PS Audio Lanrover USB transport discussion

[davide256]

This device has caught my attention, given the options like Regen and Intona on the market which try to make up for poor electrical coexistence between a digital source and a DAC. The idea of electrically isolating in network ethernet signal paths using optical connection works, the one defect I can see with the device is that its still a wired connection between the input and output boxes unless you spend another $150 on FMC's and optical cables. Anyone tried this yet, if so would you mind sharing your results?

 

LANRover USB Transporter | PS Audio

 

 

Also seeing today this review in Positive Feedback Online

 

Brief Impressions from an Editor’s Notebook:Â* The PS Audio LANRover USB Transport - Positive Feedback

[Abide68]

Heres a link to a review/comparison from Audio Bacon:

 

https://audiobacon.net/2016/12/01/ps-audio-lanrover-review-vs-microrendu-uptone-ultracap-lps-1/

 

looks interesting........Also keen to hear from anyone whos had a good listen!

[Speed Racer]

24 minutes ago, Abide68 said:

Heres a link to a review/comparison from Audio Bacon:

 

https://audiobacon.net/2016/12/01/ps-audio-lanrover-review-vs-microrendu-uptone-ultracap-lps-1/

 

looks interesting........Also keen to hear from anyone whos had a good listen!

 

Okay, I have a problem with this article in regards to the PS Audio Lanrover. 

 

Ethernet isn't USB as all it is sending over the wire is packetized data. There are no clock, ground, or power lines or signals. The data is guaranteed to make it intact as well. How the heck can the ethernet cable used make a difference in the sound quality since, no matter what, the data is the same when it gets to the receiver Lanrover. This is a case where it truly is just digital data.

 

Or am I missing something? Because I don't see it.....and I am an ex datacenter manager for a web hosting company.

[Superdad]

7 hours ago, Speed Racer said:

How the heck can the ethernet cable used make a difference in the sound quality since, no matter what, the data is the same when it gets to the receiver Lanrover. This is a case where it truly is just digital data.

 

Or am I missing something?

 

Actually, you were warm.  The receiver in the LANrover (or any Ethernet or USB device) is a PHY (physical interface), and the packets of data coming in are not fast marching little ones and zeros.  It is a high frequency analog voltage, and the job of the PHY chip is to decode that into a binary data state.  And the PHY chips are nasty, complex little buggers containing multiple PLLs, and clocking systems--and the harder they have to work decoding the incoming signal, the more perturbations they generate: bursty power draw spikes, ground-plane noise, "packet-data-noise," etc.

Ethernet cables and USB cables (and of course USB hub chips and other interfaces such as our REGEN, etc.) exhibit variations in signal integrity (as seen on an eye-pattern) which is a mix of amplitude, slew, noise, jitter, etc.

Improved SI (as well as improved impedance match in the case of USB) makes the job of the PHY easier, resulting in less device-internal generation of the issues listed above.

 

In the case of a USB (or Ethernet) interface located inside a DAC (or USB>S/PDIF converter), better signal integrity readily translates into better sound as the deleterious stuff generated by the PHY sails though most any isolation attempts, ultimately making its way to the master clock.

 

So while the Ethernet cable between the two USB-based LANrover devices is a bit removed from direct DAC/converter PHY interaction, its own PHYs may be affected by SI variation which somehow gets carried over into the SI of the LANrover's USB output--and THAT we KNOW is important.

 

That is also why a really good power supply for the LANrover has proven worthwhile.  Ideally one that preserves the galvanic isolation offered by the Ethernet connection by blocking leakage currents and keeping the "leakage loop" from being re-formed with the upstream computer, etc.

(I think you all know the sort of power I'm referring too.  Hey, my time to spell out the mechanisms of all this weird stuff is not free, so perhaps my small product plug is earned? )

[Speed Racer]

Alex,

 

I get all of that. However, as a datacenter guy, I know that these interfaces can handle a lot more data than they are being sent for USB 2.0 audio. It's nothing for Gigabit Ethernet. And ethernet is nothing like USB. As I said, there are no ground, power, or clock signals. The data lines are differential. Data that doesn't make it is resent. I see no reason that a quality cable that works properly can be out done by a "better" cable. This is digital information encoded in these signals. These devices provide complete isolation from the PC ground, power, and clocking issues. The PHY is not being corrupted by anything from the sender side and as long as the data is intact, so how can there be a problem there?

[Superdad]

46 minutes ago, Speed Racer said:

Alex,

 

I get all of that. However, as a datacenter guy, I know that these interfaces can handle a lot more data than they are being sent for USB 2.0 audio. It's nothing for Gigabit Ethernet. And ethernet is nothing like USB. As I said, there are no ground, power, or clock signals. The data lines are differential. Data that doesn't make it is resent. I see no reason that a quality cable that works properly can be out done by a "better" cable. This is digital information encoded in these signals. These devices provide complete isolation from the PC ground, power, and clocking issues. The PHY is not being corrupted by anything from the sender side and as long as the data is intact, so how can there be a problem there?

 

 

It is a rabbit hole I know.  But remember two things:

1) It is not actually "data" (ones and zeros) until the PHY turns it back into such;

2) We are not talking at all about corrupted bits--we are talking about perturbations taking place inside the device (in the activity of the PHY) which are effecting the ground-plane elsewhere in the device.  And in the case of the LANrover, likely affecting its USB output SI.

 

I am not arguing that this is a major sonic variable (USB signal integrity going into a DAC is vastly more significant), but I have personally compared a pile of 25 foot Ethernet cables (mostly generics of chosen differing construction;  just going Mac to Mac for fetching of shared music files), and the BlueJeans/Belden (10GX) Cat6a came out on top.  Again, not a knock you over the hear SQ difference, but one that certainly withstood multiple swappings (I hope I don't attack the double-blind flies with that statement ). 

[Speed Racer]

I know it's not just ones and zeroes. I know the voltages are essentially analog. But we aren't dealing with power, ground, or clock signals either. I am also talking about difference between a properly designed, built and in spec cable that would actually work at GigE speeds which are MUCH faster than USB 2.0 speeds. Yes, the device has to re-encode the data into USB packets and send them along. But I don't see what, from the ethernet side, could corrupt that process. Again, no power, no ground, and no clock are being passed.

 

I ran a datacenter that had huge amounts of data running between network attached storage and servers where performance was critical. Yet, we never found more expensive cables, beyond a quality cable built to spec, to make any difference in transfer speeds or errors seen on the network.

 

I realize this is audio. But again, nothing bad is transferred over the ethernet wire. If the receiver is getting clean signals, and they are differential and must clean to work at GigE speeds, the interface is going to get proper and easy to handle signals.

 

I guess I need to get a more complete technical explanation as to how this could happen because it makes no sense to me.

[asdf1000]

5 hours ago, Speed Racer said:

 

I realize this is audio. But again, nothing bad is transferred over the ethernet wire. 

 

Not an expert but groundloops can travel through the shielding of ethernet that is shielded end to end which may affect sound quality - unless you have a floating shield design like the Cat 6a Blue Jeans / Belden that Alex mentioned. 

 

I'm sure Alex or another expert will jump in and correct this.

[Speed Racer]

I am pretty sure we are talking UTP here......

[asdf1000]

34 minutes ago, Speed Racer said:

I am pretty sure we are talking UTP here......

 

UTP can still have an overall foil shield can't they? So if this outer shielding is connected to ground end to end, then you can have a groundloop possibly? But the BJC/Belden Cat 6a floating shield design may break this groundloop.

 

Alex is much more qualified on this stuff than me @Superdad

 

[Speed Racer]

UTP = Unshielded Twisted Pair

 

With unshielded twisted pair there is nothing to ground and UTP connectors have not metal except for the pins.

[asdf1000]

1 hour ago, Speed Racer said:

UTP = Unshielded Twisted Pair

 

With unshielded twisted pair there is nothing to ground and UTP connectors have not metal except for the pins.

 

 

[Speed Racer]

The BlueJeans Cat6a cable is effective unshielded for purposes of this conversation. All that are connected are the differential transmit and received lines. There are there are no ground, power, or clock signals to get mucked up.