Hissing sound coming from tweeters

12-28-11: Magfan
Pre / Power amp impedance mismatch?

No. Preamp output impedance is 31 ohms/62 ohms unbalanced/balanced (per JA); power amp input impedance is 23.5K/33K (per mfr). No problem.

Best regards,
-- Al

The RCA cables were actually emitting a humming noise when I connected them in place of the XLR's. They have never done that before. I don't have any other amps to put in place of the monos. I know somone with McIntosh MC-501's mono blocks that are hooked up to Klipsch Chorus II, but they are too much work to bring over to my place. I wonder if any Mcintosh power amps would work well with the Ayre?

The attenuators might be worth a try. I have never heard of them, but it sounds like they would reduce the hiss. Are there any ill effects from using the attenuators?

Are there any ill effects from using the attenuators?

A lot of people are happy with them, but there have been some reports of adverse effects on dynamics, etc. I suspect that they would do fine when driven from a component having very low output impedance, such as your Ayre preamp, and assuming that the input impedance of the amp does not vary significantly as a function of frequency (which I would expect to be the case).

I wonder if any Mcintosh power amps would work well with the Ayre?

The key thing is that you want an amp having significantly lower gain than your present amp. More often than not that will correlate with having a lower maximum power rating than your present amp. The MC501 is an exception, though, having greater power capability but significantly lower gain. See JA's measurements.

The hum you are now hearing with rca's is most likely due to a ground loop problem, assuming that the interconnects are not running close to and in parallel with any power cords. I suspect that if you are hearing just hiss and not hum with the xlr's that the hiss is not being caused by ground loop issues, but you can verify that by using cheater plugs as DTC suggested. As I had indicated, xlr interfaces are inherently less susceptible to ground loop issues than rca interfaces, at least if they are well implemented.

Regards,
-- Al

Well it looks like I'm stuck with the hiss for now. It won't cause any damage to my equipment right? I'm going to keep my eyes out for another power amp though. Considering the Mcintosh MC252 if I can find one for the right price.

No, the hiss won't cause any damage.

The MC252 will reduce the 32db gain of your present amp to roughly around 23db, according to my calculations. Not sure that will be enough of a reduction to be satisfactory. Also, using a 250 watt amp with 101db speakers most likely means that you will be paying for a lot of watts that you'll never use, unless you are envisioning going to less efficient speakers in the future.

Regards,
-- Al