SPDIF with slave clocking

  • I have technical problems to quote with my iPad, that's why I create new posts.


    To the OP:
    Eventide and Lexicon have a perfect implentation for digital audio!
    Can you name other companies that do complex DSP outboard equipment providing a complete implementation?

    Tc Electronics Fireworx can slave to the KPA too.
    Not have much use to slave the KPA to other boxes though myself.

  • 8|?(


    I like the way CK has handled the many feature requests - he tries to implement what is possible - and says what is not.


    SPDIF Master seams NOT to be possible.



    On the other side - 44.1KHz is common for audio (because of the old CD's) - and 48KHz is common for Video.
    KPA supports 44.1KHz - AxeFx 48Khz.



    No need to cancel the KPA-Wiki project IMHO.


    Another good reason why all the internet stuff (Forum, Wiki, ...) should be managed by the manufacturer - as well as the basic toolkits like editor... (just remember what happened to the first AxeFx editor) ...



    Kiss and make peace :)

    (All trademarks are trademarks of their respective owners, which are in no way associated or affiliated with soundside.de)


    Great Profiles --> soundside.de

  • Agreed, Armin. I think a relatively small issue is being blown out of proportion. Just read the thread where people were apprehending that wikpa.org had been shut down by lightbox, except it hadn't. I also agree with his point of view that he has also done a lot for that resource, no contest. Hope he'll just chill out, we have nothing against him and I'm sure neither does Mr CK.


    I think a lot of the problem is just in how written English sometimes translates. For instance, I was recently reported for being racist when all I said that I bought a white Kemper hoping to make it a (SPDIF) slave and then found I couldn't. Had to edit it on DonPeterson's orders, but only after pointing out that the "humour"(poor or otherwise) was probably misinterpreted by the reader.


    Hoping lightbox will "forgive this aspect of the Kemper and stay cool. He's been an important member of the community.


    DukeOURL: Separate wordclock required? Didn't know that, thanks for the clarification. Those things start real cheap and go to really expensive.


  • ...
    For instance, I was recently reported for being racist when all I said that I bought a white Kemper hoping to make it a (SPDIF) slave and then found I couldn't.
    ...


    :rolleyes:


    That's why I own now a white and a black one. ;)

    (All trademarks are trademarks of their respective owners, which are in no way associated or affiliated with soundside.de)


    Great Profiles --> soundside.de

  • DukeOURL: Separate wordclock required? Didn't know that, thanks for the clarification. Those things start real cheap and go to really expensive.


    yeah man... this spdif thang is really bumming me out... I get CK's reluctance but still there's got to be a better way... of course that's not going to happen LOL! :)


    Still, having to deal with it in the studio environment is a pain.. who wants to spend an extra grand on interfacing the unit to make it a slave... I'm thinking of the guenterhaas approach of just doing analog I/O and dropping the effects from the KPA... substituting plugins at the board.. control the whole thing on a single mono track for amped and one for DI... it's like going back to way we recorded with amps... so not much of a loss; just convenience. :wacko:

    Gettin' funky up in here..

  • ... it requires that the studio provide a separate word clock generator in order to use the KPA unit as a slave.


    Not necessarily a separate word clock. If your audio interface provides a word clock output (like the Focusrite Liquid Saffire 56 or RME Firefaces) you can use it, of course. The separate word clock generator is only required if you have e.g. multiple studios (mixing/mastering/recording/editing rooms) and want to have every studio sync'ed to one central master clock.
    I haven't seen an audio interface that provides a word clock input but lacking a word clock output.

  • The topic seems to be pretty much solved by now. Still I will try to go deeper into the topic, even though I have explained the situation deeper in earlier topics. But terms like 'reluctant', 'ignorant' and 'design flaw' require an answer.



    I am aware that there is a need and request for different sampling rates, 44.1, 48 and 96 kHz. However, I have decided to stay with 44.1 kHz because it allows the most calculation power while not sacrifying the sound quality. As a side effect, it fullfills the requirements for the omnipresent audio CD standard.
    Matching all sampling rates in a complex audio device is very challenging, because every single process has to be programmed and proven for variable sampling rate. It has to be assured that the formulas work in a way that the sound does not vary with different sampling rates. We have tried to put our manpower in creating a great sounding guitar amp and new features, rather than making our features adaptive to different digital formats that do not increase audio quality.


    My observation is that in the last 10 years most manufacturer of digital musical instruments or digital guitar amps avoided that challenge as well, due to the same reasons. The only exceptions that I can see are Eventide and Lexicon, as they come from a pure high professional studio background. Nevertheless many other devices provide digital I/O. The following conditions for seamless SPDIF or AES/EBU are mandatory, if no word clock connection is provided:


    - The acceptance of at least 44.1 and 48 kHz sampling rate
    - The slave ability to take the digital input as a clock source, enabled by a dedicated sample clock source selector


    A respective chapter in the manual is mandatory to explain what is going on with master and slave. In detail the following must be well described to avoid system failure:


    - Even when you only use the digital audio output on your digital guitar amp or keyboard (which is very likely) you must connect the digital input cable to provide the clock signal to the sending device. The clock source must be external. If this is not documented, a less trained user must assume that by only connecting the digital output to the audio interface is a save situation.
    - Alternatively the receiving device must be set to slave.
    - It must be avoided that both devices are set to be slave, causing the sample clock to breakdown due to the lack of a master.


    Earlier discussions about Spdif made me examine the digital audio capabilities and their documentation. As a result I have rarely discovered a device from the music instrument industries (exept pro studio, pro live, audio interfaces) of the last 10 years fulfilling these rules.
    Seen from this point the whole MI industry makes Spdif a technical flop. And yes, we are a part of this flop! But people rarely take notice of the big picture, but blame individual manufacturers.


    As I mentioned before, there is quite a simple solution for this problem, that would render all the above reasons and strict rules unnessesary:


    If audio interfaces would provide sample rate converters on their Spdif or AES interfaces, you would simply connect ins and outs as it was analog cables.
    You could even save money by not needing a Spdif in connection, when only the output is needed.


    I assume that the audio interface industry is not aware of this potential need, since they get no requests from their users, since you ask me for a solution, not them :). Also they might think that their users believe that SRC have a bad sound. Truth is: they sound great and the interface manufacturers know about that.


    This is a thesis of mine, and probably you would not find a similar call on the web yet. Spread the word!
    Ask me if you have further questions.

  • I must say I brought the KPA on the strength of the sound never once before I brought it did I consider anything else. I am one of the people who yes would of loved the KPA to be set to slave coz it drives me insane having the KPA on when I'm just mixing otherwise Pro Tools HD tell me my sync has changed, but hey I never brought it for the SPDIF capabilities and the way CK has designed it is how it is so I just get on with recording this great sound and think to myself well at least I'm not having to mic cabs up with loads of mics hire a load of amps that I could never afford to buy :)


    All the nice little feature that kemper keep adding are great but if nothing else would have been added when I brought my first KPA 18 months ago I would still be one of the happiest guitar players/studio owners in the world. The KPA has saved me time and money to once again thank you CK and thank you for chiming in and explaining your reason for making the KPA master only :)


    Now get back to getting that KFC released coz I've got some money burning a hole in my pocket ;)




  • ...So bottom line, implementing the requested feature would have made my kemper more expensive due to cost of components, more programming, longer testing of firmware updates, higher probablility of failure, longer firmware roll-out times, etc. etc. I understand the request for both higher sample rates and slave ability, and I would have liked those features as well. But I gladly trade that for a more affordable and potentially more stable unit. I would have bought it regardless if it only had analogue connections (like a mic in front of a cabinet), so it's not such a great loss to me.


    Thanks for the explanation, mr. CK. If I were you, I would copy it and keep it handy - like the clean sense, I am sure you will have ample opportunity to post it again (the nature of the internet) :-).

  • Thanks for reminding me!
    Its true that I save those long messages for later. I am collecting for a technic blog.


    I might add to the story that - beside the efforts of the implentation and calculation power issues- we have underestimated the need for a full Spdif implementation. We have oriented ourself to the general level of the MI industry, which is just basic and not unified. We had to conclude that the demand is not significant.


    Do not complain just here. Go to the forums for audio interfaces and ask for Spdif inputs with SRCs. Be loud!

  • I appreciate the long post. Good read, thanks!


    Here's my thoughts on what you wrote, CK:


    First of all I want to make it clear to everyone, that I accept that the current Profiler can't and won't get any changes in terms of digital I/O/sync. So everything I write is meant as food for thought for future incarnations of the Profiler (and maybe even the Virus synths).


    Second I want to note that we shouldn't bring the discussion down to "well, the others don't do, so why should we do?". If this way of thinking was best practice how could we have a Profiler in the first place? ;)


    Now let's get into a bit more detail.
    When you started to create the Profiler, it was perfectly ok to go the way you went with digital I/O. There had been other fields that needed your attention. Everyone should be aware of the limitations in this regard by now and it shouldn't be a deal breaker at all. But still there clearly seems to be a need for improvement in digital I/O in future generations of the Profiler, not only because I've been pretty vocal about it.
    The only problem that we could blame you for is the big hole in the back of the Profiler Head that would have been a nice place for expansions like the power amp or maybe even a digital I/O board for studio use. But sadly it turned out to be an issue to fill this hole after the fact. Maybe the reason why the rack version didn't even have a hole anymore. Anyway, it's the way it is now. But this bad experience should have given you enough food for thought to prevent this from happening again. :)


    You state that different digital audio formats wouldn't increase audio quality. That's not entirely true. In a simple home setup you're probably right. But in a more complex setup the risk grows to get all sorts of problems with old school analog audio. That's the reason why many manufacturers have switched to or at least added different kinds of digital audio implementations from word clocked AES/EBU via XLR cables to various incarnations of audio via Ethernet (EtherSound, Cobra, Dante) or embedded audio in the video/broadcast world (SDI, HD-SDI).
    S/PDIF has been a consumer audio technology from day one. For simple home audio setups it might have been sufficient but in the pro world it's never been a go-to solution. The only digital audio format close to S/PDIF that had some acceptance was the ADAT protocol (48kHz) ... probably due to the lack of better alternatives. And this might have been the reason for 48kHz to be an industry standard in some audio related fields until today.


    You're 100% right when you say that S/PDIF is a flop. And that's the reason why some (me included) ask for improved capabilities in future Profilers (and Virus if you like). And you will forgive us to just ignore the fact that most other's don't do it. We're here beause you successfully did something unbelievably great that nobody else did, you see?


    You've stated that most of the pro audio industry are reluctant to add proper digital audio I/O capabilities with very few exceptions. I want to state that the opposite is true, imho. All serious pro audio equipment manufacturers offer a plethora of options. All you need to do is to offer options that comply with these interfaces. Not necessarily all available options in a stock "Profiler Pro". But at least the means to add the required / preferred digital I/O options through expansion slots or whatever you come up with.


    Sadly your prior posts had given me the impression that you're not planning to improve on the current state. Hopefully just a misunderstanding but the way I read it until your long post above it seemed like you completely ignore the need for something better than S/PDIF. That's why I called you ignorant. Really hope I was wrong with my impression and the fact that you wrote this long post shows that you're interested and investigating.


    Only thing that still worries me is the fact that you keep asking us to press the pro audio interface manufacturers to add capabilities (S/PDIF + SRCs) they likely won't ever implement because they can't be considered pro level digital audio connectivity. You better change your mindset and offer existing pro level digital audio connectivity in a future Profiler (and Virus) incarnation. For a pro user it doesn't even matter a lot which technology you choose. If you (e.g.) think that word clocked AES/EBU through XLR isn't your preferred technology for some reason, offer something else ... or find a way to discuss available options with those seriously interested in pro level digital audio connectivity.


    Regarding the current limitation to 44.1kHz processing and processing power restrictions:
    I have no idea about DSP and how fast processing power is rising in this industry, but from watching IT in general, there's a never stopping increase of processing power. For a future Profiler v2 or Profiler Pro there should be DSP options that don't limit you to 44.1kHz!? Again, the current Profiler is as it is, I'm sure everybody can understand that. At least I can and I'm talking about future products only!


    Cheers
    Martin

  • hat's the reason why many manufacturers have switched to or at least added different kinds of digital audio implementations from word clocked AES/EBU via XLR cables to various incarnations of audio via Ethernet (EtherSound, Cobra, Dante) or embedded audio in the video/broadcast world (SDI, HD-SDI).


    yep.. it would be awesome to have in a future Profiler V2... AES/EBU or preferably Ethernet/Dante.... or both. It's a shame that there wasn't expansion capabilities included in the Profiler V1 but hey.. as stated, CK changed the world for us guitar players and studio aficionados..



    until hopefully then... :thumbup:

    Gettin' funky up in here..

  • The only problem that we could blame you for is the big hole in the back of the Profiler Head that would have been a nice place for expansions like the power amp or maybe even a digital I/O board for studio use. But sadly it turned out to be an issue to fill this hole after the fact. Maybe the reason why the rack version didn't even have a hole anymore. Anyway, it's the way it is now. But this bad experience should have given you enough food for thought to prevent this from happening again. :)


    The space in the back was intended to be reserved for a power amp, which was originally supposed to be an upgrade option that could be done at home. Unfortunately, Kemper Amplifiers didn't take into account European regulations on such retrofits, which could have been potentially hazardous to users. As a result, the all-in-one power rack amplifiers were launched with a built in ICE module. Nevertheless, there are still third party options available to intrepid users such as myself that plan to explore this option at some future date. I don't see this as a drawback at all.


    You state that different digital audio formats wouldn't increase audio quality. That's not entirely true. In a simple home setup you're probably right. But in a more complex setup the risk grows to get all sorts of problems with old school analog audio. That's the reason why many manufacturers have switched to or at least added different kinds of digital audio implementations from word clocked AES/EBU via XLR cables to various incarnations of audio via Ethernet (EtherSound, Cobra, Dante) or embedded audio in the video/broadcast world (SDI, HD-SDI).


    Mr CK is correct, switching audio formats will not make a difference in audio quality. You're referring to synchronisation problems in a large studio setup, particularly in a video/broadcast environment where you have to use a common clock for different pieces of equipment. The sound quality would be the same if the SPDIF clock speed was 48 khz as it is right now.


    S/PDIF has been a consumer audio technology from day one. For simple home audio setups it might have been sufficient but in the pro world it's never been a go-to solution. The only digital audio format close to S/PDIF that had some acceptance was the ADAT protocol (48kHz) ... probably due to the lack of better alternatives. And this might have been the reason for 48kHz to be an industry standard in some audio related fields until today.


    You're 100% right when you say that S/PDIF is a flop. And that's the reason why some (me included) ask for improved capabilities in future Profilers (and Virus if you like). And you will forgive us to just ignore the fact that most other's don't do it. We're here because you successfully did something unbelievably great that nobody else did, you see?


    I don't really have much of an opinion on the success or failure of SPDIF, because I believe implementation is everything and it is clearly possible to have a device lock to an external SPDIF clock, like my interface does with my Kemper. There were clearly cost factors involved in the decision. Since I see no reason to record audio at sample rates other than 41 khz, it's a moot point to me whether the additional cost would have been justified, seeing how hard it was for me to afford the Version 1 product and I sincerely hope there isn't a Version 2 anywhere on the near horizon, I have a phobia of products that have a development cycle like iphones and ipads. Clearly, you're disappointed that the Kemper ïs missing this feature, but to me and a lot of other users, it already is a "Swiss (German)" knife with a lot of great input and output options.


    You've stated that most of the pro audio industry are reluctant to add proper digital audio I/O capabilities with very few exceptions. I want to state that the opposite is true, imho. All serious pro audio equipment manufacturers offer a plethora of options. All you need to do is to offer options that comply with these interfaces. Not necessarily all available options in a stock "Profiler Pro". But at least the means to add the required / preferred digital I/O options through expansion slots or whatever you come up with.


    Sadly your prior posts had given me the impression that you're not planning to improve on the current state. Hopefully just a misunderstanding but the way I read it until your long post above it seemed like you completely ignore the need for something better than S/PDIF. That's why I called you ignorant. Really hope I was wrong with my impression and the fact that you wrote this long post shows that you're interested and investigating.


    I still don't see any justification for the name calling. If you're willing to pay for an expansion, I don't see what problem you'd have springing for a word clock and one of those Behringer type devices. SPDIF is a consumer format as well as a professional format and arguing about its merits and demerits is like arguing about midi, which also has a ton of shortcomings. I'm pretty sure you wouldn't have had this problem if the Kemper was master at 48 khz, but unfortunately, Mr CK saw more of a use in 41 khz, since he assumed that much of its attraction would be CD quality audio.


    Only thing that still worries me is the fact that you keep asking us to press the pro audio interface manufacturers to add capabilities (S/PDIF + SRCs) they likely won't ever implement because they can't be considered pro level digital audio connectivity. You better change your mindset and offer existing pro level digital audio connectivity in a future Profiler (and Virus) incarnation. For a pro user it doesn't even matter a lot which technology you choose. If you (e.g.) think that word clocked AES/EBU through XLR isn't your preferred technology for some reason, offer something else ... or find a way to discuss available options with those seriously interested in pro level digital audio connectivity.


    Just use analog out. All this stuff you're saying about problems in recording an analog signal are bogus, especially if the studio you're using is a professional one, as you keep touting. There is absolutely nothing wrong with just recording with a 1/4", I refuse to buy your argument that it doesn't cut it. No way, that's not true, not in the least. :thumbdown:


    Regarding the current limitation to 44.1kHz processing and processing power restrictions:
    I have no idea about DSP and how fast processing power is rising in this industry, but from watching IT in general, there's a never stopping increase of processing power. For a future Profiler v2 or Profiler Pro there should be DSP options that don't limit you to 44.1kHz!? Again, the current Profiler is as it is, I'm sure everybody can understand that. At least I can and I'm talking about future products only!


    Why stop there? In the future, we'll just have to tap our b@lls or raise an eyebrow and the Kemper should come flying to us like an Iron Man suit from our houses :thumbup:


    Honestly, rather than working on a Kemper V2, I'm really looking forward to Mr CK adding features like slot assignable delay on the Kemper. A spring reverb. More unconventional FX that would stop us from even saying the words Axe FX ever again. I do see a use in extra DSP power, but perhaps Mr CK could make that an add-on or upgrade in the form of a floorboard such as the KFC, with the DSP used for additional FX and advanced looping functions, etc.


    I mean, I'm just a one-tone guy, this really doesn't make that much difference to me, especially since Mr CK doesn't plan to change the core tone engine any time in the conceivable future. Yes, having AES/EBU, ADAT and other connection options would definitely be a plus. It'll never replace 1/4" for recording though, can you imagine people spending money on a Kemper and then spending even more money on an interface with connection options beyond 1/4" and SPDIF? I have an RME Fireface, but I reiterate, better just buy that Behringer thingie haha ^^

  • I won't comment on a "you don't need X because I don't need X" type of post.
    Just FYI, I do have word clock, I do have synced S/PDIF, I do have 2 externally clocked Behringer SRCs ... I could afford as many SRCs and interfaces as I like ... but that doesn't change my overall opinion that digital audio connectivity needs some more love.