Pro-Ject Pre Box S2 Digital Impression Thread

Discussion in 'Dedicated Source Components' started by onsionsi, Aug 18, 2017.
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  1. Left Channel
    The designer of this DAC recently posted over on pinkfishmedia that "the supplied switching supply (or any other switching supply) should not be used at the same time as USB power due to high earth leakage currents".

    A couple months ago he had simply recommended any kind of external power over USB power alone (despite the manual warning against this), so I asked for clarification. He confirmed that "in the best interests of sound quality avoid a switching PSU under any condition", that "it's better to have the DAC connected to the PC via USB ONLY than using a switching PSU", and "a Linear PSU is the very best solution (or battery power)".

    I hear an improvement with just the switching supply, and don't hear a further improvement with my cheap linear wall-wart, but (a) like I said it is cheap and (b) I have very clean power here and in another house the difference might be very clear.
     
    barondla likes this.
  2. fgribas
    This is really interesting! So an "American" sound should be what exactly? Warm, but not as warm as French/Chinese warm?

    Well, I've been reading a lot of impressions of Magni 3 here (26 pages do far), and actually quite a lot of people say it's only a little warm, or even completely neutral and clear. If it would be a small change on the sound signature over the pure S2 sound, it might not worth it for me.So I might end up trying the Vali 2 or other cheap/small chinese tubes amp. Unfortunately for me it's a hit or miss as I can't listen before buying and cannot return after buying.

    Yes, that was me on pinkfishmedia asking about a data only USB cable + power supply adding to your previous question :)
     
  3. Left Channel
    Apparently, based on that NuPrime chart. Also louder. And big. Like a crossover SUV, but for music and movies instead of the offroad vehicles we mostly just take to the mall.

    I am very confused by the conflicting opinions on the Magni 3 thread. Everyone's ears and brains are different I guess. All I can tell you is that for me the Magni 2 Uber is a improvement in warmth and power over the Pro-Ject. I dislike the headphone amp in this Pro-Ject product, and even more dislike the sound of a Pro-Ject Amp Box I've tried. I use the Pre Box S2 Digital as a DAC only at this point.

    John really surprised me there. I guess his thinking on this topic has "evolved". Or something. But of course, all us early adopters had long since moved on to linear power, USB reclockers, and more gadgets. Can't leave well enough alone. We have a condition.
     
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  4. gto88
    I am confused.
    Is it ok to use switching PSU or not?
    Is a Linear PSU different from switching PSU?
    Or does it mean to use battery power supply or Linear PSU is ok?
    Can you help to finalize it?
    Thanks,
     
  5. Left Channel
    I know, right?

    Switching means for example it will work on both 120 volts and 240 volts. Linear is only 120 or only 240.

    This product includes a switching power adapter. Use that with coaxial or optical input.

    The designer says: if using USB input, let the unit draw power via USB only and don't use the included power adapter.

    But he also says for the best sound quality, for all inputs buy a linear power supply or a battery.
     
    barondla likes this.
  6. gto88
    Ok, that is clear.
    I will have to return the switching PSU I ordered, and look for a linear one.
    Thanks,
     
  7. Left Channel
    @gto88 you may find a switching PSU provides a sonic improvement and creates no problems, as there are many factors involved. But now you have the designer's latest recommendation.

    I use a cheap $10 linear wall-wart with a microUSB adapter, and hear no further benefit over the stock switching adapter so haven't upgraded further. Both improve the sound over USB power alone, but now John says to use only the linear adapter. (When this DAC is connected to my PC I also insert an anti-jitter accessory, the UpTone USB REGEN, for a small further improvement.)

    For my Sonore ultraRendu I have ordered an UpTone UltraCap LPS-1 linear power supply. Until that arrives however, the ultraRendu is working just fine on a 9v version of the same cheap wall-wart. For the Pro-Ject, I see no reason to spend the same price as the DAC on a power supply.

    There are many choices in-between those two extremes. Looking forward to your listening impressions.
     
    barondla likes this.
  8. fgribas
    As far as I know, the main difference between linear PSU and switching PSU is that the linear PSU uses a (big and heavy) transformer to drop the voltage, while the switching PSU doesn't have a transformer and uses pulse width modulation (PWM) to regulate the output voltage. The PWM process generates high frequency noise, and that is exactly what we try to eliminate in our audio chain.

    High frequency noise usually is not a problem for industrial stuff. And switching PSU generates less heat because it has a better power efficiency than linear PSU. So switching PSUs is better for some applications.

    But noise is something we always should avoid, so linear PSUs are better for sensitive applications, like our entire audio chain.

    Oh, HDPlex is one example of a linear PSU that has an AC 110v/220v switch. This would be great for me, as I travel around 110v and 220v cities. What I don't know is whether this 110/220 switch on the PSU can affect the sound quality.

    Red switch for 110/220 on the HDPlex PSU.
    [​IMG]
     
  9. Left Channel
    @fgribas yes I could probably fry an egg on my little linear wall-wart. A very small egg. That HD Plex must have separate circuitry for the two voltage input ranges, but who knows it's all isolated enough for audio purists. At that price (almost the same price as the Pre Box S2 Digital) you should also look at the lighter and perhaps more sophisticated UpTone UltraCap LPS-1. It comes with a "world-voltage compatible power supply" that it then completely isolates from the audio device with a separate "ultracapacitor-based, ultra-low-noise external linear power supply". The LPS-1 has been a hit with audiophiles.
     
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  10. fgribas
    I've been looking and loving the LPS-1 for the past weeks. That would be the best solution for me regarding size, weight and SQ. But it's $400 for only one DC output (that would be for the S2). I would still need another LPSU for the mini-PC (NAA) and ideally another one for the notebook (roon server + HQ player upsampling). So the costs of power supplies vs. DAC+miniPC wouldn't make much sense, even though the SQ would be great.

    The good thing about HDPLex is that it can power the DAC + miniPC + notebook (+ even the possible Magni 3 I'm looking for). So one power supply for everything, with a 110/220 switch.

    The bad things about HDPlex are (considering my travel setup):

    - size
    - weight
    - it uses the LT1083 LDO which has high noise and low rejection ratio ( details here https://www.head-fi.org/threads/aud...oute-new-devices-opens-up-new-options.822160/ )
    - price (specially considering the high noise LDO)

    There are cheap chinese linear PSUs that uses the same LT1083, like this one ( $80 shipped with dual output: 5v for DAC + 12v for miniPC) https://www.ebay.com/itm/322041785157

    This $80 seems to be the best option to me for now, considering not to spend the same or even more in PSU vs the DAC itself.

    In my dreams I would get an Uptone Ultracap LPS-1 and an Uptone JS-2 to power everything.
     
  11. gto88
  12. TooFrank
    Please help clarifying: the s2 comes with a power supply. I supponer that is not a “switching” PSU? I have connected the s2 to my “old” imac. Tried to switch between USB power (wireworld cable) and the external power supply. Can’t hear any difference even with hi—res files. Do I need a better PSU or is the power from the iMac sufficient, I.e not causing poorer SQ?
     
  13. Left Channel
    @fgribas dreams are good. Keep on dreaming.

    @gto88 if nothing else many switching power supplies create noise just because they are cheaply-made, not because they are switching. Many are happy with the switching $50 iFi iPower, and I would certainly hope there is no such problem with the $2,995 Benchmark AGB2! But in this case, the designer of the Pre Box S2 Digital is concerned primarily with one issue: galvanic isolation. Both the stock adapter and my third-party adapter sound the same to me though. YMMV. A lot depends on the quality of the power you're plugging into, and what else is sharing the circuit. Best to wait and listen to the Pro-Ject before buying anything else.

    @TooFrank it comes with a switching supply originally intended to power coaxial or optical input, and when I plug that in I hear an improvement. If you don't, then celebrate because your iMac may be giving you a good USB signal. That may change if you move the power or other wiring of the iMac, but fingers crossed you'll be happy with it for a long time. You may hear no improvement from an upgraded adapter (I don't), or from a USB reclocker (I do, though it's subtle).
     
    Last edited: Jan 1, 2018
  14. barondla
    Is the designer worried about using switching power supply with usb because of noise or safety? High leakage in the ground sounds like it could be dangerous?
     
  15. Left Channel
    Edit: I've changed this post a couple of times to throw theories out there, but I really have no idea exactly what John means, and It's been difficult to get much information out of him lately. If we get more info I'll cross-post it here. But I really don't think it's a dangerous thing. I've used the switching supply and USB with this DAC many times with no problem, that combo sounds better, linear just seems like a good idea to me and others say that sounds even better, and now we have yet another reason to use linear PSUs.
     
    Last edited: Jan 2, 2018
    barondla likes this.
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