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Unison Research S9 Integrated Valve Amplifier


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Warranty length 1 Year (2 Years on registration)
Brand Unison Research
Product Award What HiFi Award 5 Stars

Tech Specs

Output Impedance: 4 - 8 Ohms
Inputs: 4 x Line, 1 x Tape
Operation: Pure Class-A
Bandwidth: 20Hz-50kHz


- 4 x SV572-10
- 4 x ECC82


Stage: Parallel single-ended
Output Power: 35 watts/channel


Dimensions: 41 x 57 x 25cm
Weight: 50kg

Product Description

Unison Research S9 valve amplifier is an advance in modern all-tube design integrated amps and uses the new SV-572 tube to offer superb musical performance across the full audio spectrum.

When partnered with loudspeakers of suitable quality it will provide a convincing listening experience to satisfy the most demanding audiophile or music lover.

Organic Sound

The Unison S9 great strength is that's it's a very organic-sounding amp. Few amplifiers combine such resolution with such a self-effacing sound. Highs are sweet and beautifully layered, producing a shimmering treble few rivals get close to. The sheer quality of the S9 makes itself felt when you go back to more conventional alternatives.


The output power valves of this amplifier are the SV572 from the russian Svetlana. The main characteristics of SV 572 are: Directly heated thoriated tungsten filament for soft glow and warm sound. Hard glass envelope with white ceramic base.

Low microphonic construction with ceramic internal spacers. Graphite plate with titanium coating for extremely high power capability and a small physical size. The bias of output stage is manual controlled for each tube and it has obtained by aid of a precision analogic mA meter.

Output Performance

The output transformers have been studied, designed and produced in the factory to exalt at maximum the exceptional sound characteristics of the SV572. The total negative feedback of S9 is very low, about 9dB, nonetheless is bandwidth is from 30Hz to 50kHz with extremely low THD.

The anodic power supply, more than 1kV, has supported with 8.000 uF capacitors filters. The filaments of each power valves has supplied by a dedicated power supply with Shotky diodes.

Press Reviews

  • 'Sweet, seductive presentation; wonderfully revealing treble and midrange; lovely build...highs are sweetly layered, offering a shimmering treble few competitors get close to' (What Hi-Fi Magazine January 2010)

  • 'The Unison Research S9 is an intoxicating combination of brilliant and barmy. We can’t help but love it.' (What Hi-Fi Magazine January 2010)

  • 'Build quality is as good as you'd expect for the price. There's something quite appealing about the simplicity of an amp with just three control knobs... it also has more than a spark of brilliance to it. Take a good long listen. If the S9 suits your tastes, we doubt you'll find better...' (What Hi-Fi Magazine January 2010)

  • 'For some, only a valve amp will do, and this is a beautiful example. It packs in the latest valve designs for classical sound reproduction that makes appropriately high-end speakers truly sing, and looks just fantastic. And all of this comes in a fairly compact unit.' (T3 Magazine October 2017)

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