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RE: Surprisingly

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In Reply to: RE: Surprisingly posted by audiohound on November 05, 2009 at 16:59:12

"What is PLL?"

Phase-locked-loop - its an oscillator with an adaptive feedback loop

"If a transport has jitter issues, does it tend to be the same amount on SPDIF vs. Toslink."

Yes, but the Toslink will be a bit worse due to the additional conversions. If you system has a bad ground-loop, the Toslink will eliminate this, making the Toslink appear better.

"I'm of the belief that SPDIF is usually better, so this is what I was using when I happened to notice better sound from the less expensive transport. Is it possible that there would be better performance around jitter if I try Toslink on my more expensive Toshiba...or do both signals tend to perform the same?"

It may be a combination ground-loop and jitter difference.

"Lastly, as another person had posted...do you think it's possible that other systems matching issues (not having to do with jitter) could cause one transport to sound better than another with a particular DAC?"

It is unlikely but possible. If you system has other sibilance problems, then the lower jitter source may actually sound more harsh by unmasking this other sibilance in your system. It happens.

Steve N.

Follow Ups:

RE: Surprisingly - Todd Krieger 13:18:12 11/06/09 (15)
"Yes, but the Toslink will be a bit worse due to the additional conversions. If you system has a bad ground-loop, the Toslink will eliminate this, making the Toslink appear better."

IMO, the disadvantage of additional conversions is more than offset by the advantage of RF isolation. The RFI generated at the transport stays at the transport. It doesn't add to the RFI produced at the DAC. This is the main reason why Toslink is my choice for digital interconnect type. (I find such isolation almost requisite if your "transport" happens to be a desktop PC.)
- No RF through TOSLINK? - Slider 11:17:19 11/07/09 (2)
  Are you saying that the bandwidth of the TOSLINK convertors is so much lower than a normal driver and cable connection that the high frequencies (RF) are completely attenuated, or that the optical cable is immune to outside airborne RFI that may be picked up on a conventional cable? The latter is true, though that won't stop RF from the transport, which will be on the signal line and passed through either wire or TOSLINK connections, though many TOSLINK implementations have pretty severe rise time filtering to avoid ringing on the transmission side. That filtering is one of the reasons that the TOSLINK connection usually results in much higher jitter in the recovered clock in the DAC.
  
  One of the main benefits of TOSLINK or glass fibre connections in audio systems is to prevent the radiated RFI from the digital cable that happens in some installations.
  - Electrically-Conducted RFI............. - Todd Krieger 18:50:36 11/07/09 (1)
    "Are you saying that the bandwidth of the TOSLINK convertors is so much lower than a normal driver and cable connection that the high frequencies (RF) are completely attenuated, or that the optical cable is immune to outside airborne RFI that may be picked up on a conventional cable?"
    Neither actually....... Unlike the electrical type cable, the optical Toslink does not conduct *electrical* borne RFI that's present in the transport to the DAC. Whatever RFI that is generated that can affect the audio is solely in the DAC, as opposed to both the transport and the DAC.
    Now you are correct that there might be some airborne RFI from the transport, but its effect should be minimal compared to the conducted RFI via an electrical digital cable.
    "The latter is true, though that won't stop RF from the transport, which will be on the signal line and passed through either wire or TOSLINK connections,"
    I think a lot of the RFI is transferred via the common side of a coax cable. With the Toslink, there is nothing electrically bringing the transport's RFI to the DAC.
    "though many TOSLINK implementations have pretty severe rise time filtering to avoid ringing on the transmission side."
    If that were true, Toslink would have major jitter issues. (Caused by slow rise time in the presence of noise. And the noise is unavoidable.) It was purported to have slow rise times simply due to less bandwidth (no actual filtering), but I personally hear virtually no negative effects from a jitter standpoint.
    "That filtering is one of the reasons that the TOSLINK connection usually results in much higher jitter in the recovered clock in the DAC."
    I don't know if the filtering is really taking place in most cases- If it is, it's a mistake..... I personally haven't encountered a Toslink system that to me had any more audible artifacts of jitter than other means of transmission.
    "One of the main benefits of TOSLINK or glass fibre connections in audio systems is to prevent the radiated RFI from the digital cable that happens in some installations."
    It might be radiated RFI, but it's mostly the RFI that originates at the transport, and is simply conducted electrically to the DAC.
    
    Edits: 11/07/09 11/07/09
    - Hmmm - Slider 23:09:15 11/07/09 (0)
      Not sure I fully understand your electrical RFI argument. The TOSLINK does use an electrical device at each end, on the transmit side there is a IR LED driver, and at the receive side there is a photo transistor, the two ends coupled with a plastic fiber optic cable. If these electrical devices have sufficient bandwidth, the signal at the DAC end recovered from the photo transistor should be the same as the signal that drove the LED at the transport end, RFI and all. Typically it isn't of course, with the addition of noise and other components, along with bandwidth limitations and built-in filtering. In addition, due to the very high amplification required in the receiver, they are very sensitive to ground and power supply issues, and need very good screening, things that don't happen with the integrated package normally used.
      In any case, TOSLINK can help remove the very large 120 Hz jitter component seen in many DACs. And if your DAC has very good jitter immunity, could very well be a good choice. I have seen measurement results that indicate the commonly used TORX transmitter and receiver do add large amounts of jitter to the recovered clock compared to a well implemented wire connection, but a lot of the additional jitter is high frequency phase noise related in the tests I've seen. One of the tests I recall was just a clock test, measuring a large increase in jitter when TORX xmtr/rcvr and fiber was added to path, so much of that phase noise jitter would convert to data correlated jitter in the presence of audio data.
      
      Edits: 11/08/09
- Todd: Toslink being better.... - audiohound 20:41:03 11/06/09 (8)
  Todd,
  
  I think you're one of the few that say Toslink is better. I've used it in my system a few times and was surprised at how good it sounds with the right DAC. Do you feel it pays to buy an expensive Toslink cable, or are they all created equal once basic QC parameters are met? I think mine is a cheapie from Blue Jeans.
  
  And let's say one uses digital coax, does it make sense to spend a lot on this type of cable? I ask because, unlike an analog sound signal, I wonder if a digital signal either succeeds in being transmitted...or it doesn't...without a lot of room for fine-tuning?
  - RE: Todd: Toslink being better.... - audioengr 10:42:53 11/07/09 (6)
    The issue with S/PDIF is Price. To get a high quality Toslink, it's $50. A high-quality S/PDIF is over $500. S/PDIF is better though if you can afford it.
    - RE: Todd: Toslink being better.... - roscoeiii 21:18:25 11/07/09 (2)
      Any specific Toslink cables that you recommend at around $50?
      - RE: Todd: Toslink being better.... - Todd Krieger 12:25:00 11/10/09 (0)
        
        In Reply to: RE: Todd: Toslink being better.... posted by roscoeiii on November 07, 2009 at 21:18:25
        
        "Any specific Toslink cables that you recommend at around $50?"
        
        The QED One 1.5m cable goes for about $50..... The problem is they can only be sourced from the UK.
        
        Email me..... I can send you a couple to try.
      - RE: Todd: Toslink being better.... - audioengr 11:07:17 11/08/09 (0)
        
        In Reply to: RE: Todd: Toslink being better.... posted by roscoeiii on November 07, 2009 at 21:18:25
        
        I have one I really like, but they dont offer it anymore. It's glass with rotating connectors. Very flexible and sounds great. I use it for my home theater.
    - RE: Todd: Toslink being better.... - Todd Krieger 18:53:06 11/07/09 (2)
      "A high-quality S/PDIF is over $500."
      
      I never realized S/PDIF devices even existed that would cost that much........ Can you maybe recommend a good one that might be used to upgrade a transport? Thanks.
      - Transparent - sbrians 13:39:18 11/08/09 (0)
        
        In Reply to: RE: Todd: Toslink being better.... posted by Todd Krieger on November 07, 2009 at 18:53:06
        
        I have an old Transparent digital cable that I thought was expensive but worth it in my system at the time.
      - Cable - audioengr 11:09:30 11/08/09 (0)
        
        In Reply to: RE: Todd: Toslink being better.... posted by Todd Krieger on November 07, 2009 at 18:53:06
        
        I'm talking about a 1.5m RCA terminated cable. email me and I'll give you some recommendations.
        
        Not that the S/PDIF output on the transport does not need modding, because it usually does, as well as the clock.....
  - RE: Todd: Toslink being better.... - Todd Krieger 23:57:24 11/06/09 (0)
    Like anything else, expense with Toslink cables does not mean better performance. I have the expensive AudioQuest Optilink 5 that I don't care for.
    
    My two favorite Tos cables right now are the QED One and the Japanese Saec. The latter is my reference, but it is expensive and can only be sourced from Japan. The Nordost White Light Glass is good to, as is the Van den Hul Optocoupler and for a low-priced cable, the Apogee Wyde Eye.
- Why not both? - audioengr 14:48:33 11/06/09 (2)
  My choice is to have both isolation and S/PDIF coax. The best of both worlds.
  - Good Question............. - Todd Krieger 18:14:49 11/06/09 (1)
    "My choice is to have both isolation and S/PDIF coax. The best of both worlds."
    I guess you mean the isolation being internal...... That's a nice idea, except for one little problem- Much of the RFI goes through on the common side......... So if you use a coax with isolation inside the DAC, for example, much of the RFI from the transport will still get through via the S/PDIF shield and then the DAC chassis. (This is why I don't like plugging analog devices into the same outlets as the digital devices.)
    Now if you can somehow do this with a balanced line (AES/EBU), it should work..........
    
    Edits: 11/06/09
    - RE: Good Question............. - audioengr 10:44:26 11/07/09 (0)
      All you need is transformer coupling. Treat S/PDIF just like AES.

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