Pre/Power Amplifiers

Not so much monoblocks as monoliths, these new flagship power amps from Germany's T+A certainly have what you'd call 'in room presence'. At least they do when you have got them in position, a task hampered by the fact each is a 50kg+ dead weight, although admittedly the two substantial handles sprouting from the top panel – and the assistance of a friend – will help.

Derived from the M10 model launched back at the beginning of the decade [HFN Aug '12], and designated M 40 HV to mark both the company's 40 years in business and its use of a 'High Voltage' working methodology, these imposing power amps are yours for £37,500 a pair. If you're tempted, you will need to don your skates: T+A says its M 40 HV Anniversary Edition (to give the amplifier its full moniker) 'will only be built in our anniversary year'.

So it's a case of 'get 'em while they're hot'. Except that, in practice, and despite all their prodigious power – rated at 550W/8ohm apiece (but, as PM's Lab Report shows, capable of rather more under dynamic conditions) – their use of valves in the preamp stage and the absence of fan-cooling, these are remarkably well-mannered power amps.

Split Decision
Gratifyingly, the M 40 HVs don't require extensive running-in and the substantial heatsinks bulging from their flanks do a good job of dissipating heat. They may dominate the room, especially when used in a 'long interconnect, amps beside speakers' configuration, but they're not going to make your listening space uncomfortably muggy in the fashion of some pure valve amplifiers.

Monoblocks these may be, but they use two separate power amp sections within, as is revealed if one opens up the amplifier to have a look inside. The preamp section lifts on a hinge, and then the two output stages, each with their five pairs of bipolar transistors bolted directly to their heatsinks, swing out like doors. This reveals the massive power supply capacitor banks, located low down in the centre of the amplifier and offering a total of more than 180,000µF, and the steel shielding below which lurk the equally substantial transformers, each rated at 1000W.

Also noticeable is the large amount of 'fresh air engineering' going on here, but this is by no means a matter of poor packaging. Rather, the design is informed by the function of the various sections, and the need to maintain a healthy distance between them. So why two power amps in a monoblock? Well, in normal working the two operate in parallel to drive the speaker to which the M 40 HV is connected, but there are options, selected by tiny slider switches located between the mains input and the RJ45-type sockets for the company's HLink remote control system.

The one to the right switches the amp into bi-amping mode, in which each amp module supplies one of the two sets of substantial speaker terminals provided. T+A also says that even with single-wired speakers one can use parallel runs of cable from the two sets of terminals to the speakers, giving optimum damping for the speaker and, by inference, improved resolution. Meanwhile to the left is a High Current/High Power selector, of which more in a moment.

Even the input provision is slightly unusual – the RCA phono and three-pin XLR socket are pretty standard, but the M 40 HV also has a four-pin XLR input for use with those preamps providing line-level audio plus a trigger voltage for remote switch on/off. There's also a signal-sensing facility, with auto power-off after 30 minutes of no signal, although T+A recommends that its HLink, trigger switching or the main power switch is used rather than this signal-sensing, due to the time the amp takes to power up, pre-heat the input valves and lift the speaker muting relays.