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Post by JohnH on Mar 21, 2009 1:13:57 GMT -5
I’d like to show you this fine old English mixer that I picked up recently: Its a Carlsbro Constellation 12/2, and I’m interested in any opinions as to how old it is. I bought it for not much, to use as the front end of a PA for our band, along with some 15” powered speakers that I bought new for a good price. The mixer is heavy construction, full of old-school electronics. Full sized components, mainly separate transistors, labels big enough to see, knobs big enough to turn. I like it a lot! Inside, everything indicates solid professional construction, and there’s nothing I can’t service myself. It has 12 balanced inputs, switchable from mic to line level, gain, 3 band EQ, pan, aux and fold-back knobs for each channel. Faders for each channel, plus left, right and fold-back. Aux send and return levels, phones. Everything I think we need. It sounds good, with just a little retro-styled hiss, but fine if the levels are set right. All the ins and outs were originally ¼”jacks. At some point, a dude with a tin opener and an oxy-torch converted 5 of them to the more modern 3-pin Cannon type. Luckily his work is functional and his metalwork sins are hidden. I tracked down the maker, which is (was) a smallish amp and audio builder in England. There was a forum for it, Great! I thought – I can get all the info, and there were lots of feedback on schematics and manuals. Unfortunately, the guy who answered all the questions died three week before I got the mixer. And the company went into receivership two weeks before I got it! Bummer! Anyway, I can trace enough of the circuitry to follow what is going on. The input features a pair of PNP silicon transistors in a push pull arrangement. Etc Anyway – I’m interested in your guesses as to its age – from any perspective you like. Heres some clues I think may be relevant: Solid construction – not miniaturised Use of all ¼”jacks – also 5-pin DIN for tape connection Cheesy wood-grain end panels – like the HiFi I wish my Dad had in the 70s LED indicator bars – made of separate LEDs, red and green. I think the greens came in well after the reds – I don’t remember green being common on budget equipment until the 80s Discreet transistors, and some Op-amps type 741. I know that at least by the mid 80s, there were pin compatible, lower noise, economical alternatives to these generic types So what do you reckon? My guess is about 1980+ More photos: cheers John
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Post by cynical1 on Mar 21, 2009 2:55:20 GMT -5
Yeah, that sure looks like something out of the 80's...I loved those cool little knobs with the different colors on them...and those big decals identifying the corresponding track...never too wasted to read those...and the wood grain... Oh yeah, it screams early 80's... I saw your posting on the other forum. Too bad your contact died, the title block from the drawings could have given you a pretty good idea on the mfg. date. On the Carlsboro site they have their corporate history detailed in a .pdf. The name on the model plate might get you in the ballpark. Seems they've changed the official name of the company several times since 1959. I never saw one of those in the States, but it looks like it's built like a Mallee bull. Seems like you made a lucky find there. Happy Trails Cynical One
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Post by newey on Mar 21, 2009 4:01:24 GMT -5
Early '80s is as good a guess as any. If it was a guitar or an amp, it would be called "classic" or "vintage"and all sorts of information would probably be available. But PA equipment gets no respect, it's not 'vintage', just "old". In your first photo, it looks like several of the rectangular slider knobs were replaced with round ones, but in the later photos it looks like several are just missing- and not the same ones that appear to be round ones in the first photo.
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Post by JohnH on Mar 21, 2009 4:46:59 GMT -5
Cyn1 - that's a good insightful link!
At the back of the unit, it lists the manuafacturers name as 'Carlsbro Sound Equipment' - so it's therefore dated at no later than 1980, when they changed it to 'Carlsbro Electronics'. Thats a clear result.
Newey - good spotting - the photos are from different times over the last couple of weeks. It came with 5 fader knobs missing - and I have not yet sourced replacements, but I put the round ones on which work OK for now. I've also cleaned and lubed all the pots, and it now works smoothly with no crackles as pots are turned. I've replaced a slide switch plus the power supply filter caps which were visibly oozed though still functional
cheers
John
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Post by cynical1 on Mar 21, 2009 11:11:32 GMT -5
Glad the link helped. Looking at that mixer reminded me of a time when I had hair...and it was brown...
Happy Trails
Cynical One
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Post by ashcatlt on Mar 21, 2009 12:03:42 GMT -5
I was also going to say early 80s. I'm amazed at how clean the thing is, both inside and out. And you say it works great after just a lube and some caps? I think you'd be hard pressed to find a mixxer made in the 90s that's held up so well!
Now, when you say "the more modern 3-pin Cannon type," you mean XLR, no? Are the quarter-inchers balanced? Can't quite tell from the pics. And the "Lo-Hi" switches. Is that impedance or (more likely) gain?
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Post by JohnH on Mar 21, 2009 14:31:11 GMT -5
Ash - yes it does seem to work good and everything is useable.
The sheet steel case has a few rusty chips on the front edge, and since the photos were taken I have resprayed the base section which includes the front edge. I wont change any of hte nice silk screened lettering on the front and rear panels. Inside though, its as if it was made yesterday.
The newer sockets are XLR. But the old original ones are balanced 1/4" jacks - ie with ground, tip and ring connectors. The Hi and Lo settings change the gain, and also change input impedance from about 47k for line level to 1k for mics. I havent yet yraced how that gain change works, but the impedance change is just a 1k resistor that shunts the input.
John
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Post by sumgai on Mar 21, 2009 18:48:49 GMT -5
If it was a guitar or an amp, it would be called "classic" or "vintage"and all sorts of information would probably be available. But PA equipment gets no respect, it's not 'vintage', just "old". Now if all the early Yardbirds future-gawds had gotten their tone by playing through WEM or Selmer PA systems, then the story might be just a tad different these days, eh? sumgai
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Post by ChrisK on Mar 22, 2009 21:17:54 GMT -5
Look at the ICs. Look for a 4 digit number such as "4385" (and not just part of the part number such as LM1458). This would be the 43rd week of 19 85. This means of course, that the product was made usually slightly thereafter (after all, who buys actual semiconductors as an investment - ). If you don't find this, let us know the logo/manufacturer, the part number, and any other markings. Depending on the practice afoot, the PCBs may also have a similar number in the circuit. PCB houses often edit the films to indicate the date of manufacture. This product likely was made before the widespread use of CAD. When I was in college, I was designing and project managing the construction of the new department lab. I found several parts drawers filled with industry donated ICs sorted by a professor by the date of manufacture. Needless to say, finding data sheet info was somewhat difficult until I "decoded things". This was in the mid 70's, so computers were somewhat scarce (or analog (Heathkit) based on tubes).
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Post by JohnH on Mar 23, 2009 5:30:05 GMT -5
thanks Chris - the 741 opamps dont seem to have such a reference. the typical writing on them is CA741CG and RCA 941 below
John
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Post by ChrisK on Mar 27, 2009 23:28:19 GMT -5
Well, the "RCA" indicates that they were likely produced before GE semiconductor took control of RCA in 1986. The RCA semiconductor division was sold to Harris in the late 80's, and then subsequently sold to TI in the late 90's.
I have seen parts from the 70's and 80's with a three digit date code.
I believe then that these likely were produced in 1979 during week 41.
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Post by JohnH on Mar 27, 2009 23:57:09 GMT -5
Thanks very much! Overall, thats cool sleuthing - it was built after about say, November '79, and before the end of 1980. That about nails it. Little did I know, while doing the first year of my engineering degree, that meanwhile.in a factory not so far away, my future mixer was about to be born........(gasp!)
cheers
John
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tore
Rookie Solder Flinger
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Post by tore on Feb 9, 2024 1:28:30 GMT -5
Hi, I have come across, and bought this same mixer:) Did you find any schematics and manuals for it?
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Post by JohnH on Feb 9, 2024 2:19:57 GMT -5
Hi tore and welcome to GN2! At last after 15 years, there's someone to talk about my old mixer with!
I still have it, and yes I did get schematics, just in time before Carlsboro disappeared for a while. Ill see if i can find them,.....
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Post by JohnH on Feb 9, 2024 2:34:18 GMT -5
... I have 8 pages of original schematics, and the manual, all as pdf scans. How best to share them?
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tore
Rookie Solder Flinger
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Post by tore on Feb 9, 2024 2:51:48 GMT -5
Thank you:)
Thats cool! I dont know the best way to share documents here?...
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Post by JohnH on Feb 9, 2024 3:03:25 GMT -5
Ive sent you a PM with an email link. Send me a message there and Ill send what I have
cheers John
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