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Pro-Ject Pre Box S2 digital DAC

Discussion in 'audio' started by miero, May 9, 2017.

  1. DimitryZ

    DimitryZ pfm Member

    IFI IDefender will break the computer USB power connection at the USB plug, so your DAC will not get noisy computer power...Maybe worth trying for $50, feeding the side micro USB power plug with LPS.
  2. sberry20118

    sberry20118 pfm Member

    True but ground / leakage current loops can still happen via the ground.

    iFi's iGalvanic3.0 is the one you really want but some people have compatibility issues (similar issues with the Uptone Audio ISO REGEN - they both use the same digital isolator).

    If you can try the iGalvanic3.0 risk free and return it for a full refund, that's the one to try.
    Mark Dirac likes this.
  3. slavedata

    slavedata pfm Member

    But it costs more than the Project S2 did! Seems a touch unbalanced, the isolator costing more than the device it drives.
  4. Mark Dirac

    Mark Dirac pfm Member

    What sources are exhibiting this Fred? Foobar? Tidal? PC? streamer? How have you ensured that their volume controls are disabled? Tidal is notorious for being opaque to set up properly. Even once set up, Tidal is easily able to decide to re-insert Windows's volume control.
  5. sberry20118

    sberry20118 pfm Member

    Hehe yes I wish those gadgets were a little cheaper but at the same time the S2D punches way above it's weight and could easily be priced a couple of hundred dollars more and still be great value (in my opinion).
  6. DimitryZ

    DimitryZ pfm Member

    So...PC or Mac for streaming? I have been using cheap tablet Pcs and it has been frustrating.
  7. MagnusH

    MagnusH pfm Member

    If you have a very noisy PC, try the toslink connection. Sure, you get limited sample rates, but toslink filters away 100% of all electrical noise from the PC so it might be worth it. I am running toslink myself right now, but I have ordered an USBridge for USB isolation.
  8. Mark Dirac

    Mark Dirac pfm Member

    If you are asking "PC or Mac" with relation to the S2D, then you will see on the thread summary Google Doc that we have not had any significant feedback about compatibility with Macs (since the very early days, when I recall there were some difficulties, since resolved IIRC).

    If you are asking "PC or Mac" generally, then I reckon you might get more response by starting a new thread.
  9. sberry20118

    sberry20118 pfm Member

    The cool thing about the USBridge compared with Sonore and SOtM streamers (apart from better price) is it can run off a 5V powerbank charger.

    For critical listening I did try this, running off WiFi with the included WiFi adapter also. In this setup you get isolation as good as optical (no electrical connection to mains power). It's a pain with having to re-charge the battery though. And still in the end I found Toslink as enjoyable, with much less effort required.

    Something cheap to try anyway, when you already have the USBridge.
  10. MagnusH

    MagnusH pfm Member

    I also ordered a iFI iPower 5v (and have one for spare since before), so I plan to remove that jumper and power sparky and USBridge individually with decent power. Then I have a linear power to my S2. I will try with Ethernet first, see if I get any ground loop humming (I hope not).
  11. sberry20118

    sberry20118 pfm Member

    Last edited: Apr 16, 2018
    Mark Dirac likes this.
  12. MagnusH

    MagnusH pfm Member

    I know the iPower is not linear, but using my ears it does sound good for a low price. Having said that, you can of course get better (SBooster, UpTone LPS-1, etc) but they are a little pricey for a $400 DAC.

    Here is a review of 3 PSUs, including the iPower:
  13. DimitryZ

    DimitryZ pfm Member

    I have a S2 question...

    I am finding a bit of a deficit in dynamics from the RCA jacks, though maybe its too early to draw any conclusions. However, has anyone tried using the headphone jack for line level drive? I don't think typical headphone output has a lot of gain. The ESS chip the device uses seems to be pretty highly spec'd and has a very low output impedance.
  14. sberry20118

    sberry20118 pfm Member

    I completely understand.

    It's beyond my expertise anyway but I guess people can watch the Hanz B video and then read John Westlake's posts and make their own conclusion who to believe, when used with this DAC that John designed.



    But as you say, trust your ears above anything/anyone else! We agree there for sure.
    Last edited: Apr 17, 2018
  15. DimitryZ

    DimitryZ pfm Member

    Headphone output sounds better, denser sound with "meatier" midrange. No appreciable gain over RCAs. AQ Golden Gate with Furutech 1/4 plug.

    Also liked Pangea Premier XL USB, but won't handshake with the power leg plugged into an LPS, has to be in a second computer USB port...stayed locked when the power leg was unplugged after initial handshake. I am using it the standard way, but will experiment with yanking the power leg.
    Diego Humanes and Mark Dirac like this.
  16. Mark Dirac

    Mark Dirac pfm Member

    Thanks Dimitry. Interesting. If I have understood correctly ... You connected the S2D to a USB cable which has the data and power connections split into two distinct connectors at the far end. But you found that the S2D wouldn't function when the far end USB power connector was connected to your discrete power supply; the S2D would only function when the far end USB power connector was connected to a USB socket on a computer. However, once the S2D had begun functioning, you could then disconnect the far end USB power connector, and the S2D would still function.

    Interesting - why would the S2D care if its power comes from a discrete power supply or from a computer?
  17. sberry20118

    sberry20118 pfm Member

    "The generic answer to this question is yes, the VBUS (+5V from cable) must be connected to the device even if it is self-powered. The reason is as follows:

    To start the connect process on host side, the device must pull up D+ (in case of FS/HS mode), or D- (in case of LS device).

    However, USB specifications have a mandatory requirement that no USB device should source any current on any interface pin unless it is connected to a cable, see section, which reads,

    The voltage source on the pull-up resistor must be derived from or controlled by the power supplied on the USB cable such that when VBUS is removed, the pull-up resistor does not supply current on the data line to which it is attached.

    If a USB device doesn't have this control, one of data lines will be a source of current. Premature assertion of pull-ups were a source of problems for some legacy USB hosts. That's why this rule was instituted, and there is a special test for this in USB-IF certification program.

    Therefore, the USB VBUS is an important "side-band" signal in USB connect protocol. As such, normal USB device ICs do have a separate input pin to sense the presence of USB host. Some IC manufacturers (e.g. FT232H, MCP2221, etc.) skip on this requirement, assuming that their chip will be solely used in bus-powered configuration, where the pull-up control requirement is automatically satisfied. However, when designing these chips into self-powered designs, some extra circuit efforts are needed to link the enabling of pull-ups with presence of VBUS on the USB port.

    Regarding the USB connect "handshake" protocol, USB doesn't rely on current drawn from VBUS. The protocol is this: Host port must have VBUS active; VBUS is connected to device; device sees the VBUS and pulls-up 1.5k on one of D+/D- wires; host sees this connect, and after a 100ms delay asserts USB_RESET signaling (SE0 etc.)."

    Mark Dirac likes this.
  18. DimitryZ

    DimitryZ pfm Member

    It seems that this is "normal" behavior for an USB handshake protocol as described by sberry...

    I did not experiment immediately with the "handshake-disconnect" mode, since I wasn't sure if the connection would be stable over long periods of time. I was concerned that after some set time the USB protocol would need to be "re-asserted" (maybe with MQA start/restart, which happens when Tidal is slow) and without the full dual USB port connection (signal and power legs), the connection will die. Also, seems like plugging and unplugging the power USB connection is a chore...

    By the way, my cheap tablet has two USB connections, with USB3 taken up by an AC wifi adapter (built in wifi was cutting out on Tidal, though the signal is strong and it is 75 mbps wifi), so I have both legs of the Pangea cable plugged into a tiny USB dual port hub that is running from USB2 port. Works well, though it did not work with Shiit Wyrd decrapifier - S2 would disconnect from the PC when the music started playing through Tidal. It's all very mysterious.

    This is the tiny USB hub I am using...comes in different colors for the interior design sensitive audiophile.
    Mark Dirac likes this.
  19. pj.walczak

    pj.walczak Active Member

    If I were you I would buy Roon license, buy Intel NUC and install ROCK on it (it will be your core server) and buy Allo USBridge that toghether with S2D will be your Roon endpoint.
    Your tablet will be your Roon remote.
    RickFer likes this.
  20. DimitryZ

    DimitryZ pfm Member

    I definitely have a lot to learn about the modern streaming world...I only have a notional idea of what Roon does. I am a real streaming novice...I am really just an old fashioned audiophile (LP, CD, etc.) and only recently have been investigating computer-based options. As a "sideband" I recently established an 8 track capability for my system, which can sound excellent, musically, if not technically.

    Currently, the tablet sits on a shelf above the stereo, together with an IPAD air. I use Google Remote Access on my phone to "control" my tablet, which can be frustrating at times.

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