Philips AG9016 tube amplifier Lab Report

Lab Report

Tested via its 'Radio' (R) input, this vintage specialty achieved a full 18.6dB gain from its ECC83/EL95 triode/pentode combo, requiring 332mV for 1W/8ohm (the standard line level was 500mV in the day). Class A operation was claimed and the 26W dissipation is, indeed, unchanged whether the AG9016 is at idle or full power. The rear of the amplifier has a single set of outputs optimised for a 5ohm load – a good compromise even with today's '4-8ohm' loudspeakers – and rated at 2W/channel under unspecified conditions. In practice it achieved 2x1.3W/8ohm and 2x1.2W/4ohm at 1kHz with 2% distortion, increasing under dynamic conditions to 1.8W and 1.7W into 8 and 4ohm loads, respectively. There's a current limit of ~0.65A so the output falls into lower impedances, the AG9016 achieving 0.8W/2ohm and 0.4W/1ohm at a full 5% THD [see Graph 1, below]. There's no escaping the fact that the AG9016 must be used with speakers offering a 4ohm+ nominal load and very high 92dB+ sensitivity.

Aside from low power, the AG9016 retains plenty of other 'character'. Distortion increases with output level and at low bass/high treble frequencies [see Graph 2], from 0.4-1.15% at 100mW (0.1W) to 1.3-15.5% at 1W/8ohm (all from 100Hz-20kHz). Distortion increases markedly below 100Hz as the output is filtered – the response gently declining to –3.0dB/10kHz, –4.9dB/20kHz (and –22dB/100kHz) but peaking at +1.9dB/70Hz before rolling away to –23dB/20Hz [blue trace, Graph 2]. There's a corresponding 'bump' in output impedance from 1.4ohm to 3.7ohm at 70Hz while noise, from the rectifier in particular, resulted in a high –46dBV (5mV) residual and below average A-wtd S/N ratio of 72.1dB (re. 0dBW) in our sample. 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 0.65A


Freq. response (re. 0.5W/8ohm, blue) and THD vs. freq from 100Hz-40kHz (100mW, black; 1W, red)

Power output (<2% THD, 8/4ohm) 1.3W / 1.2W
Dynamic power (<5% THD, 8/4/2/1ohm) 1.8W / 1.7W / 0.8W / 0.4W
Output imp. (20Hz–20kHz/100kHz) 3.7–1.4ohm / 16.5ohm
Freq. resp. (50Hz–20kHz/100kHz, 0.5W) +1.9dB to –4.9dB/–22dB
Input sensitivity (for 0dBW/2W) 332mV / 470mV
A-wtd S/N ratio (re. 0dBW/2W) 72.1dB / 75.1dB
Distortion (100Hz-20kHz, 1W/8ohm) 1.3–15.5%
Power consumption (Idle/rated output) 26W / 26W
Dimensions (WHD) / Weight 310x85x250mm / 4.5kg