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Srajan Ebaen
Financial Interests: click here
Source: 2TB iMac 27" quad-core with 16GB of RAM (AIFF) running OSX 10.8.2 and PureMusic 1.94g in hybrid memory play with pre-allocated RAM, Audirvana 1.5.10 in direct/integer mode 1, Metrum Hex, SOtM dX-USB HD with Super-clock upgrade & mBPS-d2s, AURALiC Vega, Aqua Hifi La Voce II, Apple iPod Classic 160 AIFF-loaded, Cambridge Audio iD100, Pure i20, Pro-Ject Dock Box S Digital, RWA-modifed Astell&Kern AK100, Lindemann Audio musicbook:15 [on review]
Preamplifier: Nagra Jazz, Bent Audio Tap-X, Esoteric C-03
Power & integrated amplifiers: FirstWatt S1 monos, SIT2, F6 DIY; Crayon Audio CFA-02, Bakoon AMP-12R, Goldmund/Job 225, Gato DIA-250, Clones 25i [on loan], Aura Note Premier, AURALiC Merak [on loan]
Loudspeakers: Albedo Audio Aptica,soundkaos Wave 40, Boenicke Audio W5se, German Physiks HRS-120, Zu Audio Submission, Elac 4pi Plus.2 [on review]
Cables: Complete Zu Event loom; KingRex uArt, Zu Event and Light Harmonic LightSpeed split USB cables; Tombo Trøn S/PDIF; Van den Hul AES/EBU; AudioQuest Diamond glass-fiber Toslink, Arkana Research RCA/XLR and speaker cables [on loan]
Powerline conditioning: GigaWatt PF-2 + Vibex Two 1R on amps, Vibex Three 11R on front-end components
Equipment rack:
Artesania Exoteryc double-wide three tier with optional glass shelf, Rajasthani hardwood rack for amps
Sundry accessories: Extensive use of Acoustic System Resonators, noise filters and phase inverters
Desktop system: iPod/AK100 digital transports, Wyred4Sound minT, Gato Audio DIA-250, Gallo Strada II + TR-3D
Room size:
Irregularly shaped 9.5 x 9.5m open floor plan combines the living/listening room, kitchen and office. Added to this space the speakers see the air volume of the entry hall and a long corridor plus the 2nd-storey 6 x 9.5m loft. Wood-panel ceiling slopes up to the loft. Parquet flooring. Lots of non-parallel surfaces ('vertical gable' windows, twin-angle ceiling, spiral staircase enclosure, fireplace enclosure). For a pictorial tour, see here.
Review component retail in Europe: $3'500

6 F not moons.
"I just wanted to drop you a note to say how great your coverage of the Munich show was. By far the best I’ve seen. Best, np." This surprise email from Nelson Pass provided the perfect op to inquire about a rumour a reader had shared. "He was under the impression the F6 might enter formal production. I was under the impression that this was purely a DIY project. If I misunderstood or things have changed, let me know." The reader had been right. "I just threw the switch on the F6. Delivery in a couple weeks at MSRP $3'500. In the owner’s manual is a discussion of how the design progressed from the original—which you have and reviewed—to a Mosfet version and why. I will be sending you one shortly and you will be able to make the comparison yourself." In a subsequent email he added that "the thing with the Mosfets was a surprise. One of my partners and best listener pushed me to try it. It works well and it has put another brick in the wall in terms of helping with an over-arching theory of which approaches sound good. Soon I will have to stand back and try to see the forest on this. I have lots more SS Jfets in case I’m wrong."

The simplified upshot of this exchange is of course what many have believed and practiced all along. For a single-ended circuit like his two SIT amps, triode-type transistors are preferable. For a push/pull topology like the F6 (or F5 before it), a pentode-type Mosfet really might have the edge. "I think that conclusion was reached by the marketplace some time ago. Still, it seems like there’s more to it. Prior to the SIT-1 and 2, the commercial SIT amplifiers have all been push-pull. And I did have good success with the Sony Commemoratives which were push-pull too. I'm still regarding the problem like the pieces on a chessboard halfway through a game. The players are triode and pentode. The topologies are common plate and common cathode; single-ended and push-pull; single stage and multi stage. The correction techniques are loop feedback and degeneration; cancellation and cascoding."

DIY FirstWatt amp by Vladimir Djuric seen here

"Of course they all are Class A. Since each of these has a wide variety of possibilities, there's a huge number of permutations. That's why I am not concerned about running out of things to play with in my lifetime." A few months later, production was imminent. "In accord with my 'don’t push the river, it flows by itself' process, I’m going to let my subconscious do the heavy lifting on this whilst I sit on the beach. Meanwhile I received the circuit boards for the production F6. I’ll be stuffing them up here at the coast for shipping at the beginning of the month. Yours will be the first pair out the door." Wasn't it tantalizing to think that Nelson might be working on a type of unified field theory for the various conditions which will lead to good amplifier sound? Pentodes for push/pull, triodes for single-ended really was too simplistic a scenario. It didn't account for "some examples of SE pentodes that sounded good; and it also doesn’t explain why the Sony VFETs do so well with push-pull".