output impedence and pseudo balancing

[buschfsu]

ive been reading on how to balance using impeadance matching for direct outs without transformers. sounds good and cheap.

question is how do i determine the output impeadance of say a pm1k so i can throw the proper resister on pin 3 of my output xlr. thereby getting some balanced benefits without a transformer?

thanks

 

[NewYorkDave]

sounds good and cheap

Well, it's cheap. The "good" part is debatable. It can have some advantages when designed-in to a new piece of equipment, but attempting to tack it on to an existing unit does not necessarily yield improvement.

Sticking that resistor in the low side reduces your output level to some extent and also doubles your output impedance, which can outweigh whatever advantages you might be getting from a more-or-less balanced source impedance.

Don't automatically assume that you must have a balanced or quasi-balanced output. In smaller installations--which describes what most people here are operating--unbalanced interconnections, done with care, can work just fine. And balanced inputs work fine with unbalanced outputs.

 

[clintrubber]

[quote author="buschfsu"]question is how do i determine the output impeadance of say a pm1k[/quote]

A method:
http://www.jensentransformers.com/as/as048.pdf

 

[buschfsu]

thanks for your input. as for the application, it will be going into a balance input of a soundcard (emu 1820m) which has a 10k input impeadance if i recall.

my rack is pretty tall and these modules will be at the top. this means cable runs that may go past pwr xformers. (i try to keep signal on one side and ac mains on the other but sometimes...)

i guess i have to just try and see. im thinking of a switch that would either float pin 3 or put a resistor to ground. ill post the result.