I apologize for taking so long to weigh in on the not-so-recent mini meet. Here's my take on the proceedings before my memories of the occasion dematerialize as surely as those tangy sourdough loaves.
My first impression of the RudiStor RP6-DQ, after I received it from its previous owner, was of its vivid soundstage. On that occasion, a very brief encounter, it was being fed from my MSB LinkDAC III. Compared with the AudioValve RKV that normally amplifies the LinkDAC's output, the Rudi added extra width to my Sennheiser HD600's presentation and even managed to make my AKG K501s sound two dimensional. (Note to Romanee -- I do have a second pair of HD600s, with Oehlbach cables.
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The ex-Ray X-Ray arrived after the Rudi, so the meet was the first time I had heard them together. (Neither is part of my regular home setup.) The combination confirmed what I had noted earlier, while the meet provided the opportunity to audition the amp with Oski's DT880/Highflyin9, Romanee's well-worn K501s, my HD600/Blue Dragon and HD650/Equinox, and Lan's SA-5000s. It was soon apparent that the RP6 has the ability to make a wide assortment of headphones sound great. It has strong bass and extended, but delicate, treble. I believe that this attention to the frequency extremes, rather than the midrange so often associated with tube amplification, is what gives the RP6 its extraordinary ambience retrieval. Reverberation and reflection artifacts were presented in abundant detail, making it so much easier to imagine the recording space. This was particularly apparent with the album "Deep River" by Cantus, recorded by John Atkinson in a lushly reverberant hall. The RP6 midrange is liquid but not prominent, so it didn't "lift the Sennheiser veil" in the same way that my Perreaux SXH1 does, for instance. This isn't a problem in my view: when you're basking in the glorious hall sound, it doesn't matter if you're not sitting in the front row. Like many of Rudi's designs, the RP6 has tube voltage amplification followed by a solid state high current output stage.
The RP6 was specifically designed for Qualias but lacking the real thing, we had to make do with the SA-5000s. Up until this meet, I was a Sony virgin, so I have nothing with which to compare the RP6. Based on the comments of others, I expected the SA5k to sound ultra-detailed to the point of irritation but it was not to be. They certainly were more resolving than the HD650s but I didn't get the impression that they were trying to reveal stuff that wasn't actually in the recording. One thing that did annoy me, however, was a strange effect with sounds emanating from the center of the stage. One of the singers in Cantus was clearly center-stage but was apparently swaying a little from side to side. With the Sennheisers, I could hear him doing just that; with the Sonys, he seemed to be leaping from side to side. It was as though there was a gap in the center of the Sonys' soundstage that forced the sonic image to move to one side or the other, as if subject to magnetic repulsion. Very odd!
My favorite headphones with the RP6 were the HD650/Equinox combination. I still prefer the DT880s with the EarMax Pro and I'm still looking for an amp that can really tame the K501's inherent harshness. I must admit that Romanee's 501s are the best-sounding that I've heard---they're streets ahead of mine---but there's something crazy about headphones that aren't burned in until the pads are burned out.
I have high hopes for the K701s that should arrive soon (if AKG gets around to shipping some more); but I plan to burn them in for a long, long time without a head between them. (OK, who's the smart-ass who said I might as well wear them?)
I couldn't get enthusiastic about the all-solid-state Rudi RP33. Even allowing for the RP6-withdrawal factor, it seemed lifeless to me. The bass was awesome but somebody had stolen the treble. Its sonic balance reminded me of the Shure E5c. The Rudi NKK02 was a lot of fun, and one of the more civilized in-your-face amps I have heard to date. It's not as extreme as the Hornet in that respect, as it retains the smoothness of a tube stage (just in case you didn't notice those glass gadgets poking through the top panel). I think I would find it tiring with classical music for any length of time, but it made for a pleasant diversion for those of a Faithless persuasion and would probably work quite well with a close-miked jazz combo, too.
A word about that Ultrasone disc that had everyone's eyes popping. Ultrasone devotes a lot of advertising effort to their claim that a special placement/orientation of the drivers reduces the "head-bound" effect of less highly evolved (or intelligently designed) headphones. Both my pairs shipped with a demonstration CD containing selections aimed at proving this assertion. Some of them are obviously processed via an algorithm that is not disclosed on the CD jacket. My guess is that it's something akin to Dolby Headphone (in that format's least echoey version). The opening track features a jazz group and presents a soundstage that has most listeners looking around in an attempt to locate the musicians that appear to surround them. It's very convincing; but Ultrasone omits to mention that the effect is just as startling with anything better than Apple earbuds.
I didn't spend much time with Romanee's selection of portable amps, so my SR-71's future is still secure. The Sennheiser PX300 headphones sounded pretty good through the Hornet and their convenience factor cannot be denied. I was disappointed by the apparent ineffectiveness of the noise cancellation; but it's not too surprising given the small size of the supra-aural pads. I'll be sticking with IEMs for my winter commute.
Thanks, Oski, for letting us invade your super-tidy home once again!
