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.

My audiophile 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 next.

Recently, however, 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 friend.

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:

1. About how good is an Audio Horizons line preamplifier compared to a comparably priced model of more widely known brand?

2. Should you consider upgrading to the Audio Horizon VRX model from an earlier Audio Horizon version?

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.

My stereo 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.

For this 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 follows.

Analog (LP):

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.

Digital:

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 Hagegard

-   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; intimate staging.

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 session.

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.

I used 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.

Grainy: 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.

Scale: 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 component.

Soundstage: 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.

Imaging: On a proper soundstage, the instrumental sounds are distinctly reproduced, not “jumbled together.”

Dynamic range: Dynamic range is the headroom a system has to reproduce sudden sonic bursts—the ability to go from a whisper to triple forte.

Definition: 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: 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.

Timbre: 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 its fidelity.

Low-level detail: The ability of the system to reproduce music at low sound pressure levels without the music falling away into a thin whisper.

Coherence: 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: 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.

Evaluation

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 listener.

The 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 detail.

All music 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 my preferences.

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.

Listening 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.  

Reviewing my 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.

1. The Audio Horizons line preamplifier is very good when compared to one comparable model of a more widely known brand.

2. Yes, an upgrade to the VRX model can be recommended if your ideal system will be coherent and musical as any that I have heard.

After my 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.

Below I’ve 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 it at

https://positive-feedback.com/Issue50/audio_horizons.htm

Unfortunately, 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.

 

The Audio Horizons technical description of the VRX line preamplifier is published at

http://www.audio-horizons.com/pages/pre.html

The bench measurements of the preamplifier are not described extensively here, but you learn certain important facts about the design and the circuitry of the preamplifier.

 

Lastly, here 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 output.

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 Record SE.

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, CD.

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 maximum.

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