Digital word length, dithering: Yamaha 03D, Tascam DA-38

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Joined: 01/12/2004

Hi,
First off your site is great and very helpful (I own a DA-88). Thanks.

At my school's studio we have a 38 and a Yamaha O3D digital mixer with YGDAI (tdif) card. The board is capable of outputting longer than 16bit words. Would it be advantageous to set the board's output to 18bit words to take advantage of the 38's 18bit D/A converters? Would I have to set dither to "on"?

I don't know if you can help me with this one but while I'm at it . . . I'm hoping to do a surround recording to the 38. Do you know of any easy and cheap DVD-A or ideally DVD-V authoring programmes that will encode 5.1 sound?

Thank you very much,
N.M.

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Joined: 02/12/2009

This is important to figure out and makes a big difference so it's great that you care enough to get it right! That's the sign of a quality-minded engineer.

visitor wrote:Would it be advantageous to set the board's output to 18bit words to take advantage of the 38's 18bit D/A converters? Would I have to set dither to "on"?

First, one correction. If you are sending audio digitally via a 25-pin TDIF cable, it never passes through the converters (that's the benefit of this extra work). So, the quality of the converters will have no bearing here.

[ Also, a caution. Converter specs are not absolute indicators of quality. One 18-bit converter may be better than another 18-bit converter. A crappy 18-bit converter might even be worse that a great 16-bit converter. Listen and make up your own mind! ]

What's more important is the # of bits that each device can handle:

TDIF by nature can handle 24 bits, so we know the protocol is not a bottleneck.

The DA-38 only records at 16 bits. Since the 03D can output at more than 16 bits, you have to decide where to dither it down to 16 bits. You can do this either in the 03D (I assume it at least offers a choice of 24 or 16) or in the DA-38. It might be hard to tell which has a better quality dither algorithm (if there is any difference at all), so convenience factors might be the deciding factor:

Remember that the DA-38's dither setting is lost when you power down:
http://www.silentway.com/definitive-dtrs-guide-chapter-8-tascam-da-38

OK, but what about when you use the converters to record an analog source? According to the 03D's specs,
"Internal auto processing is performed at 32 bits... ...20-bit, 64-times oversampling AD converters on each input and 18-bit, 8-times oversampling DA converters on the stereo and monitor output. Bus and aux send outputs use 18-bit, 8-times oversampling DA converters."

So, the 03D has 20-bit AD and the DA-38 only has 18 bit AD. This means that the 03D should be a better front end (in theory), compared to recording straight into the DA-38.

Since the DA-38 has 18 bit analog converters (but only records at 16), I generally turn on the dither for analog inputs. But that's a judgement call, determined mostly by the type of audio you are recording (Classical? Rock?). Give it a listen with and without. Then make up your own mind.

Again, these AD/DA converter specs don't matter during a digital connection, but it's still good to know for the future. Also, be sure to get your wordclock right for any TDIF connection. Remember that the DA-38 has no word clock out jack (just in) so you'll have to send clock from the 03D to the DA-38.

Read more about dithering in these articles:
http://www.digido.com/portal/pmodule_id=11/pmdmode=fullscreen/pageadder_page_id=27/
and
http://rogernichols.com/EQ/EQ_98-08.html

visitor wrote:Do you know of any easy and cheap DVD-A or ideally DVD-V authoring programmes that will encode 5.1 sound?

Sorry, I'm not up-to-date on that topic. I don't do surround mixing projects and am waiting for the dust to settle on all of the standards and formats.

n/a
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