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Author Topic: Dolby units for Barclay Crocker and Ampex Dolby Tapes  (Read 10648 times)

Offline scully280

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Dolby units for Barclay Crocker and Ampex Dolby Tapes
« on: March 03, 2007, 03:32:59 PM »
Sounds like there are a few out there enjoying Dolby type B pre-recorded tapes whether they are Barclay-Crocker, Stereotape or late Ampex.  What sorts of Dolby play electronics are folks using?  I'll start with my unit, a Dolby Labs Model 330 "Tape Duplication Unit" purchased on ebay.  Any others?
Richard Lane
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Offline ironbut

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Re: Dolby units for Barclay Crocker and Ampex Dolby Tapes
« Reply #1 on: March 03, 2007, 09:03:40 PM »
I have an Integrex decode only unit. I went through several that were very muffled sounding until I found this one. Luckily, most of the "doorstops" I bought were less than $20. The Integrex is pretty transparent. I think one of the main reasons for this is the electrolytic caps in the signal path are pretty high quality. They're a British make and were actually sold by BC in their catalogs. The Dolby circuit is IC based. I don't really use it that much because it does seem to take a little of the edge off of transients.I don't really notice this with my big rig, but on headphones it's noticeable. I'm planning on going through it and upgrade the usual suspects one of these days.
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Offline U47

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Re: Dolby units for Barclay Crocker and Ampex Dolby Tapes
« Reply #2 on: March 04, 2007, 12:17:27 AM »
I used to have hundreds of dolby a and dolby b tapes. Now, I'm down to about 6 reels total in either dolby format. I have used in the past the following: Advent 100 and 100a, Dolby Labs 334, Teac an-180 and Nakamichi NR-200B-c as well as Charlie's Dolby Labs A-301 beast. I really liked the A-301,as it was amazing for Dolby A tapes and pretty damn fine for the B tapes as well.The Dolby Labs A-360/361 pro units did not come close to the sound of the old A-301, which was the original Dolby Labs processor from 1966. Decca started using it in 1966 or 1967.  I now have a stock Advent 100, which is all discrete. I think the 100A went to ICs. I find the stock 100 to be on the warm side and the Teacs to be a bit brighter sounding.

It would be interesting to hear one of the Advents in stock versus modified forms.

Rich Brown
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Offline scully280

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Re: Dolby units for Barclay Crocker and Ampex Dolby Tapes
« Reply #3 on: March 08, 2007, 10:24:35 PM »
Anybody have a source for schematics for the Dolby Labs 330?
Richard Lane
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Offline slbender

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Re: Dolby units for Barclay Crocker and Ampex Dolby Tapes
« Reply #4 on: March 16, 2007, 11:24:50 AM »
As far as I can remember (I have the 100A Service Manual somewhere) the Advent 100 and 100A were both discrete transistors and FET's, except that one IC used as a microphone preamp in the earlier Model 100.  The Advent Model 100A's had Line 1 and Line 2 inputs (the leftmost pots) instead of a Microphone input and a Line input, and so I believe it lacked the UA-739 IC.  If not recording, all signals passed through discrete circuits only.

I also had a Teac AN-60 and AN-180.  Not quite sure about what the AN-60 had inside, but I did not like its sound, it soured me on Teac RTR's, which I also tended to think sounded shrill and "transistory".  I later found out the AN-180 was stuffed with nasty sounding UA-709 IC's in the signal path, which makes me glad I never used it, tho it did look nice~!

Anything as old as 1960's-1975 RTR's or Dolby units will be much less than optimum some 30, 35, or 40 years later.  Most RTR units I see these days, are not even coming close to meeting original factory specifications for frequency response, distortion, wow and flutter, and signal-to-noise ratio, without significant rebuilds, upgrades, or repairs.

I have some Dolby A-361's, and find it quite interesting that you say the A-301 was much better sounding.  Having looked inside, and based upon the massive use of cheapie tantalum caps inside the A-361's, I'm not surprised at all.  IC's and Tant caps, there are so many, some have to be in the signal path.  I'd love to go in and replace them all with lytics, or polypropylenes (as if there would be enough room...) and then do a comparison, but I don't have any extra A-361 units, or any A-301's to run such a comparison.


Steven L. Bender, Designer of Vintage Audio Equipment


I have used in the past the following: Advent 100 and 100a, Dolby Labs 334, Teac an-180 and Nakamichi NR-200B-c as well as Charlie's Dolby Labs A-301 beast. I really liked the A-301,as it was amazing for Dolby A tapes and pretty damn fine for the B tapes as well.The Dolby Labs A-360/361 pro units did not come close to the sound of the old A-301, which was the original Dolby Labs processor from 1966. Decca started using it in 1966 or 1967.  I now have a stock Advent 100, which is all discrete. I think the 100A went to ICs. I find the stock 100 to be on the warm side and the Teacs to be a bit brighter sounding.

It would be interesting to hear one of the Advents in stock versus modified forms.

Rich Brown
Acoustic Arts
Portland, Oregon

Offline n1uvu

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Re: Dolby units for Barclay Crocker and Ampex Dolby Tapes
« Reply #5 on: January 30, 2011, 02:46:53 PM »
for my b-c tapes, i use a teac a-2300sd deck, along with a sony nr-115  dolby b adaptor w/ my sony 766-2.

Offline High and Outside

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Re: Dolby units for Barclay Crocker and Ampex Dolby Tapes
« Reply #6 on: January 30, 2011, 04:31:26 PM »
The Dolby Labs A-360/361 pro units did not come close to the sound of the old A-301, which was the original Dolby Labs processor from 1966.

I have three of the A301 units for sale if anyone wants to make me an offer.

Note that these units don't decode Dolby B, which was the original question. They decode (or encode for that matter) two channels of Dolby A. And they're big.
Paul Stubblebine
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Offline jeri

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Re: Dolby units for Barclay Crocker and Ampex Dolby Tapes
« Reply #7 on: February 23, 2011, 01:53:59 PM »
Paul,

Are the Dolby A301's still for sale?

Jeri
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Offline Stevebol

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Re: Dolby units for Barclay Crocker and Ampex Dolby Tapes
« Reply #8 on: April 07, 2011, 01:43:46 AM »
I have 3 Advents- 2 100A's and a 100. I'm having one of the 100A's recapped and I'll probably do the others myself. Once cassette tapes have been encoded with Dolby B it's hard to decide what to do. I finally got around to trying mixing the encoded and non-encoded sound in a small mixer before going to the computer.
If anyone is interested I'll let you know how the Advent sounds after a total recap.

Offline jeri

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Re: Dolby units for Barclay Crocker and Ampex Dolby Tapes
« Reply #9 on: April 07, 2011, 10:49:05 AM »
Steve,

I am very interested.  I have a couple of these (sitting unused), and it would be great to hear about your experience putting them to use.
Jeri

Offline Stevebol

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Re: Dolby units for Barclay Crocker and Ampex Dolby Tapes
« Reply #10 on: April 09, 2011, 08:40:50 PM »
I'll let you know jeri. I missed the fedx guy today but I should get the 100A on Tuesday. Atlas Audio repair said they are doing a total recap. If you're farmiliar with the 100/100A series they have 6(5?) boards that pop in and out. I'm going to recap one of the 100's with higher grade caps, Panasonic-Nichicon-Elnas, to see if there is any difference. I'd like to replace other components on the output board.
I'll post my findings (just by listening) over the next couple weeks. There may be a burn-in time for the new electrolytics. I got a third 100 just a few days ago in excellent condition and it's working on both channels. I'll try to compare all three units and record them.

Offline Guglielmo

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Re: Dolby units for Barclay Crocker and Ampex Dolby Tapes
« Reply #11 on: April 12, 2011, 06:31:15 AM »
Hi to all.

When l wish to listen to my BC's tapes I utilise an outboard unit, the Nakamichi NR 200. Very versatile and well performing.

By the way I play the BC's reels with a Revox A77 MkIII 4 tracks. The Nakamichi NR 200 got a separate play/record section so even when I wish to record on-field with my Nagra IV-SJ with Dolby B at 15ips it may be successfully interfaced!

Cheers,

Guglielmo

Offline Stevebol

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Re: Dolby units for Barclay Crocker and Ampex Dolby Tapes
« Reply #12 on: April 13, 2011, 10:54:50 PM »
Hey jeri.

I actually have all three units running. The 100A was fixed and calibrated and it's the quietest of the three, probably due to calibration. It has all new caps. It's not suited for mixing of a processed and unproccessed signal because the 2 channels probably use the same section for the dolby. The 100's are different and they have separate channels for dolby. The 100 I got last week looks like it was well cared for and I see a number of parts were replaced individually. I just finished recapping the other 100 and it seemes to be OK. I'll be sending it off to be calibrated in the future.
The manual mentions that one of the side effects of dolby, high frequency loss, can be a benefit in some cases. It says it can be used as a high filter. That's basically what I'm doing by mixing the dolby and non-dolby sound through a mixer.
I don't know about the Barclay Crocker and Ampex Dolby Tapes but I would think these Advents can be useful to anyone interested in tapes. They bring out low overtones in a nice way and they sound much better than low eq boost, to my ears anyway.
Atlas Audio repair did an excellent job.