XLR to RCA to XLR


I decided to try the KUBE (KEF's equalizer) with KEF R104.2s in a balanced system. By careful routing of cables my system is silent to an ear at the speaker. But the KUBE has only RCA connectors, and adding it to my system introduced a sizzle, a kind of HF hum. I removed the KUBE, and silence returned. Is there any way of going from XLR to RCA that might avoid the noise?

Balanced lines (about 15') run from a Cary 11a processor to a Proceed Amp 3 that sits near the R104.2s. The third line to the center speaker did not run through the KUBE and thus remained balanced.

db
Ag insider logo xs@2xdbphd
Hi Dbphd,

FWIW, I had the same problem running from my SE preamp to XLR only amp. I ended up trying a Sablon Audio interconnect (specially terminated RCA-XLR), and i went back to silent. the designer said it could have been luck. (I have Transparent Audio Ref in the rest of my system). sablonaudio.com

BTW, excellent cables in the upper TA league. 30-day trial period.
Assuming that the KUBE is connected between the processor and the amp, and if it has a 3-prong AC power plug, chances are that the noise is being caused by a ground loop between the KUBE and one or both of the other two components.

To verify that, temporarily isolate the AC safety ground pin on the KUBE's power plug by connecting it via a 3-prong to 2-prong adapter (a "cheater" plug), with the adapter's ground lug or ground wire left unconnected.

That will break any ground loops between the KUBE and the components it is connected to. If that eliminates the noise, remove the adapter from the KUBE's plug and use it on the plugs of each of the other two components, one at a time. That will enable you to determine which interconnection is causing the problematic ground loop (although the answer might be both).

Post back your results, and also see the following references:

http://www.jensen-transformers.com/an/an003.pdf.

http://www.jensen-transformers.com/an/an004.pdf.

Also, if you are connecting the KUBE to the power amp by means of an unbalanced RCA cable followed by an RCA-female to XLR-male adapter at the amp's input, you may be able to improve the noise by instead using an RCA-male to XLR-male adapter at the KUBE's output followed by a balanced XLR cable. That would be electrically equivalent to the approach shown in Figure 2.1 of the first reference. Although as indicated in the reference that approach is less ideal than a well implemented transformer-based approach.

Regards,
-- Al
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