Mark Knecht wrote: >>Another thing about the quattro is that even the windows drivers will >>not allow you to record and playback on all 4 channels at one time. >> >>You can use >> >>4 in, 2 out 48khz 24 bit >>2 in, 4 out >>2 in, 2 out 94 khz 24 bit >> >>I think I am running up against this with my latest attempts. It may be >>that the quattro cannot do all 8 channels because of a hardware switch >>maybe for power consumption or something. They do run awfully hot and I >>can imagine that it would be possible to melt something if their is too >>much power running through them. >> > > > USB 1.0/1.1 is built on a 12Mb/Sec physical layer. > > 96000 * 24-bits * 4-channels = 9.216Mb/S if I did the calculations > correctly. that should be divided by three to get bytes as there are 8 bits in every byte the quattro uses 24 with 3 periods (not packed in four like other cards). 24 * 3 bytes * 48000 = 3072000 bytes => 3072 Kb => 3.072 Mb/S > > I think that's probably more than USB can really handle. When I worked for a > company that did USB hardware, we found in many PCs (at that time - > 1996-1999) that most USB implementations would really do much more than > about 2Mb/Sec reliably. The newer implementations are much better, but these > numbers bring you up to 75% bus efficiency. Even 1394 doesn't get much > beyond that and it uses much larger packet sizes to get some of that. > That comes as no surprise to me that the usb protocol cannot handle effectively it's full bandwidth. But it should be easily able to handle this: 44100 * 2 bytes * 8 channels (4 in, 4 out) = 705600 bytes => 705.6 Kb/S -- Patrick Shirkey - Boost Hardware Ltd. Http://www.boosthardware.com Http://www.djcj.org - The Linux Audio Users guide ======================================== Being on stage with the band in front of crowds shouting, "Get off! No! We want normal music!", I think that was more like acting than anything I've ever done. Goldie, 8 Nov, 2002 The Scotsman
