UTC transformer questions?? Hey CJ you there?

[ChuckD]

Hello!

OK I have some general transformer questions that hopefully someone can help me with.
I have been struggling with a customized build and think I have confused myself on how certain types of UTC transformers function.

1) If a UTC transformer has a Split type winding what does that mean exactly? Can both windings be treated separately from each other, meaning could they be used to sum an input A+B  onto the output?

2) Can most UTC transformers be used backwards ( I remember this question years ago but cannot find the answer)? Even if not ideal would it still work? If not can you explain why?

3) More specific to UTC A-43. This transformer model has 1 600 primary and 2 600 secondarys. What does , in this case, 2 secondarys mean? Can this model be used backwards to sum A+B to the output? Or is it somehow hooked up different inside?

4) Finally I asked this in the PM660 thread but it wasn't yet answered and seems more general. What would cause an Audio transformer to vibrate and produce and external humming noise? I hooked all the ground shield connections to ground. was wondering what could make this phenomenon happen in general.


Hopefully these questions aren't too lame and maybe they can help others with builds as well.
Any help would be greatly appreciated!


Chuck

 

[CJ]

the twin coil arrangement is best for noise/hum rejection,

use both coils for best operation noise wise, they give you 4 cans, why not go for the -92 db?

both coils share a common mag pipeline, ie the core, what happens in vegas also happens in S.F.


you can use the transformer backwards, eg> fairchild 670 input is a UTC A-26 used backwards,

a-43, have i hacked one of those?

you can strap the 2 sec windings to get a 1:2 ratio, = 600:2400  (1^2 : 2^2 imp. ratio)

also look to the 670 matrix switching, the transformers are used to do just what you are after,

noisy lams happens only at about 400 cps or below, anything above that is the wire singing.

you do not want the wire to sing, if it were to vibrate as much as it wanted, no induction.

ever study the falling loop in a mag field in physics?

squeeze a singing coil on a scope and watch the voltage go up,

so if you wind a sponge out of #50 wire,  you better boil it in wax,

nickel lams have to expand and contract, otherwise you get distortion, so the smart lams are loose.

the rest of the questions someone else can answer,

i am good at hacking, but not a theory expert,

only after i hack do i become the theory expert for that particular model,

and even then, i f*ck up now and then,

thats why i keep hackin... ;D

 

[PRR]

> Can both windings be treated separately from each other, meaning could they be used to sum an input A+B  onto the output?

What CJ said. They are on the SAME core. In effect you are shorting A to B.

When stuff had soft 600 ohm output impedance, that "worked". Maybe not optimally, but....

Now that stuff has 60 ohm output but expects >600 ohm load, shorting outputs together just makes distortion.

You fix that with mix resistors. Cheap. Thought-free.

So why do you need a transformer?

Same for splits. You "can" take a dual-winding transformer to two loads. But if one load shorts, the core flux and the source is shorted, the other output goes dead.

There IS a way to mix with transformers. Have a transformer on each source. Wire all the secondaries in -series-. The output is (as inspection will see) A+B+C+... The total impedance is also A+B+C+..., so a 16-in 600r mixer has to be loaded in >10K. But each transformer adds capacitance, against the 10K, and you can lose high frequency response. And if one source is disconnected, all sources suffer. And it is awful expensive compared to resistors.

But why ask? Get sig-gen and audio meter, whack some set-ups together, measure gain and response including unlikely conditions (some ins/outs shorted or open).

> Can most UTC transformers be used backwards

ALL transformers swing both ways.

 

[ChuckD]

Ok thanks CJ and PRR!

So what I thought was yes I can use the A-43 and a basis for M/S switching by having them both forwards and backwards using the 2 secondaries to either perform subtraction or addition.

I also wanted to use some A-15's for the fairchild network and split the secondary to dual 500 ohms. So for use in the Poorman 670 (10K: 500 + 500)  both forward and backwards in the interstage of the design.
This would make the M/S mod easy to implement with relays.



Like this photo I here  Sorry I didn't finish the Input but you get the idea.  Just 1 channel mirrored on the second basically

Did I misunderstand? Or are you saying that is will not work PRR?
I get a lot of attenuation on the 1st stage.

Still wondering on the vibrating and humming ...


Thanks

Chuck

 

[emrr]

I've never seen vibration and hum on transformers like these.  In the PM660, it makes me wonder if you are well over the expected total current draw of the transformers, and that's where it's coming from.  But only the A-15 as output of signal amp. 

I have tried a few UTC mixing transformers (LS-15?), and found much greater loss and lesser quality sound, than with a semi-comparable single connection primary.  I imagine there are some differences in the wind, due to the target usage, but I don't know.  With transformers, things are somewhat universally interchangeable (hence the name), yet at the same time entirely dependent on the surroundings.  Many are pretty easy to screw up, in the interface aspect. 

 

[CJ]

Doh!  it just dawned on me after 5 years, the 670 A-33 shield cans,

since they use an output for an input, they have no mu cans, thus, the external can added.

  whats my iq? 

some people are a little slow, but they catch up sooner or ...





















































later.  :-X

 

[emrr]

There's a 1970's RCA piece that uses the A-24 backwards as an input; A-33 shields on that one too.  My IQ was right there with yours...........

 

[ChuckD]

So in your opinions would this work as I have drawn????  Let's assume I got the network correct as per the design

Chuck

 

[ChuckD]

Hello?

Could someone share some more wisdom n this?

I tried an Edcor 10K:600 as output of the PM660 signal amp and it reads 18db of gain which is expected.
I then tried an UTC A15 in the same spot wire as only 10K:500 basically the same. Only -1db is the output.

Why is there such a difference between Edcor and UTC in this particular circuit? I have never seen this before. Is there something special about the A-15? OR UTC in general?
Anyone out there with ideas? I want to use these UTC transformers.

Thanks

Chuck

 

[ChuckD]

I have tried a bunch of UTC transformers but none give anything above unity...  ???
For some reason the Edcors do?
The difference is way beyond what I would consider reasonable.
Can someone please explain why to me?

Chuck

 

[CJ]

strap 1 -3  and 4 -6 pri,
and 9-10 sec, , scope it, take two asprin and call me in the morning, i'm deep in the  middle of a utc ha 100 x secondary madness, 2250 turns each pie, foldback winding in case 8i don't wake up tomorrow,
with another ..wait, wrong thread!    ,

 

[ChuckD]

What ? That made no sense man

Chuck