Walter,
Am I still sort of right - that the goal would be to ideally get the
peak within a given recording to just reach 0dB for no more than the
one or two samples in a row? If I understand, your clearly telling
me that that much dynamic range is completely unnecessary (and
perhaps even not readily later reproduced). Even worse, I see from
some previous posts that the input on the Sony DATs has historically
been well known to "block up" when hit too hard - something the mic
limiter circuitry will obviously do if enabled.
My electronic measurment experience reminds me that if you push any
of the components, microphone/preamp/ or A/D to their rails, your
bound to enter the territory of non-linearities where everything
starts to degrade. Almost without exception, things are always
designed for optimized performance well within the normal operating
range - not at the endpoints.
I have not quite figured out how to read the individual sample values
using any of my audio editing software to see where the level meters
on the DAT recorder trip. It seems the common definition of "clip"
is three or more consecutive samples at 0dB. I'm thinking of taking
a look on the web for how a wav file is formatted and just take a
quick look directly using my all time favorite programming
environment - National Instruments LabVIEW (primarily optimized for
automation of electronic test instrumentation). While I don't
currently have a clue how to build a plug-in for any of the editing
software, LabVIEW is rich in signal processing and analysis functions
that could come in handy.
Anyway, thanks for all of the great thoughts you provide within this
group. I learn something almost every day from your posts.
Brian Bystrek
--- In Walter Knapp <> wrote:
> bbystrek wrote:
> >
> > What is the correct way to establish a preamp gain setting? My
> > current understanding is to always set it as high as possible
without
> > clipping to maximize dynamic range. Is this correct? Of couse
it's
> > difficult to deal with digital overs in post recording editing,
and
> > from everything I have read, you have to test your recorders level
> > indicators to see how they actually work to see where clipping is
> > actually occuring - given that they don't all necessarily
represent
> > the output of the digitizer, but sometimes a value derived from
the
> > amplifier.
>
> That's the traditional recommendation for analog tape, and is not
> justified for digital. In fact it's dangerous. Analog required this
as
> it's dynamic range was limiting, and it's clipping was pretty soft.
> Always set your levels with a pad, digital has plenty of dynamic
range
> to spare. For a starting point with frogs try 20 dB down. You can
narrow
> that, but only if you monitor while watching the level meter for a
> while. That's problematic with DAT like you use as it should not be
> paused long.
>
> Yes, it's well worthwhile testing you level indicators to know what
they mean.
>
> What counts for digital clipping is the level of the analog signal
being
> fed into the A/D converter. And making sure you don't increase the
gain
> in any of the digital processing steps.
>
> > Am I right in also concluding that the perceived noise generated
by
> > the microphone is unaffected by gain setting of the preamp (given
> > that input sections are typically much much quieter than mics)
such
> > that if the final recording were later amplitude normalized, the
> > quality of the recording is the same?
>
> The mic noise is amplified right along with the signal you want by
the
> preamp. Only way to get gain without increasing the mic noise too
is to
> do it before the sound reaches the mic, like is done by a parabolic
mic.
>
> That's why if you opt for a shotgun mic, you have to spend bucks on
a
> real low noise one. It has no extra gain over a regular mic, so you
need
> to use a preamp to get gain for increasing reach. The preamp has to
be a
> low noise one too, don't assume a preamp is low noise, not all are.
>
> Walt
>
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