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Zero Cool 20th February 2007 11:50 AM

Dual transformer polarity/wiring
I need to replace the transformer in a device and i am wondering about the best wire to wire two transformers for lowest noise.

Both transformers are the same brand model, and both have a single secondary winding. I need to wire the transformers together to develop a center tap.

Is is best to wire the transformers to that the Primaries are in parrallel 1 to 1 and 2 to 2 and then wire the secondaries in series. 1-2+1-2

or would it be better to wire the primaries with opposite polarity and then wire the secondaries to match?

1 to 2 and 2 to 1 on the primary side. then wire 1-2+2-1 on the seconday side?

Which way would be the lowest noise??


BWRX 20th February 2007 02:36 PM

It's probably best to just wire the primaries in parallel and the secondaries in series.

KBK 24th February 2007 04:18 PM

See if you can place the two transformers so that their fields overlay or overlap, so they are in the same magnetic field (observing polarity). This will work best. It can be done, just be careful. There was a thread on that recently. Heat and noise will be the result if done wrong (incorrect orientation), you will be aware of this immediately. In seconds.

AndrewT 24th February 2007 05:58 PM

if you put the primary and the secondary connections through a terminal strip you will be able to change between the two options and listen for any changes.

Remember that light bulb before you switch on.

XEAGLEKEEPER 28th February 2007 11:30 PM

I would think primaries in parallel(in phase) secondaries in series.:)
READ THIS !!!!;)

AndrewT 1st March 2007 06:51 AM

Hi Eagle,
that does not help us.
He is asking what is better. To connect the two transformer primaries out of phase with the secondaries also wired out of phase to give the correct output
wire the primaries (two transformers) in phase and wire the secondaries in phase to achieve correct output.

Which sounds better?

AMV8 1st March 2007 12:24 PM


I have tried both ways in the past. Wiring the primaries in parallel and the secondaries in series worked. Wiring your second option did not produce good results.
I rang the transformer manufacturer - I think it was Avel Lindberg - it was I just checked - they said only use your initial suggestion as the other would may/would cause heating of the transformer. I think I did detect heating in mine but I blew a fuse in the transformer at that point ( I connected the wrong primary ) and never tried anything else as I already had a working system.

It is currently being used on an Aleph amp delivering 2 amps at 28v from a 130va transformer. It seems happy and quiet.


Zero Cool 1st March 2007 03:48 PM

Well I have tried both ways and in this particular device i can detect no difference in sound quality of transformer temp.

I think that because the transformers are about 1" apart that there isnt sufficient magnetic coupling to cause heating.

This is a pro audio EQ and maybe this circuit just doesnt let me hear the differences well enough. A-B'ing the wiring seems to make no audible difference in noise, or sound quality. I think thta is it s poor circuit to begin with and any differences are masked by the poor circuit.

My thoughts were that if the primaries were wired out of phase then any incoming noise would be canceled. Power line noise rejection to me is most important as this will be used in many places with bad power.


AndrewT 1st March 2007 07:38 PM


if the primaries were wired out of phase then any incoming noise would be canceled.
I don't think so.

XEAGLEKEEPER 1st March 2007 11:10 PM

if the primaries were wired out of phase then any incoming noise would be canceled.
Two transformers---primaries paralleled(in phase)--secondaries in series(in phase) 1---2+1---2

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