On 11/01/2012 21:30, Tom Fine wrote:
> Dolby became necessary when everyone was using 8, 16 and then 24
> tracks for rock, pop, some jazz and even some classical recording. I
> can see it being a huge benefit to keep hiss buildup at bay when
> you're combining all those tracks. However, it became an obsession in
> the 70's and 80's. Why was it necessary to be used again on a 2-track
> master? 15IPS 2-track on low-noise tape is very quiet, and the Dolby
> can and often does squashes the sound, making "presence" and "high
> end" tweaks necessary in LP and CD mastering. The Dolby tracking falls
> off as the tape self-erases, even if you set to Dolby tones at the
> beginning, as I understand self-erasure that doesn't mean that all
> components of all dynamics erased at the same rates/ratios, so the
> Dolby tracking should be adversely effected (further "deadening" the
> sound and "washing out" the top end).
>
> There are examples out there from the early days of 16-track where the
> multitrack was running low-noise tape at 30IPS, no NR, and the 2-track
> master was recorded at 30IPS, no NR. They are not especially hissy.
> Dolby did allow economies of tape usage, no doubt there.
>
> Sonically, it was a real mixed bag. As I understand it (having never
> used it), SR was a leap forward. I think the whole obsession with hiss
> was over-rated, but I agree that 16 or 24 hissy tracks mixed together
> is too noisy. If it were me producing, I would have gone with higher
> speeds and higher levels first, turning to NR only if nothing else
> worked. The advent and wide acceptance of Dolby also probably cut off
> some R&D in the tape world. What about thicker emulsions like 35mm
> mag-film? Also, what about 12 tracks per 2" instead of 16? That's the
> same track width as 3-track 1/2" and should make for low-noise
> recording if low-noise tape was used at higher operating levels.
>
> -- Tom Fine
>
> ----- Original Message ----- From: "Richard L. Hess"
> <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Wednesday, January 11, 2012 4:10 PM
> Subject: Re: [ARSCLIST] Dolby Plugin
>
>
>> Hi, Jamie,
>>
>> You caused me to go look at the CAT22 schematic again and I noticed
>> some interesting things.
>>
>> (1) You're right that there are odd diode-ninja things in he drive to
>> the FETs, but there are also two FETs driven from the same line,
>> producing, what would appear at first glance, a steeper attenuation
>> slope.
>>
>> (2) There is another nasty thing--fairly hard diode clipping (which
>> isn't as hard as digital clipping as you know) on the base of the
>> compressor's audio output emitter follower. Joy!
>>
>> I'm glad I've got a bunch of CAT22 cards to carry me into the future.
>>
>> Fortunately, failure modes appear to be MOSTLY coupling caps.
>>
>> Cheers,
>>
>> Richard
>>
>> On 2012-01-11 3:12 PM, Jamie Howarth wrote:
>>> 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.
>>
>> --
>> Richard L. Hess email: [log in to unmask]
>> Aurora, Ontario, Canada (905) 713 6733 1-877-TAPE-FIX
>> http://www.richardhess.com/tape/contact.htm
>> Quality tape transfers -- even from hard-to-play tapes.
>>
>
Well, as one who used Dolby A in anger in a closely controlled
environment with meticulous line-ups, I have to say we found it
completely transparent. If your tape didn't behave, yes, you had
problems, but the tape had to be well out of order before these became
obvious. I remember Bob Auger telling me of a hairy dubbing session
where a bad batch of Scotch 206 (I think) was wandering in output, and
he had to put the Dolby input on a fader to keep the thing in line.
The best solution to the Dolby retrieval problem is to keep some
appropriate hardware. The stuff was well built, and chances are that
even a 301 will just need a change of electrolytics and a tickle up to
perform as new.
|