MikoKensington
Well-known member
Anyone have some documentation on these preamps? They're not that easy to find. Has anyone any experience with these? The old Altec 250 consoles sure are sexy. I'd like to know what they sound like.
Altec 458 and 459 preamp info?
- Thread starter MikoKensington
- Start date
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NewYorkDave
Well-known member
PLEASE tell me that a 250 console wasn't ripped apart to get those preamps. That would be a crime, punishable by a hearty ass-kicking.
:twisted:
Anyway, did these come from a 250SU, or some other variant?
IIRC, the 458 is a preamp/booster and the 459 is a line amp. I think I have some documentation. I'll look around.
:twisted:
Anyway, did these come from a 250SU, or some other variant?
IIRC, the 458 is a preamp/booster and the 459 is a line amp. I think I have some documentation. I'll look around.
ciminosound
Well-known member
Waltzing Bear has the 459 and 428 pre...
http://waltzingbear.com/Schematics/Schematics.html
Gerry
http://waltzingbear.com/Schematics/Schematics.html
Gerry
NewYorkDave
Well-known member
MikoKensington
Well-known member
I don't have any, Dave. I was just looking for info. I heard they're pretty simple. If that was true I was going to try to throw something together one day.
Any ideas for what the transformer ratios may be? CJ! What's an ALTEC or Peerless 4745 and 16526?
Any ideas for what the transformer ratios may be? CJ! What's an ALTEC or Peerless 4745 and 16526?
NewYorkDave
Well-known member
You heard wrong :wink: For one thing, the transformers are of special design. Matter of fact, a whole AES paper was written about these amplifiers:
High Quality High Reliability Amplifiers
for Speech Input Systems
JAMES J. NOBLE
Altec Lansing Corporation, Anaheim, California
JOURNAL OF THE AUDIO ENGINEERING SOCIETY
APRIL 1961, VOLUME 9, NUMBER 2
It's a good paper, and it demonstrates that a lot of thought went into the design of these amps. I'm afraid I can't post it because of copyright, but it's available from the AES for a reasonable fee.
MikoKensington
Well-known member
Oh well. I'll just save my pennies and get a 250SU. That should only take 48 years.
> I heard they're pretty simple. Any ideas for what the transformer ratios may be?
The wiring is simple. The transformers are NOT simple. In this case the tube-dood dumped all his problems on the transformer guys: the trannies have to be EXTREMELY special. This could only work with close cooperation between the preamp factory and a captive or highly motivated tranny-winder. And a specific design limit was "reached when with progressively finer wire difficulty in handling causes the cost factor to rise sharply and reliablilty to be questionable". You are NOT going to find trannies like this anywhere outside these preamps.
Ask Brian Sowter if he has looked at this amp. While he is not the only guy who "could" wind these things today, he's probably the only guy who "would". Others could approximate the ratio but not all the fine details needed to get these over-worked transformers sounding right.
And not to be critical (well, actually I do need to be critical here for copyright reasons): this scheme only makes sense if you pay for tubes but have a core-winder on salary and not doing much. Yes, there are reliability issues too, but fewer tubes working VERY hot and #44 wire is not necessarily more reliable.
The wiring is simple. The transformers are NOT simple. In this case the tube-dood dumped all his problems on the transformer guys: the trannies have to be EXTREMELY special. This could only work with close cooperation between the preamp factory and a captive or highly motivated tranny-winder. And a specific design limit was "reached when with progressively finer wire difficulty in handling causes the cost factor to rise sharply and reliablilty to be questionable". You are NOT going to find trannies like this anywhere outside these preamps.
Ask Brian Sowter if he has looked at this amp. While he is not the only guy who "could" wind these things today, he's probably the only guy who "would". Others could approximate the ratio but not all the fine details needed to get these over-worked transformers sounding right.
And not to be critical (well, actually I do need to be critical here for copyright reasons): this scheme only makes sense if you pay for tubes but have a core-winder on salary and not doing much. Yes, there are reliability issues too, but fewer tubes working VERY hot and #44 wire is not necessarily more reliable.
> can we see figures 3a and 3b?
Very ordinary equivalent circuits. See any good transformer book.
> or perhaps the whole article?
No. The AES has a special pole where they hang the heads of people who rip-off their copyrights. They may ask me to take down that snippet.
The article is a VERY good read if you are into 1961-think. Personally I think they jammed the transformer-winder's knobs between a rock and a hard place to get this thing to work reasonably well; I'm not too sorry to see such days go away.
Very ordinary equivalent circuits. See any good transformer book.
> or perhaps the whole article?
No. The AES has a special pole where they hang the heads of people who rip-off their copyrights. They may ask me to take down that snippet.
The article is a VERY good read if you are into 1961-think. Personally I think they jammed the transformer-winder's knobs between a rock and a hard place to get this thing to work reasonably well; I'm not too sorry to see such days go away.
The input is not too unlike the Fairchild signal input, Sowter's 8346 £95.95.
And while the exact performance will differ, you can get a working properly balanced amplifier with a Fairchild output, 8344 £49.03. Max unclipped output power will be a little lower, but THD may also be lower up to the clipping point.
The dog ate my $/£ decoder ring, but this does not look like a casual "throw-together" project.
And while the exact performance will differ, you can get a working properly balanced amplifier with a Fairchild output, 8344 £49.03. Max unclipped output power will be a little lower, but THD may also be lower up to the clipping point.
The dog ate my $/£ decoder ring, but this does not look like a casual "throw-together" project.
NewYorkDave
Well-known member
Just a pic for anyone who's never seen a 250SU :grin:
http://www.oldradio.com/archives/hardware/Altec-250SU.jpg
Now, if you can't mix a record on that, you shouldn't be in the business. :thumb:
http://www.oldradio.com/archives/hardware/Altec-250SU.jpg
Now, if you can't mix a record on that, you shouldn't be in the business. :thumb:
MikoKensington
Well-known member
Thanks for the info PRR! From pictures they looked so "nuts and bolts". But now I see that those little black boxes house all the complexity you could possibly fit in such a small package. Ah well, it was worth the call. I tip my hat to a generation of engineers that didn't take the easy way. :thumb:
