

That doesn’t mean everyone will necessarily hear improvements or difference, when he says performance is improved… so I wouldn’t stress too much about it.

(Magnus) #879

Better power gives better clarity, quieter backgrund and more details. Part of it is because the power is better (more stable, less varied), but also because switched power supply tends to inject lots of electronic noise which is nice to get away from.

The best sound I could get from the Pro-Ject DAC is with this chain:
Computer/Roon server -> ethernet switch -> FMC -> fiber -> battery powered FMC -> Allo USBridge -> UpTone USPCB A>B -> batteri driven Pro-Ject Pre Box S2

Lots of tweaks I know, but they do make a difference.

(Ralph Pantuso) #880


All those tweeks might be too much for me. I love that way the Pre Box S2 Digital sounds in “stock” mode driving my Beyerdynamic T5ps - clear as a bell with lots of inner detail.

The only knock on this great little giant killer is that it really doesn’t enough power to drive full size high impedance headphones, like the Sennheiser HD800s or the Beyerdynamic T1s. But when using lower impedance, easier to drive headphones the Pre Box S2 Digital is wonderful.

(Sean) #881

I agree. The DAC section is excellent. I use the state of the art (and underpriced) THX 789 for separate headamp duties.

Brilliant combination that can drive everything with ultra low distortion.

And well under $1k total…


No comments?

(Sean) #883

What did AAdvisor say/do?

(Sean) #884

JA’s measurements agree with your ears.



Sumiko is handling the RMA for Audio Advisor…

BTW …just picked up the massdrop thx aaa 789 (used) even-though I got in on the last drop (462 gone in 2 hours) but shipping in the middle of May,
I will sell the new one and keep the used one.

(Sean) #886

Nice, that’ll make a brilliant combination.

Get a pair of these cables, as recommended to me by the THX Power and Analogue Engineer, Andrew Mason.

The performance of Pro-Ject S2 + THX 789 doesn’t sound far off my Hugo2 alone directly driving the same headphones… to my ears anyway.


I like monoprice (I live in LA not far from them).
I’m gonna make my own cables using higher end Mogomi.
Pacific sales in Burbank carries it in bulk.They work with a lot of the film studios in town.

Didn’t you use something like that?