They also do some weird attack and release ninja with diodes that is really hard to mock up. The while enchilada has strange xfer curves beyond just the compression ratio, bandpasses, and thresholds- which is why they invert-added through the same screwball circuit - building two of these won't match.
Knowing what I know now about this self-nulling circuit and tape compression there's no way it can't be heard mistracking. Comparing a dolby a encode-immediate-decode through wire is audible if the dolby dot levels are even slightly mismatched. Off tape it's hilarious. Of course who likes hiss...
But that's why hot 15IPS or hot 30IPS was the preferred "evil" ... Dolby a changes stuff a lot.
Sent from my iPhone
On Jan 11, 2012, at 2:42 PM, "Richard L. Hess" <[log in to unmask]> wrote:
> The EQ is fixed. There are the four compressors, but we do really nice compression/expansion in DAWs these days <smile>.
> In fact, in theory, one could mock up a Dolby decoder using the built-in filters and compressors.
> Note, I said "one" not "I".
> On 2012-01-11 1:56 PM, Roderic G Stephens wrote:
>> I misspoke when I said, "doesn't a Dolby decoder adjust to the incoming data and change its compression and EQ accordingly?" I should have said "expansion". Also, the descriptions of Dolby refer to "dynamic processing". Isn't that all about a real time situation through a decoder. I'm asking as one who wants to understand more about the subject.
> Richard L. Hess email: [log in to unmask]
> Aurora, Ontario, Canada (905) 713 6733 1-877-TAPE-FIX
> Quality tape transfers -- even from hard-to-play tapes.