Hissing sound coming from tweeters

The speaker sensitivity is 101dB so you are going to need an amp with a very low noise floor to not get some hiss. As Joselm said, disconnect everything to determine if it is the amp noise floor or not. The amp certainly looks like it could be the weak link. If possible, borrow another amp to try. You probably do not need a lot of power for those speakers. The UPA-1 is 200 watts and has a gain of 32dB, which is a lot for 101 dB speakers. It is the entry level Emotiva which may just not be quiet enough for your very sensitive speakers.

To further elaborate on the test methods recommended when disconnecting the interconnects from the amp use shorting plugs at the amps inputs.

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What Dtc said

IMHO your amps are not an ideal match for your speakers. You have way too much gain and even though price does not always indicate quality you have a $3,500 preamp with $300 amplifiers. I think you need to pony up for an amp that is a better match; less power, less gain, higher quality.

To test it don't just power it up with the inputs disconnected, many amps will be noisy when run without inputs. You need some shorting plugs in the inputs then turn it on to see if it hisses by itself. Or disconnect the interconnects at the preamp and short the middle pin to the ring. Stuff a little aluminum foil in there or use a jumper with clips.

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Looks like the amps had been designed with insufficient feedback making them unstable and hiss the tweeters.

Thanks for all the helpful information. I'm at work right now, but when I get home tonight I will disconnect the amps from the pre-amp to determine if this is just a noise floor issue. I understand that the Ayre pre-amp might not pair well with the cheap Emotivas, or maybe the Emotivas have too much gain for my sensitive Klipsch speakers. Once the music is on you dont hear the hiss and it sounds amazing. The hiss is most annoying when you're trying to watch a blu-ray during a quiet scene.

@Herman: In this hobby you can't always afford to buy all the nice gear in one purchase. I just picked up the Ayre and will be looking to upgrade my mono amps in the future. I am 25 years old and my system is a work in progress.