Hissing sound coming from tweeters

I'm beginning to think that the Ayre just doesn't pair well with my amps.

Given the findings you've described, I suspect that you're right. When you connect the cables to the preamp, you are introducing the possibility of ground loop-related noise, but I would expect the xlr connections to be much less susceptible to that than the rca connections, and you are saying that the results are fairly similar either way.

So even though the noise performance of the Ayre preamp is probably very good (I note that John Atkinson describes the noise performance of the presumably similar K5-xeMP as "superb"), the little bit of noise it generates in the circuitry that follows the volume control is being boosted to bothersome levels by the combination of the high gain of the amp and the high sensitivity of the speakers.

The only solution that occurs to me other than replacing the amps or the speakers would be to put in-line attenuators at the inputs to the amps. The Rothwell's, which are available in both balanced and unbalanced form, are an example, although the 10db of attenuation they provide might not be as much as you would want. I believe some others are available that provide 20db or thereabouts, but I'm not sure if they are available in balanced as well as unbalanced form.

Regards,
-- Al

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?