Anyone Using the Dithered Mixer?

[tomhartman]

Downloaded it last night but haven't used it yet.

I'm a bit confused...I thought a Mix Plus system was 64 tracks....but this said something like "you'll get a smaller mixer than the usual 59x2" with this thing....what gives?

Also, mainly wondering if anyone feels they can hear a difference....thanks

[Noiz2]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:<HR>Originally posted by tomhartman:
Downloaded it last night but haven't used it yet.

I'm a bit confused...I thought a Mix Plus system was 64 tracks....but this said something like "you'll get a smaller mixer than the usual 59x2" with this thing....what gives?<HR></BLOCKQUOTE>

No 64 Voices, you get something like 128 "tracks" used to be 250 ish (actualy almost unlimited if you were tricky). The "mixer" they're talking about is the TDM mixer architecture, a single dsp chip suports X big a mixer the dithered mixer uses more dsp so you get a smaller mixer per chip. If you dig through the manual theres a section on TDM stuff and how much each mixer part takes in DSP. All you realy need to know is that the new mixer uses more DSP and if you tend to have large sessions you should be aware of it. I downloaded the mixer but haven't tried it, I don't expect to hear a diference.
SK

[ June 16, 2001: Message edited by: Noiz2 ]

[minstrel]

I'd be lying if I said I hear a difference in a specific direction. It's kind of difficult to make an honest and objective A/B comparison when you have to switch mixer plug and actually quit and relaunch PT, unless you had 2 identical PT rigs running through the same monitoring system. Anyway, could someone report what the technical difference is? I'm assuming that the regular mixer takes up less DSP since it's not processing the signal by dithering it. What can we expect from a non-dithered signal as opposed to a dithered one? Also, are we assuming that in absence of a dithering mixer we're actually losing a certain amount of resolution (48 to 24?)? I'd appreciate some enlightenment. Thanks.

[hrob]

The dithered mixer applies dither at the 24 bit level when it rounds the 48+ bit sum from the mixer back to 24 bits to put it onto the TDM bus. Dither is basically white or pink noise applied at a signal level which just make it audible (i.e. at roughly the signal level of the low order bit flipping). If you don't dither, the truncation effects cause signal related non-harmonic distortion: The distortion products are at discreet frequencies, but those frequencies are essentially random. These tend to be unpleasant sound-wise. Dither randomixes the rounding/truncation process and effectively turns the unpleasant discreet frequencies into white noise (which is relatively benign). With 24 bit signals, the dither is down something like -145dB and you would think people couldn't hear a difference, but apparently some people can.

You are right, the difference is subtle. If you are going to hear it (and believe you can hear it), you need to bounce something using the different mixers and do an ABX test with the results. An ABX test plays A, B and then an unknown, X. The person taking the test is supposed to figure out what X is. You then have one person make up a PT session file containing ABX tripples and have another person take the test blind (without knowing what the X's are) and see how many you get right. You might want to try this at lower bit sizes first to get an idea of what to listen for.

I gave one to myself (which isn't totally regorous, because I might have subconciously remember the order). At first, I didn't think i could hear it, but then I discovered that I got the first 6 of 12 trials totally correct and the last 6 totally wrong. I think that means it's likely that I could hear something, but only just barely. I know my ears are not in the same league as many other people; so, I do believe that dither at this level makes a slightly audible difference. in my copious spare time, I want to try the test again with shorter samples and shorter time between the A, B and X: I left several seconds and that leaves time for one to partially forget what one hear previously.


Oh yeah, if you aren't using a good 24 bit D/A, you won't hear it and you probably need really good speakers, too.

[Zep Dude]

hrob, it sounds like you may have heard a difference. Don't forget, when doing these tests, your first few impressions are usually the most accurate. After a while, the ears just get a little worn. I haven't had the chance to compare them but will soon.

[Ask Otis]

You can always try this:

Do a mix with a medium to large size project. It seems that the differences will become more apparent with more tracks since this will have more places for truncation errors.

Do a mix with the standard mixer. Bounce to disk at 24 bit multi mono. Quit PT and swap in the dithered mixer. Open the session again and bounce to disk again. Now import the two bounced files into a new session and you can A/B these mixes. You can also try inserting the trim plugin onto both mixes and invert the phase on one only and see what you hear.