Circle Labs M500

The M500 is a hybrid power amplifier that combines years of experience in amplifier design, cutting-edge technologies, and custom-designed circuits developed from the ground up. The M500 offers monoblock operation (fully balanced circuit) with 600 W at 8Ω and up to 1.2 kW at 4Ω. In stereo mode, its power output is 180 W at 8Ω and 340 W at 4Ω. It features a three-step sensitivity adjustment, increasing versatility in preamplifier selection.

The M500 is a hybrid power amplifier that combines years of experience in amplifier design, new technologies, and custom-designed circuits. The M500 offers monoblock operation (fully balanced circuit) at 600 W into 8Ω and up to 1.2 kW at 4Ω. In stereo mode, its power output is 180 W at 8Ω and 340 W at 4Ω. It features three-step sensitivity adjustment, increasing versatility in preamplifier selection.

At the heart of the M500 is a precisely selected ECC88/6922 triode operating in an SRPP configuration, which ensures unique sound quality. The single-tube input stage, featuring a single resistor and a top-of-the-line Mundorf Silver Gold Oil signal capacitor, combines a short signal path with excellent performance, minimizing losses and distortion.

The innovative design of the Circle Power output stages brings the M500 closer to SE amplifier topology, guaranteeing unmatched detail, natural sound color, and at the same time full control over the low frequencies, typical of high-efficiency amplifiers. The input stages utilize the latest ultra-low-noise Burr-Brown J-FET transistors, while the M500’s power stages are based on powerful, high-current Sanken bipolar transistors, ensuring dynamic, clear sound with unparalleled control over the speakers.

The M500 is a dual-mono design with separate power supply circuits for each channel, supported by a DC-blocker circuit and toroidal transformers with a total power rating of 1200 W. This ensures stability and reliability. The tube preamp section features a shielded EI-core transformer, which further enhances signal quality. The amplifier’s power supply is equipped with capacitors with a total capacitance of 880,000 μF.