NZtechfreak
Headphoneus Supremus
- Joined
- Jan 19, 2012
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I use the "site:" search in Google a lot. Nice tip for those unaware!
Is there a usb otg cable that I could use that I don't need the adapter cable first? I prefer it to end in usb b since that is what my dac/amp allow right now.
Is there a usb otg cable that I could use that I don't need the adapter cable first? I prefer it to end in usb b since that is what my dac/amp allow right now.
Thank you for the excellent post, however there are some things that are not quite right and might be causing you a little misunderstanding? The main ones are.
"it's arguably impossible to have bit perfect playback in a real-time system"
I must be misunderstanding you? Computers all have bit perfect playback in real time. Any errors in the bits have to be corrected in real time, or .zip files would always be corrupted, the numbers on bank accounts would be way off and so on.
"Because audio is real time, there is no error correction that can be done to this square wave, any resulting wave form IS your music."
This is not quite right, look up hysteresis loops as commonly used on input gates on digital logic, they "condition" the output levels and rise/fall times. Used with the clock pulses, the width of the output pulses are synced with the clock pulses to produce output pules that are of the correct width and timing.
"Jitter is an alteration of the duty cycle"
No, it is an alteration of the timing. The pulse can be the same width, but delayed for example - The rising edge and the falling edge being delayed by the same amount. The pulse is still within normal parameters, just delayed.
For example - In the example you give of jitter causing problems, he sorted it out, even though it was a delay of just 358ps, which translates to a frequency of a little over 2.793GHz for a delay of a whole pulse.
Which is why jitter is important in computer circuits, but massively less of a problem with circuits working for audio. Even the fastest digital circuitry associated with the actual audio signal is working at < 100MHz for even the highest quality (say a sampling rate of 384000Hz x 24 bits x 2 for Nyquist = 18.432Mhz BUT good rise times typically require at least the fifth harmonic, so = 92.16Mhz bandwidth requirement). Jitter might be important there you might consider, but it is not, because it is already allowed for in the Nyquist frequency choice and the fifth harmonic. Jitter on a pulse could affect the rise time, but it gets corrected by the circuits. You can feed a sine wave into a hysteresis loop and get a square wave out, that is how good they are. I have tried to keep this as simple as possible, but where stubborn problems remain, more sophisticated circuits are used to correct jitter, like PLLs, and are another safeguard. Any digital system has all the time-sensitive parts of it running from a single clock to reduce jitter further - Think of genlock in professional video gear to keep all cameras and processing equipment locked to exactly the same frequency and instant.
There are quite a few others, but you should be able to sort them out when you sort out the ones I've mentioned.
Thank you for the tip!
"Information search" added!
http://www.head-fi.org/t/595071/android-phones-and-usb-dacs/6285#post_11306308
is anyone aware of a list that shows tablets that are confirmed usb/otg/dac friendly, that can stream digital music (files and/or services) without the need of special music players (usb audio player pro, etc.)?
That would be complicated. Too many variables.