Preamp Noise with High-Efficiency Speakers

Worth seeing if changes in location of preamp (and associated ICs, especially if not shielded) relative to surrounding gear and any other electric gear, power cords or appliances results in any change in the buzz level. If so, take note of where noise level is minimal and use that to help identify what the external source of the noise might be. Repositioning gear alone might be a practical solution. The further each piece is away physically from each other and other potential noise sources, the better. Flourescent and halogen lighting as well as dimming devices are also often culprits for causing noise and interference with other devices, as are many digital devices and devices with large power transformers, like many power amps for example. Use of mu-metal sheets to provide additional isolation is another cost effective option to help in many cases. I use mu metal as an external barrier around my phono step up transformer device. Low level phono sections/gear are the most noticeably sensitive usually to external sources of noise.

No doubt very high sensitivity speakers like Avantegarde up the ante in terms of need for that feeding them to keep noise levels minimal.

Wow, lots of good suggestions on possible cause of, and solutions to, the noise problem. I personally had a problem with hum and buzz that came from a different source. Although my audio system and video system are separate, they share the same branch of power from the main panel. When my system seemed to suddenly develop a noise problem, I looked at the usual suspects and then tried something else. I cut the 75 ohm cable feed to the video system. That completely cured the problem. It appears that the cable feed managed to contaminate the power line even though the buzz/hum was not that big a deal with the video system (audio system is relatively high in efficiency, and thus, more susceptible to noise issues). Even though the entire video system was itself on a Furman power conditioner, the noise managed to infect the power feed to the audio system. I tried isolation transformers on the cable feed, but that did not work. The problem had to be cured by the cable company.

Yingtonggao, just set the input impedance of your FL100 to the max, which is 57kohm and feed your AMR DP-777 straight in and use it's volume control, which quote is a "Direct-Coupled Analogue Volume Control." No extra caps in the signal path.
This will be the most transparent/dynamic sound you will get PERIOD! As it is basiclly then a straight wire from the 777 to the fl100 then (no impedance mismatches). And you will have bags of gain left over still on the AMR's volume control.
If after that you still prefer an active preamp, then it's the colouration/distortion of it you like, which is a bandaid fix for something else that's wrong. Remember it is impossible for an active preamp to extract any more music than what is on the disc and being presented by your DP777, it can just add artificial things, as it does not make music itself.

Cheers George

Just got an email from the maker of the FL100 and your amp is also dc coupled. No caps in the signal path from your DP777 volume control all the way to the speakers, that is a big plus always.

If it sounds like white noise, then the signal to noise ratio on your preamp is not high enough to use with the AG horns. If it sounds like 50/60Hz harmonics, then it may be due to your power supply/transformer saturation/DC offset etc.
Finding high quality pre and power amps to run with ultra high efficiency speakers like the AGs is hard. I have a pair of Duos and run mine with TRON amplifiers (www.tron-electric.co.uk).
TRON amplifiers have been specifically designed to work with ultra high efficiency speakers. The designer, Graham Tricker, is the Uk distributor for Avantgarde and has a pair of Trios in his listening room. Ralph Cessaro uses TRON as his preferred amplifiers for his Liszt speakers.
TRON are distributed by Jeff Catalano at Highwater Sound in NYC. Thomas Woschnick (TW Acustic turntable designer) uses TRON for his own personal system.

If after that you still prefer an active preamp, then it's the colouration/distortion of it you like, which is a bandaid fix for something else that's wrong.

Its not a bandaid- an active line section can control an interconnect cable and reduce its artifact. A passive cannot.