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Total preamp gain, for comparison between recorders. Note that most

Subject: Total preamp gain, for comparison between recorders. Note that most
recorders have separate preamps and level controls, so the preamp gain runs
100% all the time, and the level control of many recorders attenuates the
signal before the A/D. Other recorders have but one amp/level stage, others
have cascading amps. The preamp determines most of the character of the
sound. Cannot be measured directly (by comparing the immeasurably-small
microvoltage of an input signal with the output of the preamp stage), so
we'd have to get it by measuring the level of a known (mV range) audio
signal voltage at the input with the gain turned to a minimum, then find th=
difference in dB between min level and max level. Okay, so that one isn't s=

You are right, the noise specs of the NHF800 (I MD recorder I have) are
above the theoretical minimum of -131 dBu (my measurement was -125 dBu into
a resistive load, pretty good for a puny box). My 670 was about -113 dBu,
way above the noise contributed by most good mics.

Bruce Wilson
-----Original Message-----
 On Behalf Of stoatwizard
Sent: Thursday, November 16, 2006 3:20 PM
Subject: [Nature Recordists] Re: comprehensive specs and tests (decent
portable mic pre with optical out

--- In  Rob Danielson <> wrote:

> Useful apples and apples measurements incorporating gain and noise
> from the manufs, as you describe, would be huge. Maybe that's our
> job, to provide some incentive?  In addition to such numbers, having
> comparison tests to listen to and evaluate would still be very
> important for me. I learn a lot from this tangibility.

True - for instance the measurements don't totally indicate the
difference in character of the noise between say the NH700 and the RH-1
(with the advantage to the NH700 due to the absence of the OLED hum ;)

However, at the moment we struggle to know the basics like sensitivity
and noise level. I'm almost at the level of considering putting
together a box which puts out low noise low-level tone at about 0.2mV
which could be mailed to someone with a Edirol CF recorder, Zoom et al.
>From about 60 seconds WAV of that recorded with the machine flat out I
could derive the sensitivity and the noise floor of the device, though
not the overload margin, which seems to be a weakness of some machines
like the PMD660. So far anecdotal reports seem to indicate midrange CF
recorders are lacking in gain and have relatively noisy mic input
stages, but it would be nice to _know_ this as a fact. I keep on being
tempted as new models come out as the ergonomics of a HiMD suck as it
is, and suck even more with an outboard phantom PSU in the field.
However, that doesn't suck as much as throwing out the performance of
my mics with rotten preamps. Some science in this subject would be
nice. The manufacturers only need to match the performance of the NH700
(-66dBu for 0dBFS and about -116dBu noise 20-20k) to work okay with
most capacitor mics, it can't be too much to ask. That performance is
not that hard as an engineering challenge - it isn't anywhere near the
theoretical minimum. I'd gladly kiss goodbye to all the frippery like
DSP effects and backlighting/OLED displays to get a basic CF recorder
with that performance.

"Microphones are not ears,
Loudspeakers are not birds,
A listening room is not nature."
Klas Strandberg
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