The original Phono One phono stage was one of the most admired and
beloved products in Unison Research history. When production was
discontinued some years ago, the requests for a replacement never
ceased. For that reason, we decided to improve and reintroduce this
design.
We retained the exterior appearance of the original since we have always
considered this design to be timeless, its aesthetic appeal is still
undiminished and best left untouched. While the circuit used in the
Phono One has many features in common with the more affordable Simply
Phono, one more valve has been added, bringing the number of triodes
(i. e. five ECC83/12AX7 double triodes) up to ten.
All of the gain stages now implement a parallel configuration for the
best noise and distortion performances. This solution increases also the
overall gain to approximately 54dB, enough for all MM and most MC
cartridges. The same passive RIAA network has been adopted, but with
specially selected components that ensure strict tolerances to the
equalization curve.
Increased values for the output capacitors improve bandwidth and phase
rotation at low frequencies. In order to avoid the problem of DC voltage
and bump during the warm up and switch off time of the unit, a delayed
muting function has been implemented. This way the output is disabled
until the tubes reaches their optimal temperature. In addition, loud
bumps at switch on and switch off are also avoided.
In the Simply Phono, only the resistive component of input impedance is
selectable. With the Phono One, both resistance and capacitance can be
matched to the requirements of any cartridge for the best performance.
A dedicated free location on the PCB allows the installation of custom
value resistors in order to set the interface parameters even at any
non-common values. Particular care has been dedicated to the power
supply design.
In order to minimize cross-talk and inter-stage interference, an
independent RC filter cell has been placed near every gain stage, thus
reducing the cross-talk (especially at low frequencies). This cell
results in more than a 20dB reduction in comparison to the already
extraordinary performance of the Simply Phono.
In the new Phono One, low frequency cross-talk is practically immeasurable at less than -90dB.
A careful design of the layout improves channel separation and
interference rejection, and an elastic suspension of the amplifier board
helps bring the sonic performance of the new Phono One to a supreme
level of natural detail and musical clarity. As expected for a
no-compromise design, all the supply voltages are regulated and heavily
filtered.
Nothing has been neglected in the overall design: all of the signal
wiring is hand-soldered using shielded wire, the placement of the valves
addresses the mechanical micro-distortion of the physical parts of the
tubes when operated in horizontal position, and oversized power
components and adequate cooling ensures high reliability.
We are sure the new Phono One will be highly appreciated by anyone
looking for a phono preamplifier that offers a highly involving
listening experience.
Technical characteristics
Type: Stereo Phono Valve preamplifierClass: pure ARIAA : passive +/- 0.1 dB (20 Hz / 20 KHz)Output Impedance: 800 ohm. Outputs: 1 x line Gain : 54 dBTotal Harmonic Distorti on (THD): 0.1 % at 1 volt outputSignal to Noise Ratio (S/N): minus; 80 dBInputs: 1 per fonorivalatore MM o MCInput Impedance: 47 Kohm minus; 100 minus; 50 minus; 22 ohm / 100 minus; 200 minus; 320 minus; 420 pF ( modifiable )Feedback factor: 0 dB. Valves: 5 x ECC83 / 12AX7 Alimentatore: esterno Dimension: 37.3 x 5.84 x h 24.63 cm. Net Weight: 3.6 Kg circa (including power supply)



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