Am Mittwoch, 18. November 2009 schrieb Karl Hammar: > Martin Homuth-Rosemann: > ... > > > Hi Karl, hi LAU users > > Hello and welcome to the discussion. > > > I've followed the discussion about timing and synchronisation - what do > > you think about separation of number crunching and communication > > (ATNGW100) from the "dirty business" of ADC. > > Shall take that as a question (you have no ?)? I asked you (and the LAU audience) to hear your/their opinion about my (maybe silly) idea. I see this discussion in the early project status mainly as a kind of brainstorming. To speed up the process of prototyping and to allow many participants I suggested the use of "ready mades" - don't reinvent the wheel! The atmel board ATNGW100 is easy available and not expensive, no time consuming soldering (and hw debuging) needed - this will be a standard platform for colaboration. The same goes for the ADC, if we use available units with an (open) standard communication protocol like AES-3, ADAT or MADI we can concentrate on the difficult and more exciting part - finding new solutions / algorithms for syncing different sources, internet transfer, ... > > Don't you always have to separate the digital and the analog domains? > > My plan is to build a card frame based system with one main power > module, one cpu card, with the possibility to add a lot of different > i/o cards. One such card could be for audio input/output. (Although > my main interest is industrial measurement and control.) Ok, a slightly different focus. > > With this the "dirty business" of ADC is separated to another card > like an ordinary old soundcard you attached to your motherboard. > > Do we need more separation? Could it possible be because of: > . space constraints > . noise and audio quality > . power constraints > . economical factors > . "time-to-market" > etc. > > What are the key factors for you ? See above ^ > > > We need the codec, some kind of amplification, a clean power supply etc. > > to get a good S/N ratio - and we need it for a lot of channels. > > Do you have a spec. which you'd like to discuss ? > E.g. how many channels are you regulary using, what s/n ratio is a > minimal requirement for you ? We (no pluralis maiestatis, I summed my impression from some postings of the LAU audience) need more than two channels, more than 16 bit and more than 100dB S/N at minimal 48 kHz, preferably 96 kHz. > > > There exist many (more or less) pro-audio devices with well documented > > interfaces (SPDIF/AES-3; ADAT; MADI) > > Is your point, that the system should behave as an spdif etc. > device instead of delivering the audio over ethernet? No - just the other way round - I thought of replacing the chips TLC4545ID or AD7762 (SPI or parallel interface) with a "black box" (AES-3, ADAT or MADI interface) - just another way to get audio samples into our communication processor which delivers them via ethernet into the linux computer. > > SPDIF [1], seems to be able to carry 20bit (maybe 24) 2 or 4 channels > at 44.1 or 48kHz (possible other) sampling rates. > > AES-3 [2], seems to have the similar (24bit though) carrying capacity. > > ADAT [3], seems to be limited to 8 channels at 48 kHz, 24 bit. > > MADI [4], seems to be limited to 64 channels at 96kHz, 24 bit. > > If this project shall implement any of theese interfaces it might > then be the ADAT or MADI, since I see no reason to implement the > smaller interfaces. But AES-3 (or AES-42 for digital microphone) is a standard for digital audio connection. > > But if we successfully implement adat or madi, we are still missing > the adat/madi part on the pc. So we still have a problem... No, our "LAU-interface" is this part on the pc. > > And if we get i/o capacity problems with ethernet, we could easily add > another ethernet card at relatively low cost. But then you might find > that the rest of the computer is to small. > > > - a cheap one is e.g. the Behringer > > ADA8000 for about 200 € [1] with eight mic (phantom power) or line inputs > > and eight line outputs. The codecs are 24bit@xxxx/48 kHz [2] > > > > [1] http://www.thomann.de/gb/behringer_ultragain_pro8_digital_ada8000.htm > > [2] http://images4.thomann.de/pics/prod/164573_manual_eng.pdf > > Are you suggesting that that unit's spec is something to aim at ? Of course not - as Fons stated^^ Behringer rhymes with "beware of" ;) But it may give simpler and quicker results for testing than soldering small smd ics onto veroboard ;) (Frederick Brooks; The Mythical Man-Month: "plan to throw one away; you will, anyhow.") > > Or is your point that it would be better to do a ADAT, or MADI > interface for the pc instead of doing a "soundcard" ? Not better but different (brainstorming....) > > Doing a adat/madi interface for the pc is outside of the scope of > my projet, so I cannot help you there. Ok! Sorry Karl for buggin' you. > > Regards, > /Karl > > [1] http://en.wikipedia.org/wiki/S/PDIF > [2] http://en.wikipedia.org/wiki/AES/EBU > [3] http://en.wikipedia.org/wiki/ADAT > [4] http://en.wikipedia.org/wiki/MADI Ciao Martin _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/mailman/listinfo/linux-audio-user
