Mark Sealey

Q: Airfoil and Airport Express, is there latency/delay?

I want to be able to direct the output of my 'Late 2014' 5K iMac (10.11.6) to my (ParaSound P3/A23) stereo system using AirFoil 5 with Airport Extreme > Airport Express.

 

But the audio output has to be 'real time'; that is, no delay or latency at all. Both are in the same room!

 

I'm using notation software (Sibelius) and need to hear what I write immediately; unlike streaming where I believe there is an acceptable (2 second?) delay for buffering?

 

Can this be done, please?

 

If not with AirFoil, any advice on how gratefully received :-)

iMac with Retina 5K display, OS X El Capitan (10.11.6), Clean machine... no haxies; no Microsoft etc

Posted on Aug 22, 2016 1:09 PM

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Q: Airfoil and Airport Express, is there latency/delay?

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  • by Tesserax,Helpful

    Tesserax Tesserax Aug 22, 2016 2:08 PM in response to Mark Sealey
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    Wireless
    Aug 22, 2016 2:08 PM in response to Mark Sealey

    I want to be able to direct the output of my 'Late 2014' 5K iMac (10.11.6) to my (ParaSound P3/A23) stereo system using AirFoil 5 with Airport Extreme > Airport Express.

    With AirPlay (or Bluetooth) there will always be some form of delay or latency with streaming audio.

     

    In this scenario, an audio stream (over AirPlay) will first go from your iMac to the AirPort Extreme, and then, to the AirPort Express.

     

    To help understand why there are going to be delays, let's take a high-level look "behind the scenes" on how AirPlay works:

     

    For the AirPort Express (AX,) audio input is primarily provided by iTunes. Of course, it can also get input from other sources as you know, like Rogue Amoeba's Airfoil.

     

    For streaming, iTunes or Airfoil does most of the work. When either app plays back standard audio content (AAC, MP3, audiobooks, Internet music streams, etc., it decompresses those file formats and creates what's essentially a raw, uncompressed audio stream. That stream is compressed using Apple's Lossless Compression (via a QuickTime codec), encrypted with 128-bit AES, and then, streamed (via AirPlay) to the AX. The stream is buffered for approximately 2 seconds before the stream is sent. The AX decrypts the stream, decodes it, and outputs it in either a digital PCM stream or analog (using a built-in DAC) to its multi-purpose analog/optical-digital audio port.

     

    So, with the above you can see that audio does not simply move from the source to the destination without a lot more going on. You will not be able to eliminate the delay entirely. Sorry!

  • by Mark Sealey,

    Mark Sealey Mark Sealey Aug 22, 2016 2:08 PM in response to Tesserax
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    Aug 22, 2016 2:08 PM in response to Tesserax

    @Tesserax,

     

    Thanks so much for that quick, informative and helpful answer.

     

    It looks to me very much as though I won't be able to use AirFoil then.

     

    I note that Advanced Speaker Prefs seem to allow 'compensation' of up to 1.0 (which I'm assuming is 1 second).

     

    I really do need instant/completely synchronized audio 'playback': while writing music, it's vital to hear each note as I enter it - sometimes its duration is as little as a sixteenth of a note.

     

    Is there any synchronous wireless solution?

  • by Tesserax,

    Tesserax Tesserax Aug 22, 2016 2:35 PM in response to Mark Sealey
    Level 9 (54,035 points)
    Wireless
    Aug 22, 2016 2:35 PM in response to Mark Sealey

    I note that Advanced Speaker Prefs seem to allow 'compensation' of up to 1.0 (which I'm assuming is 1 second).

    According to Airfoil's own documentation this option is to adjust the amount of delay for the purposes of syncing multiple speakers. It doesn't mention the measurement base, but I would tend to agree with you that it is in seconds with the maximum introduced delay being 1s.

    Is there any synchronous wireless solution?

    Possibly the only "relief" you will get is to use direct connections between the source and the destination. Wireless, will inherently be the worst possible scenario.

     

    FWIW, my daughter too writes music and, amongst her arsenal of software tools, she uses Sibelius to score. In her case, she is using a 2009 Mac Pro that she has a pair of studio-quality powered monitors attached which seems to work for her.

  • by Mark Sealey,

    Mark Sealey Mark Sealey Aug 22, 2016 7:46 PM in response to Tesserax
    Level 2 (362 points)
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    Aug 22, 2016 7:46 PM in response to Tesserax

    Thanks so much, Tesserax! Your clear and unambiguous replies are really helpful :-)

     

    I could attach headphone or speakers - but was hoping to use my good quality main stereo system.

     

    I have direct connections (phono/RCA) at present but I get an unacceptable hum…

  • by Tesserax,

    Tesserax Tesserax Aug 23, 2016 8:12 AM in response to Mark Sealey
    Level 9 (54,035 points)
    Wireless
    Aug 23, 2016 8:12 AM in response to Mark Sealey

    I downloaded a copy of the P3's user manual and noticed that it doesn't appear to have any digital inputs. I believe you would have gotten better performance results if you could of used the AirPort's optical-digital output vs. the unit's built-in DAC's analog output.

     

    A number of folks with analog-only pre-amps, that use the Express, do so with an external dedicated DAC with good results ... but that is more for audio quality than elimination of any delays. One operational glitch is that the Express does not utilize a local clock circuit. When an incoming stream is interrupted, there is no longer a digital output to feed the internal DAC. In some cases, a dedicated DAC can tolerate these interruptions better and provide overall better results.

  • by Mark Sealey,

    Mark Sealey Mark Sealey Aug 23, 2016 8:17 AM in response to Tesserax
    Level 2 (362 points)
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    Aug 23, 2016 8:17 AM in response to Tesserax

    Thanks again! Yes, that's a limitation. I've all but abandoned wireless.

     

    From your experience, Tesserax, would you say that I'd get less hum if I:

     

    1. used one of the other inputs than 'Direct 1'… the XLR Balanced, for instance?
    2. bought better cables?

     

    I did notice that if I disconnect the iMac from the cabling which I currently use (RCA-to-RCA to Y-splitter to 3.5mm jack into the headphone output), the hum goes away.

     

    Even when the iMac is powered down, it reappears as soon as I connect the cable!

  • by Tesserax,

    Tesserax Tesserax Aug 23, 2016 9:35 AM in response to Mark Sealey
    Level 9 (54,035 points)
    Wireless
    Aug 23, 2016 9:35 AM in response to Mark Sealey

    Typically, a hum would indicate a grounding issue ... or bad capacitors in the unit. I assume that the power cable is three-pronged and is connected to a like wall outlet with a known good ground connection.

     

    You may want to connect the P3/A23 units into separate wall sockets or use a good quality power strip if not already doing so.

     

    As far as which inputs on the P3, I would suggest trying the Aux-Phono jack. Be sure to move the Aux Select switch to the "Aux-Line" jacks position. You do not want to use the Phono side for this as it would be too sensitive. Remember, the phono jack would normally have a turntable connected to it. The voltage coming from the phono needle is extremely low.

     

    Equally, you could use either the Tuner or Tape Play/In jacks.

     

    Another note. The audio quality on the iMac's audio port is different from that of the base station, specifically on the analog side. For analog, the Mac provides a higher quality output via a 24-bit/44.1-192 kHz DAC. The Express uses a 16-bit/44.1 kHz sampling rate only.

  • by Mark Sealey,

    Mark Sealey Mark Sealey Aug 23, 2016 9:44 AM in response to Tesserax
    Level 2 (362 points)
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    Aug 23, 2016 9:44 AM in response to Tesserax

    Both Parasound and Mac are relatively new so I hope it's not a hardware fault in either of them. Each is indeed connected to a separate wall socket - though in the same room, so presumably on the same wiring circuit.

     

    The iMac into a UPS and the entire stereo system into a Monster power-cleaning strip. Even when I increase the gain to literally the maximum, there is almost silence; I've always taken this to mean that the actual 110v current reaching the audio system is good and clean.

     

    Thanks, I'll try the Aux-Phono jack… in fact, Yes, it does have a turntable atm - rarely used, obviously. Each of the others (Tuner and Tape) is also in use. But I would sacrifice convenience for humlessness :-)

     

    Given that I've now ruled out any kind of wireless solution because of the delay, there's no other way of getting sound out of this iMac, is there?

  • by Tesserax,

    Tesserax Tesserax Aug 23, 2016 9:58 AM in response to Mark Sealey
    Level 9 (54,035 points)
    Wireless
    Aug 23, 2016 9:58 AM in response to Mark Sealey

    Given that I've now ruled out any kind of wireless solution because of the delay, there's no other way of getting sound out of this iMac, is there?

    If you mean other than the iMac's audio port, then any alternative audio path will be subject to additional delays. In theory, you can stream audio from your iMac via Wi-Fi, Ethernet, Bluetooth, and, of course, its audio port. Each has its plus and minuses.

     

    The headphone jack on your iMac (nice, btw) is also dual-purpose, like the base station's. That is, it supports audio output in both analog and optical-digital formats. Again, the iMac's DAC is superior to that of the Express for analog audio, but in par with the Express for digital.

  • by Mark Sealey,

    Mark Sealey Mark Sealey Aug 23, 2016 10:02 AM in response to Tesserax
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    Aug 23, 2016 10:02 AM in response to Tesserax

    I see; so my RCA cabling is using analog to the preamp from the headphone jack.

     

    Don't I then have options with its optical-digital formats?

     

    Could there be a solution there?

  • by Tesserax,

    Tesserax Tesserax Aug 23, 2016 10:09 AM in response to Mark Sealey
    Level 9 (54,035 points)
    Wireless
    Aug 23, 2016 10:09 AM in response to Mark Sealey

    I see; so my RCA cabling is using analog to the preamp from the headphone jack.

    Yes, that is correct.

    Don't I then have options with its optical-digital formats?

     

    Could there be a solution there?

    From the iMac to the Express, yes. From the Express to the P3, no. Same with between the iMac and the P3. You would need a DAC for each connection to get the audio to your P3.

     

    Unless I misread something in the P3's owner's manual, it does not appear to have any form of digital audio inputs. Hopefully, I'm wrong but I don't have the unit physically in front of me and the images in the manual I downloaded are a bit fuzzy. Maybe you can verify?

  • by Mark Sealey,Helpful

    Mark Sealey Mark Sealey Aug 23, 2016 10:44 AM in response to Tesserax
    Level 2 (362 points)
    Desktops
    Aug 23, 2016 10:44 AM in response to Tesserax

    No, you're correct, Tesserax: all analog at the P3 end.

     

    ParaSound does now have its own DAC units. But I don't feel I can justify that cost ($400-$500).

     

    Is there perhaps another DAC which would offer decent sound quality commensurate with the level of fidelity (which is one of the main reasons why I'm doing this - as opposed to cheap monitor speakers or even headphones either side of my iMac)?

     

    And which I could connect easily from my iMac's headphone socket?

  • by Tesserax,Solvedanswer

    Tesserax Tesserax Aug 23, 2016 10:40 AM in response to Mark Sealey
    Level 9 (54,035 points)
    Wireless
    Aug 23, 2016 10:40 AM in response to Mark Sealey

    $400-$500 would be typical, if not on the low end. You can expect to pay much more for audiophile-quality DACs. Sorry. I don't really have any I could recommend at a lower price point.

     

    I still think your best bet, at this point, it to use your iMac's built-in DAC by connecting directly between the Mac's headphone port and your P3. If possible use a cable that has a pre-molded 3.5 mm stereo connector on one end and twin RCA connectors on the other.

     

    Remember using a DAC will inherently add delays in the signal path, but are unavoidable if you only have analog equipment connected to a computer. Usually, but not always, the more they cost, the lower the signal conversion transient delays through the DAC. Whatever DAC you do decide on, check with the return policy just in case it doesn't work out for you.

     

    ... or just connect a high-quality pair of stereo headphones to the same port.

  • by Mark Sealey,

    Mark Sealey Mark Sealey Aug 23, 2016 10:43 AM in response to Tesserax
    Level 2 (362 points)
    Desktops
    Aug 23, 2016 10:43 AM in response to Tesserax

    Thank you again for all your advice and help here, Tesserax!

     

    I'll do as you suggest. My cables can definitely be improved. But first I'll try different inputs on the P3.

     

    Very much appreciated :-)

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