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Author Topic: Speaking of Dolby,..  (Read 8100 times)

Offline ironbut

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Speaking of Dolby,..
« on: May 10, 2008, 05:02:51 PM »
For those of you who have Dolby B encoded tapes and either one of Doc's wonderful Repo amps or another machine that has switchable NAB>IEC eq settings, without looking at the various eq or Dolby curves, try listening to your B tapes with IEC eq. Of course it isn't correctly eq'ed but, if you're like me, and you've been listening to the encoded tapes with straight NAB, explain to me why this is worse. Anyway, this is just an experiment Rex Pavlov. Give it a try if you have been decoding your tapes and post your impressions.

steve koto
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Offline astrotoy

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Re: Speaking of Dolby,..
« Reply #1 on: May 11, 2008, 11:21:28 AM »
Steve, I tried your suggestion last night. The IEC setting is definitely better than the NAB- it tames the high frequency brightness. However, decoding on my Advent 100 dolby B is still much better and more realistic. However, it imparts the transistor sound which I still want to improve. SO I am still looking for a tube sounding dolby B decoder.   Thanks, Larry
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Offline ironbut

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Re: Speaking of Dolby,..
« Reply #2 on: May 11, 2008, 01:59:10 PM »
Yeah, the colorations from all the Dolby units is a real hurdle for me. Could you go into a little more detail on what you prefer about your Advent to the straight IEC?
thanks
Steve
steve koto
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Offline astrotoy

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Re: Speaking of Dolby,..
« Reply #3 on: May 11, 2008, 05:16:02 PM »
Steve, Playing a dolby B tape through the decoder makes it sound richer and fuller, with more depth and less hiss than just with IEC EQ. It still has a somewhat metallic sound that I do not like from the transistor electronics.  Have you had any luck on getting a tube based dolby B?  Maybe Doc has thought about that.   Thanks, Larry
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Offline ironbut

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Re: Speaking of Dolby,..
« Reply #4 on: May 11, 2008, 08:17:10 PM »
Coming from a purist standpoint (audiophile at least), I reel in horror every time I look inside of one of those units. I do have a couple that are IC based so it doesn't look quite as bad, but it is crazy complicated in there. One of the reasons that I doubt that a tube circuit would work very well, is that so many of the components have to be very closely matched to what the specs called for in the circuit that it's a insert and measure sort of procedure to replace any. So parts with any drift would constantly have to be calibrated. The original  builders made decisions based more on stability, rather than the best sound they could get. Don't get me wrong though, I'm still trying to get better sound out of them. I hope to have more time to spend on it this summer (talk about amateur hour though!).
steve koto
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Offline Studer Fool

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Re: Speaking of Dolby,..
« Reply #5 on: May 12, 2008, 07:37:00 AM »
Well actually, a long, long, long, time ago, I read somewhere that David Berning did a design for a tube based Dolby B for his own personal use (never offered as a product).  I've never seen any other mention of it, That would point to actual confirmation of its existence.  IF it really existed I guess we could try doing a collective Group Beg & Grovel of David on the very off-chance that a) it existed; b) he still has the design; c) he would be crazy enough to want to share it and suffer the endless questions that could engender; d) he has time these days, as he appears to be offering fewer and fewer products these days, suggesting he has found better ways to earn a living; e) any of us would have the skills and/or the time to fabricate such a design (BIG HUGE ASSUMPTION GUYS).  Still, if anyone knows David, as he does seem to be a really great guy and clearly an exceptional design engineer (who loves bicycles too).  Or anyone live nearby in MD?  I'm too chicken, I think we should leave him alone.  Well, maybe ONE phone call, by ONE of us?
The David Berning Company
12430 McCrossin Lane, Potomac, MD, 20854
Tel.: 301-926-3371, infoat davidberning dotcom



While I've always been curious as to the above, honestly my gut tells me that the best genuine real avenue approach in-the-here-and-now to explore, is to try modding the Advent 100 Dolby B.  Why?  Because it's all discrete devices with relatively simple circuit topography.  Some basic standard mod approaches (pwr supply improvements and coupling & eq. cap upgrades) should easily provide some immediate improvements.  Plus a couple of us appear to have one.  Wether that would be enough to be worth it is the mystery.

I have a scan of the 100A schematic if anyone can guide me as to how I insert it here. (Or even wants it)


Yours Truly, in Tape Tom Foolery,
cdw
Christopher D. Wait
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Offline astrotoy

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Re: Speaking of Dolby,..
« Reply #6 on: May 12, 2008, 04:04:37 PM »
As you can see with my question on opening tape head cleaner cans, I am not the one to do a modding of my Advent 100. However, I am interested in financing or help financing someone who is interested in trying a mod. I'm not sure how easy it is to find an Advent 100 on ebay. I bought mine that way, bidding $20 and I was the only one who bid. I don't do much on eBay, so perhaps there are those on the list who are more knowledgeable about how often the Advent 100's come up.  Thanks, Larry
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Offline astrotoy

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Re: Speaking of Dolby - Advent 100 vs. 100A
« Reply #7 on: May 13, 2008, 09:45:30 PM »
Can someone help me here?  I have seen on the net both an Advent 100 and 100A Dolby units. They look very similar in their pictures. What is the difference?  Is one better than the other sonically? I have a Model 100 now.   Thanks, Larry
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Offline U47

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Re: Speaking of Dolby,..
« Reply #8 on: May 13, 2008, 09:58:59 PM »

I've owned both the 100 and 100A and found the 100 to be superior. Pretty sure the 100 is all discrete circuitry. I would like to hear one with new caps and improved power supply. Then again, I only own 3 Dolby B tapes....

Rich Brown
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Offline Studer Fool

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Re: Speaking of Dolby,..
« Reply #9 on: May 14, 2008, 01:40:17 AM »
I have a "100A" and it is also all discrete devices.  I don't know what the difference is between the models, but if someone has the schematic for the "100" and wants to send it to me, I'd be happy to peruse it and report back what I find.
Christopher D. Wait
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Offline astrotoy

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Re: Speaking of Dolby,..
« Reply #10 on: May 14, 2008, 09:51:27 AM »
Thanks, folks. There is a schematic at the bottom of my 100. I'll take a shot of it and send it off.  Thanks, Larry
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Offline ironbut

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Re: Speaking of Dolby,..
« Reply #11 on: May 14, 2008, 05:44:21 PM »
Duhh, thanks Larry, I was looking all over the place for that schematic and thank god your post reminded me where it is. I have a 100 too but mine is kind of a basket case so I 've left it for last. I'm currently trying to make something out of the 2 Dolby Labs 330's I have. The first experiment didn't really pan out. But so far, it's the most musical of the Dolby units I have. Here's a list of the ones I currently have;
Teac 180, Integrex decode only, Advent 100, Concord 10, Panasonic (?), and the 2 Dolby Labs units. I want to try the Nak NR200 but I've alway been outbid on them. I know there's a member here that has one and I'd love to hear his impressions of it.
I've been too busy to mess with it in the last month or so, but after VSAC, I should be able to devote more time to it.
That's fantastic if David Berning built a tube dolby unit. Even if it's just the output stage that's tube.  He'll be on my short list to weasel some info from this summer.
steve koto
 Sony scd 777es(R. Kern mods)> Vpi Aires>Dynavector XX-2mkll>Bent mu>CAT ultimate>CJ premeir 140>Magnepan 1.6qr(Jensen xover)Headphone Eddie Current Zana Deux>AT ad2000,HD800 ,Metric Halo ULN-2 (battery powered),
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Offline astrotoy

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Re: Speaking of Dolby,..
« Reply #12 on: May 15, 2008, 02:25:08 AM »
Steve, is it possible for you to send a copy of the schematic from the Model 100 to Chris for his perusal. I tried to photograph my 100 today and I can't get it into good focus with my camera. Thanks, Larry
Larry Toy CharterMember-BHReproTechnics1506/Akai747dbx/OtariMX5050B3-ClassicalVinylFreak-15Krecs-VPIHRXRimDrv-LyraSkala-HelikonMono-HerronVTSP3A/BHPhonoPre-PacificMicrosonics Model2 - Pyramix&MykerinosCard-OppoNE-Proceed AVP2+6/CVP2-CJ MET1-Cary 2A3SE-AvantgardeDuos-3Solos-VelodyneDD18Sub