Mic Splitter with Haufe RK284 transformers

Hi!

I bought those transformers to build microphone splitters (to connect my recording system on a P.A. patch, in order to record the sources that are on stage).

The technical document about this transformer can be seen here :
http://audio.kubarth.com/rundfunk/index.cgi
Type "ctrl+F" and search "RK284" to find the link called "HAUFE RK284" (i'm sorry, the direct link to the .pdf file doesn't work...)

I'd like to have a direct output connected directly on the input, to give the signal to the P.A. system, and to have an isolated output for my recording system. So i'll only use one circuit of the transformer.

What i thought was to connect the primary to the input (2-3 of the "input" XLR connected to 5-6 of the transformer) and the secondary to the isolated output (2-3 of the "isolated output" XLR connected to 1-2 or 3-4 of the transformer).

My problem then is : what should i do with the ground? should i connect pin 1 of both input and output to pin 7 of the transformer? if i do that, am i still isolated of the P.A. system?

Thanx in advance for answers, and have a nice day!

thanx for answering so quickly!

what do you mean by "terminate unused secundaries"?

hi!

i finally drew a scheme :
http://insidecircus.free.fr/schema_splitter.gif

i also put the documentation of the transfos on my ftp for an easier access :
http://insidecircus.free.fr/haufe_rk284.pdf

I'm wondering if i can suppress the red connexion, like this the direct output would be exactly like if the splitters were a cable, totally separated to the isolated output. If you have any other remarks, don't hesitate!

have a nice evening!

eric

I'd rather wire the secondary windings in series. Eliminates the resistor and gives 6 dB more level.

Check the Jensen Transformers website for some good technical papers on passive splitter design. IIRC it will answer your Qs regarding grounding.

Samuel

i found this interesting document about jensen splitters :
http://insidecircus.free.fr/jensen_splitters.pdf

i got inspired from it and redraw my scheme :
http://insidecircus.free.fr/schema_splitter_v2.gif

there are a few differences between my scheme and the one in the end of the jensen's one :

- there is no individual shield for each of the 3 windings of the haufe transformer, so i deleted those connexion. the global shield of the haufe transformer is linked directly to the earth.

- i don't like the idea of wiring channel 1's pin 1 to the ground, because this would link the P.A.'s ground directly to mine if i don't lift every grounds of the output. i prefer the solution of doing an intentionnal ground connexion (with a cable connected to the mains ground), as described in the 2.3.1 part of the jensen document.

does it seem ok?

thank you all for your help.

-> kubi : as i only want one isolated output, i think samuel's idea idea good!

thanx

Does it seem OK?

Click to expand...

You forgot to show the Faraday shield in the drawing. I think that should go to "Isolated Out", pin 1. Otherwise it looks fine.

Samuel

by "faraday shield", do you mean the case, connected to the ground?

By "Faraday shield", do you mean the case, connected to the ground?

Click to expand...

No, the Faraday screen is the static screen between the windings, pin 7. Very important to get good CMRR/isolation and must be grounded in any case.

[Edit: I didn't read the datasheet well--pin 7 is both Faraday shield and case, so all is well. I was confused as your drawing doesn't show the Faraday screen. It's common to draw it as it makes quite a difference if a transformer has one or not.]

@Darius: he just want's a 2 way split--one direct out and one isolated. Such as this one: mbc.pdf

Samuel

You are better off terminating all the shields at the transformer and lifting all the shields at the final connectors of the isolated outs. You will never need to tie the shield from the iso out to the record rig, so don't waste any time on a bunch of lift switches.