Pro-Ject Pre Box S2 Digital

(Magnus) #807

Do you know what type of cable would be suited for connection between battery and DAC? A thin silver plated copper cable? What stat to focus on, resistance, capacitance, …?

(Martin Webster) #808

22AWG/ 0.8mm multi-strand tin coated copper wire would be fine for this application.

(Martin Webster) #809

Just to add, you really ought to put a fuse on that battery (12Ah) with these wires since they are only rated at around 3A. If you get a short they could quite easily turn into a hot wire!

(Magnus) #810

Fuse sounds like a good idea, but what kind? I was thinking that a 2A would be enough, and something easy to solder and with few extra contact areas like this one: image
Yes, I have to replace and solder if it breaks, but that should not happen very often (I hope)

(Martin Webster) #811

I’d probably go for a 20mm inline fuse holder like this since it connects directly on the battery terminal. Alternatively, you can get some that take an auto fuse (mini or standard.) But yes, 2A would be okay.

(Magnus) #812

I figured since this is all about clean power, that I should stay away as much as possible from contact areas, and solder everything. But it probably don’t matter very much.

Thanks for the help, going to order stuff now :slight_smile:

(Sean) #813

There was a company a few years ago that sold an SLA battery and it had the safety control electronics mounted and had DC output read to go and you could vary the regulated DC output from 12V down to 6V. Had safe charging too, with auto shutoff. I can’t find them anymore with Googling.

They came out a few years too early!

(Robin Carmack) #814

I no longer have the S2 but I used this to power it and the Ultrarendu. Worked really well. Battery power is the way to go:


Battery power is relatively inexpensive and the performance I have read is amazing, I’m personally using an LPS 1.1 for the s2 and the Sq is comparable to way more expensive dacs, but overall it may be more cost than effective to use the battery

(Magnus) #816

I don’t know if @John_Westlake still checks these forums, but if he do maybe he could tell how damaging it is to feed 6.7v to the Pro-Ject DAC.

(Sean) #817

While we wait for his reply (hopefully)… since it’s still working for you, I would assume the switching regulator at the power input can allow for more than USB 2.0 spec of 5.25Vdc, otherwise you would have already damaged it by now. After that it gets regulated to 3.3Vdc to all the various parts around the board.

Surprisingly I think you’re ok… although I wouldn’t risk it myself and wouldn’t recommend anyone else try it hehe.

You don’t seem to have tripped the over voltage protection yet, which is good…

If it was a linear regulator at the power input, I think you might have more risk of longer term damage with over voltage… I THINK all the linear regulators are all in the analogue section (3.3Vdc).

You might have better luck with a quick reply from John by messaging him on the Pink Fish Media forum, where he is active. If you do and he replies, let us know here what he says.


I was wondering if the firmware he was developing (JW) it is been already released?

(Magnus) #819

Me to, he mentioned some “community edition” a few months ago. But I think he has been busy with streaming boards, MDAC2 and so on (he seems to be a busy guy) :slight_smile:

(Magnus) #820

I wonder which chip in the DAC gets warmer because of extra voltage. Maybe its possible to add some self-adhesive heat-sinks (lots of them available for Raspberry so easy to get and cheap). Its low-priority, but might increase the lifespan of the DAC now that it gets warmer than usual.

(Mark Hyland) #821

Does anybody else get a “white or pink noise” effect using this DAC when it changes to hires audio (such as DSD)?
I get it occasionally when I feed it a DSD file (via Roon Nucleus connected via USB). The noise reduces down to an inaudible level over the course of about 6 seconds, where the music takes over.
Running the latest FW on the Pro-Ject.

(OuYang, Ming-Kang) #822

IF you use Native DSD on Roon, try to change it to DoP.

(Sean) #823

I’m no expert but I’ll pretend to play armchair expert here while you/we wait from John Westlake’s reply…

Everything in the DAC is powered by 3.3Vdc or lower. As long as the regulators (especially the linear ones) aren’t getting more than 3.3V, they won’t get warmer than usual.

So I’m more curious to know more about the switching regulator right at the power input. If it can handle up to 7Vdc (or whatever the number is) and still output 3.3V to the rest the circuit, you have nothing to worry about.

I doubt that it’s a linear regulator there at the power input but if it is, then that could be getting warmer than usual.

But that’s the first thing I’d try to find out about - what is at the power input and what’s the official input range. I wouldn’t be surprised if it’s a switching regulator that can take up to 7Vdc, based on the fact yours is still working. I aint’ gonna test to find out though hehe.

After a few hours of music playback, do you feel the case getting any warmer than usual or not?

Have you emailed Pro-Ject Technical Support? You could be honest and tell them that you’re aware you may be voiding warranty… Then they might be more honest with you and give you all the technical nitty gritty with the disclosure that you’re doing things at your own risk. But at least you can then do your own risk assessment with all the right info.

(Magnus) #824

Same here, but I solved it by up-sampling everything to DSD256 (and I let Roon do the first unfold for MQA).

(Magnus) #825

The case gets warmer, but not hot. But I could not see any voltage regulator that uses the case for cooling.

(Mark Hyland) #826

Would you be so kind as to take a screenshot of the recommended settings Magnus?