Tempo is a stereo amp that weighs 5kg and measures 280 x 95 x 180mm. That's unusually compact and breezy to move. It does 100/200wpc into 8/4Ω so more than enough for most loads. Further specs list THD+N below 0.01% at 10w/1kHz, 5Hz-80kHz bandwidth, >94% efficiency, 40kΩ input impedance (600Ω upon request), 800kHz PWM switching and auto-sensing 110-240V global voltage. Hardly a surprise given the breed, Tempo runs barely warm. Since it was designed as a GaN affair priced well below the Audion monos, its simplified stereo case is free from the company's signature glass. Individuals who deem pseudo valves blasphemous in a class D device should find Tempo's visual modesty more up their purist alley. It takes up very little space and I can tell you this early that it behaves brilliantly where it counts. Tempo's petite chassis with gently rounded edges mills from solid aluminium billet and its overall execution is nice to put it mildly. Cheeks and bonnet are clean, a pushbutton on its forehead goes red with a light press to communicate readiness for duty. The rear houses a fused IEC inlet with the power mains which neighbors easy-to-use binding posts and XLR/RCA inputs mirrored on the other end. Between them sit 12V trigger i/o and selector knobs that switch inputs and engage stereo/bridge configuration. Yes, diminutive Tempo can turn into a 200-watt mono amp. It sits on four heavy aluminium discs with rubber washers so is most stackable.

Naturally I had to ask how this latest amp fares against its more expensive brethren. I was told that it runs the exact same circuit as the nearly thrice-costlier Vivace monos. Significant savings were had by releasing it as a visually simpler stereo power amp whose critical GaNFet power stage installs internally on the same board as the power supply. No acrylic peekaboo hoods or aluminium chimneys here. Although less flamboyant and no dual-mono affair, Tempo still features a fully differential innovative circuit. Its critical power module is a dual depletion-mode gallium-nitride micro Mosfet of low i/o capacitance that operates as a cascade half-bridge for the shortest connection between switches. Its 800kHz PWM frequency is set by the power supply's own 800kHz switching and the engineering trick was a power transfer without spikes or/and delays to avoid distortion. Alberto explained how a higher switching frequency would net diminishing returns and increase operational temperature. The 700-800kHz range is his sweet spot. Tempo performs as it does because its internal PSU, PWM block for voltage/current conversion and GaNFet outputs were optimized in triptych. Tempo at work is super silent, ready for action several seconds after turn-on and available either in satin black/silver ($5'500) or fully polished ($6'300).

If Tempo is Vivace in smaller more cost-effective threads, Alto is Andante without DAC or streamer but still MC/MM. It measures 280 x 180 x 90mm WxDxH and weighs 5kg like Tempo so the two make a visually uniform stack. Alto's specs list 1Hz-100kHz (±0.2dB) bandwidth, sub 50Ω output impedance, THD+N (XLR) below 0.005% and S/NR better than 130dB. Input impedance and S/NR for MM/MC are respectively 47kΩ/420Ω and ≥80/70dB, THD% is ≤0.05%, RIAA accuracy sub 0.1dB and frequency response 20Hz-20kHz. Alto is a fully balanced design with direct-coupled outputs. It sells for $4'999. One quick look at it sees Andante in the flesh. Alto is 10cm shallower yet otherwise identical and its forehead is busy with the same utilities. Its screen recessed a fair bit behind a thick acrylic window serves unusually deep 3D info perfectly legible from afar. Orange signs on pitch black nicely contrasted my loaner's silver housing. Two rows of petite stainless-steel heads in illuminated acrylic recesses next to the display are touch sensors based on capacitive coupling.

A light touch triggers the desired function. That forms a lightning-fast quiet interface which only clicks during volume changes to be a joy to use. These highly responsive nubs work as quick as your fingers allow. The first four volume steps change SPL by 1dB, thereafter 3dB. Within Alto's menu one may adjust channel balance, display brightness, invert phase, teach a learning remote and select between MM/MC. The main screen shows current volume from 0-99 and selected input. The included remote wand duplicates all commands without exception. Alto sits on four aluminium pucks with rubber inserts like Tempo and its top and sides are just as clean. The business end sports a fused IEC power inlet with mains rocker, three analog outs (6.4Vrms XLR and 2 x RCA), a 12V trigger out and four analog inputs of XLR, phono RCA and two line-level RCA. One analog out is an HT thru-put to bypass the volume control and Alto's internal op-amp output buffers can accommodate a hi/lo pass filter upon request. Voltage gain is just 6dB for lowest noise so standard listening levels showed 80 or more with regular speakers. That's perfectly normal. My 92dB sound|kaos Vox 3afw monitors didn't make sound below 30 yet were plenty loud at 85 and so were Boenicke's W11 SE+ floorstandes. Although Alto has us play in its upper volume range, I had no issues finding my ideal SPL.

Alto's interior houses a display/interface board with microcontroller behind a large steel screen. A switching PSU feeds four shielded encapsulated medical-grade modules that do voltage step-down from the mains to a DC bus subject to linear ultra-low-noise regulators (LT3081 and Ti TPS7A4901D) under small heatsinks. The PCB with analog i/o and ladder attenuator connects to a small phono daughter board which despite the dimensions is designed with a fully balanced topology of 4 differential amplification stages with R & C input selection via dip switches. Alto's 8-bit attenuation circuit sports 16 ATE-grade (automatic test equipment) relays each inside its tiny enclosure resilient to external factors to outlast regular counterparts. The buffer board mounts directly on the output block and incorporates the company THAT's pro audio chipset designed specifically for recording analog sources. After my earlier audition of the Andante/Vivace stack, expectations for Alto and Tempo were high but justified. However, one major thing had changed in my system since July 2020 of my earlier review. Now the newcomer twins had to battle Trilogy's roughly seven times dearer 915R linestage and 995R class A/AB monos which I didn't have two years ago. Boenicke W11 SE+ speakers I used back when remained an ideal load for today's assignment. Since my LampizatOr Pacific DAC is single-ended, both the 915R and Alto connected via their RCA inputs then sent out signal to their respective amps via XLR. Several LessLoss C-Marc power cords and the Boenicke Power Gate's captive M2 cords infused with the same noise-killing tech nicely levelled the battleground. The game was afoot.