Unison Research - Simply Phono - Class A Valve Phono Preamplifier

Unison Research - Simply Phono - Class A Valve Phono Preamplifier

While phono preamps with valves are becoming increasingly common, not all of them offer stunning performance within their respective price classes. The Unison Research Simply Phono is simply that—an outstanding tubed phono stage that offers incredible performance for the price.

As can be easily verified there’s a renewed interest for vinyl in the hi-fi market. The Black Disk seems to catch the attention of a wider audience that the consolidated lovers it always could rely on.

Aware of this trend Unison Research decided to enhance its catalogue adding a new turntable+arm+cartridge system named Giro and to work on a new release of two of its standalone phono stages: SimplyPhono and PhonoOne.

The new SimplyPhono bears the same name and indeed shares the same appearance as its predecessors but thanks to a revisited circuitry and improved layout it exhibits noticeably better audio performances.

As its predecessor the new SimplyPhono is an all-tube phono preamplifier. All the stages work in pure class A and no global negative feedback neither local feedback is applied. It employs 4 ECC83/12AX7 double triode (versus the 3 ones used in the previous release of the unit).

The tubes are arranged so that the first couple of triodes acts in parallel as a maximum gain stage implementing a particular configuration named “ionic bias” in order to prevent the cathode self-polarizing circuit from introducing unwanted local reverse-effects and with improved performances as regards noise and distortion.

For the RIAA equalization network a completely passive solution has been chosen after some listening test. The use of strict tolerance resistors and hand picked, measured and selected capacitors ensures a precision of 0.1dB of the frequency response.

The equalization network is followed by a second gain stage direct coupled with a cathode follower output stage as an optimal solution in order to achieve the needed overall gain and a low output impedance.

Particular care has been put in the power supply stages. In order to maximize the dynamic response of the unit a high value for the anodic supply has been chosen. A particular circuit using a series power MOSFET and a precise voltage regulator ensures a stable low ripple supply voltage of more than 300V. A further filter feeds the second and output stages of both channel with a very stable voltage.

In order to minimize cross-talk and PSRR (power supply rejection ratio) in the first (and more tricky) gain stage a last couple of RC filters and a zener regulations has been implemented, one for each channel.

As usual for Unison Research technical staff, a great care has been dedicated to the design of the layout of the board. This is a key feature that is often undervalued but that can heavily affect the final result. A smart symmetrical design, outcome of a long dated knowledge, improved even more cross-talk and noise parameters.

As an example we can measure a huge improvement of cross-talk over all the audio spectrum with a reduction of 20dB at middle band frequencies.

With a gain that makes it suitable for all MM and medium to high level MC cartridges, with a noticeable improvement of sonic performances, with improved quality RCA connectors and input impedance variable setting the new SimplyPhono accentuates it already high value.