Streamers in 2023 - Discussion, Impressions, etc

Discussion in 'Digital: DACs, USB converters, decrapifiers' started by rhythmdevils, Feb 9, 2023.

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  1. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    Yggdrasil (all versions) uses a Digital Signal Processor (DSP). This is a microprocessor optimized for handling digital audio data. Internal to this chip are 8 SRCs, one for each input the DSP has. The AES decoding function is done by an AKM AK4113. A good chip, but not the top of the line. However, the SRC in the DSP makes that much less important.
     
  2. zottel

    zottel Friend

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    Ah, thanks for the clarification. So the term “reclocking” is used for finding the clock of the signal? I thought that was called “clock recovery”, and reclocking means regenerating the signal with another clock source using a buffer (SRC)? I’m not sure about the correct terms myself, especially in English. :)

    But what you said about the quality of the recovered clock makes lots of sense, too. So the clock is recovered and used as clock source for the D/A circuit, right? So the better the streamer’s clock source, the easier it is for the DAC to recover the signal’s clock.

    But what role does the DAC’s own clock source play then? Does it make clock recovery better because the expected times of signal arrivals match the actual times better, provided that the source has a good clock?
     
  3. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    no, you had it right, clock recovery is when you extract the clock from the input data stream. Re-clocking is when you use an internal clock. Note that most DAC’s do not have a re-clocking circuit. They use the recovered clock from the input circuit.

    so unless the DAC does re-clocking, it does not have an internal clock other than what it uses with the PLL to recover the input clock.
     
  4. lithium

    lithium Almost "Made"

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    I also wanted to highlight this from the yggdrasil manual which I think is relevant to this amazing discussion. I believe this answer would imply that the DSP in the Yggdrasil does this analyzing and reclocking.

    "Hey, the “buy better gear” light came on. What does that mean? That means you have a crap source. Yggdrasil analyzes the incoming center frequency and jitter to determine if it can use VCXO reclocking, which requires a precise center frequency and reasonably low jitter. If it cannot use VCXO regeneration, it switches to VCO regeneration, which still provides orders of magnitude improvement in the reconstructed clock. However, the source is still crap. Yes, even if it’s a $10000 CD player you purchased 15 years ago. Those go off-frequency all the time."
     
  5. lehmanhill

    lehmanhill Almost "Made"

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    Thank you Michael. Very instructive, even if I did need to read a couple of times to get it clear.

    I hesitate to complicate this further, but...

    Let's say there are 3 devices in the chain, all using i2s. First is an Ethernet switch that reclocks the data stream, then a Pi2AES, for example, and dac that reclocks the data using an SRC. The connection between the switch and the Pi2AES is Ethernet. while the connection between the Pi2ASES the dac is HDMI. Since the data format is i2s all the way to the dac input, there should be no re-clocking to that point as the i2s clock data is within the i2s data. Is that correct?

    Internally, is the dac likely to re-clock the i2s data through it's SRC?
     
    Last edited: Feb 24, 2023
  6. lehmanhill

    lehmanhill Almost "Made"

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    One of the advantages of the Squeezebox was that it was WiFi. My computer wasn't in the same room as the stereo.

    When my Squeezebox Touch died after only a couple years, I took it apart and found it looked rather like a Raspberry Pi. It was a 1 board computer with an ARM processor and some ports. It appears that the Metrum Ambre literally was an RPi with some software and attention to power supply. After all, you could burn an image to an SD card and use your own choice of Pi music software.

    As for the forum being active, yes it is and so is the LMS programing community. I intermittently update the LMS and Squeezelite software versions.
     
  7. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    Ethernet is NOT I2S. It is a transport that send the audio data to the PI. It is the PI that outputs that data through it's I2S port. In our instance, the PI2AES supplies the clocks to the PI (which acts as a slave) while the pi clocks out the data. If the output from the PI2AES being used is I2S over HDMI, then that data is only buffered. no changes to the clock or the data.
     
  8. zottel

    zottel Friend

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    An Ethernet switch cannot use I2S because … well, because it uses Ethernet, which is a different protocol and hardware specification for transmitting digital data.

    Network data transfers will always be buffered on the receiving side because network data packets can come in in a different order than they were sent, like part 3 of the message arriving before part 2, and the original order is then reconstructed at the receiving side. So you don’t have to worry about clocks and timing there, there is stuff going on at a much larger scale, and the receiving device will reconstruct the stream and send it on with a completely new clocking.

    The difference between S/PDIF and I2S is that I2S provides a clock signal so that the D/A circuit of the receiver can directly use the same clock as the sender (streamer). Think of it as a separate wire where clock ticks are transmitted, they are not really part of the payload data itself. If the DAC then reclocks the signal with its own clock, the clock signal from I2S is discarded (it is only used for receiving the data, not for the D/A circuit of the DAC).

    In S/PDIF, there is no separate wire for the clock. It has to be reconstructed from the signal. Think of it as special markers in the data that are repeated often so that it’s easy to reconstruct the clock from the occurrence of these markers during a certain time.

    In both cases, if the clock from the signal is directly fed into the D/A circuit of the DAC, a good clock source in the streamer is vital for good results. If the DAC reclocks the signal, the streamer’s clock source is not so important.

    EDIT: BTW, this last paragraph is a big new insight for me, thanks @Michael Kelly for providing that info! I always thought all DACs used their own clocks for playing the data they get. Which made quality streamers a bit of mystery to me, “seem to make stuff better, but I’m not sure why, maybe it’s less flipped bits or something … ?” This makes a lot more sense now.
     
    Last edited: Feb 24, 2023
  9. Thad E Ginathom

    Thad E Ginathom Friend

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    Happy to know that! So sad that Logitech ditched that range. And so stupid. They were ahead of their time: they could have been leading the field today. I think that the first Squeezebox predated Sonus?
     
  10. Armaegis

    Armaegis Friend

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    This is the simplified analogy that I've got in my head to understand clocking. Someone please correct me if I'm far off base because I'm just making this crap up.

    Picture a street intersection that has barrier arms that lift up to let cars in and out of the intersection. If source and receiver are not connected, then the arm that lifts up to send the car sends no info. The receiving side waits until the car arrives, detects it, then lifts up the arm to let it out of the intersection. The process works, but there's some clunkiness and mild traffic jams, but no crashes because we pretend machines are smart enough to not go smash boom and everybody gets to their destination eventually.

    If they are connected, then the sending and receiving barrier arms talk with each other and know when the car is coming. Overall smoother operation as it can preemptively start to lift the arm so there's no waiting in the intersection.

    If there's some master clock running everything, it's like you have actual traffic monitoring and control that sees everything, the arms barely even come down they just know when to send the cars at what speed and things flow and pass through each other.
     
  11. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    BTW the last post mentioned the master clock. This is NOT a required signal for the I2S bus. The bit clock is the most critical for the DAC to generate accurate analog signals. MCLK is only used for digital filtering aka over sampling. NOS or non-over sampling DAC’s don’t use this. It’s why some I2S pinouts have no MCLK.
     
  12. zottel

    zottel Friend

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    Nice picture. To make it a bit more precise: The arm on the sending side will always go up and down at the same intervals, that’s the nature of a clock. It will not pause because the intersection is full already (such stuff is possible in network protocols, but not in USB Audio or S/PDIF or I2S).

    If there is one clock that the receiver and the sender share, the equivalent would be that the receiving side knows when the arm at the sending side goes up and can move its own arm at same time intervals. That’s the case with an external clock that is connected to both the streamer and the DAC, or with I2S.

    With S/PDIF, the receiving side looks at the frequency in which cars arrive and lifts its arm accordingly. Which should normally work without problems, too, at least if the interval when the sender lifts its arm is constant (good clock source in the streamer), and probably even if it isn’t—the artefacts show up later when the data is converted into analog signals.
     
    Last edited: Feb 24, 2023
  13. Woland

    Woland Friend

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    For the AES/ SPDIF protocols we've been discussing, they don't talk to each other. Communication is one way only; the sender / streamer transmits and has no way to know if anyone is listening or is able to decode the signal. It's like a radio station broadcasting.
     
  14. Armaegis

    Armaegis Friend

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    I think this is where something like the eye patterns and impedance matching matters right? because the exact timing of the pulses varies a bit since it's not a perfect on/off but a hump and only when the pulse gets above a certain threshold does it actually detect.

    Great, now the picture in my head is the sender is just a traffic cop shouting "incoming" after waving a car through.
     
  15. lithium

    lithium Almost "Made"

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    I am going to pollute this thread with my subjective impressions again - Zen stream ( illuminati PS) vs Pi2AES ( Farad PS) . Please refer to Post #88 for fine print - battle royale part deux.

    1. Music: Grant Green (Green Street) - Round about midnight/Grant's dimensions
    Zen stream - magnificent black background on quieter sections, more depth of soundstage
    Pi2AES - more flattened soundstage but demands attention and very involving. I prefer the Pi2AES slightly as its more engaging overall.

    2. Music: Autechre (EPs 1991-2002) - Basscadet (Bcdtmx)
    I would be hard pressed to tell them apart. This is dense textured stuff and both perform impressively to create a holographic sphere of sound. I think the zen stream has a tighter bass but I might have imagined this. At same point I stopped caring which one was better.
     
  16. zottel

    zottel Friend

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    Yes, but they matter for I2C and external clocks, too. Eye patterns are measurements of the quality of a digital transmission. All signals are humps, and no signal is ever perfect.

    Want some more to obsess about? :) Clock signals aren’t perfect, either, and they are subject to interference and noise etc. like any other signal. There are people who say that the problems introduced by the rather long cables of external clocks are more severe than the problems they try to solve, and you have to use very good cables with the correct impedance and so on.

    Note that I have no idea how valid that claim is. I’m not an expert for this at all, it’s just something I stumbled on when I read about this stuff, so do take that with a grain of salt! But it might be that overthinking such stuff might be detrimental.
     
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  17. Justrukin

    Justrukin New

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    New guy here, rocking the Pi2 Mercury v2 with the Denafrips Venus II 12th DAC... I tried the Zen as everyone told me it was an upgrade from the Node... I could not get the Zen to work, very unstable and too many hoops to jump through to get anything to work, so I sent it back. Received the Mercury v2 with the Volumio installed, same issues I had with the Zen. So, I installed RoPieeeXL and everything works, incredibly stable and very happy. The Mercury and the Venus play incredibly well together, "clocking"? Even swapping out cables has a noticeable difference in overall SQ, again, very happy with this combination. My network is hardwired, no wifi.
     
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  18. Pocomo

    Pocomo Friend

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    Been running RoPieeeXL on Pi2-AES for a long while now; it's been fantastically reliable. Throw a donation to @Spockfish when you can, he's earned it.
     
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  19. Justrukin

    Justrukin New

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    After 24 hours of solid playback from everything I threw at the Mercury, I shot him off a donation. I think I will go on a monthly with him, as RoPieeeXL is seriously, THAT GOOD! I would rather send @Spockfish money than some of these services, like Volumio. I cannot believe they charge folks for that. ;-)
     
  20. Justrukin

    Justrukin New

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    I'm sitting here with mom, just made dinner for us, listening to some BB King, damn this sounds good! The Venus II 12th and the Mercury v2, KLH Model 5's... I'm in heaven! And that big old 800 pound gorilla in the room, the Emotiva XPA-2. Really drives the 5's. And the two SVS-SB3000 subs hitting the low notes... ;-)
     

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