Integrated Amplifiers

Carefully positioned under the Quad 3’s wrap-around bonnet is a Class AB power amp rated at 2x65W/8ohm and 2x100W/4ohm, figures that are comfortably met at 2x74W and 2x120W, respectively, and with sufficient headroom in its partnering linear PSU to accommodate 91W, 170W and 145W into 8, 4 and 2ohm under dynamic conditions [see Graph 1]. Output into the lowest 1ohm loads is limited to 80W (or 9A re. 1kHz/10msec/<1% THD). Overall gain is a sensible +29.3dB (the preamp section is 0dB) to get good use out of the volume control while noise is very low and the A-wtd S/N ratio a fine 92.4dB (re. 0dBW). Distortion is low and very consistent with power output at 0.0008-0.001% from 1W to the rated 65W (re. 1kHz/8ohm) and increases only at higher frequencies – 0.045%/20kHz/10W. Output impedance is a usefully low 0.025ohm and the response deep and extended with 1dB points at 1Hz-68kHz (–1.6dB/100kHz).

Tested via the pre outs, the Quad 3’s digital stage is steered by the choice of ES9038Q2M DAC, although only five filters are offered here. The Linear, Minimum and Hybrid Fast filters afford a good 83dB, 75dB and 98dB suppression of stopband images, respectively, vs. 14dB and 18dB from the Linear and Minimum Slow choices, although the latter suffer less ‘ringing’ in the time domain. Responses are flattest at –0.0dB/20kHz, –0.15dB/45kHz and –0.8dB/90kHz with Minimum Fast and ‘gentler’ at –5.0dB/20kHz, –7.1dB/45kHz and –7.4dB/90kHz with Minimum Slow (all re. 48kHz, 96kHz and 192kHz media, respectively). The A-wtd S/N is a wide 109.3dB and distortion falls to a minimum of 0.00005-0.0005% at –10dBFs [see Graph 2] while jitter is incredibly low at <5psec across all sample rates. PM