Hissing sound coming from tweeters

Sounds like it could be a ground loop issue.

You should try cheater plugs on the power cables. These are the 3 prong to 2 prong adapters found at hardware stores. Cheap and easy to try.

I keep a CleanBox II around to try to detect ground loops. It lifts the ground on the cables (source to pre or pre to amp) to eliminate ground loops. It takes a 1/4" TRS jack, so you will need either balanced or singled ended XLR/RCA to TRS adapters or cables (Monoprice has XLR to TRS cables). Since you have mono blocks you could do one side at a time, meaning fewer adapters to buy. It is not a long term solution, but it can help identify if there is a ground loop carried by the ground. CleanBox II is $35 to $55 depending on where you get it. Alternatively, if you can make cables, you can try making either RCA or balanced ones with the ground not connected, as a test.

Do you have any other pre-amp or amp you can test to see if you still have the hum issue? So, the Ayre with another amp or another pre with the Emotiva?

Pre / Power amp impedance mismatch?

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