DAT-heads Digest #202

Contents:
  re: digest #183 - fading ("john e. bogus")
  Joe Walsh set times? ("john e. bogus")
  security questions for State Fairgrounds in Des Moines ("john e. bogus")


From: "john e. bogus" <bogusisme@surfbest.net>
Subject: re: digest #183 - fading
Date: Wed, 15 Aug 2007 19:13:29 -0500

In response to my last post, I did receive an offlist message from 
Len.....since I did find this informative, I will reproduce it here, as 
surely others will find it of interest:

"john e. bogus" wrote:

> ...But interestingly enough, Coresound claims on their website
> that the Microtrack's internal A / D converter is only capable of
> 16 / 48 khz, meaning that you need an external converter to
> record at a bit depth and sampling rate exceeding that of DAT

That's not quite what we said.

The MicroTrack's internal mic pre and A/D have only 16-bits of dynamic
range -- that's 16-bits of resolution.  If you want 24-bits, you'll have to
use an external mic pre & A/D, and feed the MicroTrack's S/PDIF digital
audio input.

It records fine at 96 KS/s.  But in our opinion, if you record using a true
24-bits (with an external mic pre and A/D) there's little value in using
sampling rates higher than 48 KS/s.

So with the MicroTrack, if you are recording at 24-bits using the internal
mic pre and A/D, or recording at sample rates higher than 48 KS/s, you are
simply wasting storage.

> ...my question is if what Coresound claims is true, why
> is this same information not posted anywhere that I could find on
> M-Audio's
> own site?

They do, but you have to understand what specifications mean.

On the M-Audio MicroTrack 24/96 Web page, they cite the Mic input's dynamic
range and Signal-to-Noise specifications as 98 dB (A-weighted).  That's a
hair more than 16 bits, and less if you consider the unweighted numbers.

They don't tell you how that spec degrades as you turn up the gain.  But
then most manufacturers don't.


Len Moskowitz (moskowit@core-sound.com)
Core Sound
www.core-sound.com
Home of TetraMic and PDAudio


Len, thanks for the additional clarification.  When you consider the 
definition of all the terms involved, it only makes sense that the input s/n 
ratio or dynamic range is also one of the things that defines bit depth (and 
vice-versa).  I guess I'm just used to thinking in older, analog terms....I 
had always assumed that when the s/n ratio or dynamic range spec was given, 
that that was for the analog stage only and would always be the limiting 
factor in terms of performance.  But how does this relate numerically?  What 
exactly tells you that so many db's of s/n ratio or dynamic range equals so 
much bit depth (or vice versa)?  If you need an A-weighted s/n ratio or 
dynamic range of 98 db to make full use of a 16 bit depth, how many db's of 
improvement are necessary to make full use of a 24 bit depth?  I amagine 
there's a formula out there somewhere....  If the analog front end circuitry 
in a mic or line input is capable of "only" 98 or 100 db or whatever, and 
cannot be improved by upgrading components (such as low noise op amps and 
fets, metal film resistors, polypropylene caps, teflon circuit boards, etc), 
then the implication is that no matter how good the resolution of the A / D 
converter is in terms of bit depth, the "A" circuitry that precedes it will 
always be the limiting factor.....if we need however many db's of s/n ratio 
or dynamic range to make full use of a 24 bit depth A / D conversion, is it 
even possible to build *any* analog circuit that is that quiet?  (gaasfets 
cooled with liquid nitrogen would seem a mite impractical for stealth).... 
Perhaps someone who knows the mathematical end of these things can weigh in 
here and explain how we can get around the noise of an analog circuit so as 
to make full use of a 24 bit depth A / D conversion.....

Yours Truly,
john e. bogus 




From: "john e. bogus" <bogusisme@surfbest.net>
Subject: Joe Walsh set times?
Date: Wed, 15 Aug 2007 19:13:40 -0500

Can anybody tell me how long the set times are for Joe Walsh's current tour? 
I need to know if I am planning for a 2 hour or a 3 hour show....

TIA,
john e. bogus 




From: "john e. bogus" <bogusisme@surfbest.net>
Subject: security questions for State Fairgrounds in Des Moines
Date: Wed, 15 Aug 2007 19:13:35 -0500

Ok, I've got tix to see a show here on Friday night.....as the last time 
that I taped at this venue was in 1986 (!), I imagine that security is not 
as slack as it was 20 years ago - or is it?  (I can't see a place going from 
GA to reserved seating, and having security remain as slack as it 
was....grrrrr)  Where is security positioned in the stands?  Is it possible 
to get away with video in this part of the venue?  Did anyone just happen to 
be there for Alice Cooper and BOC last weekend?  Any info on current 
security procedures would be most helpful.....

TIA,
john e. bogus 



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