"Sound" Advice: TDIF vs AES vs ADAT with D8B???

[topdiggy2]

Hello Guys -

I am looking at purchasing a Tascam MX2424 for my live rig. It comes with 24 channel i/o AES cards. I currently have 4 PDI-AES cards on hand. however, on studio setup, i go into my DAW via DIO-8 TDIF on my master d8b, and ADAT i/o using the mackie DIO cards one the slave d8b, into and my MOTU 2408.

So, my question is when using the D8b as a front end, are there any audible sound differences between the sound formats?

[Crash]

Nope but you may want to read up on the polarity flip in regards to the DIO.8 card when using light pipe.

[Bruce Graham]

Hey there;

There is also a concern regarding "emphasis" and the PDI-8 AES/EBU I/O Cards. (FYI no one uses emphasis anymore).

It has to do with the "flag" that the is part of the AES/EBU Protocol (Channel Status Bit) and whether it gets "turned on" or not. It affects the brightness of the sound. There is no way to change it not to know if it is on or not other than how it sounds. This is outlined in Mike Rivers HDR book.

I use PDI-8 card exclusively and have not had a problem, but it is something to be aware of.

Rock on!
Bruce

[Crash]

There is also a concern regarding "emphasis" and the PDI-8 AES/EBU I/O Cards. (FYI no one uses emphasis anymore).

I was not aware of that. Good call Bruce.

[topdiggy2]

Hey there;

There is also a concern regarding "emphasis" and the PDI-8 AES/EBU I/O Cards. (FYI no one uses emphasis anymore).

It has to do with the "flag" that the is part of the AES/EBU Protocol (Channel Status Bit) and whether it gets "turned on" or not. It affects the brightness of the sound. There is no way to change it not to know if it is on or not other than how it sounds. This is outlined in Mike Rivers HDR book.

Bruce -

What are you referring to here exactly. This is the first time I am hearing of such a thing?

[Crash]

Gleened from the site....

I have some early generation digital material that originated from DAT. When I bring this material thru the PDI-8 card, it sound unusually bright. Is there something wrong with my card?

No. Early digital material derived from DAT (for example) may have the Emphasis flag enabled when the material was recorded. When this material is passed thru the PDI-8 card, it will not be de-emphasized - thus, sounding too bright. No real work-around other than making an analog transfer first.

Hopefully this clears this up.

[topdiggy2]

Oh ok....thats not a issue for me...thanks! I thought we were talking about something REALLY problematic. lol

Thanks guys!!!

[Bruce Graham]

This is really Techy stuff and it goes way back to the beginnings of Digital Audio, for which I am a bit (no pun intended), rusty on but let's see if this makes sense.

In the early days fs (sampling frequencies) where lower. (ie 32khz used in early DAT and transmission lines for Radio) so some of the actual high frequencies would "bleed over" to the fs causing problems with the A to D conversion. To rectify this, the engineers developed a method that would reduce the high frequencies upon encoding, (Emphasis) and then restore the high frequencies upon de-coding (De-empahasis). For those of us whom are old enough to remember Dobly "C" and "SR", it is like that in the digital domain. They did this with the use of one of the "Bits in the Digital Word called the emphasis Bit or flag. If the Bit was left on (in the emphasis mode upon decoding, he audio would sound very dull. If the flag was not turned on when encoding and left not turned on upon decoding the audio would sound too bright.

Long and short of it is 2 things.
#1 This Flag is longer used and hasn't been for years. That Bit is used for other things now.
#2 The d8b can not recognise when to turn it on or off and there is no way to do it within the d8b so sometimes it is in the wrong state and we don't know it other than by listening.

Mike Rivers book "The Last Mackie Hard Disk Recorder" book does a great job at explaining this in a non techy way.

Hope that helps and doesn't add to the confusion.

Bruce

[topdiggy2]

@ Bruce

Yes it did, thanks!!!