Up for sale is the amp that introduced me to good sound. The Rudistor RP5.1 is pure magic with the HD650 and will perform excellently with many other cans as well. It's capable of driving both Hi and Low impedance headphones due to it's hybrid tube/Solid state design. The sound is dynamic and detailed thanks to Rudi's techniques used in the tube stage - it's silky and neutral with a deep soundstage. I compared the RP5.1 to the Burson Soloist and Woo Audio WA7 driving HD650's and the RP5.1 betters both of them to my ears. Alas, I've now moved on to LCD-2.3s though and can't afford to keep extra gear around - my HD650s have sold so now I need to unload the RP5.1.
The amp has an extremely handy gain knob on the back so you can easily adjust the gain depending on whether you're using high or low sensitivity headphones. Another neat features is a ground switch in the back.
Amp is class-A and comes with a pair of NOS 1971 GE Jan 6922 tubes, which have great detail. The amp sounds very involving and musical - it sucks you right in.
There's a screw missing on the lower right face plate, but I didn't bother with it since the faceplate is very secure. You can easily get a new one to replace it if you want. Only other cosmetic issues are some small scratches around the screw holes on the top plate and a small ding on the volume knob (neither of which you'll notice during regular use).
The Rudi RP5.1 is a rare sighting on head-fi, as most Rudi amps.
From an online professional review:
My first thoughts of this amp were a combination of amazement and enjoyment. The music it made was beautiful, dynamic, and full range. To sum things up in one word -- the RP5.1 just sounded right. In fact, it sounded so right that I stayed up that first night until four in the morning, swapping disc after disc to hear how some of my favorite recordings sounded when played through it. Oh yeah, this little amp was one of those unexpected, Christmas-gift surprises.
One of the rather amazing traits of the RP5.1 is just how lively its sound is. Headphone amps, especially tubed headphone amps, can sometimes sound rather slow, sluggish and boring. This is the antithesis of how the hybrid RP5.1 sounds. Listening session after listening session with the RP5.1 impressed me with how much enjoyment its lively and fast character brought. Terry Talbot’s guitar work on his and Barry McGuire’s album When Dinosaurs Walked the Earth [Sparrow TM-1001] had crispness and snap, and this created a realistic illusion that he was in the room playing. Again, each pluck of the strings sounded right, which is no mean feat at all. Many a headphone amp has failed to reproduce these notes with the proper amount of snap and attack, setting the RudiStor RP5.1 apart right away.
Edited by mojolo - 2/21/14 at 7:11pm