- Choosing a selection results in a full page refresh.
Special Order
You may return most items within 60 days of delivery. Returns made within 30 days qualify for a full refund, while returns from 31 to 60 days are eligible for store credit or an exchange. If the return is due to our error (incorrect or defective item), we’ll cover the return shipping costs.
Refunds are typically processed within one week of receiving your return.
To start a return, log in to your account, go to Complete Orders, and click Return Item(s). We’ll notify you by email once your refund is processed.
For full details, please review our return policy!
The Unico 90 is a hybrid integrated amplifier developed according to specific sonic and scientific criteria set by the design team at Unison Research. These criteria led to a product completely different from anything else Unison Research has ever released. That means it’s also different from every other amplifier, valve or solid state, on the market.
The Unico 90 is a model of structural simplicity. Today’s amplification devices are not perfect— they basically distort as amplification stages are added. If Unison Research puts many amplification stages in a design, one after the other, the structure of the distortion becomes more complicated. This is the reason why structural simplicity is a coveted goal in amplifier design.
Their research at Unison Research led to two circuit performance standards that are, to us, considered essential for excellent performance: a 3-stage circuit and a 2-stage circuit, both with zero global feedback. The first type is used in the new Unico 150, and is more suitable for integrated amplifiers with higher-than average power. The second type, used in the Unico 90, is a more effective application for medium-powered amplifiers.
Both of these approaches allow Unison Research to reach a standard of linearity that is almost impossible with the usual technologies that are matched to single-ended driving capabilities. In fact, the linearity of these new designs is downright remarkable and typical of the best solid state amplification available.
Circuit
The heart of the Unico 90 circuit is found in its hybrid structure. All of the gain, and subsequently the "character" of the amp, is determined by the only tube stage made with ECC83 and ECC 81in particular multiple-parallel-totempole. This stage is made with the six triodes for channel, and is configured so that they present limited gain with the least output impedance possible. The choice of the triode was determined by multiple factors during the development process although Unison Research’s testing and research made their ultimate choices rather obvious. These factors included the following:
Transistors (bipolar or field effect that they are) and valves distort. But in terms of high order residues, valves are unsurpassed and allow invariant residues across almost the entire range of frequencies audible to the human ear. Many audiophiles speak of valves having a soft sound, and this feature is immediately identifiable on an oscilloscope. In fact, you can see on display the waveform of residual distortion of a valve circuit that the signal never changes that quickly, especially compared to the norm of almost all transistor circuits. When those valve circuits are in parallel, however, the measurement of distortion within the frequency of the input signal trend is nearly flat.
Power
When designing the Unison Research Unico 90, consistency was one of the primary goals. This consistency is maintained practically at almost every level of power delivery, with the partial exception of the eighth highest at maximum power (a condition that no actual audio signal may take). This is due to the linearity of the first two stages of valves, and direct coupling between these and the MOSFET output. This innovative solution has allowed Unison Research to eliminate yet another stage present in virtually every other amplifier, thermal compensation, which in certain cases can be a direct or indirect source of distortion. The Unico 90 reaches nominal linearity in just a few tenths of a second, with optimal linearity achieved in little more than 10 minutes.
Preamplifier
The preamp section of the Unico 90 also incorporates a number of innovative solutions. The preamp section is totally passive. Doing otherwise, of course, would have increased the number of stages in the circuit. An ALPS potentiometer is armored in four sections, parallel in pairs, so as to reduce the already minimal noise in order to further improve the precision of the channel balance, especially in the region of high attenuation. The selected sources are connected one at a time, lifting the mass from those not connected in order to interrupt the ground loops associated with the connections not used. (These could otherwise act as an antenna and reveal the electromagnetic signals present in the environment, in addition to generating crosstalk between the channels.) Switching is performed by purely mechanical miniature relays that are armored and placed behind the sockets. The terminals of the input not used are deflected toward their ground through resistors of suitable value to preserve integrity in order to eliminate the risk of capacitive coupling through the movable contacts. The balanced inputs are not obtained by electrical means, which would be considered a “fall back” solution, given the impossibility of obtaining symmetry on the terminals of opposite polarities. Instead, Unison Research uses transformers which allow a truly balanced transmission of signals and galvanic isolation. In addition, this approach creates powerful aid against the ability to break down interference coming from anywhere else. Although optimized for this function, the use of these transformers may offer slightly worse electrical performance at lower frequencies, particularly with sources where the output impedance is not low. All listening tests conducted in the course of development, however, have confirmed the effectiveness of this choice, which was therefore maintained despite the significant increase in cost.
Construction
The Unico 90 is a dual mono amplifier with a single power transformer capable of delivering 600 continuously. The power MOSFET of each channel can handle power up to 900 watts and stationary currents up to + -40 amperes. These circuits, of course, are protected and are weighted on 70% of their maximum specifications so as to maintain an adequate margin of safety without affecting significant drive capabilities. The total transparency of the sound of these circuits is easily verifiable--they protect in real-time and can disconnect the load when activated by the intervention of a single half-wave signal.
Loudspeaker Matching
Unico 90 can drive loudspeakers that are very challenging loads, but it is advisable not to choose extreme speakers with a minimum impedance of less than 2 ohms. Its design is based on a balance of features, and altering it would involve sacrifices in certain directions. Increasing the number of MOSFETs, for example, would permit the use of loudspeakers with impedances of less than 2 ohms without altering the production cost significantly, but this would compromise that consistency and linearity across the high frequencies. Unison Research could have extended the frequencies a few tenths of a Hz, and it would have been very easy to do so, but it would have increased the overdriving of the inputs resulting in badly-digested tube power due to the potential positive effects of the grid.
Capacitors
All capacitors "touched" by the signal are the types that exhibit very low loss and excellent behavior at high frequencies. The polypropylene capacitors in particular, have been widely used for supporting the speed and acceleration of the signal. Three Mundorf capacitors with very low stray inductance are used in each channel to provide a final energy reserve, small but nearly instantaneous, and used in parallel they reduce the effect of parasitic inductance of the slopes connecting to the main large electrolytic tank. As usual for Unison Research, these electrolytic caps are constructed from Italian Itelcond and have a low stray inductance, and are doubled on each branch to lower the inductance further
Conclusion
Unison Research has accounted for every detail, and thousands of simulations have been carried out in their research labs to arrive at the Unico 90 integrated amplifier. They have built dozens of prototypes to test every conceivable variation until they have realized their goals through extensive listening tests.
The Unico 90 is an amplifier where the measurements are the electrical function of the desired sound—not the other way around.
What to expect in the box:
Product Details:
Thanks for subscribing!
This email has been registered!
placeholder
