I've heard people say and I'm sure you have too, that
certain equipment is great on rock but not so great on classicalor vice versa. I've
always thought that if a piece of gear is good on one kind of music, it ought to be just
as good on the other. I mean good is good, right? The bulling blocks of music don't change
with the program. A system still has to reproduce dynamics, timbres, pitches, rhythms, and
tempt whether you're listening to Janis Joplin or Byron Janis. But the $3,500 Pass Aleph
0s amplifier that I am about to review has forced me to rethink the idea that the
reproduction of music is a democracy Simply put, here is an amp that is realistic on
certain material and not quite as realistic (although by no means a slouch) on other
material. The twist is that the material isn't rock versus classical. If you want to know
what gives, read on.
First a bit of general info. The Aleph 0s, as you may already know, is an
exceptionally innovative producta single chassis, stereo version of the Aleph 0, the
world's first single-ended, transistor (actually Mosfet) amplifier. For those of you who
have been hibernating for the past year, single-ended amplification, triode tube or
solid-state, is probably the hottestand most hotly debated subject in Fi-dom.
What single-endeds do, in a nutshell, is simplify the gain strategy Instead of splitting a
signal into positive and negative halves and amplifying each half with a separate device,
as push-pull amps do, s-e's amplify the signal with one device.
The advantages of single-endedness are many: fewer parts in the signal
path, less complicated circuitry, no negative feedback, no phase splitting and attendant
crossover notch distortions, super Class A operation, and a transfer curve that is more
consonant with the sound of music because it is richer in even-order harmonics. On the
negative sideto get push-pull for a momentsingle-endeds, at least in their
triode tube incarnations, are low powered, not particularly extended at either frequency
extreme or flat in between, shockingly high in harmonic distortions, and generally poor
performers on all standard tests. John Atkinson of Stereophile has-called them, wittily
"bent wires with no gain".
In response to such criticism, the gifted designer of the Aleph 0s, Nelson
Pass, takes the same common sense, "proof of the pudding" approach that most of
us do. We don't listen to test results; we listen to music. And when it comes to creating
a persuasive illusion of music, well engineered single-endeds have less to apologize for
than many a better testing, better measuring design.
Nelson buttresses the case for s-e's by pointing to the ways in which the
asymmetrical transfer curve of single-endeds mirrors the asymmetrical transfer
characteristics of air itself. (For one thing, both emphasize even order harmonics). And
while he doesn't say it outright because (bless him) he doesn't feel that standard
measurements are relevant to the listening experience, it is a fact that his Mosfet s-e's
do not have the distortion, bandwidth, and power limitations of triode circuits.1 For
example, the Aleph 0s puts out a hefty 40 watts into 8 ohms, 80 watts in 4 ohms, and 160
watts into 2 ohms at a bandwidth that extends from DC to 100KHz. It is capable of
delivering 25amp/30 volt peaks; and its distortion levels never rise above 1% at full
output. This, folks, is not typical single-ended triode behavior.
But then the Aleph 0s does not sound like a typical single-ended amp.
What it shares with its tube brethren is a certain kind of clarity.
Single-endeds are more "direct" sounding than push-pull amps, more transparent,
more immediate, less hi-fi sounding. They make other amps sound the way TVs look when
you're not quite tuned in to the channelsnowy, electrical, out of focus. If the true
test of hi-fi greatness is when a component calls less attention to itself and more
attention to the music, then see's are touched with greatness. They simply provide a
clearer window on the music.
The Aleph 0s is very clear and direct sounding. It is also very fast -
exceeding so throughout its entire range. This is the sort of amp that reveals
transient details that other amps (even s-e amps) obscure, such as the action of a piano's
dampers or the click of its keys. It is an amp that can tell you immediately whether a
plucked guitar string is translucent nylon or singing steel, and whether it's plucked with
fingertip, pick, or nail. If a contrabass is slapped beneath a sforzando pedal point, the
Aleph 0s let's you know. In short, if it's part of transient attack, the Aleph 0s brings
it to startlingly clear life.
When the leading edges of transients are reproduced with the Aleph's speed
and impact, the presence of the instrument producing them is enhanced. Because transients
are strong in upper partials, they quite literally have a sonic edge to them, which
dissipates within a fraction of a second after the instrument is struck, plucked or bowed.
But for the split second after they are sounded, instrumental transients deliver enough
extra harmonic content with enough intensity to cut through the fabric of accompanying
sounds, focusing us on their loci like a beam of light. The Aleph 0s is superlative at
reproducing these intensity-based details.
In addition to its clarity, speed, and presence, the Aleph 0s is also
neutral in balance (albeit a bit to the "white" side of dead center neutral). In
this respect, it beats out many of its overly ripe in the lower midband, rolled-in-the
high end triode counterparts. The Aleph 0s has none of the chestiness that makes male
voice sound dark and plummy, none of the nasality that makes female voice sound pinched
and peaked, and little of the sibilance that makes the upper registers of violin sound
sharply etched. When it comes to the clean reproduction of pitches, it is exceptional.
Where the Aleph 0s begins to sound less like a single-ended triode amp is
in the way it handles the timbres of instruments and the durations of notes. Clarity,
speed, presence, and accurate pitch reflect the Aleph 0s' excellent reproduction of
attack. But the dynamic of a played note has three time-dependent parts: attack, growth,
and decay It is on the decay side of notes that the Aleph 0s shows its solid-state
Without sugar coating this point, let me say that instruments reproduced
through the Aleph 0s do not have all of the texturethe three-dimensional body,
(small-scale) dynamic nuance, or rich harmonic colorthat they have with single-ended
tube amps and in life.
For example, with a great single-ended triode amp on a great recording
like the Brahms Piano Quartet in C Minor, Op. 60 [LSC 2330], you can hear the bow in
violinist Szymon Goldberg's hand literally grabbing the strings of his Strad. You hear the
faint nasal buzz of rosin and horse hair riding above those strings. You hear the strings
vibrating beneath the bow, distinct in pitch but enveloped in a soft glow of harmonics
that is resonant with the deep wood colors of the violin neck and body You hear all these
thingsbow,, vibrating string, harmonic glow, resonating woodas one rich,
unfolding event, a violin played by a master.
With the Aleph 0s, you hear these same things, but they do not unfold at
the same lifelike pace. The draw of the bow seems to have less rosiny buzz; the clearly
pitched string less vibrato, harmonic glow, and woody resonance. Such textural details are
not being obliterated by the 0s; they are being compressed, abbreviated, if you will. What
such abbreviation suggests to me is that the Aleph is less adept at recovering the growth
and decay of notes than it is at presenting their attack. Like many another solid-state
amp, the 0s doesn't seem to allow harmonically complex musical events the time to unfold
in all their richness.
In real space, the interval of decay augments the primary growth of
sounded notes, enriching them with reverberation that reinforces tempt, colors timbres,
and reveals subtle dynamic nuances. Decay not only gives us the "back half" of a
note, it gives us the back halves of the instruments that are producing those
notesthe vibrating bodies of violins, pianos, vocalists and the harmonically charged
air surrounding them. It is for these reasonsand not simply because it adds to the
illusion of a transparent "soundstage"that we want amps to recover the
"decay" of an instrument in a hall or recording venue, for in recovering decay
we are also recovering music and musicians. The Aleph 0s, like every solid-state amp I've
heard, seems to abbreviate the intervals of growth and decay, reducing reverberation times
and, thereby reducing the color and duration of notes.
This is not to say that the Aleph 0s makes Szymon Goldberg's violin sound
unrealistic. It does not. It simply makes it sound more like a recorded instrument and
less like one that is "there" in the room with you, because there is literally
less "there," in the sense of the resonance of the instrument and reverberation
of the recording site, there.
Now, having said this, let me quickly note that this squat, black,
innovative amplifier can sound quite present on the right material. By "material, I
do not mean pop versus classical. I mean music or recordings which are rich
in-growth/decay-related textures versus those that are less so.
Different kinds of music require different optimal reverberation times to
sound their best. Relatively speaking, orchestral music requires the longest optimal
reverberation times; speech the shortest. The Aleph 0s truly shines brightest on solo or
small ensemble pieces and on closely miked recordings where resonance and reverberation
are not as much of a factor. On studio recordings of solo voice, on instruments played
percussively on electrically amplified instruments, on closely miked music of every sort,
it is quite realistic sounding (albeit consistently and predictably more
"forward" than other fine amps). Indeed, the Aleph 0s is capable of sounding so
realistic on certain recordings that it is impossible to dismiss because it doesn't have
all of the presence of kilobuck single-ended triodes with superior growth/decay retrieval.
Usually when a reviewer says something sounds "real," he means
"real to him" After all, in the majority of cases, we are guessing about what
the "real thing" sounded like at a recording session. But with the Aleph 0s I
can do better than a guess.
The week before I wrote this review Steve Sullivan visited me in
Cincinnati. A well known broadcaster on NYC classical music stations, Steve also happens
to be a trained singer. Recently he recorded a Christmas lullaby on the Athena label,
which he brought with him on CD for me to audition. I don't think I've ever had the
opportunity to sit and talk with someone I know well and then listen, immediately
afterwards, to his (professionally) recorded voice played back on my own stereo. Steve's
visit provided the occasion for a classic "live-versus-Memorex" experiment.
Now, let me tell you what I expected to hear and what I actually heard, so
that you can understand why I am slightly perplexed by the Aleph 0s. My two amps of
choice, at the moment , are both single-ended triodeone of which uses 300B output
tubes, the other parallel 2A3s. Although they don't sound alike, there is a strong family
resemblance. Both of them are gorgeously rich in color, very good on transient attack and
superb on decay quite transparent, and remarkable at recovering ambiance (and the three
dimensional bodies of vocalists and instruments). In short, they do many of the things
superlatively well that the Aleph 0s doesn't do quite as wellthe very things, by the
way that I think of as adding concert hall realism to recorded sound.
In the course of an evening's listening, Steve and I (and my wife
Katherine) listened to his CD played back through all three amps (and several others, to
boot). To my astonishment (and to Steve's), the Aleph 0s proved to be, far and away the
most realistic sounding of the bunch!
Understand that I am talking about listening to a recording of the guy
who's sitting next to you. Understand, as well, that in my bewilderment I actually had
Steve stand between the speakers and sing along with the CD! All I can tell you is
thatwithout possessing the fully dimensional body richness of color and harmonics,
or ultimate transparency of the triode ampsthe Aleph 0s sounded more like Steve
Sullivan. (Or, at least, like Steve Sullivan singing a few scant feet away from me in my
listening room-an interesting and telling difference.)
It is obvious that the Aleph 0s is doing something so right with balance
and speed of attack that its relative weakness on decay doesn't seem to matter as much on
closely miked recordings of voice such as Steve's CD or, say the Guitar Gabriel disc from
Music Maker Recordings [MMCD 0494]. Alternately because of its forward imaging and
superior transient response, what the 0s may be doing is making all discs sound more
closely miked, and therefore more immediately present. Or it could be that, in certain
respects, the Aleph 0s is just one accurate son of-a-gun.
I have had this "accuracy" versus "musicality"
argument before, in other places,with other folks. Now, thanks to the Aleph 0s, I'm having
it with myself. While I don't know that I've been this hard pressed by a piece of
equipment that is perhaps a touch more accurate than it is musical, I will simply say that
I find the sound of a competitive tube amp like the Audio Note Neiro too musically
engaging to dismiss because of a single experiment that was, after all, limited to about
an octave-and-a-half of closely miked male voice. Still, that experiment has given me
The great film critic Pauline Kael once said about WC. Fields that his
aggressive but honest brand of humor was an acquired taste, like the taste of sour mash
whiskey Finally, I suppose, this is how I feel about the Aleph 0s. It is not as purely
gorgeous sounding, as rich in color, body and nuance, or as sensuously attractive as some
other very fine (triode) amps. It does not always engage me with music to the same degree
that triodes do. But the Aleph 0s's aggressive but honest presentation is exciting to
hear, even on music that is less than ideally suited to its aggressive character; and at
its best, it is quite convincingly realistic. It may not see everythingwhat amp
does.?but what it sees it sees pretty damn clearly.
Just as I completed this review a new single-ended, stereo, solid-state
amp from Pass Labs arrived at my door, the budget priced, 30 watt/channel, pure Class A
Aleph 3. The product of further innovative thinking from a manufacturer who is, without
doubt, the most innovative currently at work on solid-state amplification in this country,
the Aleph 3 represents a major step forward in single-ended solid-state design.
With only two gain stages (as opposed to the three gain stages in the
Aleph 0s and other amps in the Aleph series) and concomitant reductions in negative
feedback, plus a newly designed current source that optimizes the gain stage into reactive
loads, the Aleph 3 recovers much of the low level, growth and decay-related information
that the 0s does not, while maintaining the Aleph's fundamental neutrality of palette and
most of its superior transient response.
The net result is a solid-state, single-ended amplifier with an increased
measure of the body dimensionality, and instrumental texture of single-ended triode
amplification. This does not mean that Aleph 3 sounds exactly like, say the 300-B
Wavelength Cardinals (although it's surprisingly close). There is a fineness of grain
structure with tube amplification that transistor amps, even superior ones like the Aleph
3, simply do not have. Edge definition is softer with triodes; silences are deeper and
more liquid; balances are fullerdenser in color, less "white, lean, and bright
overall (albeit less realistically extended at either extreme); harmonic and dynamic
nuances are more fully recovered. Still and all, the Aleph 3 is one transistor amp that
dispenses musical details at a pace that is very close to what one hears with great triode
amplification (and in life).
Let me give you an exampleand save further comments on the Aleph 3
for a later issue. The Shirley Horn album / Thought About Ku [Verve Digital 833 235-2] has
some realistic (and three-dimensional) voice on it. With the Aleph 0s, Ms. Horn sounds
quite immediately present, all right, but somewhat deracinated in color and flattened in
volume, as if the Aleph has moved her a step closer to the microphone (and a step further
out of the distinctively ambient room-night club, actuallyin which she is singing).
With the Aleph 3, Ms. Horn recedes a pace and the distinctive resonance of
her voice as it echoes in the room around and behind her is made more audible. (Which is
another way of saying that transparency is increased.) There is now more "there"
theremore of the growth and decay-related information that is so crucial to
recovering the bodies of instruments and the color and duration of notes. You hear Ms.
Horn and her ensemble reproduced not only with transient immediacy but with fullbodied
presence. Through a great speaker, like the Avantgarde Acoustic Profile Trio, this added
dimensionality is so vividly presented that you can actually "peer around" each
performer, hearing deeply into the ambient space that cushions the bodies of their
instruments and sustains the decays of notes. When you combine this level of ambiance (and
decay) retrieval with the Aleph's excellent (if not quite 0-esque) transient response, you
get what may be the most realistic presentations I have heard from solid-state.
Even on brief acquaintance, it is obvious that the Aleph 3 is a remarkable
productand one helluva bargain. Although it has a few shortcomings (among which are
its too closely spaced output jacks), at $2000 they are eminently forgivable. Indeed, the
more I listen to this amp, the more convinced I become that it is a solid-state stereo
masterpiece. Provided you have enough speaker, I strongly urge you to give the Pass Labs
Aleph 3 the audition it deserves.
1. In all fairness, they are not fully single-ended either. When the Aleph
0s (and other amps in the original, three-gain stage Aleph series) is worked beyond its
bias point, it engages a "pull" stage that is built into the circuit. While you
have to drive the Aleph 0s quite hard to exceed bias, the fact is that the
"pull" circuitry is there whether it's being called upon to work for its living