Subject: Re: Audio interfaces survey From: Elena Grassi <egrassi(at)UMD.EDU> Date: Thu, 1 Dec 2005 16:15:25 -0500Olivier, one issue to consider is how many channels you need and what sampling rate you want to use, as well as how much external circuitry (like preamplification and antialiasing filters) you will need. For multiple channels general DAQ cards can be a good choice. I'm currently using 4 National Instrument PCI-6071E cards, all together in a computer and I'm acquiring from 128 channels at 39.0625 Ksamples/sec each. This cards do require external preamps and unfortunately NI does not offer any solution for this high channel count that could make sense from the size/price point of view. Regarding the sampling rate, multi channel cards usually divide their max sampling rate among the number of channels used. Another issue to consider is leak between consecutive channels, which is an issue if you have signals of very different sizes. and ... one more issue ... if you need to synchronize input and output accurately, on the same clock, you may want to consider a card that has also D/A. The above cards have 2 of these channels each which you can trigger with a hardware trigger (and independently from A/D if you want). Hope this information helps. Best, -elena Regis Rossi A. Faria wrote: > Hi, > > sound cards generally target PC/Mac buses, like PCI or USB or Firewire: > this is an issue: connectivity! Firewire is apparently more stable than > USB for audio applications specially regarding high bitrates transfer > sustain, and PCI bus is the one which offers lower latencies. Terratec, > Yamaha, Creative and many others target this market. > > digital audio interfaces target not only computer buses, but also studio > gear which connectivity to analog mixers and analog/digital/analog > converters: RME, MOTU, Egosys, M-Audio, and many others target this > market. Usually they offer lots os possible digital formats/protocols > for I/O: ADAT, TDIF (both now decrasing popularity), Firewire and USB > (increasing popularity), PCI, SPDIF, AES/EBU, very few would support > MADI (AES10) and some are very focused in having multiple (usually 8) > analog I/O. > > D/A and A/D conversion are now stable in the range 96 kHz/20bit, most > cards accept simultaneous I/O of multiple channels in this format, and > lots of cards/interfaces offer now 192 kHz/24bits, although not > supporting many inputs or outputs operating at the same time in realtime. > > You should pay attention to the pictures of the back and front panels, > where you will really realize how many inputs and outputs the interface > has, and then how many inputs and outputs you can connect phisically: > many manufacturers count on maximum possible digital channels supported > by the card, but these figures generally are not accessible in the real > conectors, or require that you have several different gear at the same > thime, for example an ADAT system, a SPDIF I/O, RCA line inputs and the > TRS/XLR I/Os. That's tricky. > > Other issues regards to OS compatibility and support, THD and SNR > figures, dependency of a PC/Mac to operate or standalone, mobile or rack > mount, and support to additional formats (ex: MIDI). > > Hope this helps, > regards, > > Regis Rossi Faria > LSI-University of Sao Paulo > regis(at)lsi.usp.br > > Olivier Tache escreveu: > >> Dear list, >> >> I'm currently working on a very general survey of digital audio >> interfaces, but i'm unfortunately lacking practical experience on the >> subject. It would be very kind if those who are willing to could >> briefly tell me about the typical issues they encounter when dealing >> with sound cards (latency, D/A and A/D conversion, etc.) or provide >> pointers to ressources that could help me in my *quest* (apart from >> those wich have already been given here a few months ago). >> >> Thanks a lot. >> >> Regards, >> Olivier >> -- Elena Grassi, Ph.D. Perceptual Interfaces and Reality Lab University of Maryland 3355 A. V. Williams Bldg College Park, MD 20742 301-405-2876 (office) 301-314-9920 (fax)