T+A M 40 HV power amplifier Lab Report

Each of T+A's monoblocks comprises two entirely separate power amplifiers, combined in parallel for its 'High Power' and 'High Current' modes but separated in its bi-amp mode. With its default 'High Power' and enriched Class A 'High Current' modes (HP and HC, respectively), T+A's M 40 HV amp is a tale of two very distinct halves. The 550W/1kW 8/4ohm specification was not quite met in practice at 540W/940W in HP mode although this develops to 600W, 1.16kW, 2.05kW and a full 3.47kW into 8, 4, 2 and 1ohm loads under dynamic conditions [grey, pink, cyan and green infills, Graph 1]. This is, by any measure, a true powerhouse... Switching to HC mode halves the PSU rail voltage and limits the power output to 130W/8ohm and 250W/4ohm, although the dynamic headroom of 135W, 270W, 510W and 945W into 8, 4, 2 and 1ohm [black, red, blue and green lines, Graph 1] still demonstrates great load tolerance.


Dynamic power output vs. THD into 8ohm (grey/black, HC), 4ohm (pink/red), 2ohm (cyan, blue) and 1ohm (green) speaker loads. Max current 58.9A


Distortion versus extended frequency at 10W/8ohm (black, high current; red, high power)

Overall gain remains unchanged at +26.1dB but the A-wtd S/N falls by 2dB from 86.1dB (HP) to 84.1dB in HC mode (all re. 0dBW). Distortion, and in particular how distortion changes with level and frequency, also differs between HP and HC modes. In HP guise, distortion increases only marginally from 0.015%/1W to 0.03%/10W, 0.04%/100W and 0.15%/500W with remarkable consistency over the 20Hz-20kHz audioband [red infill, Graph 2]. Switching to HC sees a progressive increase in THD with level and frequency, albeit starting from a lower level: 0.003%/1W to 0.01%/10W and 0.2%/100W with ~0.01% from 20Hz-1kHz increasing to 0.13%/20kHz [black trace, Graph 2]. The response is largely unaltered at –0.35dB/20kHz but output impedance is usefully lower at 0.035ohm in HC mode vs. 0.06ohm in HP. PM

Power output (<1% THD, 8/4ohm): 540W / 940W (130W/250W, HC)
Dynamic power (<1% THD, 8/4/2/1ohm): 600W / 1.16kW / 2.05kW / 3.47kW
Output imp. (20Hz–20kHz/100kHz): 0.060–0.067ohm / 0.125ohm
Freq. resp. (20Hz–20kHz/100kHz): +0.0 to –0.35dB / –1.95dB
Input sensitivity (for 0dBW/500W): 142mV / 3315mV (balanced)
A-wtd S/N ratio (re. 0dBW/rated o/p): 86.1/113.0dB (84.1/105.1dB, HC)
Distortion (20Hz-20kHz, 10W/8ohm): 0.029–0.031% (0.008-0.13%, HC)
Power consump. (idle/rated o/p): 175W / 837W
Dimensions (HWD) / Weight: 560x360x470mm / 52kg (each)
Price: £37,500 (pair)

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