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ryansupak 19th December 2012 04:20 AM

How to wire up Audio Matching Transformer?
Hi, I've got some 600:600 Audio Matching Transformers that I'm hoping to use in a project (a mixer).

Here is the diagram printed on the item:

(Pri 600)      (Sec 600)
Pin 1 ---+ | +--- Pin 4
        | | |
        | | |
        | | |
Pin 2 ---+ | +--- Pin 5
        Pin 3 (C.T.)

I've wired one into an audio channel. I have the input wired to Pin 1 and the output wired to Pin 4. I have the ground for both the input and the output wired to Pin 3.

I can hear sound clearly coming through, but it is attenuated quite a lot, and it sounds like it is going through a high-pass filter. I have learned that many transformers are designed to filter out certain frequencies, but this is not noted anywhere on the transformer itself, or in any specifications I can find for it.

Have I got something wired incorrectly? I've searched for a clear explanation of this with no luck.

gmphadte 19th December 2012 04:46 AM

Show the product details so that someone can help you.

Gajanan Phadte

ryansupak 19th December 2012 04:50 AM

The product is:

No data I have found on transformers in this series refers to frequency filtering. This "lack of information" and the diagram on the transformer itself which I have reproduced above, is all the information that I have been able to find.


DF96 19th December 2012 10:21 AM

Pin 2 and pin 5 need to be connected too! Without them, all you get is a tiny bit of capacitive coupling.

Note that this transformer is intended for 600 ohm circuits, so it is unlikely to work too well at other impedances.

sreten 19th December 2012 02:05 PM


According to your pin out input is between 1&2, output between 4&5,
3 is overall screen. You can float the input (usually) or the output.
Floating the inputs will prevent earth loops (hum) developing.

Make sure you don't wire them to be phase inverting, you can
get signal cancellations if you do and start mixing the outputs.

rgds, sreten.

Can't make out the very murky picture on e-bay :

ryansupak 19th December 2012 02:28 PM

Thanks for the help folks.

For some reason I had the idea that connecting one input and one output was sufficient, though now I understand that was incorrect.

I tried floating the input but without its ground wired to the CT, I was getting lots of hum.

Another question: My understanding is that the output pins will be phase-inverted from each other. My circuit is not a balanced circuit, so I'm thinking I'll only need one or the other of the outputs. Should I ground the other one, or tie them together?

Thanks again for any help on these extremely basic questions.


DF96 19th December 2012 04:56 PM

Both the input and the output require both pins to be used - see post 5 (based on your own diagram in post 1). How you use them (floating balanced or one side grounded) is up to you.

Why are you using a transformer, as you appear not to understand what it does?

sreten 19th December 2012 07:06 PM


If you can't float the input with no hum, your doing something wrong.

There is no reason to wire it as phase inverting, as in my warning.

As DF96 states, why are you using them and for what purpose ?

If there is no problem to fix, 1:1 transformers have no useful purpose.

rgds, sreten.

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