What to build from a spare 1:1 transformer?

[somorastik]

Hi,

I have one spare 1:1 audio (probably line in) transformer.
What would you recomend building from it?

I was thinking maybe a passive DI:
http://www.nu9n.com/tx.html

http://www.engineeringradio.us/blog/2011/03/unbalanced-to-balanced-audio/

Or a stereo to mono converter:
http://brashleraudio.files.wordpress.com/2012/08/screenhunter_03-aug-27-19-35.gif


What would you do?

Thanks a lot for help!

 

[Di_Sousa]

You could build something like the ART DTI,
it's as isolation box. Its amazing tool, use it all the time

http://artproaudio.com/artcessories/audio_solutions/product/dti/

 

[Ego Tripper]

Passive direct boxes require a much higher ratio transformer-- in the range of 1:12 to 1:24. You're not just balancing the signal, you're also presenting the source with a higher impedance than the destination's input impedance (which is too low if the source is a guitar/bass and the load is a preamp input). However, you could go the other way and make yourself a re-amp box with that 1:1--
http://www.jensen-transformers.com/as/as092.pdf

Additionally, most active direct boxes utilize a transformer for isolation and if I recall correctly, sometimes it's a 1:1.

Also, Whoops has a good suggestion in making a balancing box. These are handy to have around the studio in a myriad of random situations. You can kludge one onto the output of a piece of unbalanced gear via a nice 6" TS patch cable to give yourself a balanced output. And you can accessorize that project by wiring up a Y-cable with a couple of series resistors like the left half of the crude stereo-to-mono converter in your last link to give yourself that capability as well.

And then there's a speaker-to-line box, great for taking a silent output from a tube amp for a guitarist that won't use a POD for a scratch track that you don't want bleeding onto another track. This schematic can be endlessly tweaked (e.g., add a switch to select different dummy load impedances or a speaker throughput jack, build in higher power handling)--
http://www.jensen-transformers.com/as/as061.pdf

P.S.:
I should add that the frequency response and level handling of your transformer will probably dictate one of these applications for which it's best suited.

 

[somorastik]

Ego Tripper, thank you for great suggestions!
Speaker to Line box sounds the best. Im thinking of building the schematic as is, and for J1 use aligator clips, which I can connect to any speaker.

I googled extensively for an active DI box with 1:1 transformer, but couldn't find any...

The only good thing I found is the DI, form diyfactory.com (link dead-use "Way Back Machine") and Bo Hansen DI box (which I am building two pieces), both use 1:4, 1:5 transformers.

Anyone have a better idea?