Yamaha C-5000/M-5000 Pre/Power Amplifier Lab Report

Lab Report

Despite its continuous mechanical action the C-5000's volume control is actually stepwise in operation and configured so that both distortion and response are influenced by volume position as much as actual output. For example, with the volume knob wound fully clockwise, distortion is a very low 0.0003%/1kHz [see black trace, Graph 2] and the response flat to –0.5dB/100kHz but at the 12 o'clock position THD is 0.0019%/1kHz and the HF roll-off increased to –0.3dB/20kHz and –4.1dB/100kHz (all at 1V output). Note also that the subsonic filter is ineffective on the balanced output – this has a –3dB point of 2Hz – while the input overload is just 3.2V in its max. (+20dB) gain setting. Beware balanced line sources with a 'standard' 4V or 6V output...

These minor niggles aside, the C-5000 is very 'clean' and, like almost every Yamaha amp, boasts very low noise and a spectacularly wide S/N ratio of, in this instance, a full 102dB (A-wtd, re. 0dBV). The partnering M-5000 is also incredibly 'quiet' with a huge 99dB A-wtd S/N (re. 0dBW) and distortion increasing gently from 0.001%/1W to 0.003%/10W and 0.005% at the rated 100W/8ohm (all 1kHz). At HF there's a mild (but expected) uptick to 0.01%/20kHz/10W [red trace. Graph 2] while the response is both flat and extended with –1dB limits of 5Hz-100kHz. And power? Plenty of it, despite those big meters over-reading: at 10W/8ohm output the needle is close to '50W' on the scale and at the rated 100W output is bouncing off the dial at the '+3dB' position. In reality it kicks out a full 2x145W/8ohm and 2x256W/4ohm with headroom for 167W, 317W, 590W and 995W into 8, 4, 2 and 1ohm loads under dynamic conditions [see Graph 1, below]. This is one very capable '100-watter'! PM


Dynamic power output versus distortion into 8ohm (black trace), 4ohm (red), 2ohm (blue) and 1ohm (green) speaker loads. Max. current is 31.5A


THD versus extended freq. for C-5000 preamp (1V out, black trace) versus M-5000 (10W/8ohm, red)

Continuous power (<1% THD, 8/4ohm) 145W / 256W
Dynamic power (<1% THD, 8/4/2/1ohm) 167W / 317W / 590W / 995W
Output imp. (20Hz–20kHz, pre/power) 74-92ohm / 0.0026–0.070ohm
Freq. resp. (20Hz–100kHz, pre/power) –0.05 to –0.5dB / –0.07 to –1.1dB
Input sensitivity (for 0dBV/0dBW) 98mV (pre) / 199mV (power)
A-wtd S/N ratio (re. 0dBV/0dBW) 101.5dB (pre) / 99.0dB (power)
Distortion (20Hz-20kHz, 1V/10W) 0.0001–0.002%/0.003–0.012%
Power consumption (Idle/Rated o/p) 73W/362W (48W, Preamp)
Dimensions (WHD, Pre/Power) 435x142x451/435x180x464mm
Prices £6499 (each)

Yamaha Corporation
Supplied by: Yamaha Music Europe GmbH (UK)
0844 811 1116