Yamaha M-70 Natural Sound Stereo Power Amplifier 200 Watts Per Channel Tested 1982
Yamaha M-70 Natural Sound Stereo Power Amplifier (1982) — tested, fully functional, and currently in daily use.
The M-70 is Yamaha's flagship Natural Sound power amplifier from the early '80s: 200 watts per channel into 8Ω, discrete Class A/B output, independent left and right power supplies, and high current capability for demanding speakers. The large illuminated dual power meters are the centerpiece of the M-series, and on this unit they work exactly as they should. It's the natural partner to a Yamaha C-70 or C-80 control amplifier. Made in Japan.
IN USE RIGHT NOW
This amplifier isn't sitting on a shelf waiting for a buyer. It's currently set up and running in Spencer's own listening system at home, and it will stay in service until it sells. That's the most thorough burn-in test we can give a unit — hours of real use on real speakers, not a five-minute bench check.
WHAT WE TESTED
- Both channels driven under load — clean output, no distortion, no dropout, no channel imbalance
- All power meter segments illuminate correctly on both channels, with full sweep
- PEAK HOLD, RANGE, and METER OFF all function as intended
- Protection circuitry engages and releases correctly on power-up and power-down
- Speaker A/B switching verified on both banks
- LEFT and RIGHT level controls verified through full rotation — smooth, no scratchiness
- RCA line inputs verified on both channels
- Rear unswitched AC outlet verified live
WHAT WE DID
This unit did not require repair. No parts were replaced. Controls, switches, and internal connections were cleaned with electrical contact cleaner, and the chassis was cleaned inside and out. Everything else is original and working. We'd rather tell you that plainly than dress it up — a 1982 amplifier that still performs to spec without intervention is a good sign, not a shortcut.
COSMETIC CONDITION — 8/10
Honest and itemized. This is a forty-year-old amplifier and it shows its age in the places you'd expect. All flaws below are pictured.
- Scratch on the right side of the front faceplate, visible under direct light
- Light scratching and haze on the smoked meter window — does not obstruct the meter reading
- Light scuffing along the top front edge of the faceplate
- Minor mark on the left side panel
- Top cover, vents, knobs, and rear panel are otherwise clean. All knobs and switch caps present and original.
The orange inventory marking visible in our rear-panel photos is our internal tracking and will be removed before the unit ships.
WHAT'S INCLUDED
- Yamaha M-70 Natural Sound Stereo Power Amplifier
- High-quality speaker wire
Power cord is permanently attached to the chassis.
NOT INCLUDED: original box, manual, or rack hardware.
TESTED AND WARRANTIED
Every unit we sell is tested by hand before it lists. This amplifier is backed by our 30-day warranty from the date of delivery. If it arrives not performing as described, contact us and we'll make it right.
SHIPPING AND PACKING
30 lbs. Double-boxed and foam-suspended, with the faceplate and meter window protected against transit damage.
Local pickup available at our Mesa location.
SPECIFICATIONS
- Power output: 200 watts per channel into 8Ω (stereo)
- Dynamic power: 400W (4 ohms)
- Frequency response: 1Hz to 100kHz
- Total harmonic distortion: 0.002%
- Damping factor: 200
- Input sensitivity: 1.41V
- Signal to noise ratio: 124dB
- Natural Sound discrete Class A/B output design
- Independent left/right power supplies
- Speaker A/B switching
- Inputs: RCA line in x1 L/R (rear)
- Outputs: Speakers x2 L/R (rear), unswitched AC outlet (rear)
- Power requirements: 120V AC, 60Hz
- Dimensions: 17.13" W x 14.9" D x 5.2" H
- Weight: 30 lbs
- Manufactured 1982, Nippon Gakki Co. Ltd., Made in Japan
