UTC A-21 Wiring

[dukeofearl]

I ended up with a pair of these transformers with some other things I bought and thought I'd wire up a color box to pass line signal through for mixing etc. I was hoping someone could tell me the best way to wire it. I don't think I'll ever fully grasp impedance, but I can definitely solder something this simple.

I inspected photos of one someone else had done and it looked like the following, but it was a little hard to see (and could be wrong) so I thought I'd double check here. Thanks!

2: input +
3: input -
4: output +
5: output -
shields to ground terminal

 

[Murdock]

For „normal“use I would connect it as follows:
1: input +
3: input -
4: output +
6: output -
It seems it doesn’t have a shield terminal. But if so, then yes, to ground.

But if you want to get more distortion or bass roll of you can connect it as you wrote.
I would say try both and look what you like more.
Even „better“ would be a switch to choose between all three options (500, 200 and 50 Ohm).

 

[dukeofearl]

Great thanks, a switch is a good idea. Correct me if I'm wrong - the option you sent would be for 500 ohms.

Then for 200 ohms:
1: input +
2: input -
4: output +
5: output -

and for 50 ohms:
2: input +
3: input -
5: output +
6: output -

 

[Murdock]

Correct

 

[CJ]

The lower the impedance, the lower the turns which means the core will be getting hit with more flux which means the core will saturate at a lower voltage input assuming that you ever get to that point.

The 50 ohm input scenario might drop your input level depending on how stiff your source is.

 

[dukeofearl]

this leads to one more question. what type of switch? i guess you'd need one for input and one for output? a switch that has one balanced input and three balanced outputs.

or is there some kind of switch that would switch between three separate balanced input/output options?

 

[Murdock]

If I’m not mistaken you should use a 4 pole 3 position switch.
1. pole -> input +
2. pole -> input -
3. pole -> output +
4. pole -> output -

It’s best to draw it to understand. Look for a diagram of such switch.

That is, if you want to maintain a ratio of 1:1.
If you want to play with different ratios you probably want two switches. One for the primary and one for the secondary.

 

[dukeofearl]

Surprisingly confusing to wrap my head around these switches. I think I've figured out what it would look like if I had two switches, one for input and one for output. Two DP3T switches I think would work like what I drew here.

 

[Murdock]

I can understand. It can get quite confusing with switches.
Look at this diagram of a 4 pole 3 position switch


13, 14, 15 and 16 are input +, input -, output + and output - respectively.
First position is drawn. Look at the rectangles at the positions 1, 4, 7 and 10. This means that is where the “wiper contact” is at this switch position.
Now for 500 ohm you connect contact 1 of the switch to terminal 1 of the transformer.
Contact 4 to terminal 3.
Contact 7 to terminal 4.
Contact 10 to terminal 6.
Try to route the other position/switch contacts for 200 and 50 ohm.

That is for one transformer. As you want it for stereo use, you need a 2 deck, 4 poles per deck, 3 position switch.

 

[dukeofearl]

thanks - i'll have to spend a fair amount of time staring at this!