Pre/Power Amplifiers

During our review, editor Paul Miller took the opportunity to talk with VAC's co-founder and guiding light, Kevin Hayes. We discussed Kevin's studied application of what – to the casual observer – might look like a nest of multi-coloured point-to-point wiring to 'fine-tune' the performance of both pre and power amp, before moving swiftly on to the enviable power output achieved by the Signature 200iQ's seemingly modest array of tubes. Are these running particularly hot?

'With respect to overall power, it's generally been forgotten that very soon after the inception of the KT88, nearly 70 years ago, the GEC/Genalex data sheets showed a 100W/pair operating point in its application circuits' says Kevin. 'In practice, we find that some pairs of KT88s will exceed 100W. The KT88 delivers exceptional sound under these conditions and, in our circuits, average tube life is quite good – typically 6000-8000 hours.'

VAC's custom output transformers are also core to the amp's 'real world' performance. 'In stereo mode the taps are effectively for 2, 4 and 8ohm; in mono, a parallel operating configuration, they are effectively 1, 2 and 4ohm. So, in mono mode [as tested here] the maximum power, lowest distortion, and widest freq. response occur into a 4ohm load on the top tap, which is labelled "4-8".

'Most audiophiles will try more than one tap to see which best suits their loudspeaker (with its varying impedance curve), so we label the taps with a range rather than a single number'. PM