Unico nuovo - Unison Research

designed around a pair of solid aluminium knobs driving a couple of heavy duty
rotary encoders by ALPS especially selected for their high reliability and precise
and firm operation.
But a look inside the Unico50 won't be less satisfactory than the physical
contact, since it's in the circuit design that the breaking point has been set.
When removing the top cover a well engineered amplifier is disclosed to the
observer eyes but there's much more to know about the details of the design.
The input stage employs a refined version of the digitally controlled volume
control deigned firstly in Unico100; thanks to new integrated circuits the
allowed input signal swing is increased up to around 27V peak-to-peak and
fully protected from over voltage spikes. As in the previous design every input
is treated as a balanced signal preventing any possible ground loop and noise
generated by the cable connections.
The Unico50 is a hybrid amplifier, as per Unison Research tradition; the
tubes used are the well known ECC82/12AU7, pure class A biased, with
precisely regulated heater and high anodic voltage. But the in this new project
the preamp stage is an independent circuit working as a stand alone tube
preamplifier. There's no feedback from the power output to the input stage,
thus leading to a zero global feedback design! There's no feedback from the
output of the preamp stage even! The couple of triodes in the tube are
arranged respectively as a common cathode gain stage followed by a cathode
follower low impedance output stage.
The following driver stage derives directly from a well known and long time
tested topology designed by Unison Research. However, never tired of going
further, the technical staff refined the design in order to increase the inner
input impedance thus offering a better load to the preamp stage. In this
configuration the interface parameters are the same you can find when
matching a standalone preamplifier and a power amp.
Another revolutionary feature involves the power stage design: no more power
MOSFETs but power BJTs.
The bias control is the usual one, a proprietary design tested a refined with