About This Item

The Onkyo Integra M-508 is a stereo power amplifier designed around a Real-Phase amplifier topology, which prioritizes accurate phase and soundfield reproduction. To prevent out-of-phase speaker current from returning into the amplifier circuit, independent power in-phase transformers are installed for each channel in the current path, eliminating common-mode AC line noise and improving phase characteristics. The power supply consists of four transformers in total — two dedicated in-phase transformers for L and R plus a main supply — together with eight 10,000µF capacitors for high-power, short-distance delivery. The output stage employs a triple push-pull transistor configuration. Low-level distortion is suppressed through a linear switching bias circuit, LED-based low-noise bias setting, and a W-sensing servo circuit. Peak power meters feature two switchable ranges and can be turned on or off independently.

🎛 Configuration

· Type: Stereo power amplifier

· Output stage: Triple push-pull transistor

· Power supply: 4-transformer (2× in-phase + main), 8 × 10,000µF capacitors

· Inputs: Variable × 1, Direct × 1

· Outputs: Speaker terminals × 2 (A/B)

· Level control: Independent L/R high-precision multi-brush attenuators

· Peak meters: 2-range switchable (×1 / ×0.1), on/off switchable

📈 Performance

· Rated output: 200W + 200W (8Ω) / 240W + 240W (6Ω) / 290W + 290W (4Ω)

· Dynamic power: 270W + 270W (8Ω) / 460W + 460W (4Ω) / 690W + 690W (2Ω)

· THD: 0.002% (20Hz–20kHz, 8Ω, rated output)

· IM distortion: 0.003%

· Frequency response: 1Hz–100kHz (+0, –1.5dB)

· Power bandwidth: 5Hz–100kHz (IHF –3dB, THD 0.2%)

· S/N ratio: 124dB (IHF-A, input shorted)

· Damping factor: 140 (8Ω, 50Hz)

· Gain: 32dB

🛠 Service (K-WORKS, March 2026)

· Speaker relays × 3 (RL781, RL782, RL783): disassembled and cleaned

· Speaker terminal (SPEAKER-2, L-channel red): replaced

· Solder joints on speaker terminal board and main board: inspected and corrected

· RCA input terminals, AC plug terminals, fuse holder terminals: polished and cleaned

· Bottom panel: mold deposits removed and cleaned

· DC balance: confirmed ±0.000V

· Idling current: adjusted to ±0.015V

· Post-service listening test: approx. 8 hours, normal operation confirmed

📊 Measured Performance After Service

· Maximum output: 188W / 188W (8Ω, 1kHz, both channels)

· THD: 0.0052% / 0.0025% (L/R, 1kHz, 8Ω)

· S/N ratio: 104dB / 106dB (L/R, IHF-A weighted)

📐 Dimensions & Weight

· 465(W) × 187(H) × 426(D) mm

· Net weight: 25 kg

This is a 100V Japanese domestic model. A step-up transformer is required for use outside Japan.

Shipping

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