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MDAC first listen thread

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Glad I guessed right, as I don't have an MDAC and I haven't rtfm. I'm simply reverse engineering the designer's devious brain ;-)
 
sonddek said:
I may be wrong about this, but I'm going to try to explain the bit perfect thing for you since I don't find the other explanations here very clear.

As I understand it, it's possible to configure your computer to output a modified bitstream, i.e. not the original music data that your music files contain. At that point all bets about sound quality are off, since various software on your computer could potentially degrade the original signal.

The MDAC producers would like you to enjoy the MDAC by feeding it the exact original data in your music files, not a version modified by some software or hardware. To help you achieve that they have provided a standard file which the MDAC recognises because it has a version in its own firmware. The MDAC can therefore check that its own standard file matches exactly the file sent by your streamer/computer. If it matches perfectly then that's a good indication that your computer is configured to send exact original music files to the DAC. That then constitutes "passing the bitperfect test", and you can be fairly assured that your MDAC is not being let down by degradation further upstream.

Cunningly, rather than send around a music signal file which would use up bandwidth and disc space, the MDAC designers have made the standard file a data sequence which can be generated by a small programme in the Java language so that almost any computer can generate it locally rather than having to download a big file. Consequently you only run the Java programme once to generate the 'music' file, which you then send to the MDAC in order that the MDAC can verify that your computer/streamer is not degrading its output. You send the generated file by simply playing it through your normal computer/streamer audio player.

Please correct me if any of that is wrong, but I thought it needed clarifying for those who aren't too familiar with such things.
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Thanks for this sonddek - This finally makes sense now!
 
isn't this form of raw file transfer between the computer and the DAC something that's present for years at better DACs aimed for PC audio?

the first comes to mind mirko weizig's bd-design crazy T from 2007....
 
Not sure what you mean by 'raw file transfer'. The Mdac uses and asynchronous USB protocol to transfer data, this method has been increasing in popularity for a couple of years now. Prior to about 24 months ago it simply didn't exist, no one had written the code that allowed a dac to talk to a pc and control the rate of the data flow as it saw fit.

Firewire connections between dac and pc can do the same, and have done for a long time. You could say that the only real difference between async firewire and async usb is that firewire has its own built in hardware controller on the pc side where usb does not. Certainly you'd have to look no further than firewire to see where the guy who first tried async usb took the idea from.
 
how similar is asynchronous to an actual asio driver?

i was under the impression asio is that kind of data stream......anybody?
 
@sq225917
by raw file transfer i exactly mean what mdac does - takes an unprocessed file from PC and works with, instead of "streaming" a (wave) file processed by a SW player from the PC
 
anubisgrau said:
@sq225917
by raw file transfer i exactly mean what mdac does - takes an unprocessed file from PC and works with, instead of "streaming" a (wave) file processed by a SW player from the PC
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The normal protocol for transferring music data to DACs is AES3. If you were to send an unprocessed mp3 file to a DAC, the DAC would pretty much need to be a PC in order to process the file. Then you would effectively have a Squeezebox.
 
John (and fellow MDAcers). I collected my MDAC on Saturday, and am having a problem with it. Listening to a CD on headphones via the coax input, there's a low-level 'whistling' noise. The nearest comparison I can make is to the sound a modem makes when trying to connect, but quieter. The sound is there whichever filter setting I use. Any thoughts about possible causes/solutions?
 
darrylfunk said:
how similar is asynchronous to an actual asio driver?

i was under the impression asio is that kind of data stream......anybody?
Click to expand...

Darryl - you are describing two unlike things.

ASIO is a protocol (a method of talking) that exists between an audio application (music player software) and the computer's audio system (which consists primarily, but not exclusively, of the sound card). Some sound cards' makers have developed and include support for ASIO (Advanced Steinberg I/O). ASIO was developed by Steinberg (a developer of audio production software) specifically to reduce the significant latency (delays) inherent in conventional computer audio. The main way in which this was achieved was to bypass the processing introduced by the OS. and this is why ASIO is usually "bit-perfect". ASIO was not (and probably still isn't) officially acknowledged by Microsoft who, subsequently, developed their own official version which is known as WASAPI, but note that the two, although similar in principle, are not interchangeable.

Asynchronous USB is the method by which the USB hardware operates - think of it as the receiver being in control of the transfer as opposed to the usual arrangement which is governed by the sender.
 
hi bottleneck and purite audio, can you please tell me what are their different presentation ? What is their sonic carachter?

sorry but i cant test both .
tnx
 
Does Purite Audio carry the mdac? I just browsed their website and they are a m2tech dealer, no mention of the mdac
 
hmm...downloaded bit perfect and couldn't get any sound out of the mac.

Had to trash it in the end and now everything is working again.
Not good.
 
spxy said:
hmm...downloaded bit perfect and couldn't get any sound out of the mac.

Had to trash it in the end and now everything is working again.
Not good.
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Hi spxy

If you are referring to the MDAC bitperfect test file, it doesn't make any sound.

Choose the Bitperfect test option on the MDAC.

It should say 'awaiting trigger'.

Play the test file and see the result on the MDAC display.
 
finesensations said:
If you are referring to the MDAC bitperfect test file, it doesn't make any sound
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I think he was referring to the MAC audio accessory of the same name.

BEWARE - the MDAC bit perfect test file, if it does "escape" for any reason, is very loud noise which may well cause damage.

Caveat auditor.
 
Joe Hutch said:
John (and fellow MDAcers). I collected my MDAC on Saturday, and am having a problem with it. Listening to a CD on headphones via the coax input, there's a low-level 'whistling' noise. The nearest comparison I can make is to the sound a modem makes when trying to connect, but quieter. The sound is there whichever filter setting I use. Any thoughts about possible causes/solutions?
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Hi Joe,

It looks like you have a bad MDAC - a couple of things you could try first (but unlikely):

Upon Power-up Press and Hold down the Knob on the MDAC and Power on the unit - this will bring up the software version number and more importantly the Raw Digital supply rail voltage - if you could just tell me the voltage Level.

Also, what Brand and model of Headphones are you using? Do you have a different pair you can try?

Do you have the 'whistling' noise on both channels?

Try unplugging everything from the MDAC - but power and the headphones, is the noise still present?

Sorry for your issue,

John
 
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