Perth Australia
Auditioned the Audio Research LS17 Class A Vacuum Tube Preamp against Musical Fidelity KWP [both run in with at least 100hrs], T+A R1230 and later against my own Pass Labs X2.5, and Bryston BP25 pre amps over a 3 hour period. The winner was clearly the Arc LS17 as it is so musical, well balanced and had an authorative bottom end that was lacking vastly in the KWP. It really takes you into the music, foot tapping style. The KWP has a greater soundstage and a louder lovely top end but lacking lower mid and especially bottom end resulting in a lifeless expression, poor rythem / foundation against all above pre amps tested.

Strenght: Faboulous touch of that more realistic tube endorsed sound,great overall balance, really good rythem and timing, lovely detail and 3 dimensional delivery. Takes the edge out of sharp sounds on Electrostat and Ribbon speakers, Twin XLR and one single ended output and nice remote control. Low heat output and 30kg lighter than the twin chassis KWP preamp.

Weaknesses: Shame the styling is so dated and plain looking, no balance controls and high price.

Amps Used: T+A 1530 180W, Threshold A200 class A 100W, Brytston 4BSST 300W. Speakers were PMC 3 way towers, Ambience Grand Reference 1800 hybrid ribbons and Apogee Centour minors.