UTC O-2 Transformer

What can this transformer be best used for?

Same thing as an 0-1 with a P-P  center tapped secondary. So line/mic to tube grid(s) input. It is the same as the transformer used on the Urei 175B input as well as the UA 610 mic pre. So it was intended for a push-pull input configuration as opposed to a single grid input. But it can be used for either purpose.

Thanks for your reply.

Could it lend itself to a passive DI?

Yes, the 50K winding can go to the instrument and the low impedance line windings can go to the balanced output. The 'O' series is not huge, but it should be big enough for any passive pickup and many electronic devices such as keyboards and the like. It's rated at +8dBm, so it should be able to handle pretty hefty signals, but not for example a line level signal from a modern converter decoding a near full scale signal.

That's awesome!

If I'm reading this right, I'd take pins 1 and 5 to the balanced out? Would 3 be a ground?
Instrument connections would go to 6 and 7?

Is that right?

From my documentation, the instrument should go between pin 6 and pin 8. You could use pin 7 (the center tap) and pin 6 if you wanted 6dB lower gain and a lower impedance reflected to the high Z input, but in general, I think that's not such a good idea. Use the whole secondary… between pins 6 and 8.

The low impedance output can be between pin 1 and pin 5, but you could also use pin 2 and pin 4 if you want mike amp's impedance to be reflected to a higher value at the high Z coil (between pin 6 and 8). It's not clear that a typical mike amp's input impedance of 1500 ohms will be any more 'right or wrong' into the primary when wired for 200 ohms or 500 ohms. If in doubt, you could try pins 1-5 and also 2-4 and see what works out best of your purposes.

Best of luck!

Check this:

http://www.jensen-transformers.com/wp-content/uploads/2014/08/jt-db-e.pdf

The additional components are for capacitive loss over long cable runs like stage snakes.

*M.M.- thanks so much for your thoughts. I wired the instrument to 6 and 8 and wired the output to 1 and 5. Signal passes through, however there is a hum....  Any thoughts on where to wire an earth line?

*Pip- thanks for the link. Trying to figure it out.

Here is what it sounds like.

https://soundcloud.com/poiu-2/utc-0-2-di-test-1

There's no internal screen between windings on an O-2, but there is often a terminal marked with a ground symbol that is attached to the case. This should be connected to the XLR pin 1 of the low Z output, also connected  to the case of the DI.

There's also the issue of whether the high impedance coil should be referenced to ground or not. This is basically what the 'ground lift' switch does on a DI - it will either connect or disconnect pin 8 to ground. On a DI, the XLR pin 1 and the chassis should always be connected together, and this ground can optionally be connected to pin 8 or not with a ground lift switch.

Otherwise, there shouldn't be much hum if the wiring is neat and compact. Twisting the connections from the transformer to their connectors is also a good idea - the pin 6 and 8 connection should have their wires twisted from the transformer to the 1/4" jack and ground lift switch. Likewise, the pin 1 and pin 5 connections should have their wires twisted along the way to the XLR pin 2 and pin 3 connections.

UTC made a slip on mu metal shield for the O series, and this can help if you're unlucky enough to mount the transformer near a large power transformer for example. You should not need this normally, but they do exist and can be found occasionally.

*M.M.

Again, thank you for your insight.

The writing on the xformer is unfortunately quite worn away and Im not able to really read it.

I will wire 1 to the box itself and check in in a bit.

Thanks again

There are UTC catalogs with wiring diagrams all over the internet. 

Thanks to everyone for their help!

It works!