Late 60's Ampex input transformers: Uses?

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Late 60's Ampex input transformers: Uses?

Postby Gonecat » Wed Mar 12, 2014 1:08 am

I build websites and do online marketing for a living and a client has proffered an exchange with me - which I love doing - for some vintage parts in exchange for web work.

He worked at Mullard in the early 60's and has built a collection of stuff ever since then. He just gave me a '62 NOS Tung-Sol 7025 to get things started (which sounded better than the RCA blackplate 12ax7 or the '62 Mullard in my home-made Fender Princeton - better noise, better top end, tight low end).

Then on to his storage room where there was a McIntosh 3 channel power amplifier, monoblocks from the 50's, distortion measurement machines, signal generators, transformers, etc. I was a kid in a candy shop.

The things that caught my eye off the bat were these untouched Ampex transformers, and since I don't have any gear with transformer-based inputs I am thinking about building a preamp or perhaps adding line-input transformers to a couple channels of my soon to arrive Soundcraft 600, so I'd have a little touch of that 'sound', ay what!

Any recommendations from you guys? I'm wide open to suggestions. I guess my main hope is to use them for every last little bit of sound/color that i can squeeze out of them. I was going to get a pair of the top two on this list, or one of the last one (he only has one).

They are the following Ampex models:

4580200-01 - Line Input Transformer (x 2)

4580116-20 - Matching Input Transformer (x 2)

4010040-02 - Input transformer with built-in Mic preamp - I can't find any info on this thing, it seems really unique. (x 1)
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Re: Late 60's Ampex input transformers: Uses?

Postby Gonecat » Wed Mar 12, 2014 1:16 am

System wouldn't let me edit that last post, but i wanted to mention that the 1st one on that list, the 4580200-01, is a 'bridging' transformer.
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Re: Late 60's Ampex input transformers: Uses?

Postby Gonecat » Wed Mar 12, 2014 1:27 am

More on that bridging xfo:
"Ampex uses them on the MM-1200 multitrack tape machine to bridge a balanced line to the un-balanced input circuit"
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Re: Late 60's Ampex input transformers: Uses?

Postby Gonecat » Wed Mar 12, 2014 1:36 am

Even more on that bridging xfo (4580200-01):

Balanced-bridging transformer with unit gain and an input impedance of 20K ohms.

Fully shielded Octel Socket Bridging Transformer. These are used in
older high end recording consoles, mixers, commercial sound systems modular amplifiers
and various tape machines to isolate inputs and/or match impedances. DCR between
pins 4 & 8 (primary winding) is 1.36K, between 2 & 3 (secondary winding) 1.30K.
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Re: Late 60's Ampex input transformers: Uses?

Postby Gonecat » Wed Mar 12, 2014 1:37 am

Even more on that bridging xfo (4580200-01):

Balanced-bridging transformer with unit gain and an input impedance of 20K ohms.

Fully shielded Octel Socket Bridging Transformer. These are used in
older high end recording consoles, mixers, commercial sound systems modular amplifiers
and various tape machines to isolate inputs and/or match impedances. DCR between
pins 4 & 8 (primary winding) is 1.36K, between 2 & 3 (secondary winding) 1.30K.
Gonecat
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Re: Late 60's Ampex input transformers: Uses?

Postby vineyardgray » Tue Mar 25, 2014 11:42 pm

I'm pretty sure the input transformers you have mentioned are on my ampex AG-440b. In which case, they sound pretty good to my ear. In all cases, there's not much iron there so if you're looking for big azz saturated vintage iron, this ain't it. But like any transformer, they add some pleasant smoothness to a signal.

I seem to recall the ones with mic pre's being summarily poo-poo'd by the several folks who know better than me. As this is anecdotal evidence, its worth every cent you paid for it.

Regards,

MR
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Re: Late 60's Ampex input transformers: Uses?

Postby Gonecat » Wed Mar 26, 2014 8:52 pm

Hey MR,

Thanks for the response!

I believe they do come in a 440.

I saw another NOS one on ebay that failed to sell for $36 so I figure they aren't entirely rare.

I was thinking of either putting them in on a couple channels of the mixer, but maybe they'd be better in a DI box (and use something more easily replaced in the console?).

I have seen some of the negative reviews of the preamp card. Too bad!

Thanks again for the input, always appreciated.
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