Pre/Power Amplifiers

Shortly after the turn of the new millennium, PrimaLuna began manufacturing valve amplifiers for buyers hankering for an alternative to the stereotypical solid-state sound. The Netherlands-based company launched accessible tube designs with up-to-the-minute styling, starting with the ProLogue and then DiaLogue ranges. These played an important part in proselytising the joys of 'glass audio' to a new generation. Now, the company's new EvoLution range – EVO for short – has taken over the mantle, with 100, 200, 300 and 400 levels. The EVO 400 pre/power amplifier combination you see here (£4150 apiece) is the company's third-generation flagship.

There's no mysticism to PrimaLuna, no pretentious backstory that warrants a high-end price tag. This pre/power is devoid of gimmicks, with a neat and uncontrived design allied to solid engineering. Although the preamplifier has no internal DAC, there's a good selection of inputs – including, for the first time on a PrimaLuna amp, balanced XLR connections – that let it form the heart of a modern hi-fi system.

Perfect Pairs
The power amplifier offers excellent loudspeaker driving ability and switchable triode/ultralinear operation to taste. The traditional valve amplifier issue of reliability is addressed by careful component choice and the use of two unstressed pairs of EL34 power valves per channel, when many rivals deploy only a single pair each side. Lest we forget, the EL34 is probably the world's most popular audio output tube of all time – guitar amp users swear by them – so the valves are inexpensive and plentiful.

The EVO 400 preamp sports a number of noteworthy design features. This fully dual-mono design has twin custom-wound toroidal power transformers, said to be low in hum and electromagnetic interference. Selected passive components are fitted, including Japanese Takman resistors, DuRoch tinfoil capacitors and a motorised ALPS Blue Velvet volume pot.

Input selection is achieved using sealed relays, mounted right behind the rear panel for short signal paths. Neat, hand-wired, point-to-point wiring is employed, using Swiss-made silver-plated OFC wire. Alongside a pair of 5AR4 tube rectifiers there are three 12AU7 triodes per channel, with the four outermost being the drivers, and the central two the input valves.

The EVO 400 power amp shares the same approach in terms of power transformers, passive component choice and so on – yet there are a number of features specific to it. It sports six 12AU7 triodes and, in the standard version tested here, eight EL34 output valves, the latter configured in either triode or ultralinear modes at the press of a button on the IR remote! Claimed power output is 2x70W/8ohm in ultralinear mode, dropping down to 2x38W/8ohm in triode mode.

Ready To Roll
One bugbear of valve amplifiers is biasing the tubes – an essential job but not every owner's idea of fun. PrimaLuna has removed the need for this with its 'Adaptive AutoBias' circuit, which continuously monitors the condition of all the valves. PrimaLuna does not run its valves hard, but when the inevitable finally does happen and a tube goes down, it instantly switches the amp into protection mode and illuminates a red LED beside it.

The 'Smartwatts' system runs the output valves at minimum dissipation without going into crossover distortion. Lower plate and screen voltages mean the tubes are less stressed – the company says both are set at 417V, compared to many rivals that push north of 600V.

Meanwhile, and key for tube-rollers, the AutoBias facility also ensures the EVO 400 will accommodate almost any power tube you desire – including the 6L6G, 6L6GC, 7581A, EL34, EL37, 6550, KT66, KT77, KT88, KT90, KT120 and even the huge KT150. So power output, and sound, will also vary with your choice of tube.

The amplifier comes with 4, 8 and 16ohm taps at the back, and can be switched into monoblock operation should you find yourself able to afford an additional EVO 400. In this mode, it thumps out a claimed 140W/8ohm in ultralinear and 82W/8ohm in triode mode with the supplied EL34s.

Build quality is extremely good and there's a choice of black or silver front panels to complement a removable rounded safety cage – not just decorative but for protecting against high voltages. Both units are physically quite large, and virtually identical in size, so you'll need a chunky hi-fi rack to house them.

Thoroughly Modern
The company's founder, Herman van den Dungen, has voiced this combination to sound crisp, punchy and modern. It's a very long way from the soggy sound of Leak Stereo 20s huffing and puffing their way through beat-driven music. Despite this, the PrimaLuna EVO 400 combo still has something of a 'valve sound' – fulsome in the bass, while the midband has a subtle richness that's not something you hear from all transistor amplifiers. This said, it's also surprisingly insightful and one might even say 'well lit' in the upper mid. Treble is clean and smooth yet retains plenty of energy.