On 20/08/2010, at 1:24 AM, Rob Danielson wrote:
> This suggests to me that the maximum available gain in
> the 680's pre is around 52-55 dB.
Hi Rob,
The implicit assumption here is that the 702 has 68dB gain. This is not act=
ually true. The SD recorders have around 48/50dB gain, rather than 68/70dB=
. This error has arisen because SD measure "input to -20dBFS" rather than t=
he more commonly used "input to 0dBFS". Ignoring the "to -20dBFS" results i=
n the gain being overstated by roughly 20dB.
Raimund's tests include gain measurements which are measured "to clipping",=
rather than "to 0dBFS". Raimund might like to comment on the level differ=
ence between "to clipping" and "to 0dBFS" but my estimation is that "to cli=
pping" results in 2-3dB lower gain figures? Raimund's "to clipping" tests =
indicate that in high gain mode the DR-680 has 12dB more gain (58dB) than =
the SD722 (46dB).
>
> DR680 required about 14dB gain to match that made by the SD702. (Both
> at max gain).
The DR-680 has a low gain setting with 24dB less gain than the high settin=
g, and therefore about 34dB gain (nb: this is confirmed by Raimund's record=
er test page). I suspect Emil has used this lower gain setting for these t=
ests, and the cumulative effect of a) overestimating the SD gain by around =
20dB, and b) low gain setting on the DR-680, explains why you needed to ap=
ply 14dB gain to the DR-680 recordings.
cheers
Paul
|