I must confess that my posts on the subject of recorder preamp noise
have been misleading.
I was not giving the contribution of the mic enough consideration. I
now believe the results of my listening tests were influenced more by
the mic I was using (usually a Sennheiser ME62) than by the preamp of
the recorder.
The measurements by Raimund Specht are currently our best guide to the
noise floor level of portable recorders. Here are the pocket size
recorders, quietest first
Sony HiMD MZ-RH1...........-124dBu noise floor
Olympus LS-10.........,....-121dBu
M-Audio MicroTrack 24/96...-115dBu
Marantz PMD620.............-112dBu
Tascam DR-1................-111dBu
Edirol R-09................-106dBu
Of the machines Dr. Specht measured, the Sony Hi-MD and the Olympus
LS-10 had significantly lower noise than the others. ( dBu is a
logarithmic scale, so 6 dBu less means a reduction of noise by 50%. )
In my recent tests with the Olympus LS-10, I didn't notice lower noise
levels than with the other machines. Thanks to Rob Danielson's recent
post about matching mic performance with preamps, I now think my
results were limited by the noise contribution of the microphone.
I think it's correct to say the Olympus LS-10 sounds about the same as
the Marantz PMD620 -- when you're using a mic with a self-noise level
similar to the Sennheiser ME62 (somewhere around -108 dBu). With a
quieter mic, the LS-10 should make recordings with less noise.
Now I have to go shopping for a microphone with very low noise, and
repeat my recorder tests!
--oryoki
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