"Paul Stamler" wrote in message
...
"Arny Krueger" wrote in message
...
(2) It appears that the software Dolby B decoder is set up so that Dolby
level = digital full scale. So, I would find out how much amplification I
had to apply in the digital domain to get the tone I recorded off the
calibration tape to be FS. I would then apply that much gain to any tapes
I
transcribe, before passing them through the software Dolby digital
decoder.
Oh dear. That's bad news, since very often tapes have signal recorded at
higher than Dolby level. What was in on cassettes, 185nW/m? Or 250?
185nW/m comes to mind. Yes, it is my recollection that there were cassettes
that were recorded with peaks above Dolby level. I'm not sure that this is
as Dolby intended, but it did happen.
http://www.essex.ac.uk/dces/research...ubdocs/G43.pdf
"In practice the system employs a reference tone for calibration, where this
tone
is generated at the encoder to allow the decoder to be calibrated in level
prior to use. The
tone is set at the standard Dolby level, that in tape based applications is
related also to a
specific magnetic flux density on the tape (e.g. 185 nW/m Ampex NAB level
and 320 nW/m
DIN level)."
Dolby level corresponded to +3 Vu on a standard-conforming cassette deck.
My recollection is that going over 0 vu on a casstte machine was bad form.