A magazine reviewer once wrote the following about the Triode-Tetrode switching version of Manley 250's: "In triode mode a pair of Manleys produces a remarkably three dimensional soundfield that is both convincing and seductive. When switched into tetrode mode, the Manleys have the brawn to deliver a full symphony orchestra directly into your living room." "When I listened through the same cut through the triode mode tube amps, I cried. Yup, tears ran down my cheeks while I bounced up and down, waving my arms, physically buffeted by the raw emotion of the music. Emotion- that essential component at the very core of great music. The Manleys pass through that emotional information, but the (solid-state amps) don't." Tried and true: The Manley 500 and 250 Watt Monoblocks are our most powerful push-pull production-models. Both the circuit design and the selected componentry have been refined over years and years of development. Reliability that you can depend upon combined with musical accuracy and emotional authority is what these amplifiers promise- and deliver. They are able to switch operation modes allowing the listener to choose between the sonically seductive qualities of triode and the more powerful Ultra-Linear configuration. We use big, beefy reservoir capacitors in the high voltage supplies giving plenty of instant energy for dynamic performance of transient peaks and bass impact and weight which often exceeds that of rival solid-state amplifiers. We run high voltages on the plates of the output tubes but operate them at lower current which will result in their longer life. Although each output tube has its own bias-adjust, We carefully fit each amplifier with computer-batched tubes for optimum performance. The bias adjustment pots and measuring points are conveniently located behind the oval front panel insert.