T+A M 40 HV power amplifier Sidebar

Current Conundrum

When it comes to maximum power output into very low speaker loads, T+A's 'High Current' mode actually delivers less current than its 'High Power' mode: 30.7A versus 58.9A into 1ohm (10msec at <1% THD). But this is a twist of translation, for 'High Current' actually refers to the increased quiescent current standing in each of the amplifier's two output stages. So while the PSU rail voltage is reduced from ±100V to ±50V in 'High Current' mode, the enriched biasing is sufficient for T+A to claim Class A operation up to 60W. Overall power output is reduced to 130W/8ohm and not the '250W' quoted in T+A's literature – a figure surely referring to 4ohm, not 8ohm. However, the 'High Current' mode certainly brings advantages in lower bass/mid distortion and improved speaker damping, and despite offering lower power, this mode is still remarkably tolerant of difficult speaker loads [see Lab Report]. After all, there are very few '130W' amplifiers that will sustain just under 1kW into 1ohm! PM

T+A elektroakustik GmbH & Co.
KG, Germany
Supplied by: Kog Audio, UK
01353 721089