Output stage is a NicPoulson'sproprietary design. It combines advantages of MOSFET andbipolartransistors. The output devices are configured to operate in a highbiasstate, giving a generous envelope of Class A operation. Therelatively highdissipation, in conjunction with the high thermalinertia of the heatsink, keepsthe devices in their optimumoperating condition and improves sound quality. Thefast, agile FETonly operates within the critical first watt region. Thebipolartransistors then seamlessly contribute high current when musicconditionsdemand. It reminded me of the Devialet that sports asmall, analogue amplifieroperating in class A, combined with apowerful class D amp. Trilogy uses twoanalogue amplifiers though.
Signal's path is very short. Three fullybalanced and three single endedrear panel inputs are switched viainstrumentation grade ruthenium plated relayswithin millimeters ofthe rear panel connectors. A separately selectableauxiliary loop isprovided. In addition, a 3.5mm jack on the front panelallowsportable sources to be connected quickly and easily. A carefullyselectedaudio grade digitally controlled potentiometer providesvolume control andbalance in 1.0dB steps. Conventional extrudedheatsinks display strong resonantsignatures and have been rejectedin favor of custom, machined solid billets ofaluminum. Each weighsin excess of 5kg. Their high mass and irregular formprovideoutstanding mechanical and thermal stability for the output devices.
Trilogy 925sports three powertransformers. One supplies output stage,one preamplifier, and thirdlogic circuits. The power transformers are mountedon a thickmachined plate of K-material (same one is used inside ISOL-8powerconditioners). This high metal, low resin content composite hasexcellent mechanicalproperties and superior self damping to metal.It provides additional dampingand stiffening of the non magneticchassis too. K-material is also used for thefeet, providing theoptimum interface between the 925 and the equipment support.Custom(Mundorf?) Trilogy reservoir capacitors smooth each channel of theoutputstage DC and valve HT supplies.
This is an outstanding piece ofengineering. All aspects of the designwere carefully thoughtthrough. While the signal's path is extremely short therest of thecircuit is very complex, just like in my Solution 710poweramplifier.
