Electronics > Projects, Designs, and Technical Stuff
balanced to unbalanced audio conversion
veedub565:
I have an old military HF radio with 600ohm balanced audio in/out that I need to connect to the PC.
Actually the 600ohm transformer board is an option that is fitted. (Diagram is attached). I need to connect "aux in" and "line out" to the pc soundcard
As far as I can work out I have two options
1) use another set of transformers to convert balanced to unbalanced. So unbalanced soundcard output, convert to balanced, into the radio... where it is converted back to unbalanced again by the optional transformer board.
2) ditch the optional 600ohm balanced transformer board, and then its just easy unbalanced to unbalanced. It would probably still need a 1:1 isolating transformer though.
Option 2 seems the simplest. Does this seem a reasonable plan?
I'm not sure about impedances, not sure what the normal line in/out impedence is on a soundcard. I guess with a isolating transformer in play then it doesn't matter too much?
The specs for the radio say -16 to +10dBm is an acceptable level range.
flynwill:
I would probably start by just connecting it directly to the sound card, in both cases just use one wire of the balanced pair plus the grounded center-tap. You might need to add an attenuator between the line-out and your sound card to prevent the output from driving your sound card's input into clipping. In the other direction you may need to crank up the gain on the HF radio's input to get enough level.
veedub565:
Thanks, I will give that a try. So I can just use one leg and centre of the balanced input?
themadhippy:
cheapest/simplest/most comon way is to connect one of the balanced legs to the center tap for ground and the other balanced leg as signal,
David Hess:
The transformer isolated balanced outputs and inputs will happily interface with balanced or unbalanced lines.
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