Vintage

It’s not explicitly stated in any Philips literature that we have to hand, but the rated output of the AH 606 looks to be a very substantial 2x60W/8ohm. In practice it achieves a little more at 2x75W/8ohm and 2x85W/4ohm while developing 96W and 89W into 8/4ohm under dynamic conditions [black and red traces, Graph 1]. That decline in output into lower impedances – down to 41W/2ohm and 24W/1ohm – reflects the AH 606’s modest 4.9A current limit, so while this is a capable amplifier it is still best suited to 8ohm nominal impedance loudspeakers. Maximum gain (via the Tape 1 input) is a very useable +36.7dB while the A-wtd S/N ratio is, by today’s standards, a little below average at 80dB (re. 0dBW) albeit still perfectly adequate for sources of the day. There’s no tone defeat facility here so the AH 606’s response is still modified by the default ‘0’ position of the bass/treble tone controls, the latter providing a broad +0.6dB boost through presence/treble before rolling away to –3dB/59kHz and –7.9dB/100kHz.

The Low and High Cut filters have –3dB points at 69Hz and 7kHz, respectively, falling to –12.6dB/20Hz and –10dB/20kHz. The final amp/speaker system response may also be marginally modified by the AH 606’s ~0.2ohm source impedance but the low ~2mV DC offset of the (DC-coupled) speaker output is impressively controlled. Distortion is also low at 0.0045% through the midband, rising to ~0.04% at the 20Hz/20kHz frequency extremes (all re. 0dBW). Versus output level, midband distortion increases linearly from 0.005%/1W to 0.02%/10W, 0.04%/20W, 0.06%/40W and 0.08% at the rated 60W (all re. 1kHz/8ohm). Stereo separation is good to 70dB midband. PM

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