17' unbalanced cable v balanced with ISOMAX


I recently bought a pair of KEF 107/2s designed to be used with a 107/2 KUBE, an active crossover with equalization. The KUBE has only RCA connectors. I've been using 17' Blue Jeans balanced lines from a Cary 11a processor to a Proceed Amp 3, and can continue to do so if I use Jensen ISOMAX transformers at the amps to transition from XLR to RCA. Without the ISOMAX the XLR/RCA transition introduces an audible sizzle to an otherwise inaudible noise floor.

A 17' unbalanced Blue Jeans LC-1 cable would eliminate the need for ISOMAX transformers and be a neater setup, but I don't want to sacrifice audio quality or add noise.

Advice, comments, recommendations please.

db
dbphd

Showing 2 responses by almarg

DB, although I recall our recent related discussion, I'm not sure I understand your question. It seems apparent that you are asking about changing the connections between the outputs of the KUBE and the inputs to the Proceed to unbalanced LC-1 RCA cables, but I don't follow your description of the present configuration, that you would be changing from.

In any event, I suspect that the answer will be that there are too many variables and unknowns to be able to predict how well the long RCA cables would work, with respect to either noise or sonics.

Regards,
-- Al
Thanks for the clarification, DB. What had particularly confused me was the reference to "Jensen ISOMAX transformers at the amps to transition from XLR to RCA," but I see now that you meant physically near the amps, not electrically connected to the amps.

As I said, though, I don't think the results of a long unbalanced connection can be predicted with confidence. Among many other variables and unknowns that are involved, one important one would be the relative sonic quality of the balanced and unbalanced outputs of the Cary. Per my comments in the other thread, though, it seems conceivable to me that the reason for the noise you heard when you tried using XLR-to-RCA adapters at the KUBE inputs may have been that the adapters shorted the signals on pin 3 of the XLR connectors to ground. A direct RCA-to-RCA connection therefore MIGHT not have that noise issue.

Also, the fact that the KUBE's power supply has a two-prong power plug reduces the likelihood that noise would be an issue, because a ground loop via AC safety ground wiring would not exist (ground loops can cause high frequency buzz, as well as low frequency hum). The likelihood of ground loop issues between interconnected components having 3-prong power plugs increases if the cables connecting them are long and unbalanced.

Regards,
-- Al