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AR-T Legato II USB-S/PDIF Converter - Page 4

post #46 of 88
Quote:
Originally Posted by Viper2001 View Post

Pat is making a run of Legato II.1 PCB.  This will add 3 functions to it:

- the patched PCB will be incorporated into the main circuit

- charge LED that will change from red to green when batt is fully charged

- a circuit to shut down the unit if batt is below a certain voltage (this is to prolong the lifetime of the batt in case the user has no charger connected and keeps on playing until the batt is depleted)

 

 

Well, I am on the wait list so this progress is good news.

 

This is kind of an interesting experiment for me being I'm an audio skeptic. The description of the Legato suggests I'll never be able to surpass it (yes I can't afford a Femtoclock). If I can't hear a difference with the Legato II I'll be able to cross jitter off my list of worries.

 

If I can hear a difference, well you'll be able to read about it here.

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post #47 of 88

The Legato 2 sounds better than the direct async usb inputs into numerous DACs I tried.. including my Chord QBD76HD and Emm Labs DAC2X.


I wouldn't write off that something else that can give better performance, but it seems like few competitors.. none of which provide objective measurements even if I were willing to pay a lot more money. I haven't seen mentions of a femto or galaxy clock in a usb/spdif converter yet.


Haven't tried Legato 1 vs 2, but it should be better.. at least according to Pat.


Edited by Quest88 - 1/15/13 at 6:09pm
post #48 of 88
Quote:
Originally Posted by Quest88 View Post

The Legato 2 sounds better than the direct async usb inputs into numerous DACs I tried.. including my Chord QBD76HD and Emm Labs DAC2X.


I wouldn't write off that something else that can give better performance, but it seems like few competitors.. none of which provide objective measurements even if I were willing to pay a lot more money. I haven't seen mentions of a femto or galaxy clock in a usb/spdif converter yet.


Haven't tried Legato 1 vs 2, but it should be better.. at least according to Pat.

The Emm labs may be the best computer DAC in the world.   To say that the Legato ll has better sonics than direct connect to the EMM USB is quite a statement.

post #49 of 88

By the way,  what is the best length for te SPDIF cable from the Legato ll?

post #50 of 88
Quote:
Originally Posted by rsbrsvp View Post

The Emm labs may be the best computer DAC in the world.   To say that the Legato ll has better sonics than direct connect to the EMM USB is quite a statement.

While I certainly don't think it is the best computer DAC, I think this sentiment is only because people are still treating the usb/spdif converter as a interface between the PC and the DAC. If we can accept that different CD transport sounds different into the same DAC, I think it's not so far a stretch to imagine that another 'transport' can improve the sound into the same DAC. Using different PCs also yield quite different results.

 

If I mentioned the usb/spdif was a $5k dcs u-clock maybe people will be less surprised, as to include similar components would in theory increase the price of the DAC2X significantly (and afterall, I think its main focus is to be paired with the $15k TSDX).. but I do think the Legato 2 is very good.

 

Maybe one day when we actually get an audiophile motherboard, full discrete linear power supplies for each rail, an audiophile operating system, audiophile harddisks, sata and power cables, etc.. we can hear the potential of async usb.

 

 

Quote:
Originally Posted by rsbrsvp View Post

By the way,  what is the best length for te SPDIF cable from the Legato ll?

 

 

Believe there is no longer a length recommendation (like there might have been in legato 1 I think), but I personally prefer more than 2m.. 4m is an ideal length for some systems though I haven't heard it in mine.


Edited by Quest88 - 1/16/13 at 3:10am
post #51 of 88
Quote:
Originally Posted by Quest88 View Post

I wouldn't write off that something else that can give better performance, but it seems like few competitors.. none of which provide objective measurements even if I were willing to pay a lot more money. I haven't seen mentions of a femto or galaxy clock in a usb/spdif converter yet.

 

 

 

The Legato measurements are well below that which anyone has been able to show are audible. 

 

The only improvement that I can see as being potentially interesting is to extend that performance to higher definition audio streams. 

post #52 of 88
Quote:
Originally Posted by ehlarson View Post

 

The Legato measurements are well below that which anyone has been able to show are audible. 

 

The only improvement that I can see as being potentially interesting is to extend that performance to higher definition audio streams. 

I always assumed that the Legato, even though the jitter output is inaudible, once that signal turns into SPDIF the jitter jumps as there are reflections, and when it hits the dac chip it jumps further.

 

Therefore, cutting the jitter on the Legato ll should have audible value because there is less jitter to multiply once that signal is transfered to SPDIF and enters the DAC chip.

 

Please correct me if I am wrong.

post #53 of 88

Pulse smearing is the issue in cables. Reflections and the fact that all cables are low pass filters can induce it.

 

The measurements I've seen using loopback cables on an analyzer seem to indicate that the noise components of S/PDIF jitter are below the noise floor of commercial DACs (<130 dB). It's likely that the measurements were showing the performance of the analyzer ADC and DAC.

 

The only thing left should be the DAC performance and analog components downstream including of course the drivers.


Edited by ehlarson - 1/16/13 at 11:39am
post #54 of 88
Quote:
Originally Posted by ehlarson View Post

 

The Legato measurements are well below that which anyone has been able to show are audible. 

 

The only improvement that I can see as being potentially interesting is to extend that performance to higher definition audio streams. 

Believe the legato 2 is at its performance level at this price, because of the limitation. :) I'm continuing my search as I'd like to have hi-res at this performance level if possible (considering I have 300+ albums). I did discuss with art on the possibility but the price would be much higher if he were to do a 24/96 usb/spdif converter of the same measurements, with no option for 24/192 still.

post #55 of 88
Quote:
Originally Posted by Quest88 View Post

Believe the legato 2 is at its performance level at this price, because of the limitation. :) I'm continuing my search as I'd like to have hi-res at this performance level if possible (considering I have 300+ albums). I did discuss with art on the possibility but the price would be much higher if he were to do a 24/96 usb/spdif converter of the same measurements, with no option for 24/192 still.

 

The vast majority of my music collection is CD. Perhaps if I hear a big difference with the Legato II I'll start a quest for something that will handle 24/96.

 

I don't believe that anything higher would be useful.

post #56 of 88

I had a question about the "XFMR"   vs.  ""DIRECT".

 

How do I know if my DAC has the pulse regulator or not so I know which output to use?

post #57 of 88
Quote:
Originally Posted by ehlarson View Post

 

The vast majority of my music collection is CD. Perhaps if I hear a big difference with the Legato II I'll start a quest for something that will handle 24/96.

 

I don't believe that anything higher would be useful.

Or just bug Pat to finish his 24/96 design.. :) The vast majority of my collection is also CD, hence the Legato suits me fine. The sad part is I think hi-res downsampled to the legato may still sound better.

 

Quote:
Originally Posted by rsbrsvp View Post

I had a question about the "XFMR"   vs.  ""DIRECT".

 

How do I know if my DAC has the pulse regulator or not so I know which output to use?

Just try either one and see which you prefer. I believe my DAC has no galvanic isolation at the input, but despite this, I still preferred the sound of 'direct'.

If you are using the BNC cable that Pat may provide with the Legato 2, please remember that such cables are directional and test both ways before starting your other trials.

post #58 of 88
Thread Starter 

I'm the OP and have been in constant contact with Pat for the past 1+ year.  We just exchanged 8 emails today.  So I can pretty much answer all the questions raised in here.

 

- There have been different revisions of the original Legato.  The jitter on the latest Legato is about 10 times lower than that of the very first revision, but Pat never mention this on the website.  The original specs call for <5ps RMS jitter measured from 1Hz - 1KHz.  The very last revision of Legato I has <0.6ps.  This is less than 600 Femto Seconds.  I happened to have the last two units of the Legato production run.  So yes, you can say the Legato and Legato II have Femto Second clocks.  Pat likes to look at phase noise measurement at 1Hz.  In my particular Legato II unit, the phase noise is measured at about -90dBc @ 1Hz.

 

- MSB's Femto Galaxy clock is pretty much measured the same way (from 1Hz up) and it does 0.077ps or 77 Femto Seconds.  In phase noise terms, it measures at -99dBc @ 1Hz.  But MSB is using a clock with higher carrier freq (I believe that is 24.576MHz).  Legato I/II is using a 11.2896MHz clock.  In order to equate the phase noise measurements of the two clocks, one needs to subtract 6db from the MSB clock.  That puts it at -93dBC @ 1Hz.  So you can see, the Legato II clock is not far away from the MSB FemtoGalaxy clock!

 

- Whether one hears the improvement of the Legato II highly depends on the downstream gear.  One of Pat's references was the Berkeley Alpha DAC series 2.  The BADA dealer near him was amazed by how much the Legato II improves compared to the Legato.  Legato II is actually a very high-end USB SPDIF transport in disguise.  This is why when you feed the output to a high-end DAC, you'll hear more improvements.  If you do not hear much of any improvements, that means you have some bottlenecks downstream.  I run a bi-amp setup with active crossovers and room correction DSP engines.  I can discern the improvements brought forth by the Legato II vs the Legato I.

 

- Use the coax cable Pat supplied for the Legato II.  The length is 8' and its length has been calculated to avoid reflections on impedance mismatch, which happens in most people's gear as they have RCA SPDIF input instead of BNC.  That particular coax cable Pat used is a made by Belden.

 

- Legato I/II have a very large return loss to combat signal reflections in case you choose not to use Pat's cable.  The return loss is so large that the reflection is less than a few percent.

 

 

- So far I found that the Legato II blows away high-res transports even when the high-res files are downsampled in realtime and played as 44.1 (I use Squeezebox Touch to drive my Legato II).

 

- As for DIRECT or XFMR outputs, try both and see which one sounds better to you.  The DIRECT output should sound better in most cases.  But in my case, the XFMR output is better.  It sounds more relaxed and more emotional.  My downstream gear has pulse transformer on the input too.  So it is hard to say which output is better.  You just have to try both.


Edited by Viper2001 - 1/22/13 at 6:40am
post #59 of 88

How do I get Pat to sell me one of these.   He doesn't answer my E mails.  I guess he is very busy.

post #60 of 88
Thread Starter 
Quote:
Originally Posted by rsbrsvp View Post

How do I get Pat to sell me one of these.   He doesn't answer my E mails.  I guess he is very busy.

Yes, he is very busy.  Can you PM me your name and email addr and I'll relay your purchase request to him.

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