To complete our series of all-tube integrated amplifiers, including successful models such as the Performance and the Sinfonia, Unison Research now introduces the Preludio.
This amplifier maintains the distinctive technical elements, sound characteristics and winning look of the preceding models, and features original solutions which are the result of Unison Research’s innovative design and production experience that has been gained over the years. Along with the other models of the same series, the Preludio is an integrated amplifier which is faithful to the traditions here at Unison Research.
Integration offers several advantages, both in terms of simplicity of use and the sound quality that can be achieved at the price. Since an integrated amplifier requires less cabling than its separate counterparts–therefore allowing a substantial reduction of the effect of cable impedance on sound timbre and dynamics—there is a significant savings in production costs as well. On the other hand, the design of an integrated amplifier is much more critical and challenging than designing a separate pre-power combination. For example, we must carefully consider all the possible interferences between different components and different stages such as the power supply, control, preamplifier and output stage.
Our experience with the design and production of integrated amplifiers has grown over the years, allowing us to create successful models, such as the widely renowned Absolute 845, which are still considered classics today. The Preludio follows this tradition. Though small in size, the Preludio reaches an output power of 14-15W per channel and still mates well with a wide variety of loudspeakers.
As with the Performance and the Sinfonia, the Preludio is characterized by the presence of two large heat sinks mounted on the sides; these are required by the high voltage stabilized power supply circuits which are protected by a wide stainless steel cover. The cover material is non-magnetic and has low thermal conductivity: it has been chosen to prevent the heat generated by the two KT88 from reaching the circuits located below, thus improving the stability, the sound quality and the overall reliability of the system.
The power supply of the Preludio is based on a single toroidal transformer which is specifically designed to minimize the magnetic flux dispersion. In an audio amplifier, the anodic voltage should ideally be supplied by a battery, but this is obviously not possible for a number of reasons such as high costs, short life-expectancy, large size and weight and more.
We considered this problem in depth when we attempted to obtain a power supply stage whose electrical characteristics were the closest possible to those of a battery bank. We found an excellent compromise with a special anodic power supply circuit which features an output capacitance which is much higher than usual.