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Unbalanced pre out to balanced amp in

I have a Modwright preamp with RCA outs and Channel Island amps with balanced inputs. I have always just made up cables with RCA outs and XLR connector inputs. But I have had to extend the distance between the amps and preamp and the new run has the cables going by a few power cords, a TV, an ethernet cable and other possible sources of noise. I would like to experiment with a transformer to convert the unbalanced output to balanced and then use 3 conductor cables for the run. Does anyone have any suggestions. And has anyone used a transformer they could recommend?

Thanks,
Mark.
regalma1
marakanetz's avatar
marakanetz
5,473 posts
 
thx,
that's what I mean and sometimes use to half the resistance.
almarg's avatar
almarg
8,673 posts
 
Ralph, I think Bob raises a valid concern. This is basically a 1:1 transformer, not a transformer with a significant step-down ratio (which would obviously be inappropriate for a line-level interface).

So while adding a 600 ohm resistor to the secondary would make the transformer perform better, it would very conceivably cause problems relative to the output stage of the preamp (or source component, if that is what it is used with). If the output impedance of the preamp or source component is a significant fraction of 600 ohms, and is not perfectly constant as a function of frequency, then a frequency response irregularity would be introduced. And, depending on its specific design, the output stage might be unhappy providing the current that a 600 ohm load would draw, as well.

Or are we missing something?

Regards,
-- Al
atmasphere's avatar
atmasphere
7,068 posts
 
The specs call for a source impedance maximum of 2Kohms. There are a lot of preamps that can do that, although some of them may have trouble making bass.

IMO/IME, you are better off with a step-down transformer, maybe 10K to 600 ohms. You loose some voltage gain, but a wider range of sources can drive it.

At the input of the amp could be another transformer that is 600 to 10K... then there would be no loss in gain. The bigger the step down/step up, the more transformer artifacts are introduced. That is one of the reasons I prefer to direct-couple :)
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