The M500 is the latest hybrid stereo power amplifier from Circle Labs. It is the company’s flagship model, combining years of amplifier-building experience, new technologies, and proprietary circuits designed from scratch. The M500 can operate in monoblock mode (fully balanced design), delivering 600 W at 8Ω and up to 1.2 kW at 4Ω. In stereo mode, it provides 180 W at 8Ω and 340 W at 4Ω. It features a three-step sensitivity adjustment, increasing flexibility in pairing with different preamplifiers.
At the heart of the M500 is a carefully selected ECC88/6922 triode, working in an SRPP configuration, which ensures a unique sound quality. The input stage, with a single tube, a single resistor, and a top-class Mundorf Silver Gold Oil signal capacitor, combines a short signal path with excellent parameters, minimizing losses and distortions.
The innovative Circle Power current stage design brings the M500 close to SE amplifier topology, guaranteeing unparalleled detail, natural tonal color, and at the same time full control over the bass – a hallmark of high-efficiency amplifiers. The input stages use the latest ultra-low-noise Burr-Brown J-FET transistors, while the M500’s current stages are based on powerful, high-current Sanken bipolar transistors, ensuring dynamic, clean sound with exceptional speaker control.
The M500 features a dual-mono design with separate power supplies for each channel, supported by a DC-blocker circuit and toroidal transformers with a total power of 1200 W. This guarantees stability and reliability. The tube input stage is powered by a shielded EI-core transformer, further enhancing signal quality. The amplifier’s power supplies are equipped with capacitors of a total capacity of 880,000 µF.