XLR to RCA to XLR

Hi Dbphd

Thanks for posting this thread. I may be facing a similar issue soon. I'm have a pair of KEF 104/2s and was able to score the 104/2 Kube for them. Nothing is hooked up at the moment due to renovations being done in my house. My amp and preamp combo have XLR inputs and outputs. I was going to put the Kube in the signal path between preamp and amp and use XLR adapters for at the preamp and amp sides. I hooked up a temporary system with the KEF Kube in place and heard a faint hum from my speakers. It was only when I was close to them though. I don't think the issue is you having a KEF Kube 102/2 with your 104/2s. It may just be the KEF Kube itself. I routed the AC Adapter and it cords as far away as I could from the unbalanced cables but there was still a hum.

Al. Many thanks for your contribution as well. Always very sage advice.

Would ferrite choke cores on the plug and umbilical cord ends help reduce the hum? I was thinking about putting choke cores near where the wires meet AC adapters as well where the umbilical cord plugs in along with where the 2 prong plug is.

Here are some pics of the KEF Kube. It looks the same for the 104/2, 102/2 and 103/3 speakers.

KEF Kube rear
http://img.2dehands.be/f/normal/120814494_3-kef-104-2-kube-inbegrepen.jpg

KEF Kube front
http://img.2dehands.be/f/normal/120814494_2-kef-104-2-kube-inbegrepen.jpg

KEF Kube AC Adapter
http://p2.la-img.com/236/423/197124_1_l.jpg

If the hum still persists I may just sell the KEF Kube.

Jedinite,

As I understand it, and my understanding may be incorrect, the use of a KUBE with the 104.2s is optional -- it only extends LF. In some applications, e.g. 107.2, the KUBE also tailors audio above the usual sub crossover. Thus, if you use a sub with your 104.2s, you may not need a KUBE.

The KEF museum is a treasure trove of information where you can download the installation instructions for the 104.2 as well as a nifty brochure that shows a cutaway of the speaker.

I have KEF 102s, 102.2s, 104.2s, and plan to buy 107.2s, so I've done lots of downloading and reading.

db

Jedinite, thanks very much. Regarding ferrites, they will not help a hum problem, as they are only effective at radio frequencies (and higher).

05-29-12: Dbphd
I used a female XLR to male RCA adapter into the KUBE from the XLR line out of a Cary 11a and a male RCA to male XLR adapter to the line into a Proceed Amp 3.

Most adapters of either type short the signal on XLR pin 3 to ground (pin 1). That is what should happen when adapting to an XLR input. However, IMO it makes absolutely no sense for XLR-female adapters, that would be used on outputs, to be designed that way. As I understand it, Cardas adapters are one of the few types that (correctly) do not short pin 3 to pin 1 on XLR female adapters.

This is just a speculative guess, for which I can't formulate a precise explanation, but if you are not using Cardas adapters I'm wondering if the noise may be somehow resulting from an inability by the Cary 11a to handle having its output on pin 3 shorted to ground. Many components can handle that ok, but some cannot, this being one example. I note that you referred to "a sizzle, a kind of HF hum," while the poster in that thread referred to "buzzing," those being descriptions that are not all that dissimilar. And I suspect that the fact that the short to ground is at the far end of the cable, at the input to the KUBE, may not be helping matters.

Does the noise still occur if the Cary is turned off or disconnected? Is it sensitive to the volume control setting?

Regards,
-- Al

Mine was the winning bid on a Model 102 KUBE to use with vintage KEF 102 speakers I use for center channel. I've arranged with Tvad to try his Jenson ISOMAX transformers in the loop. I'll report back.

db

Tvad's ISOMAX transformers arrived today. I tried them using the KEF Model 200 KUBE that had previously caused the sizzle. The result was flawless: Silence at the speaker, and, even though designed for use with a different speaker, the KUBE provided substantial LF extension. I played the Ondine SACD of Saint Seans 3rd symphony. Pedal notes that were inaudible with the unaided 104.2s became audible.

Had I known the KUBE was so effective, I would have looked for one tailored for the 104.2s. Anyone have a lead on a KUBE for KEF 107.2s?

db