jensen 123-s 1:2 and 1:1

I have a pair of je-123-s transformers I am going to use as the outputs for a rack of auditronics 110 input modules. these are the original transformers from the console. They came from the factory wired for 1:2 operation. I was going to have a switch to change between 1:2 and 1:1 operation but: the jensen schematics say 1:1 = primaries parallel/secodaries parallel. The Auditronics schematic says 1:1 = primaries series/secondaries series. So it operates in 1:1 with primaries series/secondaries series and primaries parallel/secodaries parallel? whats the difference? they are both 150:600, no? Im sure this is super basic transformer theory, thanks for being patient!
-Ben

The Jensen JE-123 is a quad-filar wound output transformer. It has four equal windings. Therefore, if you use two windings for the primary and two for the secondary and connect both primaries and secondaries the same way (i.e series:series, or parallelarallel) then you will wind up with a 1:1 ratio. These would not result in 150:600 impedance ratio (that would require a 1:2 turns ratio, not 1:1)

Basically, square the secondary of the turns ratio to find the multiplier for the impedance ratio. So a 1:2 turns ratio would have a multiplier of 4 (the square of 2) and then multiply this by the primary impedance (so 150 ohm input impedance x 4 would result in a 600 ohm output = 1:2 ratio).

In theory a 1:1 ratio doesn't change level or impedance.

If you want a 1:2 ratio with a JE-123, I suggest connecting it like api does their quad-filar wound output by using a single winding for the primary and two other windings in series for the secondary. The remaining winding is unused.

JC

thanks, that makes sense. I'll probably leave the secondaries in series and have a switch to change the the primaries to series or parallel.

[quote author="rascalseven"] These would not result in 150:600 impedance ratio (that would require a 1:2 turns ratio, not 1:1)[/quote]
right - meant 600:600 too many numbers.

thanks, Ben

A detail that was not really clarified here in the previous posts, but I think it is correct to say.. 

Yes, the 1:1 relationship is correct whether the primaries and secondaries are wired in parallel or series configuration, BUT..
That's not to say these configurations are equal to each other.

Parallel 1:1 will give 150:150 ohms
Series 1:1 will give 600:600 ohms

Right?

My question is, will it change the frequency response (or other significant characteristics) to combine parallel and series connections for either step-up or step-down applications?
eg.
Parallel primary to Series secondary?  (150:600 ohms)
or
Series primary to Parallel scondary?  (600:150 ohms)

I'm wondering about this because I want to use a Jensen 123-S for the output stage of a DIY 1176 (MNATS Rev J) project, where the output transformer type B-11148 is normally configured 1:2 for 150:600 ohms.

Thanks!
Evan

The transformer impedance is something not so simple, they aren't 150Ω, they are designed to work in a 150Ω network...

For example, loaded with 600Ω and in 1:2 configuration the source (before the tx) will see 600Ω but if the same configuration is loaded by 1.2k the source will see 300Ω.

150Ω and 600Ω are the impedance to work at which it will work as said in the datasheet, so if driven by a 150Ω resistor -3dB point will be where datasheet express it.

1176 output has much lower impedance so it will be working fine with any of this configurations, if it's going to be working in a modern setup which all inputs are around 10K 600:600 (both in series) will be ok, will eat less current and have lower THD. If it may work with old stuff wich input are 600Ω or sometimes less 150:150 would be more apropiate (both in parallel) to have better LF response, but not ussual with jensen because they are rated to really low freq. If you need 1:2 not much to discuss, I'd use parallel:series in order to reduce primary DCR but not a big deal to use a single one at the input and 2 in series at output, API uses the last winding for meter IIRC.

JS

joaquins said:

The transformer impedance is something not so simple.....
JS

Click to expand...

Thank you for this informative detailed response!  Really much appreciated.
It shall be interesting to test the transformers I have here and hear the results in practice!
Cheers,

Evan.

The Sphere output trafo #7393 is really a JE-123sl  (source David Geren).  Sphere desks hook these up series/series 1:1.
I would try this arrangement first on your 110 modules.

Best

GARY