The Greek word tessera refers to the number four. Zesto Audio uses that definition (tessera; τέσσερα) to name its latest phonostage. The word is fitting in function since the Andros Téssera ($12,000) phonostage supports four inputs. The word téssera is also defined as an individual tile in a mosaic. What the reader will find out is the “individual tile in a mosaic” is correspondingly applicable to this component since the Andros Téssera also serves as a tile in the mosaic of analog music reproduction.
The Andros Téssera is a vacuum tube phonostage with the ability to receive up to four cartridge/tonearm input combinations. This is accomplished by having two banks (Zesto Audio calls them “Channel A” and “Channel B”) of inputs wherein each bank can receive one moving-coil cartridge and one moving-magnet cartridge connection simultaneously. Selector switches on the front panel set the proper connections while disconnecting the unused ones. When used as intended, the Andros Téssera accepts two moving-coil and two moving-magnet cartridges for a total of four cartridges at the same time. The maximum number of the typical moving-magnet cartridge inputs is two. However, if the user has his own step-up transformer (or Zesto Audio’s versatile Andros Allasso Step Up Transformer) and needs additional moving-coil inputs, one or both of the moving-magnet inputs can be utilized with these external step-up transformers for a total of up to four moving-coil inputs. (More information about the user controls and connections will be described below.)
The four-input capability is one of many changes that Zesto Audio has incorporated in the Andros Téssera compared to its Andros 1.2 phonostage. Besides the control/selector switches being on the front panel of the Andros Téssera (they are on the rear panel of the Andros 1.2), Zesto Audio says that the internal input transformers are of higher quality and larger than those of the Andros 1.2. In addition, there is a larger outboard external power supply, and the tube circuits have been redesigned and are different. There are now two dedicated output tubes (12AU7s) to drive new output transformers—lowering the output impedance to 150 ohms—which Zesto Audio calls a true floating differential output.
The dual-chassis Andros Téssera is shipped in a 20″ x 20″ x 16″ double-walled box (total weight approximately 54 pounds). The main unit and power supply are both inserted in a pair of closed-cell two-tiered foam structures that creates separation and support. Additional items included in the package are JJ Electronics gold-pin vacuum tubes (4x ECC83s/12AX7s and 2x ECC82s/12AU7s), a pair of white gloves (for tube installation), a spade-lugged ground wire (for turntable connection), a 3-meter umbilical cord (for main unit to power supply connection), an AC power cord, and the owner’s manual.
The Andros Téssera’s main chassis (25 pounds) is unmistakably unique (like the rest of the Zesto Audio product line) in the shape and design of its visual features. The mostly black two-tier case with chrome-plated, curved, upper-level divider and grey-colored, curved, front-panel faceplate overlays have an eye-catching charm. The top of the lower tier houses the tube sockets for the 12AX7 and 12AU7 tubes—the sockets are clearly labeled on the chassis. On the front panel from left to right are the Zesto Audio Andros Téssera name and logo, an on/off power switch (the main power switch is on the separate power supply), and two banks of input controls/selector switches that remember their settings when you switch between them. The rear panel has inputs for up to four ’arm/cartridge combos, RCA and XLR output, and a power cable connection input from the external power supply (15 pounds).
On the front panel of the Andros Téssera, the first group of rotary switches within a middle faceplate—identified as “Channel A”—are mc/mm, gain, loading, and channel (bank) controls. Within that “Channel A” group, the mc/mm rotary switch allows mc/mm 47k/mm 68k selections for the two inputs—moving coil or moving magnet (47k or 68k loading for that mm input; mm capacitance is fixed at 220pF). The gain switch allows control of the gain level of low (60dB mc, 40dB mm), medium (65dB mc, 45dB mm), and high (70dB mc, 50dB mm). The loading switch has twelve positions for selecting mc load values of between 50 ohms and 1000 ohms that can be switched on the fly during listening to make selection choice more convenient. These 12 mc load values are electrically located on the secondary side of the step-up transformer in order to allow the cartridge to deliver the full signal to the primary-side of the transformer. The final rotary switch in the group selects the bank inputs for “Channel A” (the selections just described) or “Channel B” (the rotary switch selections in the curved faceplate overlay on the right side of the front panel). An LED will illuminate on the front panel identifying which channel is active. The three remaining switches are duplicates of the mc/mm, gain, and loading for the separate “Channel B” inputs. They have the same function described above but are for the second bank of inputs on “Channel B.”
The rear panel of the Andros Téssera’s main chassis comprises three sections (“Channel A” inputs, “Channel B” inputs, and the phonostage outputs) in addition to the external power supply connection. The “Channel A” inputs have two subsection inputs (mm and mc). The moving-magnet input has RCA connectors for the tonearm cables. The moving-coil input has RCA or XLR (for balanced connection) inputs (the user selects RCA or XLR but not both at the same time). There are two ground switches on the “Channel A” inputs for left and right signal connections that can be used to break ground loops on the inputs if necessary. The “Channel B” inputs have the same functionality as those on “Channel A.” The phonostage outputs have RCA and XLR (for balanced operation) connectors. All of the RCA and XLR connectors on the Andros Téssera are gold plated. There are two ground connectors between the “Channel A” and “Channel B” input sections that allow tonearm and/or turntable ground connections to be attached. The phonostage is also supplied with a single ground cable (spade lugs on both ends) for turntable connection, if needed.
The Andros Téssera power supply chassis has a single power off/standby switch and an LED indicator for status that is controlled by the main unit’s on/off power switch. The phonostage draws 52 watts when on and 7 watts in standby mode. If the Andros Téssera power supply LED is not illuminated, the power-off/standby switch is in the “off” position or the unit is unplugged from AC power (under normal circumstances). The rear of the power supply has three fuse access points and a 15-amp IEC connector for AC power. There is also a power chassis connector for the supplied 3-meter umbilical cord that connects the two and supplies DC voltage from internal high-quality linear-regulated power supplies (250Vdc/12Vdc/12Vdc) to the main unit. Zesto Audio suggests this power supply should be placed away from the main phonostage (or possibly any other sensitive component in the signal chain) to keep the noise level as low as possible—that’s why it has a 3-meter cable so the user can place it farther away if necessary.
Some additional features of the Andros Téssera include passive-filtered RIAA equalization that is flat within +/-0.5dB, a noise figure at -90dBu below the maximum +8V output level, polypropylene capacitors, and 1% metal-film resistors throughout, all tube circuity with no solid-state components in the signal path, lowest part count possible for less component influence on sonics and increased reliability, and a 16-gauge zinc-plated steel enclosure. Each unit is hand built, with 50 hours of factory burn-in and a 2-year warranty (6 months on vacuum tubes).
The Andros Téssera received music signals from a Basis Audio Debut Vacuum ’table for most of the critical listening using three ’arms (Basis Audio SuperArm 9, Basis Audio Vector IV, and Graham Phantom III) and four different cartridges (Lyra Atlas, Ortofon Windfeld Ti, Hana SL, and van den Hul Colibri XGP). All four input connections were used at varying times throughout the evaluation process. I used the moving-magnet inputs with external step-up transformers because the only cartridges available were the low-output moving coils mentioned above. To test an unlikely low-output moving-coil cartridge scenario without the external step-up transformer, the Lyra Atlas was briefly connected, for functionality purposes, to the mm input with its highest gain setting (50dB) and it worked (very quietly, I might add) while only requiring the preamp volume to be increased (10–20dB) to compensate.
Under all conditions the contrasting characteristics between these cartridges were apparent: the Hana SL’s pure high-frequency tracing and fundamentally good baseline sound, the Windfeld Ti’s solid coherency, the Colibri XGP’s expressive presence region and smoothness, and the Atlas’ command of nearly everything.
The baseline sound of the Andros Téssera is full-bodied and composed. Everything stays in place, solidly rooted in location, and is presented with a sense of warmth. The sound created by this phonostage maintains dynamic development and much of the note’s decay when called for, but is slightly softer on the start than other configurations. Without favoring one over the other, all music genres seem to be fairly evenly represented.
Recently, I’ve listened to Diana Krall’s Turn Up The Quiet to enjoy her vocals and a cast of first-class jazz musicians. With the Andros Téssera in place, the music is full-bodied, warm, and rich with a calm that washes over the performance. Krall’s vocals favored slightly more throat and chest than mouth, while her piano playing had a solid heft about each key strike. Dynamic intensity of her vocals maintained the soft-to-loud transitions that are part of this recording. While the sound had reduced impact on the initial transients, the meat around the musical note continued to develop. The same appeared to happen with the upright bass playing of McBride or Clayton Jr. and with Jeff Hamilton’s percussion—a slightly softer attack but fully evolved tone and decay afterwards.
On simpler jazz recordings like Chet Baker’s Chet album, the Andros Téssera continued the trend of warm rich sound. On “Alone Together” Chet’s trumpet sounded big and rich and immediate—in and around the left speaker—while the sound from the echo chamber filled all of the right side of the soundstage like two distinct scenes from the same source. Cymbals were sweet and blended well with the accompanying piano in this composition. The upright bass was slightly soft but each note change was distinguishable throughout the track. Pepper Adams’ baritone sax had room-filling body (less reed sound) and intensity. Similarly, Herbie Mann’s flute was warm and smooth. With the Andros Téssera, one could get lost in this simple but beautiful music until the side of the LP was completed.
Listening to a more saturated mix tended to show how the Andros Téssera handled a dense pop arrangement. Sade’s Diamond Life album served as the subject (using “Cherry Pie” for this session). This track was mentioned in the Ortofon Windfeld Ti equipment report (via the Andros Téssera along with other phonostages). This time, the phonostage stayed the same and multiple cartridges were employed. I consistently heard a nice soundstage and no objectionable sibilance from any of the cartridges. The whole drum set was full-bodied and added a sense of weight to the listening experience. Sade’s vocals stayed smooth with her overdubs still audible, although much farther back from her main vocal. Also farther back in the mix were the cymbals (soft and clean sounding) and synthesizer. The musical message along with its timing remained intact throughout the track.
Large dynamics and a sense of physical impact can help create a visceral experience with some forms of music. The Mobile Fidelity reissue of Dire Straits’ Brothers in Arms contains an exceptional amount of low-frequency content and dynamic transients. No other pressings (reissue or original) previously listened to have this same character. Despite whatever MoFi did to achieve this result, the music stays clean and clear without a hint of harshness (for a digital sourced LP) throughout all tracks. Using the Andros Téssera phonostage, the album still maintained its big dynamics (with a slightly rounded start on transients) and its propulsive drive. “Ride Across the River” is deceptively slow at the start until the drums come in packing a wallop that can be startling on systems that can portray (and cartridge/’arms that can track) the bass transients. Turning the volume up showed the Andros Téssera to be capable of transferring the dynamic wallop of the track well.
Vocal dynamic impacts can be just as difficult, if not more, than those in the lower end of the frequency spectrum, especially for cartridges to track and phonostages to maintain without compressing sustained (or temporary) amplitudes. The late Régine Crespin singing Ravel’s Shéhérazade on the Speakers Corner reissue of a Decca (SXL 6081) album is a good example. Through the Andros Téssera, the orchestra, by itself, is very nice sounding with a full-bodied, smooth, and wide soundstage that has very good instrumental separation. Crespin’s vocal is also sweet and smooth yet powerfully effortless when it soars above the orchestra. The Andros Téssera allows her vocal intensity, as transcribed by the cartridge, to continue unhindered through her crescendos, when she appears to “blow the roof off” without sounding compressed. This ability to allow such reproduction makes the whole performance enjoyable from start to finish.
In the end, the Zesto Audio Andros Téssera phonostage embodied a certain level of surefooted calmness. Easy to operate in daily use, it appeared to be a quiet and solidly designed piece of electronics. It didn’t seem to give any more than it took from the cartridge by adding something obtrusive to the signal. It was warm and full-bodied in a preferred way, but there was nothing thick or sluggish about it—the sound retained timing and pacing along with its portrayal of musical content. With the capability to connect up to four tonearm/cartridge combinations, the user has the option to quadruple his analog front-end input choices for musical playback from a single phonostage. A look and listen are encouraged.
Specs & Pricing
Type: Tube phonostage
Tube complement: 4x ECC83s (12AX7s), 2x ECC82s (12AU7s)
Gain (moving-coil): 60dB, 65dB, 70dB
Gain (moving-magnet): 40dB, 45dB, 50dB
Cartridge loading (moving-coil): 50, 100, 150, 200, 250, 300, 350, 400, 500, 700, 800, 1000 ohms
Cartridge loading (moving-magnet): 47k, 68k ohms
Output impedance: 150 ohms
Dimensions: 17″ x 5.5″ x 14″ (main chassis); 17″ x 5″ x 8″ (power supply)
Weight: 25 lbs. (main chassis); 17 lbs. (power supply)
3138 Calle Estepa
Thousand Oaks, CA 91360
Analog vinyl: Basis Audio Debut Vacuum, Basis Audio 2800 Vacuum ’tables; Basis Audio SuperArm 9, Basis Audio Vector IV (x2), Graham Phantom III, Lyra Atlas, Lyra Atlas SL, Lyra Etna, Lyra Etna SL, Lyra Titan-i, van den Hul Colibri XGP, Hana SL
Analog tape: Otari MTR-10 Studio Mastering tape deck (¼” 2-track) with custom Flux Magnetic Mastering Series repro head and secondary custom tube output stage
Phonostages: The Raptor (Custom), Lamm LP2 Deluxe, Ayre P-5xe, Musical Surroundings Phonomena II+
Preamplifiers: Dual Placette Audio Active Linestage, Lamm L1.1 Signature, Lamm L2 Reference
Amplifiers: Custom/Modified solid-state monoblocks
Speakers: Vandersteen Model 3a Signature with dual 2Wq subwoofers using M5-HPB high-pass filter
Cables: Assortment of AudioQuest, Shunyata Research, Tara Labs, Acoustic Research, and some custom cables
Racks/Accessories: Minus-K BM-1, Neuance shelf, Maple wood shelf, Symposium Ultra, Aurios Pro, Walker Audio, Klaudio RCM, VPI RCM
Listening room: 18′ x 8′ x 43′
By Andre Jennings
My professional career has spanned 30+ years in electronics engineering. Some of the interesting products I’ve been involved with include Cellular Digital Packet Data modems, automotive ignition-interlock systems, military force protection/communications systems, and thrust-vector controls for space launch vehicles.More articles from this editor
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