Having lived thru "the cassette era" and having messed with zillions of
them (and I couldn't agree more with you, Tom, about cassettes in general,
as a format for music), the practical difference between Dolby B and Dolby
C is very little. Dolby C has slighter "truer" upper end, but if you have
to, you can often decode a Dolby C cassette with Dolby B, adjust the upper
end a little and come out OK. B and C are "somewhat compatible." As you
know, most prerecorded manufactured Dolbyized cassettes are anything but
accurate--I think they were made at very high speed, and home-recorded
Dolbyized cassettes are subject to how the Dolby electronics in the
particular cassette deck were working, which varied all over the lot..
Throw in the variations in tape formulations, which sounded very different,
and there is really nothing that is very scientific about any of this.
Cassettes are really one big crap shoot. Serious professionals did not
much rely on cassettes, so there is little or no "professional grade" where
standards are more uniform, in the cassette world. With most cassettes.we
are trying to restore now, we are going to try to decode them "right" to
get the best possible "first draft," but in most cases we are also going to
end up having to tailor the sound considerably with EQ to get an acceptable
result. You could hardly make a rasher assumption than thinking that the
Dolby decoding is "right" because you are using the right equipment.
I listened carefully to Richard's Dolby A samples and with all due respect
I will disagree with you. The third sample was so seriously flawed by
channel imbalance (the right channel was somewhat dead while the left was
unusually noisy--easily visible on the computer), I don't think we can use
Sample 3 for any purpose. Knowing how scrupulous Richard is, the culprit
is undoubtedly the Dolby A decoding, or I should say mis-decoding. We
know there is no problem with this tape, since Samples 1 and 2 are dubs
from the exact same tape.
And I do not hear the "pumping" as between Samples 1 and 2. Even sample 1
done with Satin is still a little hissy, a lot of which I would discreetly
remove if I were restoring this recording. (Used in moderation and with
judgment, Izotope RX4 does this kind of thing so successfully that there is
no effect on the music.) What you are hearing at :45 is where Richard
eliminated some music. Please see my prior detailed discussion.
As for frequency response, the difference is the easily observable stronger
upper partials ins Sample 1 (the Satin one), which I like. See my prior
discussion and analysis of how you can hear the individual voices in the
choir more clearly in the Satin one, while they are "mushed together" in
Sample 2. The choir sounds substantially different on 1 and 2, and the
clearer version has be the more "accurate" one,and is the preferable one.
There is really no "correct" to compare to here, unless you just assume
that Sample 2 is more accurate because it was done with the hardware. At
least in this case, listening does not bear that out,and I don't think we
can make that assumption.
One might think that over-emphasis in the uppermost ranges would result
less good sonic results, and that will often be true. But I don't hear it
that way here.
Best, John
On Sat, Aug 15, 2015 at 8:07 AM, Tom Fine <[log in to unmask]> wrote:
> Hi Richard:
>
> First of all, I would think dbx decoding would be easier with software
> because as I understand it's a straight compansion ratio against all
> frequency bands, so there's no complexity of frequency-specific processing.
>
> That said, could you post examples like you did for Dolby.
>
> I listened to the Dolby examples again and I really don't like the Satin
> processing. It screws up the frequency balance and also the stereophony,
> plus the pumping issue. As I said, if I were doing it, I'd use well-working
> Dolby hardware and do the decoding in the analog realm, and then do
> professional mastering (ie tasteful EQ tweaks to make it sound less
> deadened).
>
> For what it's worth, I have a 363 unit that I bought on eBay and it seems
> to work well, based on the relative levels of the Dolby warble tone and
> 100, 1k and 10k test tones on a professionally made Dolby A tape from the
> mid 1970s. I have not messed with SR because I don't have any SR tapes.
>
> What would be very useful from the folks at Satin who have at least
> partially cracked the Dolby code would be a Dolby C emulator that had a
> sensitivity control built in. A big problem with Dolby C cassettes is that
> they lose signal level and then the Dolby C doesn't decode properly. This
> also seems to be a problem with some videotapes, I'm not sure of all the
> formats but I think Betacam was one of them. I'm glad I did not use Dolby C
> for very many hard to replace cassette recordings, because it's problematic
> to get it work properly on machines not the original recorder and also with
> 25-year-old tapes that have lost signal level (see Jay McKnight's and
> others' comments on the Ampex List and elsewhere about cassettes partially
> self-erasing over time; some deny this to be possible but I have definitely
> seen these behaviors with my own Dolby C tapes made in the early 1990s).
> Anyway, I think software that allowed for sensitivity or threshold control
> for the Dolby C, for each of the bands (because the problem seems to be
> confined to that high-frequency band), might allow for better tracking of
> old cassettes. And let me say one more time, I do not miss the Compact
> Cassette one bit.
>
> -- Tom Fine
>
> ----- Original Message ----- From: "Richard L. Hess" <
> [log in to unmask]>
> To: <[log in to unmask]>
> Sent: Friday, August 14, 2015 9:52 PM
> Subject: [ARSCLIST] Satin dbx I decode
>
>
>
> Hi, all, just a heads up. The Satin decode for dbx I is very close to my
>> dbx I processor, but not exact. It is clearer and more open...again.
>>
>> So, as luck would have it, the power supply in my M-frame (I think)
>> stopped working. That MAY have been the cause of the problems (low voltage
>> perhaps someplace). I don't know.
>>
>> But I have a backlog of tapes to try and one of my two dbx frames has
>> something wrong on the power bus (I don't know if a card is pulling it down
>> or the supply is problematic) and now my Dolby M frame is out.
>>
>> Satin came along at just the right time.
>>
>> I'll try 16 tracks of Satin dbx I tomorrow on a 1" 16T tape that caused
>> me to notice the 9-16 frame was acting flaky. Now I can at least easily
>> provide raw and processed versions of the transfer without needing 32 A-D
>> channels or running an outboard realtime pass.
>>
>> What is WONDERFUL about Satin is that you don't have intermittent
>> switches and lots of pots to adjust in difficult-to-reach places.
>>
>> I am seeing very few NR tapes.
>>
>> I think I'm going to pass on buying a 363 right now.
>>
>> Cheers,
>>
>> Richard
>>
>> --
>> Richard L. Hess email: [log in to unmask]
>> Aurora, Ontario, Canada 647 479 2800
>> http://www.richardhess.com/tape/contact.htm
>> Quality tape transfers -- even from hard-to-play tapes.
>>
>>
>>
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