Icon Audio Stereo ST30 SE Integrated Amplifier Lab Report

Lab Report

While certainly more powerful than the average 300B-based SE tube amp – a clear goal for designer David Shaw – the ST30SE is still not blessed with a prodigious output and remains better suited to high sensitivity (90dB+ re. 2.83V/1m) loudspeakers. Distortion increases with power so the ST30SE's maximum output rather depends on our definition of 'hi-fi' – 17W into 8/4ohm (via the 8 and 4ohm taps) at 1% THD up to 30W into 8/4ohm at 2% THD. There is only a marginal increase to 32W with a further relaxation to 3% THD, but a reduction in output to 17-18W into 8/4ohm loads and just 10W/6W into 2/1ohm loads (via the 4ohm tap) under dynamic conditions [see Graph 1, below].

Power output in Triode mode is typically ~60% of that in Ultralinear, the ST30SE achieving 2x22W into 8/4ohm loads at 2% THD. In Ultralinear guise, and with 'Low gain/moderate feedback' selected, the output impedance is 0.85-1.17ohm (20Hz-20kHz), but this falls to 0.47-0.54ohm in Triode mode, improving LF damping. Into 'flat' non-reactive 8 and 4ohm loads the response reaches down to 6Hz and out to 50kHz (–3dB points) but there will be greater variation in the amp/speaker system response in Ultralinear mode because of its higher source impedance. Distortion is slightly lower at low power (1-5W) in Ultralinear mode at 0.2-0.5%, but in Triode mode it is more consistent at 0.58-0.62% (all at 1kHz/8ohm). Versus frequency, at 10W/8ohm, the THD trends are very similar indeed [see Graph 2, below]. Finally, there is about 1dB difference in gain between Triode and Ultralinear (+29dB vs. +30dB) but nearly 2dB advantage in A-wtd S/N at 85.1dB vs. 83.4dB, respectively, with any residual hum/flicker noise less than –64dBV. PM


Continuous (grey) and dynamic power output vs. distortion into 8ohm (black), 4ohm (red), 2ohm (blue) and 1ohm (green) loads. Max. current is 2.8A


Distortion vs. frequency, 20Hz-20kHz at 10W/8ohm (black, Ultralinear; red, Triode mode)

Power output (<2% THD, 8/4ohm) 30W / 30W
Dynamic power (<5% THD, 8/4/2/1ohm) 17W / 18W / 10W / 6W
Output imp. (20Hz–20kHz/100kHz) 0.85–1.17ohm / 1.58ohm
Freq. resp. (20Hz–20kHz/100kHz) +0.0dB to –0.6dB/–9.4dB
Gain (High/Low, Ultralinear mode) +36.9dB / +30.1dB
A-wtd S/N ratio (re. 0dBW/28W) 83.4dB / 97.9dB (Low Gain)
Distortion (20Hz-20kHz, 10W/8ohm) 0.61–10.9% (Low Gain)
Power consumption (Idle/Rated o/p) 177W / 220W (44W standby)
Dimensions (WHD) / Weight 380x240x300mm / 28kg
Price £2299

Icon Audio
Supplied by: Icon Audio
0116 2440593