[zaen]

In this corner....a MacBook Pro weighing in with a built in mini optical jack capable of 24bit-192khz stereo output (although the Audio/MIDI utility only has a setting for 96khz?)

And in this corner...the feisty little M-Audio Transit...with its fancy installer, preference pane and USB connectivity....also capable of high resolution 24bit-96khz resolution....via its full size optical out..

So...any reason why one would be better to use than the other?

I could have sworn I heard a difference when attempting to A/B them...although not entirely sure....thought there might be a technical reason to choose one over the other....

For reference the system is...

MacBook Pro --> Optical out --> Keces 131 D/A --> Burson Audio Buffer --> Cambridge Audio Amp --> ELAC speakers and sub

Cheers!

 

[fjf]

CD is 16 bit-44.1 kHz. Unless you have a better source of music, both should be more than enough...

 

[zaen]

source lately is 24bit vinyl rips and other various hi-rez files...

 

[bigshot]

Try carefully balancing your line level and doing a direct A/B comparison. I bet you won't find a difference then.

See ya
Steve

 

[nick_charles]

Quote:

Originally Posted by bigshot /img/forum/go_quote.gif Try carefully balancing your line level and doing a direct A/B comparison. I bet you won't find a difference then. See ya Steve

If you have two digital feeds and the decoded ouput of one is louder than the other then something seriously iffy is going on, i.e they are different. If the two bitstreams are in the same format viz 24/96 then both the amplitude and frequency data should be exactly the same. If they are different then either one bitstream is being mangled more than the other or is being "altered" in some way , in either case you would have verifiably different bitstreams. Best way to check this would be to stream the bits to a 2nd digital recording device and compare the 3 streams (original and two copies) using something like Audio Diffmaker.

Comparing two different SPDIF transmitters would be tricky to do in real time, the OP would require two identical audio apps running simultaneously (one on built-in spdif one on external device) and synchronized, run the two feeds to an optical switch box and run the output to the keces - then something close to instant switching may be possible.

I have done near instant switching between optical feeds from PC and CD Player but it is really hard to get thenm aligned perfectly and just that blis as you switch over is enough to distract.

 

[LnxPrgr3]

Given the options, I'd choose optical.

My MacBook's optical out has been serving me well.

I actually did a comparison last night between my external card's USB input and its optical input, both coming in from my MacBook. I ran a cable from the line out to the line in, then played some test signals at the highest supported samplerate (96kHz) and compared the results. As I expected, there was no detectable difference for any reasonable signal in the audible range (besides a very small pitch shift from the source being a different clock).

I did detect distortion over the optical for very high frequency (>40kHz) signals though -- looking at the waveform, it looked like I was dropping samples like crazy -- the waveform 'skipped.' This did not happen over USB.

I'm not too concerned though, as I don't spend much time listening to full-scale supersonic tones, and no other signal I threw at it caused a detectable problem

If I were in your position though, and if I were feeling paranoid, I would choose PCI -> Optical -> receiver over PCI -> USB -> Optical -> receiver -- fewer pieces to have a chance to screw something up.

 

[nick_charles]

oops !

 

[bigshot]

Quote:

Originally Posted by nick_charles /img/forum/go_quote.gif If you have two digital feeds and the decoded ouput of one is louder than the other then something seriously iffy is going on

He can't do a direct A/B comparison using the same DAC because I don't think his DAC has two optical inputs. He's going to need two DACs and a preamp to switch. Even if the DACs are different models, I doubt he will hear a difference if the balances of the analogue outputs match. (Especially through speakers.) If he does detect a difference, he can swap the opticals and try to see if he gets opposite results to see if the difference is the two DACs or the opticals.

See ya
Steve

 

[nick_charles]

Quote:

Originally Posted by bigshot /img/forum/go_quote.gif He can't do a direct A/B comparison using the same DAC because I don't think his DAC has two optical inputs.

But you can use an optical switch box to switch between two optical feeds into one ouput. I got one from eBay, ~ $16 (in US money) including toslink cables. The problem is that there is a finite lag while the DAC re-locks into the new signal. However it does mean relatively less extra plumbing.

The big problem is doing any kind of a switch over in near real time

 

[bigshot]

I wasn't able to get any kind of an idea of how similar SACD and CD were until I racked up the same CD in two machines and did a direct A/B.

See ya
Steve

 

[Random Access]

What playback software are you using? iTunes doesn't do bit perfect by default (verified by playing back a DTS signal to a DTS receiver). You have to disable audio improvement goo goo ga ga in iTunes and disable volume control. Try to play a DTS signal to a DTS capable receiver. If you get noise... then you're not getting bit-perfect. When you are getting bit-perfect... then you can start comparing with your M-Audio Transit.