Help identifying ADC transformers (and this mysterious thing?)

[hageir]

Hello guys & gals,
does anybody here recognize these Audio Development Company transformers? I was inherited this awesome, antique piece of test equipment which has a stunning/whopping amount of 24 ADC transformers and 12 12AU7 and 12AX7.

(My first idea was; this would be coolest passive summing mixer on the planet; add some one-knob tone control to each "channel")

 

[mjrippe]

Very cool looking piece! However, without a part number there is no way to identify those ADCs.

 

[emrr]

You need at least DC resistance of windings, inductance measurements even better. Would assume 12 identical channels, so pop the top and draw one out. Needs external PSU it appears.

I have a lot of similar things that look like they'd be cool to transform into something else, but in the end they're never quite right and it's easier to start from scratch versus kludging something into place.

 

[hageir]

Alright, alright
Thanks guys.

I'll borrow my friends' LCR meter and take some readings...
Will post them here and maybe you guys can help me determine the application and ratios?

-Geir

 

[hageir]

Update: I manned up, disassembled the chassis and got one of the ADC transformers out.
It might be that they're all the same, just wired correctly and backwards (12 and 12).

I'll take it to my friends workshop in the week and do some reading with an LCR meter.

I'm the meanwhile, I did a simple audio test and it's a powerful sound I'm getting out of it, it's very clear (the whole spectrum as far as my ears can hear) but wired differently there's an attenuation of the high-highs. Not necessarily bad, just a different character.

Maybe it's 1:2 I'm not sure, but the sound is definitely louder by a few dBs.
Exciting!

 

[hageir]

I sent a Pocket Operator* bass tom signal through the transformer and did some scoping, with different terminals connected.
The first shot (and wiring) is closest to the original waveform (the small tooth on the top of the wave).

the next two are different output wirings; there's a noticeable rolloff, which is very nice.
After the LCR readings this week, I'll determine if I can use them as the transformers for the direct outputs on my modded Stevenson Interface Electronics console!

*I recommend these Pocket Operators for the bench, they're tiny, run on batteries and can do a number of things useful for testing gear and more!

 

[hageir]

Well, did some readouts today with an LCR meter; I don't know what I'm doing so I did a bunch

I view it like this:
bottom two (they were bridged; either) are shield and right most is hot (unbalanced) -right side of 20 ohm resistor.

Top one (9 'o clock) , two and three (with the small wires cut off) are the secondary (balanced)?
That connection gave me a nice sound and a louder signal (with my first audio test).

I will post a drawing with the numbered terminals later..

Note that some of the readings are in Henries, others/one is milli-Henry / micro-Henry

 

[Disco Volante]

Exciting find. A partial trace-out of the schematic they're in would probably give us some further clues...

 

[mjrippe]

Well, did some readouts today with an LCR meter; I don't know what I'm doing so I did a bunch

I will post a drawing with the numbered terminals later..

Ok, well that is a start! Now you need to organize your data and draw out a diagram of the transformer. This should show where the pins are on each winding, the DCR between pins, and your inductance measurements. Attached are two examples from my notebook.

 

[hageir]

Wow! Awesome, thanks a ton!
I'm going to my workshop tomorrow, will follow your instructions
Thanks a million mjrippe!

 

[hageir]

Nota bene;
this is based on both the original wiring and the way it sounds best (the transformer drawing).
I have no idea if it's in reverse or connected "unorthodox" -it just sounds good and has a couple of dBs in boost

 

[mjrippe]

Hey, if it sounds good, it IS good!

I think that the drawing is a little confusing though. Here is another version:

 

[hageir]

Hehe
Yup, it sure sounds good!

So what would you say (quick guess)
this would be used for?

I'm debating if I create a passive 12 channel "blender" out of these (as is in the case/chassis)
or if I should use them as transformers for adding balanced direct outs to my old Stevenson Interface Electronics console (16 channels) -I do have some specialized NTP cards with buffer amps and all kinds of jazz; Lundahl transformers (Eurocards) that were originally meant for that.. that means an external rack; extra 24V power, 2x 16 / 4x 8 channels snakes to and fro the console to the rack and a lot of wiring...

But my original idea was to use LME49720s on the channels, driving the trannies passively, saving me huge headache...

Decisions, decisions!

 

[mjrippe]

I would guess that they were originally output transformers. Or, wired backwards, input transformers

I made a balancing box for a friend with a Stevenson console. It had six 1:1 transformers for the four buses and stereo outs. You can see that this was also a factory option at the bottom of this fuzzy pic.

 

[emrr]

Looks like push-pull tube output types.