Inca Tech Claymore amplifier Lab Report

Lab Report

Quite remarkably, having not had a sniff of 240V AC mains for nearly 35 years, this rare gold-on-nickel-plated Inca Tech Claymore powered up and delivered a 'sterling' performance right out of the gate. Demonstrating the longevity of its (now classic) Hitachi J119/K414 power MOSFETs, the amp may have lagged slightly behind its rated 50W specification at 45W/8ohm and 61W/4ohm, but under dynamic conditions it pumped out 71W, 119W, 187W and a full 226W into 8, 4, 2 and 1ohm loads at <1% THD. It's this 15A current delivery from its very loosely-regulated PSU that lies behind the Claymore's 'louder than you might expect from a 50-watter' reputation [see Graph 1, below].

Overall gain is about average for the era at +40.5dB while the 82dB A-wtd S/N ratio and 0.4dB channel balance error (re. 0dBW) are the only real suggestions of 'age' in this sample. The Claymore is a remarkably wide bandwidth design with a low 0.02-0.04ohm output impedance that maintains a ±0.2dB response from 6Hz-34kHz over a full 8-2ohm load range. The ultrasonic response is flat to ±0.3dB/100kHz! Distortion is not vanishingly low and increases at both bass and treble frequencies [see Graph 2, below] but it does remain very consistent at 0.017-0.018% over the first 35W of its output through the midrange. At 10W/8ohm this increases to 0.052%/20Hz and 0.17%/20kHz.

Stereo separation is merely adequate at ~50dB through bass and midrange, falling to ~30dB/20kHz, but the high DC offsets measured when the Claymore was 'cold' – up to 120mV on one channel – soon reduced to <20mV after some 30mins operation. Otherwise the Claymore's technical armoury is sufficiently robust to suggest it should, perhaps, have been a giant-killer. PM


Dynamic power output vs. distortion up to 1% THD into 8ohm (black trace), 4ohm (red), 2ohm (cyan) and 1ohm (green) speaker loads. Max current is 15A


Distortion vs. extended frequency from 5Hz-40kHz at 10W/8ohm (left channel, black; right, red)

Power output (<1% THD, 8/4ohm) 45W / 61W
Dynamic power (<1% THD, 8/4/2/1ohm) 71W / 119W / 187W / 226W
Output imp. (20Hz–20kHz/100kHz) 0.02–0.039ohm / 0.275ohm
Freq. resp. (20Hz–20kHz/100kHz, 0dBW) –0.03dB to –0.09dB/–0.25dB
Input sensitivity (for 0dBW/50W) 27mV / 193mV
A-wtd S/N ratio (re. 0dBW/50W) 82.2dB / 99.2dB
Distortion (20Hz-20kHz, 10W/8ohm) 0.039–0.16%
Power consumption (Idle/rated output) 6W / 175W
Dimensions (WHD) / Weight 340x94x300mm / 5kg