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Author Topic: Software Dolby/DBX decoder  (Read 8651 times)

Offline ironbut

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Software Dolby/DBX decoder
« on: August 07, 2015, 10:19:05 PM »
Just got word that someone has finally modeled some pristine encoder/decoders and released it as part of a tape emulation plug-in.
Sure, this may be something that analog mavens will put their nose up at, but if it's as good as some folks are saying, it could leave empty rack spaces in studios that do tape transfers for a living.

The plug-in is from u-he and it's called Satin. Here's the link;

There's a free demo (which I'll jump on as soon as I get time) and give you my thoughts on it.
There's beginning to be plenty of discussion on the archivist's forums and I first took notice when Richard Hess (who I greatly respect) posted about what a great job Satin did in his early tests.

"So, what have I tested?

My best test so far was done using my own recording of "A Concert in Memory of Benjamin Britten" recorded live at St. Thomas Church December 4, 1977. It is something I own the rights to, though a re-release would still require mechanicals to Boosey and Hawkes. I still have the original master tape, as well as an "up-in-the-air"--no Dolby decode/encode--safety copy which is fortunate for the first bar of the first cut on side 3 which had 3M leader pull out the mag coat on the first turn of the master.

For this recording, I have compared three different versions:

An August 2015 playback on an A80RC with both
(1) The U-He Satin decoder AND
(2) The Dolby M-frame with Cat-22 cards
(3) A 2005 playback on an APR-5000 with two 361 frames with two different Cat-22 cards.

There is Dolby tone on the tape and everything was carefully calibrated.

(2) and (3) sound similar with (3) sounding slightly more open

(1) sounds a lot better.

The private correspondent asks "is it accurate?"

Tom asks "properly working" regarding the Cat-22s.

These are hard to answer. My son (one year away from his BMus degree), my friend Don Ososke (who, among other things worked for Wally Heider and Ampex), and I all agree that the U-He is the most euphonic transfer of the Britten tape which Don has thought is one of the "crown jewels" of my recording career. Leaving St. Thomas and Dr. Gerre Hancock was the most difficult part of my 1981 departure from NYC.

The one thing that the U-He does properly is track level changes. With BOTH pairs of Cat-22 cards, certain sounds which are at different levels appear "darker" and "less open" at lower levels than with the U-He Satin. The U-He allows the tonality of the music to remain constant as it gets quieter, rather than turning muddier.

Lest you say that the recording Cat-22s were mis-adjusted, I did another test--that started this, actually, using a client tape that could have sounded better no matter how we decoded the noise reduction. In fact, it was Don's insistence that we use better source material to evaluate this which brought me to re-doing the three reels of St. Thomas masters that I own (the third being Organs of NY Vol I) which is coming through stunningly as I type.

Calibrating Dolby cards is not an easy matter. The tester only tests static levels. There are dynamics which are set by capacitors which might be aging. The fact that the 2005 transfer sounded a bit better than the 2015 one--with the Dolby decode--is a hint in that direction. The master tape does not appear to have lost much as the sounds of these three reels still impress (at least me) after 38 years. (OMG, it's been THAT long? I just turned 26 when I made this recording. Wow, how time flies!)

Just checking via a loud piece--there is no change in tonality between the U-He and the M-rack/Cat-22. All the difference occurs on the quiet parts, but I hear no pumping on either path.

This is all so very, very weird.

The first choir recording that started this digging-into-it quest, I just found out, was recorded in two different sessions: orchestra and choir with only the conductor wearing headphones listening to the orchestra. Joy! We listened to an LP and it was darker sounding than the M-Rack decode. The conductor liked the U-He version.

I'm open to thoughts/discussion.

Once I finish the choir tapes (I've got six and have done three) I'll move on to the dbx err uhx I decoder!



So, if you have the need of a decoder for digital transfer, give it a try.
steve koto
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