small transformers w/ 4 secondaries

[computerjones]

hi folks.  i got a bunch of transformers that are the small audio type.  i was looking thru many transformer schematics (octiva, and brethren) and they all have 3 secondaries, not 4.  im wondering if anyone has encountered this type of transformer, and if i can use it somehow.  i was thinking of tying the 2 center taps together to form the "middle", but im unsure if this will work well enough.  any advice is appreciated, as well as any other suggestions of what can be done with these (that cant be done with the 3 lead type).  thanks for your time.

[niftydog]

It all depends.

You probably can connect up two wires and have a centre tapped transformer... but you've gotta get the right wires!

You also may want to keep them separate for some reason.

Are there any specs or drawings on the transformers?  I'm guessing they're balancing transformers.

[computerjones]

yes they are balancing transformers, but i only know this from the context of where i got them.  i am not familiar with balancing transformers, and their uses.  could you point me to more info on this subject?  i assume this is for something like a balanced line in/out of a mixer and such?
thanks for the quick responce

[niftydog]

Yes, you're on the right track.  A balancing transformer takes a single, unbalanced signal and creates two signals 180 degrees out of phase with each other.  Hence, the three wires.

Centre tap is "common."  A signal that is essentially identical to the input comes out of one wire, and a 180 degree phase shifted signal comes out the other wire.

try this;

http://www.epanorama.net/documents/groundloop/audio_isolators.html

They can be used for ground loop isolation.  You could use either winding, or you could wire them together in phase.  (as opposed to out of phase for balancing!)

[computerjones]

yes im somewhat familiar with balancing, but im still confused as to where the 4th wire comes into play?  maybe im missing the point, but with balanced you have +, -, and ground, and with unbalanced you just have +, and gnd.  therefore a 2 primary, 3 secondary transformer is used.  now with these 4 secondary jobbies.....
is there some advantage over the 3 sec?

[niftydog]

with these 4 secondary jobbies.....
is there some advantage over the 3 sec?

well in your case yes!  I would say that in most cases, a 3 wire transformer is simply a 4 wire one, with two wires connected together.

Either one can be used for isolation.  But the four wire one allows you to wire both secondaries in phase.  This might make for better reflected impedance on the primary side or a more efficient transfer.  Or, you could use it to split the signal AND isolate them.

So not only is the input isolated from the output, but the first output is isolated from the second output!

[computerjones]

ahh makes sence now.  i found an interesting scheme on an hifi recording diy type site.
http://www.gyraf.dk/gy_pd/pultec/gy_pd_sch.gif
an interesting way to wire up the transformer for the balanced input.  i wonder if there is some real guitar possibility here?  isolating 2 amps?  strange octave up?  ring modulator?

thanks for the help!