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Most audio engineers split hairs. Eelco Grimm splits microseconds. His expertise in high-precision audio laid the groundwork for Grimm Audio, the Dutch venture he cofounded in 2004 with fellow electrical engineer Guido Tent. The company's master clocks and DACs, developed for both the pro audio and home hi-fi markets, combat tiny timing errors and jitter that can blight digital audio.

But Grimm Audio's engineering acumen also extends to the analog domain, as evidenced by the LS1c active speaker system that made the cover of Stereophile's April 2025…

van Bakel: I listened to the LS1s with and without the SB1 subs. Even without them, my brain believed it was still hearing the entire bottom octave in bass-heavy music—even though according to the specs, the main speakers bottom out around 35Hz. What was happening?

Grimm: In two-way mode, we use DSP to correct for the absence of the subs, and we can get the LS1 to play as low as 20Hz all by itself. But that does greatly increase cone excursion, so distortion sets in. That distortion has a way of accentuating the very low…

The tubes in the preamp chassis and the power supply were installed when I unpacked the two shipping boxes, but I checked that they were correctly seated before starting the testing. I performed a complete set of tests with my Audio Precision SYS2722 system after powering up the preamplifier and letting it settle for 30 minutes.

The Treehaus inverted absolute polarity with all of its inputs and outputs, which is what I would expect from a circuit that uses a single triode in the signal path. The Treehaus's input impedance is specified as a minimum of 40k…

Analog Sources: Continuum Audio Labs Caliburn, Cobra, Castellon turntable, tonearm, stand; Graham Engineering Phantom Supreme II, Kuzma 4Point tonearms; Miyajima Labs Focus mono, Lyra Atlas, Ortofon Anna cartridges.
Digital Sources: MSB Platinum Data CD IV & Platinum Diamond DAC IV CD transport & DAC & Platinum Studio ADC; BPT-modified Alesis Masterlink hard-disk recorder; Meridian Digital Media System; Pure Music software.
Preamplifier: darTZeel NHB-18ns.
Power Amplifiers: darTZeel NHB-458, Ypsilon Aelius (both monoblocks); Musical…

Analog sources: J.Sikora Standard Max Supreme turntable with KV9 Max Zirconium tonearm. Aidas Tru-Stone Gold Web phono cartridge.
Digital sources: Tascam CD player, HoloAudio May DAC.
Preamplifiers: Tavish Audio Design Adagio, Manley Chinook (phono). Rogue Audio RP-7, Shindo Allegro.
Power amplifiers: AirTight ATM-1 2024E, Rogue Stereo 100.
Integrated amplifiers: Unison Research S6, Riviera Labs Levante.
Loudspeakers: Voxativ Ampeggio 2024, DeVore Fidelity Super Nine, Volti Audio Lucera.
Cables: Interconnect: AudioQuest Pegasus,…

Description: Two-channel, stereo, tubed preamplifier with external power supply. Vacuum tube complement: two 6CJ3 rectifier tubes, two 4P1L signal tubes, all new old stock. Inputs: 5 pair single-ended (RCA). Outputs: 2 pair single-ended (RCA). Input impedance: 40k ohms. Output impedance: 150 ohms. Frequency response: 20Hz– 20kHz, ±2dB. S/N ratio: >90dB. Maximum gain: 6.5dB/13dB (user selectable). Maximum output voltage: 4V RMS at 2V RMS input (low gain setting); 8V RMS at 2V RMS input (high gain setting). THD: <0.05%. Power consumption: 65W.
Dimensions…

Analog source: Technics SL-1200MKV with KAB 3-speed mod, fluid damping and tonearm wiring; Hana SL MKII cartridge. Philips AF-887 with Shure M97xe cartridge.
Digital sources: dCS Bartók streaming DAC, Cambridge MXN10 streaming DAC, Oppo UDP-203 universal disc player.
Phono preamplifier: ProJect Phono Box RS2.
Line preamplifier: Benchmark LA-4.
Power amplifier: Benchmark AHB2.
Integrated amplifier: McIntosh MA6500.
Loudspeakers: Amphion One18, Bowers & Wilkins 808.
Accessories: Butcherblock Acoustics equipment rack, SME…

Digital sources: Moon 260D CD transport, iFi iDSD Diablo DAC.
Integrated amplifier: Grandinote Shinai.
Loudspeakers: Focal Aria K2 936, Dynaudio Contour 30i.
Cables: Interconnect: Kimber Kable 1016 (RCA). Speaker: Kimber Kable Monocle-XL (w/banana plugs). Digital: Kimber Kable D60 (RCA S/PDIF), AudioQuest Forest (USB). Power: Shunyata Research Black Mamba CX, LessLoss DFPC, DR Acoustics Red Fire Ultra.
Accessories: Shunyata Research Venom PS8 power conditioner; a component rack and a wood plinth stand (under turntable) whose brand names are…