Line Preamplifier Comparison: Audio Horizons VRX, TP2.2, and Audio Research LS17 SE
Not long ago I
met another audiophile who lives in my neighborhood. We share an interest in audio gear made by
Audio Horizons, a local company. I’ve
used Audio Horizon products for 20 years now, and upgraded my products as Audio
Horizons, has introduced them.
friend bought his first Audio Horizons product, a phono preamp, on the used
market awhile back. Then, more recently,
he acquired a used Audio Horizons DAC. Experience
with these two components convinced him of the value of their build quality and
of the engineering philosophy that inspired them.
My friend has
asked me a lot of questions about the sound quality differences of the various
Audio Horizons products I’ve owned. I’ve
been through many product changes over the years; too many for me to remember
the specific differences that led me to decide to upgrade from one version to the
I had three line preamplifiers in my care: my own VRX, an Audio Research LS17
SE, and an Audio Horizons TP2.2 just purchased by my neighborhood audiophile
My friend had
the AH TP2.2 shipped to my care because he was traveling. The AR LS17 SE is the preamp he intended to
replace. Here, I thought, was a good
opportunity to evaluate and compare the performance of each preamplifier,
particularly in regard to two questions:
how good is an Audio Horizons line preamplifier compared to a comparably priced
model of more widely known brand?
you consider upgrading to the Audio Horizon VRX model from an earlier Audio
The VRX line
preamplifier was introduced in 2020 and is priced at $6250. The Audio Research LS17 SE sold for about
$5000 when it was introduced in (about) 2010.
The Audio Horizons TP2.2, with upgrades, sold for more than $3500 when
it was introduced in (about) 2010. All
three preamplifiers use vacuum tubes.
The LS17 SE also uses a JFET in its amplification circuit.
My music system
is a particular type – tube powered components that incorporate transformer
coupling. The galvanic isolation and
carefully matched impedances deliver highly resolved detail and wide playback
bandwidth. My music system faithfully reproduces voices as well as acoustic and
amplified instruments. It can play
surprisingly loudly, but symphonic orchestra scale eludes it.
Three of the
principal components of my system, the DAC, the phono preamplifier, and the line
preamplifier are VRX models. The other
major components are:
Audio Horizons 300B SET power amplifier (nine
watt output; EML 300B tubes).
Technics SP10 Mk II turntable with Krebs upgrade
and Jelco TL850 tonearm. The stereo
cartridge is a Phase Tech P-1G, retipped by Andy Kim.
Sonic Transporter music server and UltraRendu music
streamer; Roon software.
MIT Z Center power conditioner.
loudspeakers use a full range (35 Hz - 18 kHz) 12” cone speaker in a front
ported bass reflex cabinet (~6 cubic feet), supplemented by a separate horn
tweeter that engages above 6 kHz. The
cone speaker is rated at 97 dB efficiency; the horn is rated at 110 dB
efficiency. There is no filter (xover) between
the power amp and the cone speaker. There
is a filter between the power amp and the horn tweeter that blocks signal below
6 kHz and attenuates the signal above 6kHz by 6 dB.
listening evaluation, I relied on both LP and digital recordings. I used digital recordings of a 44.1K sampling
rate in AIFF file format. The playlist
Mozart Miniaturen (Philips 6747136), Elly Ameling et. al., side four – “Divertimento”
K439, “Notturno” K437.
Not widely known or available but the bassett
horns and Elly Ameling in trio make it worth the search.
Live in Paris (Verve ORG003), Diana Krall, side two – “The Look of
Love,” “East of the Sun,” “I’ve Got You Under My Skin.” 45 rpm version.
Widely know and sometimes used for demonstration
at audio shows.
This is K2HD Sound, “Touch for Percussion,” Christopher Hardy
From the original K2HD mastering sampler. This track uses gongs and drums to project an
enormous soundstage and lingering sound decay.
Jacob’s Tracks Vol 1, “Bred dina vida vingar (Evening Hymn),” Hakan
Closely mic’ed warm baritone voice singing a
capella, excellent stage atmospherics.
Tango Tango, “Jalousie (Tango Tzigane),” Viveza
Great energy, beautiful tone, musical.
Best Audiophile Voices, “So Nice,” Stacey Kent
Lots of bass, Stacey Kent’s distinctive voice and
a lovely, round saxophone tone
Best Audiophile Voices, “Ain’t No Sunshine,” Eva Cassidy
Excellent dynamics of voice and strings
The Very Best of Peter, Paul & Mary, “Blowin’ in the Wind,” Peter,
Paul and Mary
Closely mic’ed close harmony singing. Distinctive voices in a lovely blend.
Blue Light ‘til Dawn, “Tupelo Honey,” Cassandra Wilson
Singularly rich, supple voice; low level detail
includes brief directions from lead singer two minutes + into song.
Doc & Dawg, “Summertime,” Doc Watson and David Grisman
Excellent string dynamics and Doc’s twangy tenor;
The Girl in the Other Room, “Temptation,” Diana Krall
Often used for demo at audio shows; widely known
I listened to
the playlist through the three different line preamplifiers over three days,
one amplifier per day, beginning with the LS17 SE. I made notes of each track of each listening
I focused on performance
attributes such as soundstaging, imaging, dynamic range, definition, harmonics,
timbre, low level detail, coherence, musicality. Previously I found that the Audio Horizons
VRX phono preamplifier doesn’t sing at its best until it has played for about
45 minutes. So, I was consistent in the
time I allowed for the electronics to warm up.
particular words to describe the performance of the three preamplifiers. Here are the definitions of those terms, borrowed
liberally from V. Comerchero’s essay, “Hearing and Listening,” available on the
Audio Horizons website.
The music may sound slightly blurred and out of focus, just as a digital camera
with too few mega pixels or a TV monitor with two few lines of resolution will
faintly blur the edges of the picture.
The same thing occurs sonically. This
kind of sound is grainy, just as we would describe a photograph
taken by a camera with poor resolution, grainy.
The ability of a system to adapt itself to different program materials, and to
reproduce the material in a relaxed manner (the sound is not crimped, pinched)
whether playing a classical duet or Count Basie’s orchestra. A system’s scaling ability depends greatly on
its loudspeakers. If those loudspeakers
can deliver proper scaling, then its disappearance indicates a shortcoming in a
A proper soundstage presents the performers in realistic scale and
placement. A solo voice may sing from
between the loudspeakers. A jazz
orchestra may be distributed across the soundstage that is not bounded by the
loudspeakers. Generally, a large
soundstage, one that is wide laterally and also deep, suggests a
three-dimensional quality to the music, is superior to a narrow, flat
soundstage. However, this can be
overdone. When the soundstage is too
large, the system is no longer faithful to reality.
On a proper soundstage, the instrumental sounds are distinctly reproduced, not
range: Dynamic range is the headroom
a system has to reproduce sudden sonic bursts—the ability to go from a whisper
to triple forte.
The ability to capture the smallest
musical detail, whether it exists in the foreground or in the
background, and to keep all these elements properly balanced.
harmonics are the discrete signature
overtones every single instrument makes.
Every note produces what is called a “fundamental” plus a series of
“harmonic overtones,” much the way a pebble thrown into a pond makes a plop and
then sends forth ripples. These harmonic
overtones in large part permit us to distinguish the sound of a clarinet from
that of an alto saxophone. A poor system
will do a poor job of reproducing these subtle overtones, producing perhaps the
first or second but not the third or fourth harmonic overtone.
The timbre of a music note consists
of the harmonics that distinguish the type of instrument. It is carried almost exclusively by the
harmonic overtones (see Harmonics). The ability of a sound system to reproduce not
only the fundamental but the numerous harmonic overtones—that is, to capture
the distinctive timbre of each instrument--is one of the highest expressions of
Low-level detail: The ability of the system to reproduce
music at low sound pressure levels without the music falling away into a thin
The impression that the music we hear has not been dissected and put back
together, but has remained an organic whole, and unified in its effects, that
we are indeed listening to the unmediated performance.
Musicality is the
ultimate measure of success - how well the system enhances the music and
catches us up in the musical experience.
The sound reproduction must not only be clear it must be musical—neither
too dry, nor too soft and sweet; neither overly analytical at the expense of
musical flow and continuity, nor overly warm and lush at the expense of detail
and definition. It is the “Goldilocks”
point of enjoying the performance.
On day 1, I
listened to the Audio Research LS17 SE. The
dynamics of Audio Research LS17 SE are good as evidenced, for example, in the
picking of Doc Watson and David Grisman.
Doc Watson’s voice sounds like Doc.
But his voice is a little dry. By
that I mean, the fundamental tone is there but some of the harmonic overtones are
missing. That dryness tells of the slightly
grainy texture of the LS17 SE sound, which is likely to fatigue the careful
soundstage is presented with some depth but mostly between the speakers. The LS17 SE is unable to define subtle musical
details. For instance, it slurred
Cassandra Wilson’s quiet “got it” (to the band) at 2:03 and her quietly empathetic
“hmmm” at 2:10 of Tupelo Honey. It does
not reveal subtle musical timbres. It’s
ability to scale music is missing in presentations that rely on low level
systems are not constructed to achieve the same goals. Every system emphasizes some performance
qualities, those which mirror the listening preferences of its owner, over
other qualities. My system, for example,
sacrifices some ability to reproduce the large-scale performance of, say, a
symphony or an opera. I play and enjoy
them but I know I am not front row at a Berlin Philharmonic performance. By some sacrifice of the largest scale in a
presentation, I gain performance quality in other ways: low-level detail, definition,
harmonics, and timbre. Given the music
that I prefer - classical, jazz, folk, blues – these attributes of my system match
On day 2, when
I installed the Audio Horizons TP2.2 and played warmup music through it, I was
immediately aware of its greater musicality.
Even without warmup, the musicality was audible, palpable, to me. The Audio Horizons TP2.2 is in a different,
higher order of musicality than is the AR LS17 SE.
In the Elly
Ameling trio recording, from Mozart Miniaturen, the voice pitches delivered by
the Audio Horizons TP2.2 were consistent and were not rolled off in the higher
frequencies, unlike the LS17 performance.
The Audio Horizons TP2.2 delivered detailed low level sounds that were
missing from the LS17 presentation. The bassett horn reed vibrations were more
vivid, and the horns sounded sweeter through the Audio Horizons TP2.2 than
through the LS17.
through the AH TP2.2 to Diana Krall’s “The Look of Love,” her voice was
immediately intimate, expressive and breathy.
Low level detail, missing through the LS17, captured my emotional
interest. Now my analytical interest was
drawn away from the playback quality, which seemed so reliable as to not need
my attention, to the quality of the arrangement and of the playing. Then I remembered what I was supposed to be
doing – listen to the playback quality!
I snapped my attention around to playback.
On day 3, I
explored the AH VRX. The VRX is better and more subtle. The
differences between AH TP2.2 and the AH VRX returns us to distinctions about
the music's definition, its harmonic decay, and the coherence of the
performance. In these areas, the playback differences of the TP 2.2 and the VRX
are like differences of colors dithered rather than brushed.
listening notes now, I noted various playback improvements made by the AH
VRX. Sibilances are quieted; the soundstage extends more easily to
encompass the performance group; drum thwacks are tighter; harmonically richer
gong strikes lingeringly fade; piano glissandos are more exciting; bass chords
stroke my chest; voice timbres of close harmony singers are more distinctive;
voice images are superior.
All of these
contribute. Together, do they create this
experience of a higher order of musicality?
What I know is that, through the Audio Horizons VRX preamplifier, I am
listening to a system that is highly musical.
I think I
have answers to my two questions.
Audio Horizons line preamplifier is very good when compared to one comparable
model of a more widely known brand.
an upgrade to the VRX model can be recommended if your ideal system will be
coherent and musical as any that I have heard.
audiophile friend returned, he installed the AH TP2.2 line preamplifier. Later that day, he called to tell me that the
AH TP2.2 sounded so much more … musical!
… than his previous line preamplifier.
added sources for additional information about these preamplifiers. Some of you, I hope, will want to learn more
about them and, especially, about the Audio Horizon design philosophy.
A decade ago,
a reviewer named Jeff Parks wrote about the Audio Horizons TP2.2, published in
Positive Feedback Issue 50. You can read
Jeff passed away too young, but he left us what I think is the most perceptive
review of an Audio Horizons product written to date. He lived with the TP2.2 for eight months
before publishing the review, so he knew it well.
I urge you to
read it because Jeff did a particularly good job of describing, in his own
words, the design philosophy that Joseph Chow follows.
Horizons technical description of the VRX line preamplifier is published at
measurements of the preamplifier are not described extensively here, but you
learn certain important facts about the design and the circuitry of the
are specifications of the Audio Research LS17 SE taken from the owner’s manual:
FREQUENCY RESPONSE: +0-3dB, 0.5Hz to 160kHz at
rated output (Balanced, 200k ohms load).
DISTORTION: Less than .01% at 2V RMS BAL
GAIN: Main output: 18dB Balanced output (12dB
SE output). Record output: 0dB (Processor input: 0dB SE output).
INPUT IMPEDANCE: 120K ohms Balanced, 60K ohms SE.
Inputs (7): Balanced: BAL 2, BAL 1. SE: Aux, Tuner, CD, Proc, Monitor.
OUTPUT IMPEDANCE: 700 ohms Balanced, 350 ohms SE
Main. 20K ohms minimum load and 2000pF maximum capacitance. Outputs (4): 2 main Balanced, 1 main SE, 1
OUTPUT POLARITY: Non-inverting.
MAXIMUM INPUT: 24V RMS BAL, 12V RMS SE.
RATED OUTPUTS: 2V RMS 1Hz to 100kHz into 200K ohm
balanced load (maximum balanced output capability is 15VRMS at less than 0.5%
THD at 1kHz).
CONTROLS: Rotary volume selector (104 steps,
20 LED indicators) and rotary input selector.
Push buttons: Power, Monitor, Proc, Mute. Also remote buttons: Bal 1, Bal 2, Aux, Tuner,
POWER SUPPLIES: Electronically-regulated low
and high voltage supplies. Automatic 50 sec. warm-up/ brown-out mute. Line
regulation better than .01%.
NOISE: 2.2uV RMS residual IHF weighted
balanced equivalent input noise with volume at 1 (101dB below 2V RMS output).
TUBE COMPLEMENT: 2-6H30P dual triode, (Hybrid JFET/tube
audio circuit, solid-state power supply).
POWER REQUIREMENTS: 260VAC50/60Hz) 50 watts
DIMENSIONS: 19" (48 cm) W x 5.25"
(13.4 cm) H (standard rack panel) x 12" (30.5 cm) D. Handles extend 1.50" (3.8 cm) forward of
the front panel.
WEIGHT: 13 lbs. (5.9 kg) Net