Yes true, but then you are talking oranges and apples when comparing
with other recorders. I've been looking at posts on the HDP2 and to
suggest that it has woefully low gain vs the 722 doesn't stack up. If
you compare the -70dBu for -20dBFS with -44.1dBu (based on
independent pro lab testing) for 0dBFS and you simply take the
headline figures the HDP2 should have 26dB less overall gain. If you
compare for the same level of file saturation (ie -50dBu for 0dBFS)
the difference is 6dB.
This is borne out in Rob's sun $1000 recorder tests. In the test is
Sony NH900 set at "28" which according to the wildlife-sound.org
tests is roughly 4dB down on maxium gain. The HDP2 is set at "9.2"
which is something like 6-8dB below maximum gain. The 722 is set at
maximum gain. Rob had to boost the 722 by 11dB and the HDP2 by
Message: 19.
Subject: 5dB to match the levels of the NH900.
Using John Beales 64dB or wildlife-sound.org's 66dB for the NH900
and 44.1dB from http://www.proaudioreview.com/pages/s.0035/t.
Message: 6329.
Subject: html or 46dB (tascam specs) for the HDP2 and correcting for
lower than max gain you get the following approximate gain levels
used in Robs test:
NH900 64/66dB gain less 4dB : 60/62dB
HDP2 44/46dB gain less 6dB : 38/40dB
Subtracting the +11dB correction factor from the NH900 gain gives
roughly 49/51dB gain for the 722. Similarly subtracting the +19.5dB
correction gives roughly 40.5/42.5dB for the HDP2. Obviously these
figures aren't 100% accurate. Rob's corrections were done by ear and
the corrections for less than full gain on the NH900 and HDP2 are
estimates based on tests from different sources. But they do suggest
that the gain relationship correct if you assume a 50dB mic pre gain
for the 722.
Raimund Specht's at http://www.avisoft.com/recordertests.htm tests
bear out this relationship between the SD722 and HDP2. It seems the
sensitivity figures are about 4dB lower than other testing for HDP2
I've seen, but I would assume because Raimund is using the same test
setup that his figures are consistent with each other.
If you take the approach of saying the SD722 does have 70dB gain
based on the -20dBFS figures, you really need to boost the gain
figures of the other recorders +20dB to make an accurate comparison.
The NH900 would then be -84/-86dBu for -20dBFS, and the HDP2
-64/-66dBu for -20dBFS.
Paul
On 30/10/2007, at 2:44 AM, Dan Dugan wrote:
> Perhaps the confusion has to do with talking about peak level vs
> average level. If you consider -20 dBFS as the "program level" or "0
> VU level" (typical in film and TV work), then at maximum gain the
> 700-series recorder does indeed bring a -70 dBu input signal to
> normal recording level, and that's 70 dB gain.
>
> Or 67.4 dB if the firmware update changed the gain.
>
> -Dan Dugan
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