Bounce To Disk or monitor out direct to ext. CDR?

[Doc]

I did a bit of experimentation just to try and shed some light on this BTD thing.
Firstly, I opened a song (24 bit / 44.1k) and set up a new stereo audio channel assigned to the SPdif input with it's output set to something unused (ADAT 1&2). I then routed the mix to the SPdif output and connected the SPdif in and out together and recorded the mix to that track.

Next, I did a BTD (24 bit / 44.1k) of the mix in SDii format (the session file format) and another converted to stereo interleaved wav.

Once I did all this, I set up a new session (24 bit / 44.1k SDii) and imported the SPdif tracks and the BTD's. These were placed in the playlist and each was time aligned. I then copied the files to new tracks and inverted each of them.
With all the faders set to 0dB and any one non inverted track and any one inverted track solo'd, there was absolutely no output at all with any combination.

This leads me to believe that the SPdif recording was exactly the same as the BTD files. So, either the SPdif recording and the BTD files sound bad or they both sound good. Personally, I believe the latter.

I did however do some further tests converting (using BTD and SPdif recording) to 16 bit without dither and with Digi and Waves dither. When inverted and time aligned with any of the 24 bit files there were noticeable artifacts and noise which I expected.
The one thing I was not expecting were very low level clicks and waveform distortion seemingly unrelated to the audio with all the 16 bit files whether using SPdif or BTD.
This did deteriorate the sound more than the 16 bit conversion alone.
Another interesting find was insering a Waves L1 Ultramaximiser on an inverted and a non inverted 24 bit track. One had no dither and no bit depth change (purely to maintain time alignment with the other L1), the other set to 16 bit type 2 dither and ultra shaping (I also tried other settings). When these two tracks were solo'd, the only thing I heard was the difference between the 16 and 24 bit files and the dither noise. No clicks or random waveform distortion. This is what I first expected from the 16 bit BTD files.

If anyone is interested, I can email you a screen grab of the waveforms and an audio sample of the random waveform distortion.

______
Dannii

[KennyD]

Hi Doc,

Must have been fun experimenting. Your conclusion is that since due to evidence found in testing, where no additional artifacts or sounds were discovered to be generated by the BTD and SPDIF recording, that the two methods are the same.

Isn't it possible though that the output played would still sound deteriorated despite not having any added artifacts? This is not any expertise of mine, conjecture only, but my idea is that the 1's and 0's are getting subtracted and modulated a bit and that this is the cause of deterioration quality in BTD. Or do the inversion samples make up for testing this too?

At any rate before I continue to write these things I feel I have a responsibility to do some testing myself and more ear discernment and to explain that I am doing guesswork based on only what I hear. What I'm hearing is for certain not a mere illusion, the difference is obvious to my ears. Initially I was not pleased by the results of a few BTD I'd made, 1st impressions, but beyond that alone, I haven't tested much at all and I'm not in a white lab coat here saying "I've found it!"

There has been talk of the BTD sound quality problem before by others. In fact Digi001 has a reputation among certain users for not reproducing a great bounce. I heard these complaints prior to getting mine and ignored them all until I made some bounces and discovered it myself. Like I said however, I haven't been in to it enough to qualify as any source of non-official information, and I don't pretend to be or want to be such a source, to make this clear in advance, as the thread may grow.

I am certainly interested as I presume others must be too, in what people hear and their opinions of the sound and what tests are being done and what other facts are available to explain the integrity of BTD sound quality. Decided that the quality indeed sounds worse and to compensate for it I need an alternative method of getting my audio to CD.

Thanks for sharing your discoveries Doc, et al. Keep em coming if your so inclined. Interesting stuff!


KennyD

[Doc]

KennyD,

My tests are by no means complete yet but it has been interesting so far. I haven't tried testing sample rate conversions yet and I am going to try the dither experiment with some simple waveforms (sine, square etc) to try and determine more about the clicks and other artifacts.

From what I can gather, you have been sample rate converting from 48K to 44.1K for CD. Perhaps the deterioration you are noticing is related to that process in conjunction with the 24 -> 16 bit conversion.
I do indeed believe that 24 -> 16 bit conversion reduces the quality more than what would otherwise be expected. My tests have proven this as have our ears. But then the SPdif recording mirrored this so it would appear that the fault lies with the conversion, not the BTD.
So far the only one of my tests which doesn't show any deterioration is the BTD and SPdif tests that don't perform any bit depth or sample rate conversion.

My reasons for choosing the SPdif method for comparison is partly due to the pleasing results others have experienced with this output and the fact that it is a digital transfer supposedly bit for bit.

If the BTD files are deteriorated in any way, this will show up with the phase test.

I'll keep you posted when I find out more.

Meanwhile if anybody wants a copy of the screen grabs and samples I have done so far, send me an email and I will send the results to you.

______
Dannii

[Jorge442]

maybe, if available, the 16 to 24 bit conversion should be done external to PT?

How come Tech support doesn´t add in their 2 cents??