Tape Project Forum
General Category => General Discussion => Topic started by: Stevebol on April 11, 2010, 10:27:16 PM
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This is my first post here and I have a big project to deal with. I have about 20 cassettes and 10 1/4" RTRs that I'm transfering to digital to make CD's.
They are original live classical music recordings dating from the late sixties to early nineties. The cassettes are all 90 minutes and I haven't gotten into the RTRs yet.
I'm having a problem with the cassettes marked dolby. I believe they are "B" type judging by the sound. On My Tascam 122 MKIII they sound dull and on The Marantz PDM 430 a bit bright so I'm looking into outboard dolby b units that could possible be adjusted(calibrated). A Teac AN 80 is on the way.
My basic setup is:Tascam 122 MKIII-PRP preamp-Presonus Firebox-Soundforge-Voxengo redunoise
What can I expect from the outboard Dolby B units as far as trying to match the original record settings?
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Hi Steve,
Welcome to the forum.
Unfortunately, having one Dolby B decoder that's dull sounding and another that's bright and etched sounding is par for the course. That's what I found with all the outboard decoders I tried. The best of the lot was a unit sold by a British company called Integrex. They aren't too bad but are rather difficult to find. Calibrating the units does more to balance the levels of the frequency band that's compressed/expanded with the unencoded frequencies but it doesn't do anything to change the overall character of the sound.
I'm assuming that you're doing these transfers for personal use and not for archival purposes. I mention this since there is currently some debate on whether encoded media should be archived in a decoded or encoded state ( we're talking large institutions such as the Library of Congress). If you'd like to hear some of the pro's and con's of each, you may want to post something on some of the lists where professional archivists discuss these matters. I would suggest subscribing to the ARSC list if you plan to continue doing transfers.
A good site you might find interesting is The Audio Archives. Eric Jacobs has a fine reputation amongst restoration/archivists and his site will give you an idea of what it's all about.
http://www.theaudioarchive.com/
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Thanks ironbut.
I checked out the audioarchive before and I saw that they use a Dolby 422 but I haven't been able to find one-or the users manual to see if it might be suitable for my needs. The Integrex is also hard to track down.
I'll post some examples of what I've done so far.
"Calibrating the units does more to balance the levels of the frequency band that's compressed/expanded with the unencoded frequencies but it doesn't do anything to change the overall character of the sound."
I'm not sure what you mean by this exactly so I'll have to get a handle on what these decoders are capable of doing. I have a basic understanding of the encoding-decoding process but I've always avoided dolby in the past so this is mostly new to me.
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I've spoken with Eric regarding his 422 unit. The one he's using has been modified and he's pretty happy with it. I do see them on eBay from time to time but they aren't cheap like most other Dolby B units. About the lowest I've seen one for is around $300 but most are closer to $1k. Bear in mind that these professional units are quite expensive when new (IIRC the 422 was close to $2k) so they're being sold for a fraction of what they were originally purchased for.
There's also the added cost of working with a balanced (+4 dB) into a normal consumer level (-10 dB).
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How can I post some Mp3's here?
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Near as I can tell that is not an allowed attachment file type for this forum software. Best bet might be to post it somewhere else that will host MP3s, and post a link here.
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What can I expect from the outboard Dolby B units as far as trying to match the original record settings?
If cassette tapes stored correctly and not partially demagnetized:
First you need to adjust playback head asimuth on _actual tape_ for best HF response (NR OFF),
second you need a external dolby unit that can be adjusted to actual level of you tapes, that you must adjust by ear for best result
(NR ON, minimum "breathing" and correct dynamics), or you can adjust playback level trimpots inside of your Tascam, that do the same thing, but after all you need to recalibrate playback electrionics.
Couple of days of adjustments, and you get a good result.
If tapes stored incorrectly, and slightly demagnetized you may add a parametric EQ between playback deck and dolby decoder, but in this case adjustmets take a more time an be too complicated.
(or you can try to adjust playback EQ trimpots inside tape deck).
Sorry for my poor english, I just try to share some of my experience in dolby-b encoded tape transfer.
Anton.
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Thanks docb and intell.
I've been doing the azimuth adjustment on the MKIII by ear without much trouble and I also did the others recommended by the manual. I'm waiting on an external dolby unit to arrive.
I would rather not mess with the internal adjustments on the MKIII if I can avoid it. I'll see how it goes when I get the external dolby.
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Also, there are two playback EQ options for cassette: 70usec and 120usec. Most decks let you switch between the two EQs. Try both (with dolby on) and see which sounds best.
It's a good idea not to mess with the internal calibration. It's probably set correctly if no one has messed with it. You might need to buy an azimuth tape to get the deck back to proper head alignment after you are done.
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The Tascam has automatic tape type sensing but the Marantz let's you select.
The azimuth was way off on the Tascam when I got it but it seems to be OK now. I should look into getting another deck as a backup. Maybe a Nak or a Sony ES series.
I'm tempted to go for a CR 7 that's up on audioproz for $260.
I think I have real case of analog fever.
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Update-
I got the Teac An-80 today and tried it out. It does what it's supposed to and being able to adjust channels individually is a big help. I'm still waiting for the Advent 100A to arrive.