Grimm Audio PA1: the Dutch brand's first power amplifier

Grimm Audio is known for its converters, the CC1 master clock, the LS1 loudspeaker system and the MU1 / MU2 music players. Never for its power amplifiers — the Veldhoven company had simply never sold one. That changes with the PA1, and the way it came about is rather good.

A prototype hidden under the demo table

Rewind three years, to High End in Munich. Grimm is showing the MU2, its streaming DAC and preamplifier, and needs a power amplifier transparent enough not to get in the way. The team auditions amp after amp and comes away disappointed by all of them. Fallback plan: bring along the in-house amplifier prototypes that had been used during the MU2's development. The system left Munich with a “Best Sound of Show” award.

That stopgap prototype turned into a real project. After repeated listening sessions and successive revisions to the schematic, Grimm says the production PA1 plays well above the Munich prototype. It made its public debut at High End Vienna 2026, in sound cabin M01 in Hall X4 — this time with the MU2 as source and preamp, the roles reversed.

The “Pierick Amp”, a 1985 circuit

The PA1 name isn't only about “Power Amplifier”. It's a tribute to Henk ten Pierick (†), whose output stage concept, conceived in 1985, is the starting point for the circuit. Internally, Grimm calls it the “Pierick Amp”.

The premise is a problem that a 1 kHz THD measurement never shows. In a class AB output stage, the bias point drifts with the temperature of the output transistors. Music is full of low frequencies, and those are precisely what heat the output stage and shift its operating point. The result is a crossover distortion signature that changes constantly with whatever is passing through the amplifier. It doesn't show up on a static measurement, but you hear it.

Grimm's answer looks blunt rather than elegant on paper: instead of a handful of large power devices, the PA1 lines up 96 small, fast transistors in a fully symmetrical circuit, mounted on an aluminium-substrate printed circuit board. That PCB technology gives extremely tight thermal coupling between all the transistors and their driver circuit, which sits on the same board. The consequence: the output stage impedance stays constant across the whole crossover region, even when the amplifier is delivering large low-frequency currents into the speaker. The problem is solved by design, not by correction.

The second target is phase modulation, the other distortion nobody talks about: the speed of the circuit varies with signal amplitude, so a bass line can literally smear the treble of a voice or a cymbal in time. Grimm addresses it with feedforward corrections in the output stage and the stages upstream, then applies a second-order global feedback loop to clean up what remains — again taking care not to reintroduce phase modulation inside the loop itself.

The rest follows the same logic: no series coupling capacitors on the input, the shortest possible input signal routing on multilayer PCBs, and protection circuitry designed so that series relay contacts in the speaker output could be left out entirely. On the supply side, a large Amplimo toroidal transformer chosen for minimal capacitive coupling from the mains, followed by 90,000 µF of decoupling, plus local regulation for the driver and feedback stages.

15 kg in a 25 cm cube

The enclosure is by Michiel Uylings, already responsible for the look of the MU1, MU2 and PW1. The PA1 fits in 250 × 250 × 240 mm — compact for a monoblock of this class — but weighs 15 kg apiece. It accommodates both low- and high-gain preamplifiers via switchable 26 or 18 dB gain, offers XLR and RCA inputs, and goes into standby automatically after 40 minutes of silence. The linear power supply switches to the local mains voltage on its own.

• Power: > 200 W into 4 Ω (press reports around 150 W into 8 Ω)
• THD: < 0.0001 % (1 W, 8 Ω)
• Signal-to-noise ratio: 96 dB (1 W, 8 Ω)
• Damping factor: > 800 re 8 Ω
• Frequency response: 0.1 Hz – 300 kHz
• Inputs: XLR and RCA — selectable 26 dB or 18 dB gain
• Dimensions and weight: 250 × 250 × 240 mm (W × D × H), 15 kg
• Warranty: 5 years (limited)

Availability

The PA1 is a monoblock, so a stereo system needs a pair. Grimm had not published official pricing at the time of writing, and the figures listed by European dealers don't make it clear whether they refer to a single unit or a pair. Get in touch for a firm quote and lead time — we'll come back to you with up-to-date information from the distributor.

If you want to dig into the engineering, Grimm has published an “Under the hood of the PA1” article on its site detailing the thinking behind the output stage and the treatment of phase modulation.