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altec lansing line transformers
Old 21st November 2004
  #1
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altec lansing line transformers

hey there, fellow geeks...

i recently came upon three altec lansing line transformers, part # 15356. after much google-ing, i can't really find out any information about it. i'd really like to know what gear they were used in, and most importantly, if they're any good.

there is an ebay auction for a pair, but mine are different than the ones shown. the auction is for part # 15356A; mine have no "A".

any help with this would be really appreciated.

thanks!
--jon

pic from that ebay auction (not the ones i have):
Attached Thumbnails
altec lansing line transformers-19_1_b.jpg  
Old 21st November 2004
  #2
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Jon,

While I recell seeing transformers like those over the years I couldn't specifically tell you how they perform. One thing to keep in mind though is that with transformers, size matters. The amount of material in the laminations will determine the headroom and performance at low frequencies.

I would guess that the transformers in the photo with the octal base do not have very good specs, due to the small size. If you are recording in a digital environment (hot levels, and/or lots of headroom) they might not be a good choice, though it would depend on exactly where they are in your system.

What are the primary and secondary impedances? I can't quite tell from the photo. They might have been used on the input or output of on a mixer, or the input of a power amp?

If you have test gear you could do some quick and dirty tests on your own, details if you want them.

Sorry I can't be more encouraging!
Old 22nd November 2004
  #3
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sorry... should have included these. the primary's impedance can either be 600 ohms, or 150--depending on how you strap it. the secondary is simply 600 ohms. it looks like a simple line isolation transformer to me, but i'm curious about the possibility of a 150 ohm primary. would this work as the front end of a mic pre? thanks again!

--jon
Old 23rd November 2004
  #4


Those aren't much smaller than the Jensen X-formers currently available. Headroom has to do with current desity v. saturation. The mic signal won't be pushing much current, so you are probably alright there.

These probably came off the back of an older amplifier (maybe out of a theatre). They will be at least 30 years old.

You might as well learn how to measure these things yourself. You can drive teh primary side through a 600 ohm resistor from a tone generator. Sweep the frequency and measure the voltage across a 150 or 600 ohm resistor with an O-scope. Make yourself a frequency response chart. You may want to try different drive levels as well to get an idea of saturation and voltage linearity characterisics.



-tINY

Old 23rd November 2004
  #5
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One thing to keep in mind, your Altecs are probably line transformers, so they may not be shielded well enough to be used in a microphone circuit.
Old 24th November 2004
  #6


Perhaps, but adding shielding is pretty easy if you are building your own chassis...





-tINY

Old 24th November 2004
  #7
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Hmm Tiny, all due respect, but I would have to disagree with that. A good quality mic transformer has a Faraday shield (or even two) inside, plus a good magnetic shield.

There would be no way to add a Faraday shield to to an existing transformer, and adding a magnetic shield would be quite iffy. One could try to build a mu-metal enclosure but bending and cutting mu metal is very tricky and tends to spoil it's effectiveness.

So I'm not sure how a DIY'er would pull off such a thing or whether it would be worth the effort. I mean, this is one reason why line and mic transformers are two different animals. How would you do it?
Old 24th November 2004
  #8


Well, steel will conduct flux. Building an all steel chasis will afford a modest secondary sheild (in addition to the one that is already built around the module). A faraday cage is pretty easy to make (I've made one with a shoebox, copper foil, copper tape, and some RF gasket material).

I don't believe that an electrostatic shield is needed around a mic transformer (ES shielding between input and output windings is a good thing, though). I'm not even sure how important magnetic shielding is for a DIY box used in a studio. You can always move the pre-amp away from the source of the magnetic field.

Why the wet blanket? If the project doesn't work well, a couple of newer design transformers from Sescom will answer the transformer question.



-tINY

Old 24th November 2004
  #9
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Hi Tiny,

We got into a bit of a debate here, didn't we.

The main reason I would discourage the OP from using this unit in a mic preamp is that IMHO, the sound quality he'd get would be below a baseline minimum of what one would expect. If a friend of mine phoned to ask such a question I'd give the same advice, because I wouldn't want to see them go through a lot of effort and be unhappy with the result. I'd also be concerned that a DIY'er might build such a thing, get hum or buzz, then rack his brain trying to figure out what he did wrong.

As you pointed out, a person who was really determined could probably find a workaround or two. But if you're going to the trouble and expense of building a mic pre -- which is a bit of a project no matter what -- why not spend a little bit more to get the right part, if it offers better sound and less aggravation.

That said, I applaud your inventiveness in constructing a Faraday cage -- something I've never done -- and appreciate your differing point of view. Who knows, it might be just the ticket for someone on a tight budget who wants to get his hands dirty with some garage R&D.
Old 27th November 2004
  #10
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wow... i've certainly learned a lot from this thread... and when i get around to building my next pre (after finals), i'll try the tx on the front end, and let you guys know how it works out. i also now know a new place to check as to why my last attempt was not so much a preamp as a noise generator. i had another thought, however, would it work as the output tx? i'm assuming so, as it has 600 ohm pri and secondaries. of course, this all depends on the frequency response--which i'd have to test at school (no scope or osc. at home).

thanks, and let me know what you think of them for an output tx!

--jon
Old 30th November 2004
  #11
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Tim Farrant's Avatar
 

Those transformers are definitely line level input transformers, I've seen them in old Altec gear where the plug in tranny was an option. I agree that their use as mic inputs would not be recommended, at best you are only going to get a 1:2 impedance ratio anyhow, so the amplifier section would need to have a very low noise spec at low source impedances. Most mic input transformers have a 1:5 ratio minimum.

Tim.
Old 30th November 2004
  #12


Yeah, we did David. A discussion/argument is a good way to learn things. Sometimes I'll take a position that I don't really agree with just to have a discussion and learn something in the process.

If the objective is to have a good mic pre-amp, you probably do better to find a used one to buy than build your own (spending the same money). But, the one you build yourself might sound better even if it doesn't sound better.

The value is often in the journey.



-tINY

Old 30th November 2004
  #13
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cymatics's Avatar
 

*** EDIT - I had to take down the info in the link below due to storage space limitations. PM me if you need this info***



I just so happened to have this 'laying around'....

Altec 15XXX Series

PM me if you woulk like the files in higher resolution.

These aren't anything too 'sexy'. Altec products were manufactured for the Sound Contracting market... ie, reliability takes precedence over fidelity.

There are a few gems in the old 'Green Face' product line though.

- jon
Old 30th November 2004
  #14
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hey, cymatics... that's exactly what i needed to satisfy my morbid curiosity! thanks for the help--from all of you guys!

--jon
Old 30th November 2004
  #15


Based on some of the music I hear on the radio, I'd say that lack of fidelity is the reason some of this old equipment is used.

How many vocals have you heard lately that had a slightly boxy, band limited tube compressor sound to them?



-tINY

Old 2nd December 2004
  #16
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Well, Altec, as you might already know, used a company called Peerless as their xfmr company. Peerless has been known to make a good transformer now and then. You do need more of a step up ratio to get good noise and gain but that would make a great line transformer in another project. Core size must match the application. Obviously, you would not want to use a huge output transformer core for a mic input, as the signal would be lost trying to magnatize the core. This is why a lot of your good mic inputs use a fairly small core. So size does matter, but not in the way you would think. If that transformer is in good shape and moisture has not leaked into the can, you should have good results for line level signals. As for shields, this depends on the core structure. UTC did not use an e shield on there A series input transformers because the coil/core is a humbucking configuration, that is, two coils one seperate core legs. Other companies, like Triad for instance, use a single coil on the middle leg of either an EI core or F lamination. Thus, they need a little more protection from noise and use an e shield between the pri/sec. Hope this helps.
Old 8th December 2008
  #17
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Altec Lansing Transformers

I just bought a Altec Lansing 15998 Mixer Amp.And ther were no transformers in it for the Mic.or line in . Does anyone have any ideas what or were I can get the transformers. Thanks Chuck
Old 8th December 2008
  #18
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Tim

Quote:
Originally Posted by Tim Farrant View Post
Those transformers are definitely line level input transformers, I've seen them in old Altec gear where the plug in tranny was an option. I agree that their use as mic inputs would not be recommended, at best you are only going to get a 1:2 impedance ratio anyhow, so the amplifier section would need to have a very low noise spec at low source impedances. Most mic input transformers have a 1:5 ratio minimum.

Tim.
I bought a 15998 Mixer amp and it had no transformers in it can you help me out on what to do

Thanks for any help Chuck
Old 11th December 2016
  #19
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Resurrecting a very old post with a very cool custom, hand-built mixer I just purchased that uses these Peerless 15356 transformers for MIC, -15dB and LINE (via 3-way switch on each channel). Although it appears to be very well-built and well-thought-out, even employing a wire mesh/screen Faraday cage, after reading this thread, I'm still a bit concerned about EMI interference, especially @ mic level. Can anyone offer advice on what to do?

I'm really hoping it's not a huge deal and I can keep the 15356's.....but perhaps there's a better (octal base) solution? Or I'd have no problem building a seperate cage for the 15356's....or wrapping each of them individually with copper or aluminum foil if that would help. Watcha think fellas? Thanks!
Attached Thumbnails
altec lansing line transformers-s-l1600-2-.jpg   altec lansing line transformers-s-l1600-7-.jpg   altec lansing line transformers-unnamed.jpg  
Old 11th December 2016
  #20
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Here's a link to a public Google Drive folder with far more pics, in case anyone is interested: https://drive.google.com/drive/folde...1k?usp=sharing
Old 11th December 2016
  #21
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Altec 15356

Quote:
Originally Posted by jdurango View Post
Resurrecting a very old post with a very cool custom, hand-built mixer I just purchased that uses these Peerless 15356 transformers for MIC, -15dB and LINE (via 3-way switch on each channel).
I'm really hoping it's not a huge deal and I can keep the 15356's.....but perhaps there's a better (octal base) solution?
can confirm by measurment, the 15356 does not have an electrostatic shield.
and neither does the highly regarded Altec/Peerless 4722.
if your custom mixer has no obvious interference/noise, then don't worry about it.
regarding Altec/Peerless transformers, if an internal shield is not stated in the description, then most likely not present.
the telephone equipment line of transformers including models 15189, 15192, 15257, and 15036 do have internal electrostatic shields with the connection brought out to a separate terminal.
as does the Peerless E204d.
if you mixer seems to function well with the 15356, don't fix it.
Old 11th December 2016
  #22
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Okay, will measure noise specs upon receipt. If there is a problem, it seems like capped metal tubes placed over each transformer would make great EMI shields....not full coverage 360 degree (obviously the bottom would be open), but should make a significant improvement.
Old 1st April 2017
  #23
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Recently acquired a JBL 5210 mixer (same circuit as Altec 1567A) The transformers are labeled 2608, 45908. Do you still have the Altec 15xxx series catalog? I can't find any info on these transformers, if you know if they're line or mic, impedance, etc. any help would be appreciated.
Old 1st April 2017
  #24
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Altec transformers

Quote:
Originally Posted by [email protected] View Post
Altec 15xxx series catalog?
information attached.
Attached Files
File Type: pdf 35_56_95.pdf (753.0 KB, 145 views)
Old 1st April 2017
  #25
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Thanks for sending the Altec pdf. Unfortunately my transformers aren't listed, so the search continues.
Old 1st April 2017
  #26
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JBL 5210 mixer

Quote:
Originally Posted by [email protected] View Post
Recently acquired a JBL 5210 mixer (same circuit as Altec 1567A) The transformers are labeled 2608, 45908.
please post of photo of the JBL mixer.
same circuit as Altec 1567a ? that is a little hard to believe but whatever.
and whose part numbers are those transformers ? JBL, Altec, Harman-Kardon ?
Old 1st April 2017
  #27
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two techs said it was the same circuit, part numbers are stamped on transformers from JBL 5210. I don't know how to attach the 3 photos in my images folder. If you want to email me directly, there are more photos. [email protected]
Attached Thumbnails
altec lansing line transformers-jbl-6-channel-mixer.png  
Old 2nd April 2017
  #28
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Jbl 5210

Quote:
Originally Posted by [email protected] View Post
two techs said it was the same circuit, part numbers are stamped on transformers from JBL 5210.
I'm no fan of the 1567a but your mixer is a gem if for no other reason of it scarcity.
the 1567a uses the Altec/Peerless 4722 for the inputs, and a 15095 for the output.
Your techs could compare your 2608, 45908 with the Altecs and document the pin-outs, resistance, inductance, turns-ratio.
I would expect those JBL parts to be similar if not the same.
You might be able to get some documentation over at the lansingheritage site.
In summary, very interesting!
Old 2nd April 2017
  #29
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Thanks for the Lansing Heritage site info.
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