darrylfunk
Banned
keith,
i'm not sure that is the idea of asio drivers....coming from where they do!!!
i'm not sure that is the idea of asio drivers....coming from where they do!!!
Not really, no. It achieves its primary goal of low latency by simplifying what it does, not adding to it! There's quite a good piece on Wikipedia.doesn't asio do more than just bypass the kernel though....surely it must have some other functions....?!
how does it play different simultaneous bitstreams of varying bitdepth and carrier freq?
also if it is bi directional how does it send the data to keep everything together?....cheers if you can give me any info....
ASIO/bit perfect are about sample resolution/the value within each data word, and ensuring that the digital values are not being adjusted by any process/software between the raw data source (eg. flac file, cd) and output device (eg. usb or spdif)
Jitter is about timing variations between samples/words and not about the value of the sample/word. Async usb is about controlling timing ie. jitter
ASIO/bit perfect and jitter are not the same thing
Master clocks in the record process (A->D) don't necessarily have the same effect/control as a master clock on replay (DAC).
Using a master clock in replay (DAC) we only really care about the lack of jitter within the final DAC. The source device can have jitter, because we're no longer reliant on the precise timing of each (bit (or word)) clock edge. We read the data when it's known to be stable thus removing the artefacts of jitter in the source data stream, and leaving only any jitter present within the DAC itself.
...and that's the problem with a master clock in the ADC process.
Although the master clock itself may be precise and stable, there may still be sources of jitter (noise which produces timing errors) between the external clock input and the clock as seen by the ADC chip. There may also be amplitude errors in the converted ADC value as a result of noise/distortion within the ADC - these amplitude variations cannot be rectified/improved by a master clock.
Most domestic installations do not require a dedicated clock. The internal clock within the MDAC seems fine to me, and the whole point of feeding such a device via asynchronous USB is that you allow that decent clock to do what it does best, without the need to bend to the will of some dubious source clock.
It's interesting to note that in that SoS test, most of the devices performed better on their internal clocks. Clock locking is NOT normally something you ought to get involved in unless you really HAVE to - i.e. you have the need to lock MANY different devices together. The mere need to connect one device to another does not justify the need to clock lock anything, in my view.
The issue with isochronous USB is that the data rate is locked to the USB frame clock, I think this is at 8kHz. For 44100 this obviously requires frames of differing lengths. Anyway a DAC has to run at a rate closely locked to the frame rate of the particular USB bus it is attached to.i'm just wondering how usb can be so criticised by some as properly set up i can do bit perfect recordings with asio drivers!!! how much in jitter results can asynchronous improve on a system that can make bit perfect recordings.
It's a USB-144/2. Seems pretty stable, but I have to use ASIO to record from it at 96k/24.paul , what tascam are you using? i had terrible driver problems with one of their usb interfaces....got rid in the end....