[BC] RE: Studio Grounding Info

[RichardBJohnson at comcast.net]

There is a significant problem with digital mixers, which
nobody seems to have addressed. In fact, when I was
asking questions at the NAB, I simply got hype, lies, and
more lies. The problem has to do with the available bits.
Let us say you have a 16-bit system. You can substitute
24 bits if you wish, but no audio input stages are going to
be able to resolve 24 bits because the last two bits will be
in the noise at room temperature. You have the potential
of 90 dB S/N and the distortion is 1:32767. Note that 16
bits is NOT 65536:1, but only 32767:1 because it is signed.

Suppose, some loud music is entering your board and you
need to attenuate it 20 dB with a fader to avoid distortion.
You have now DIVIDED the signal By 10 and DIVIIDED the
effective bits by over two (2 ^ 4 = 8). The distortion will now
be 20 dB worse. Every attenuator that the signal goes through
gets the effective number of bits attenuated as well. Looking at
the limit, with an attenuation of 16384:1, you have only one bit,
which is about 33.3% distortion! Some clueless so-called
engineers have decided to add “dither” (read noise) to
overcome these problems. Limited (or missing) bits make
the sound effects of crossover distortion. The same effect
occurs with very low-level signals. When you increase the
“gain,” you are MULTIPLYING the signal by some number
set by the knob! If the original signal was a ramp of 1,2,3,4,5,
all bits exercised, and you double the gain (a 6 dB attenuator
adjustment), the ramp will now be 2,4,6,8,10, with lots of
missing bits (jumps in the ramp). To make it perfectly clear,
if you had a tone, and increased its input level slightly,
NOTHING would happen. Then suddenly, it would jump to
the new level!

In my not-so-humble opinion, you should stay in the analog
domain as long as possible and convert to digital as one
of the last elements in the audio chain, where the operating
level as already been established. One can still obtain
excellent analog consoles, in fact with a digitizer and effects
processor at the end of the chain. Since digital console
manufacturers seem contentious, I will not mention the
names of those I contacted at the show. However, being
warned about these potential problems will allow you to
make the correct decision.

If you are in a noisy environment and never have to mix or
fade, simply switching high-level sources from DVDs, etc.,
then an all digital console is the way to go. However, if
you need to do some production, and have a studio designed
with low electrical and acoustical noise as essential
parameters in well executed specifications, they you need
an analog front end to take advantage of your investment.

--
Cheers,
Richard B. Johnson
Read about my book
http://www.LymanSchool.org


 -------------- Original message ----------------------
From: R A Meuser <rameuser at ieee.org>
> It really depends on the complexity of the plant and how you value the 
> cost of installation and on going maintenance. A digital installation 
> can eliminate a lot of cabling and the cost to install. Digital 
> installations can offer many benefits when properly planned.
> 
>   A good analog board is going to cost over $10K anyway.
>