Grimm Audio PA1 Mono-Block Power Amplifier

The Grimm Audio PA1 is a Class AB mono-block power amplifier from Grimm Audio, the Dutch company behind the MU1 and MU2 music players. Each PA1 drives a single channel with more than 100 watts into 8 ohms and more than 200 watts into 4 ohms, using a fully balanced circuit of 96 fast output transistors and a linear power supply. It grew out of the amplifiers Grimm built while developing the MU2, and its cabinet was drawn by industrial designer Michiel Uylings.

Key Features of the Grimm Audio PA1

• Class AB mono-block design, one chassis per channel
• More than 100 watts into 8 ohms, more than 200 watts into 4 ohms
• 96 fast power transistors on an aluminum circuit board, in an output stage that evolved from Henk ten Pierick's 1985 design
• Fully balanced signal path with no series coupling capacitors
• Linear power supply with an Amplimo toroidal transformer and 90,000 µF of reservoir capacitance
• Selectable gain of 26 dB or 18 dB to match low- and high-gain preamplifiers
• Balanced XLR and single-ended RCA inputs
• Automatic line-voltage switching and auto on/off standby
• Two-year limited warranty, extended to five years when the original owner returns the warranty card to Grimm Audio

Why Grimm Audio Built the PA1

Grimm Audio was founded in 2004 to make studio equipment, and after its LS1 active loudspeaker arrived in 2010, hi-fi became a large share of its business, with products including the MU1 and MU2 music players. When Grimm presented the MU2 in Munich, the company could not find an amplifier transparent enough to show what the MU2 could do. Many of the amplifiers it auditioned disappointed, so it brought prototypes of its own design, the ones it had used while developing the MU2. Those prototypes became the PA1, which premiered at the Vienna High End show. The circuit is an evolution of a 1985 design by the late engineer Henk ten Pierick, and Grimm calls the result the Pierick Amp.

The Pierick Amp Output Stage

At the heart of the PA1 are 96 small, fast power transistors mounted on a modern aluminum printed circuit board. The tight thermal coupling that aluminum provides holds the output stage at a precisely defined operating point. In Grimm's words, this gives "an extremely well defined power output stage setting point, through which the output stage impedance remains constant over the full cross-over region, resulting in the lowest possible distortion of dynamic signals." Grimm's stated goal is the musicality of the best tube designs with the rock-solid performance of the best solid-state designs.

A Linear Power Supply

The PA1 uses a traditional linear supply rather than a switch-mode design. A large Amplimo toroidal transformer was chosen for its minimal capacitive coupling to the mains, feeding 90,000 µF of reservoir capacitance for abundant current on demand. Separate local stabilization keeps the driver and feedback circuits working independently of the current the loudspeaker draws.

A Direct, Balanced Signal Path

The input path carries no series coupling capacitors, and protection circuitry keeps relay contacts out of the speaker signal path. Dedicated feedforward correction reduces phase-modulation distortion, the subtle time smearing that occurs when signal amplitude changes, and a second-order feedback loop lowers remaining distortion without reintroducing it. The damping factor exceeds 800, for tight control of the loudspeaker.

More from Grimm Audio

The PA1 is built to partner the Grimm Audio MU2, which combines a music streamer, DAC, and reference analog preamplifier in one chassis, with a single MU2 feeding a pair of PA1 monoblocks directly. Add the PW1 Phono Preamplifier for vinyl, or explore the LS1c active loudspeaker system.

The Listening Room Difference

We're a third-generation family business with a brick-and-mortar showroom in Chestertown, Maryland, and a reputation built on exceptional service and relentless passion for hifi. Whether you're visiting in person or ordering online, we bring decades of experience, personalized service, and honest guidance to every interaction. We don't just ship boxes. We help build systems, answer your questions like real humans, and make sure every detail of your setup is right, from the cables to the final connection. Our passion is helping you get the most out of your gear, with support that lasts well beyond the sale.

Grimm Audio PA1 Specifications