[Shahrose]

Does anyone know the ID / OD dimensions of the DC plug socket of the Teralink-X and Teralink-X2? I need to know to order an appropriate regulated PSU.

 

[neouser]

Quote:

Originally Posted by slim.a /img/forum/go_quote.gif I was also curious to see if there is a difference between transports so I made the test 2 or 3 months ago but the test were inconclusive and surprising so I don't believe I have mentioned it before. For my test, I used the EMU 0404 USB as a recording device. Since I found that it had very low measured distortions, I thought I could see the difference in the output of the dac19mk3 in the THD or IMD graphs. I tried the Teralink and the Musiland and they gave me similar results. However, when I salved the digital input of the EMU to the musiland (using a cheap toslink cable) the SNR of the dac19mk3 improved by 3db but the THD and IMD graphs didn't change. My conclusion is that trying to assess the (jitter) performance of those usb to spdif converters looking at an RMAA graph with the help of consumer grade sound card is probably pointless. In my opinion, to make worthwile measurements, the tester should have a world class ADC with a known ultra stable clock and not just a clock that is advertised being "ultra-low jitter". To make definitve conclusions about jitter, one should use something like Audio Precision 2 ... if the ADC is inferior (in the time or frequency domain) to the DAC it is measuring the results are probably skewed. Anyway, I have had a few e-mail exchanges recently with Kingwa (from Audio-gd) who told me that jitter measurements do not tell you the whole story about the quality of a transport. There are other parameters (transformers, clock phase noise, power pulse effect to the signal, ...) that will also impact the sound of the DAC. I highly doubt that the measurements done by RMAA will let anyone correctly assess the whole performance of a transport.

This is indeed the reason you have to use rmaa to measure not a digital loop, but analog loop. Using some good ADC you record the analog out of the dac fed with various digital transports. You should try first with some reference quality transport to see what should be the result of the dac working as it should (but this data should be provided by the manufacturer). Then you should try the another transports. All the factors you listed are included in this test, cause you are not measuring jitter but the final result. If there is a difference in quality of the transports, for whatever reason, you should see a difference in the analog output of the dac you are recording, I think this is obvious.

If there are sonic differences they should be visible in those recordings.

Marco

 

[slim.a]

Quote:

Originally Posted by neouser /img/forum/go_quote.gif This is indeed the reason you have to use rmaa to measure not a digital loop, but analog loop. Using some good ADC you record the analog out of the dac fed with various digital transports. You should try first with some reference quality transport to see what should be the result of the dac working as it should (but this data should be provided by the manufacturer). Then you should try the another transports. All the factors you listed are included in this test, cause you are not measuring jitter but the final result. If there is a difference in quality of the transports, for whatever reason, you should see a difference in the analog output of the dac you are recording, I think this is obvious. If there are sonic differences they should be visible in those recordings. Marco

There are a lot of reasons that make what you are asking very difficult to realize :

First, a good DAC means using something at least as good as the Lynx Aurora or Prism Dream AD-2. Not many head-fiers have that lying around I believe.

Second, the use of a reference transport. How to assess that a transport is a reference class product ? Is it by looking at its specs, digital measurements ? I guess that to be on the safe side, someone should you a CEC cd transport or other well known high end transports.

Third, the DAC itself. We have to assume that the only significant distortion that will show up will be jitter induced. So the perfect dac for this kind of test would have vanishingly low level of distortions but would still be very sensitive to the jitter/transport.

Fourth, we are assuming that the digital cables do not interact with signal being transmitted. If you read what Dan Lavry wrote about jitter in cables and impedance matching, you will realize that you won't be measuring the transport but also the whole chain (digital cables, connectors, ...)

Last, we are assuming that if there is a sonic difference it will show up on the RMAA test and that we would be able to interpret it. This hasn't been the case in my opinion. I have tried very different sounding opamps for example but nothing significant showed on RMAA tests. If RMAA held the truth, I should be listening to the EMU 0404 usb which has vanishingly low level of THD, SNR, and IMD. Since the highest harmonic (the third) is at -110 db so I don't believe I should hear any kind of distortion. However, whenever I play violin or piano recordings through it, it sounds digitized and nothing like the real thing. It is not even a subtle difference but a gross difference. On the other hand, I have listened to dacs that didn't measure as good but that outperformed the EMU 0404 usb in sound quality.

In my opinion, we still have to rely on our ears to evaluate those things because at the end of the day we wont be listening to our systems with a distortion graph but with our ears.

However, if you are still curious about how those units measure, I had already done some research and I included the results I have found in my review (first post). To save you time I copied below an extract of the paragraph :

While jitter measurements should be interpreted with great care (different results with different equipment and test protocol), it is sometimes a nice tool to make jitter comparisons in the same group of transports done with the same equipment.
Here you can find jitter measurements of the m2tech, a LynxTwo pci sound card, a Nagra DII and a Marantz CD player. In that test the m2tech was slightly better than the LynxTwo which is a professional grade PCI card, and better than the Nagra and Marantz cd player.
On a stereophile test, there were measurements of the EMU 0404 usb and other converters. The EMU had the worst jitter of the bench, and its jitter was 8 times that of the one measured with the m2tech (Granted the tests were done with different measuring equipment).

 

[neouser]

Quote:

Originally Posted by slim.a /img/forum/go_quote.gif There are a lot of reasons that make what you are asking very difficult to realize : First, a good DAC means using something at least as good as the Lynx Aurora or Prism Dream AD-2. Not many head-fiers have that lying around I believe. Second, the use of a reference transport. How to assess that a transport is a reference class product ? Is it by looking at its specs, digital measurements ? I guess that to be on the safe side, someone should you a CEC cd transport or other well known high end transports. Third, the DAC itself. We have to assume that the only significant distortion that will show up will be jitter induced. So the perfect dac for this kind of test would have vanishingly low level of distortions but would still be very sensitive to the jitter/transport. Fourth, we are assuming that the digital cables do not interact with signal being transmitted. If you read what Dan Lavry wrote about jitter in cables and impedance matching, you will realize that you won't be measuring the transport but also the whole chain (digital cables, connectors, ...) Last, we are assuming that if there is a sonic difference it will show up on the RMAA test and that we would be able to interpret it. This hasn't been the case in my opinion. I have tried very different sounding opamps for example but nothing significant showed on RMAA tests. If RMAA held the truth, I should be listening to the EMU 0404 usb which has vanishingly low level of THD, SNR, and IMD. Since the highest harmonic (the third) is at -110 db so I don't believe I should hear any kind of distortion. However, whenever I play violin or piano recordings through it, it sounds digitized and nothing like the real thing. It is not even a subtle difference but a gross difference. On the other hand, I have listened to dacs that didn't measure as good but that outperformed the EMU 0404 usb in sound quality. In my opinion, we still have to rely on our ears to evaluate those things because at the end of the day we wont be listening to our systems with a distortion graph but with our ears. However, if you are still curious about how those units measure, I had already done some research and I included the results I have found in my review (first post). To save you time I copied below an extract of the paragraph : While jitter measurements should be interpreted with great care (different results with different equipment and test protocol), it is sometimes a nice tool to make jitter comparisons in the same group of transports done with the same equipment. Here you can find jitter measurements of the m2tech, a LynxTwo pci sound card, a Nagra DII and a Marantz CD player. In that test the m2tech was slightly better than the LynxTwo which is a professional grade PCI card, and better than the Nagra and Marantz cd player. On a stereophile test, there were measurements of the EMU 0404 usb and other converters. The EMU had the worst jitter of the bench, and its jitter was 8 times that of the one measured with the m2tech (Granted the tests were done with different measuring equipment).

We are talking about digital transports, not about the sound the dac produces. To me is pointless if the dac measures 50 or 100, I said use a source sensitive dac. If is DIGITAL SIGNAL QUALITY what we are talking about, the problem is not HOW the dac sounds, but WHAT DATA arrives to dac. If there are errors of any kind, jitter or whatever you listed, you will see a degradation in dac performance, or at least a DIFFERENCE. I think the only thing would be have a GOOD ADC, cable is not important ok? Use a good belden cable and youre ok.

When I see people saying things like "rely on our ears" you can understand why 90% of reviews on this forum are totally lacking of trustworthness.
I am still convinced you can hear more difference in two listenings depending on your mood more than real sound difference.

Marco

 

[slim.a]

Quote:

Originally Posted by neouser /img/forum/go_quote.gif We are talking about digital transports, not about the sound the dac produces. To me is pointless if the dac measures 50 or 100, I said use a source sensitive dac. If is DIGITAL SIGNAL QUALITY what we are talking about, the problem is not HOW the dac sounds, but WHAT DATA arrives to dac. If there are errors of any kind, jitter or whatever you listed, you will see a degradation in dac performance, or at least a DIFFERENCE. I think the only thing would be have a GOOD ADC, cable is not important ok? Use a good belden cable and youre ok. When I see people saying things like "rely on our ears" you can understand why 90% of reviews on this forum are totally lacking of trustworthness. I am still convinced you can hear more difference in two listenings depending on your mood more than real sound difference. Marco

So you were suggesting to measure those usb to spdif converters (with a DAC) just for the sake of measuring ? Not because it would affect the sound which would ultimately come out of the DAC (and ultimately from your headphones) ?

Anyway, this is a pointless debate, I won't comment on it any further. I just wanted to save time for people but if anyone feels like they want to spend a lot of time measuring those usb to spdif converters to look at unreliable graphs, please feel free to do so.

And finally, if you feel that "90% of reviews on this forum are totally lacking of trustworthness.", you should write your own reviews as it would be more constructive and instructive for everybody instead of just criticizing other people reviews and comments.

 

[doctorcilantro]

I think Lavry also made the point that jitter matters where the DA conversion happens which is after the data enters the DAC. Each is DAC is different in how it deals with the incoming data. Something to keep in mind that's all.

 

[rosgr63]

I understand that here we are evaluating gear that improves our listening experience.
slim.a has done a great thorough job and I personally have learned a lot about Transports, DACs, Cables etc. and I am grateful as I know he has put a lot of effort.
This is a hobby not lab experiments.
Trust your ears, if you like what you hear that's fine, it doesn't mater if you have reference gear or not. We all have the right to enjoy this hobby with whatever we can afford.

 

[neouser]

Quote:

Originally Posted by slim.a /img/forum/go_quote.gif So you were suggesting to measure those usb to spdif converters (with a DAC) just for the sake of measuring ? Not because it would affect the sound which would ultimately come out of the DAC (and ultimately from your headphones) ? Anyway, this is a pointless debate, I won't comment on it any further. I just wanted to save time for people but if anyone feels like they want to spend a lot of time measuring those usb to spdif converters to look at unreliable graphs, please feel free to do so. And finally, if you feel that "90% of reviews on this forum are totally lacking of trustworthness.", you should write your own reviews as it would be more constructive and instructive for everybody instead of just criticizing other people reviews and comments.

When I say they're laking of trustworthness I am not saying this is on purposal, I used to think these reviews were useful but I am changing my mind, and I'll explain why:

usually when you have a lot of informations about something, but not all this information is reliable, by comparing and analyzing it you can have an approximation of what is the reality. Some reviewers could be completely influenced, others could be more objective, some inexperienced, some experienced etc. but in the end something valid will come out.

Actually this doesn't happen in the audio field. This mostly because, in my opinion, people say things that aren't true, believing they are. In the end, you will find, very very often, people saying "I think X is better than Y for A reason" and elsewhere "I think Y is better than X for B reason".

The principal cause, for the lack of objective benchmarks, data, real information of what counts and what doesn't.

Just my opinion.

 

[slim.a]

Quote:

Originally Posted by neouser /img/forum/go_quote.gif When I say they're laking of trustworthness I am not saying this is on purposal, I used to think these reviews were useful but I am changing my mind, and I'll explain why: usually when you have a lot of informations about something, but not all this information is reliable, by comparing and analyzing it you can have an approximation of what is the reality. Some reviewers could be completely influenced, others could be more objective, some inexperienced, some experienced etc. but in the end something valid will come out. Actually this doesn't happen in the audio field. This mostly because, in my opinion, people say things that aren't true, believing they are. In the end, you will find, very very often, people saying "I think X is better than Y for A reason" and elsewhere "I think Y is better than X for B reason". The principal cause, for the lack of objective benchmarks, data, real information of what counts and what doesn't. Just my opinion.

As rosgr63 just said this is a hobby ...

As for seeking the absolute truth in reviewing audio gear, I have found an interesting article here : Thoughts on the “Absolute Sound†and Perceived Musical Realism (Part 1) | AVguide

I copied below an extract of the article. It was written by Chris Marten.

Toward a Pragmatic Theory of Music Realism

My theory starts out with three basic hypotheses that have much to do with the nature of the sound of live music and the way that we, as humans, tend to internalize and process that sound.

Hypothesis: The sound of live music involves a variegated mix of sonic elements whose characteristics are inherently complex and diverse—more so than we may at first realize.

Hypothesis: Try though we might, humans are not fully able to attend to, emotionally comprehend, or cognitively process all of the elements of the sound of live music in real-time. When we attend live musical events, we hear all of the sounds presented to us (in a neurophysiologic sense), but can at best pay attention only to a subset of them.

Hypothesis: No two listeners are the same, and whether we do so consciously or unconsciously, we tend to apply somewhat different perceptual filters and value systems (or “weighting schemes”) to help us organize and make sense of the otherwise staggeringly complex experience of listening to live music—or to recorded music as reproduced by hi-fi systems.

If you put these hypotheses together and apply them to the tasks of building or evaluating (reviewing) high-performance audio components, some interesting conclusions begin to emerge. We all say that our objective is to have audio components that are faithful reproducers either of the sound of live music events or the sounds captured on recordings. But what we forget is that while those musical events or recordings are undeniably helpful and (relatively) reliable reference standards, the effects of our own perceptual filters and value systems are not so easy to measure or to quantify.

While the full range of sounds that comprise live music are available to each of us to use as our comparison standards, we tend in practice to comprehend the sound of live music (or reproduced music) only in part; despite our best efforts, the whole eludes our grasp. It is tempting, of course, to think, “Surely my listening experience is much like yours, so that we can compare notes and share experiences.” And to a certain extent we can and do. But at the same, I suspect that we often forget that the very sounds we hope to discuss with one another have already passed through the complex sets of filters that make up our individual schemas of musical consciousness.

 

[thoppa]

Hi,

I've just ordered one too. I plan to build a Gamma2 dac for it.

Please start a new thread with your impressions when you get it - I'm very interested to know how well the asynch does with various sample rates !

Cheers,

Tom

Quote:

Originally Posted by Shahrose /img/forum/go_quote.gif I ordered the Teralink-X2 a couple days ago and should receive it early next week. I'll probably be posting my impressions when I receive it.

 

[slim.a]

Quote:

Originally Posted by thoppa /img/forum/go_quote.gif Hi, I've just ordered one too. I plan to build a Gamma2 dac for it. Please start a new thread with your impressions when you get it - I'm very interested to know how well the asynch does with various sample rates ! Cheers, Tom

By the way, the Teralink X2 uses the older adaptive mode, it doesn't use the asynch method like the musiland or the m2tech hiface

 

[thoppa]

Quote:

Originally Posted by slim.a /img/forum/go_quote.gif By the way, the Teralink X2 uses the older adaptive mode, it doesn't use the asynch method like the musiland or the m2tech hiface

The seller says it does use async. Maybe u r confusing x and x2 ?

 

[FauDrei]

Quote:

Originally Posted by thoppa /img/forum/go_quote.gif The seller says it does use async. Maybe u r confusing x and x2 ?

With Windows generic drivers? I don't think so.

 

[thoppa]

Indeed, that's what I said too, but he insists....

http://myworld.ebay.co.uk/vintage_audio_lab/

I asked him about kernel streaming and/or asio4all and he said kernel streaming doesn't work because it is asynchronous, and asio4all will not work well.

I can't help but wonder how myself......

http://www.gfec.com.tw/pro_flypage.p...=&p_serial=131

This page says the USB controller is isochronous. Hmmm....I don't think the seller has got his facts straight...?

Is it possible that there is a buffer to change the way this thing behaves with windows ?

 

[slim.a]

The Audiotrak Prodigy Cube and Stello U2 usb to spdif converter also use that same Tenor chip. However, I don't believe that they claim they are async (like the musiland or hiface), or else they would probably need custom drivers which they don't need.

Also, saying that Kernel streaming doesn't work because it is asynchronous is BS in my opinion. The EMU 0404, musiland and Hiface which are async can work with the KS. On the other hand, the Teranlin-X which uses the old CM-108 chip doesn't work with KS but works with ASIO4ALL.

I think that the seller got confused when reading this phrase on the usb chip which says : "2 isochronous input endpoints for recording, 2 isochronous output endpoints for playback, and 1 interrupt endpoint for HID". I really don't know what they mean by it but it is the only mention to the word isochronous (and not even async). I believe that if it were true USB async such as other converters, it would be more advertised than that.

I am not saying that the Teralink-X2 is bad. If I were shopping again for usb to spdif to converters, I would go for it. It looks like it is better built than the stello or the Audiotrak Prodigy Cube but the async is probably a false claim as far as I know.