Circle Labs has unveiled two new amplifiers: the Circle Labs AS100 integrated amplifier and the Circle Labs M500 stereo power amplifier . They premiered at the Audio Video Show 2025 , which took place in Warsaw last weekend.
The Circle Labs M 500 is a flagship two-channel power amplifier built using a hybrid design. Designed from the ground up using proprietary circuit designs, it can operate in stereo or monoblock mode, delivering 180 watts per channel into a nominal 8 Ω load (stereo) or up to 1,200 watts into 4 Ω (monoblock). Three-stage input sensitivity control allows for flexible pairing with a variety of preamplifiers.
At the heart of the Circle Labs M500 amplifier is an ECC88/6922 triode vacuum tube stage in an SRPP configuration, complemented by a Mundorf Silver Gold Oil capacitor for signal purity and minimal distortion. Circle Labs' Circle Power current stage combines single-ended and solid-state topologies, using Burr-Brown J-FETs and Sanken bipolar transistors for high dynamics and low noise. The Circle Labs M500 utilizes a dual-mono design with separate 1.2 kW toroidal transformers and a total of 880,000 µF of power supply filter capacitance, ensuring stable and clean power delivery. A shielded transformer powers the vacuum tube stage, while DC-suppression circuits ensure silent operation.
The Circle Labs AS100 is a solid-state integrated amplifier delivering 75 watts per channel into 8 Ω and 140 watts into 4 Ω. It utilizes the same Circle Power topology for transparent, neutral sound. The AS100 features a 63-step, 0.1%-tolerant, relay-controlled volume control for precise channel balance, reliability, and low noise. The dual-mono design, with separate 400-watt toroidal transformers and 200,000 µF of filter capacitors, ensures low distortion and wide speaker compatibility.
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