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Srajan Ebaen
Financial Interests: click here
Source: 1TB iMac (AIFF) running OSX 10.6.6 and PureMusic 1.8 in hybrid memory play with pre-allocated RAM, 160GB iPod Classic, Onkyo NS-D1 dock, Pure i20 dock; Esoteric/APL Hifi UX-1/NWO3.0; Metrum Acoustics NOS Mini DAC Octave; April Music Eximus DP-1 [on review] ; April Music U3 [on review]
Preamplifier: Bent Audio Tap-X (remote-controlled AVC passive), Esoteric C-03 (transistor), ModWright LS100 (tubes)
Amplifier: FirstWatt F5 and J2 , Lavardin Model IT
Loudspeakers: Aries Cerat Gladius [on loan]
Cables: Complete Zu Event loom, ASI LiveLine, Crystal Cable Ultra
Stands: 2 x ASI HeartSong 3-tier, 2 x ASI HeartSong amp stand
Powerline conditioning: 1 x GigaWatt LF-2, 1 x Furutech RTP6
Sundry accessories:
Extensive use of Acoustic System Resonators, noise filters and phase inverters
Room size: 5m x 11.5m W x D, 2.6m ceiling with exposed wooden cross beams every 60cm, plaster over brick walls, suspended wood floor with Tatami-type throw rugs. The listening space opens into the second storey via a staircase and the kitchen/dining room are behind the main listening chair. The latter is thus positioned in the middle of this open floor plan without the usual nearby back wall.
Review Component Retail: TBA

May 19, 2010: "I'm in the process of spending six digits on a small run of special Jfet power amplifiers, my own version of the 'SI' Vfets you may recall from the Yamaha and Sony efforts of the 70s and related to the Digital Do Main product showcased recently on your site. Remarkable parts. Their curves look like triodes, with an output conductance on the order of 4 to 8Ω. 

"Mine are newer technology in Silicon Carbide. Some of my costs have been defrayed by borrowing R&D from radar parts which the government paid for. Theirs is the same stuff scaled up for much higher current (30A) and the same sorts of voltages (1000V). SiC is horrifically expensive but offers a better characteristic. And because the chips fail at around 800° C, I suppose we could imagine a nice quartz window on the package so we could watch the glow fets.

"It's odd to see how all applications for these parts have been conventional complicated sorts of circuits when they just beg to be used in single-ended class A without feedback. I'll tell you more about it after I actually get them. There's no simulation that can beat hands-on experience. I also just redid my FirstWatt website using a text editor. I'm feeling pretty smug having actual control and the ability to adjust content on a whim. I'm sure you will appreciate that. - np"

November 10, 2010: "It seems I can't start an email these days without explaining that my life seems to be getting fuller and more complex. It reminds me of Gleick's book Faster. In it he explains how modern life continues to operate at a faster pace as technology progresses (etc). It's a fairly short book as that goes. His writing style starts out at a normal pace. As you progress he slowly amps it up. It's slow enough that you don't notice it like a lobster in a pot. But by the time you finish you've been driven into a minor frenzy by the pace of his writing. It's somewhat disturbing. Anyway, it does make it difficult for a Type A like me to achieve the goal of being a Type B. I'm still working at it.

"You may recall my mentioning that last year I negotiated with SemiSouth for a custom lot of Silicon Carbide (SiC) power Jfets known as Static Induction Transistors (SIT). These Jfets have a structure which keeps the device out of the 'saturation region' where they normally operate and where the current through the device is relatively independent of the voltage across the device (Drain to Source voltage or Vds). Below saturation is the 'linear' or 'ohmic' region where the device behaves like a triode.

Nelson Pass and the Beast Of A 1000 JFETs

"The result is that regular Fets look like pentodes in their characteristic curve and SIT Jfets look like triodes. You can imagine the potential and indeed I did not invent this observation -:) The F3 exploited this with the Lovoltech Jfets but they were very limited in voltage and power and had to run cascoded to operate in their 'linear' region. Even with the additional complexity this works pretty well but at the low voltage involved the capacitances of the part are large and nonlinear and we saw that in the limited bandwidth of the amplifier.

"The SITs are a different story. They hold hundreds of volts and are very fast. SITs are in fact radar parts. I received them last month and they pretty much are as predicted. Given the enormous cost involved it ended the nail-biting segment of this effort and now the real work begins - building a series of real amplifiers and evaluating them with the goal of choosing one or more for production next year. I designed some prototyping boards which allow flexible configurations for a large number of different designs with minimum kludging and maximum adjustment on each, enough boards for 60 mono or stereo amplifiers. Needless to say this is going to be a lot of fun. You are the journalist who is best capable of enjoying this so if you're up for it I'll include you in the equipment loop. I leave it to you to figure out how to square playing with prototypes. - np"

  Prototype 'Ultrasymmetry' Pass Labs amps at show - "The concept amps were experimental circuits and chassis for evaluating potential future product. We have already gathered most of the information we wanted from them. One pair currently graces my listening room. The other is disassembled waiting for revised circuits. The original was slightly over 100 watts output. Our distributor wanted more power however and the final product looks to be 300 watts. Actual product is scheduled for later this year."  

There's always hope to get the real poop. When Stephæn's review of the Pass Labs INT-30A published, I sent Nelson a courtesy link with this note: "At this rate it's getting boring I admit. Perhaps you could send us something crappy for a change?" The man had a solution: "You probably realize that we do in fact make some crappy pieces but Joe Sammut doesn't let them get out the door. I once amused myself with the idea of sending you a sacrificial product that you could poop on and thus retain your street cred. Maybe you'll get a chance with some of these experimental amps. They will be pretty raw and shameless in their nature. - np"

April 24, 2011. Sit. Stay. Good dog. "Jeez, times flies. Just gives you a hint how busy life has become, exacerbated by living in two locations. On top of that business continues to accelerate. Originally my fantasy was to have a leisurely and enjoyable series of test amplifiers which could be tasted like fine wine. Alas as soon as I got a taste I behaved like the design predator I am and went for the kill. The result is that I skipped through several iterations without sharing and I apologize for that.

New Pass Labs speakers

"When my partners heard the result, the response was along the lines of "We need to find a way to bottle this!" I've explored several variations since, seeing what works with these parts and what doesn't. I'm starting to develop some insights but we're not done. At this moment however I have a little stereo amplifier which puts out about 10 watts and is mature enough for sampling. I am making up 5 copies and will be sending two out of the factory, one to you and the other to Jon ver Halen ('Mr. Full Range'). This won't represent production—still up in the air—but will get you into the loop and provide some entertainment. - np"