From: "Saved by Internet Explorer 11" Subject: Pass Zen (v.4) "Penultimate" Date: Wed, 7 Oct 2015 15:44:48 -0700 MIME-Version: 1.0 Content-Type: multipart/related; type="text/html"; boundary="----=_NextPart_000_002F_01D10117.190AD170" X-MimeOLE: Produced By Microsoft MimeOLE V6.1.7601.17609 This is a multi-part message in MIME format. ------=_NextPart_000_002F_01D10117.190AD170 Content-Type: text/html; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable Content-Location: http://www.stephenwmoore.com/index_files/Page1455.htm
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Home |
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Amplifier=20 Homepage |
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Stephen=20 W. Moore |
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Pass=20 Zen (=93Penultimate=94 v.4)=20 Amplifier |
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The=20 Zen could hardly be called =93hi-fi=94 with its unimpressive = distortion=20 figures. Is that 2.5% distortion at 10 Watts?
However,=20 it sounded wonderful with the right speakers. The speakers of the = day were=20 generally inefficient, designed to be coupled with huge amplifiers = with=20 enormous damping factors. In this case, the Zen, with its feeble = power=20 output and damping factor, simply sounded awful.
With=20 the right speakers, the Zen opened up a new sonic frontier and = helped=20 usher a new dawning of the audiophile community. Soft, luscious = sounds=20 having the emotionality of real people came through.
So,=20 in 2001, Pass started exploring further development of the Zen, = all=20 through the DIY community. The Pass Zen version 4 = =93Penultimate=94 is a=20 result of his continued=20 development. |
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=93Penultimate=94=20 Zen (v.4) Amplifier
Pass=20 authored a series of articles building on the foundation of a = 1994 minimalistic single-ended = MOSFET = amplifier he=20 dubbed the Zen=20 =85=20 =93what is the sound of one transistor clapping?=94. Although a = single-ended=20 amplifier design was far from novel, the Pass Zen was = revolutionary in=20 concept to the audiophile community. It represented backlash = against the=20 expensive, overindulgent, and overly complex solid-state = monstrosities=20 that were promoted by the audiophile community. It offered a new,=20 personal, soft single-ended sound directly at odds with the = era=92s=20 analytical and excessive predominant = offerings. |
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Pass=20 Zen Amplifier
Nelson=20 Pass=20 is one of the world=92s preeminent audio designers. He graciously = shares=20 many of his novel ideas with the DIY audio community and is an = active=20 participant on diyaudio.com = discussion=20 forums. Several Pass=20 amplifiers=20 have been given the most=20 prestigious awards=20 in available in the audio industry.
Nelson=20 Pass offers novel amplifier design ideas on his DIY web site, = passdiy.com and = publishes=20 full schematics of his niche-market specialist amplifiers at = firstwatt.com. = Pass=20 entertains discussions, dispenses advice, and generally assists = the DIY=20 community to recreate his \ amplifiers on the forums at diyaudio.com.
As=20 his amplifier designs are patented, his sharing of amplifier = designs are=20 for the =93garage enthusiast=94, and not for commercial offerings = unless=20 authorized.
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Circuit |
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I=20 won=92t discuss the circuit here in detail. Follow the link to the = Zen=20 v.4 documentation.
My=20 version used the Pass Labs circuit board, instead of drawing my = own=20 circuit board. I used mostly stock components from Digikey, = although parts=20 selection is not terribly important with this amplifier. The = sonics are in=20 the design, not necessarily the implementation. I=92ve seen some = awful=20 implementations that reportedly sounded great.
I=20
built mine with an insane Ixys TO-264 MOSFET (i.e. the IXFK=20
180N07)=20
for the capacitance multiplier (Q5) and Aleph current source (Q2). =
I used=20
the |
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Very=20 heavy heatsinks were used. The body of the heatsink is about 15mm = thick of=20 solid aluminum, so they have huge thermal mass and = stability.
Power=20 Supply
The=20 amplifier operates in single-ended mode and the circuit board has = an=20 integrated capacitance multiplier (references here and = here). = Therefore,=20 the power supply can be expected to provide constant current. I = used a big=20 Amveco toroidal transformer with two secondaries. The left and = right=20 channels used their own separate transformer winding, diode = bridge, and=20 filter capacitors.
Big=20 3=94 computer-grade can capacitors were used, along with Solen = 2.2uF film=20 capacitors. JK=20 Miller toroidal chokes=20 and Panasonic=20 ECQ-P capacitors=20 provided RF filtering for high frequency components from the AC = utility=20 grid and the diode commutation noise. The diodes were bypassed = with=20 snubber networks consisting of 0.1uF film capacitors and 110 Ohm=20 resistors.
Final=20 power supply output was filtered by an air-core=20 Jantzen Audio inductor.=20 Metal core chokes would saturate under constant DC=20 current. |
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Impressions
This=20 amplifier must=20 agree with your = speakers.=20 I=92ve tried it with numerous speakers, both commercial and DIY. = The biggest=20 surprise was the best sounding combination was with my Definitive=20 Technology=20 Celsius monitors. Just as surprisingly, the Zen v.4 sounded = relatively=20 poorly with my Triangle=20 Acoustics=20 Solaris. This was not what I expected =97 the consumer grade boxes = designed=20 for big solid-state tuners sounded good, = and the=20 high-sensitivity niche-market audiophile speakers designed for = valve=20 amplifier sounded bad. I = figured the=20 Triangle Acoustics would love the Zen, because they prefer = amplifiers with=20 high (poor) output impedance and damping factors. But they = didn=92t.=20
However,=20 with the right combination (in my case, the Celsius), the Zen = was=20 singing!=20 She had gorgeous vocals with tremendous soundstage that wrapped = around the=20 speakers and beyond. Male and female vocals were sweet and = compelling. May=20 I say sumptuous?
The=20 amplifier got lost in big orchestral passages. Symphonies were = turned into=20 mush. This amplifier is best suited for simple passages, = especially solo=20 vocals, and chamber music. Contained within these genres, it=92s a = beautiful=20 thing.
Hifi?=20 Hardly. Audiophile approved? Maybe. Buckets of fun? Absolutely! = Did it=20 compel me listen to more music? Yes, and that=92s what counts,=20 right? |
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Pass=20 Zen v.4 |
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Tube/MOSFET=20 Hybrid |
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Fostex=20 FE207E |
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EL84=20 Push Pull |