Boulder 1110/1160 Pre/Power Amplifier Lab Report

Lab Report

Segmented across the 1110's +20dB to –80dB gain, Boulder's volume control is a precision instrument in its own right, accurate to within ±0.1dB over the top 40dB of its dynamic range (volume +0.0dB to –40.0dB), ±0.2dB over a 80dB range and ±0.5dB over the full 100dB range. Distortion is vanishingly low at 0.0001-0.0003% [20Hz-20kHz; black trace, Graph 2], maximum output more than sufficient at 17.8V from a 49ohm source and the A-wtd S/N ratio very wide at 102dB (re. 0dBV). The frequency response is equally flat and extended to within ±0.01dB from 1Hz-20kHz, falling to a mere –0.5dB/100kHz.

The performance of the partnering 1160 power amp is no less impressive in its unflappable linearity. While Boulder rates the 1160 rather ambiguously at '300W into 8, 4 and 2ohm' the real world figures are 2x550/8ohm and 2x950W/4ohm with sufficient PSU reserve to accommodate 668W, 1.25kW and 2.19kW under dynamic conditions into 8, 4 and 2ohm loads at <1% THD. Electronic protection limits the output to 750W/1ohm [see Graph 1, below]. Distortion is extremely low but decreases with increasing power output from 0.0013%/1W to 0.00065%/10W and 0.0003%/100W before reaching 0.00025% at the rated 300W/8ohm (all re. 1kHz). This trend is unaffected by signal frequency although there is a steady increase in THD from, say, 0.00065%/1kHz to 0.0074%/20kHz [all re. 10W/8ohm; see Graph 2, below]. In common with the 1110, the 1160 is designed to offer a flat and extended response (±0.5dB, 1Hz-55kHz) from a low 0.005-0.009ohm source impedance (20Hz-20kHz) with very low noise – the A-wtd S/N ratio is 99.5dB (re. 0dBW). Both preamp and power amp are masterpieces of rugged engineering. PM


Dynamic power output versus distortion into 8ohm (black trace), 4ohm (red), 2ohm (blue) and 1ohm (green) speaker loads. Max current is 33.1A


Distortion vs. freq for 1110 (re. 0dBV, black) and 1160 (re. 1W/8ohm, blue; 10W, pink; 100W, red)

Continuous power (<1% THD, 8/4ohm) 550W / 950W
Dynamic power (<1% THD, 8/4/2/1ohm) 668W / 1.25kW / 2.19kW / 750W
Output imp. (20Hz–20kHz, pre/power) 48.9ohm / 0.005–0.0085ohm
Freq. resp. (20Hz–100kHz, pre/power) +0.0 to –0.5dB / +0.0 to –1.5dB
Input sensitivity (for 0dBV/0dBW) 100mV (pre) / 141mV (power)
A-wtd S/N ratio (re. 0dBV/0dBW) 102.2dB (pre) / 99.5dB (power)
Distortion (20Hz-20kHz, 1V/10W) 0.0001-0.0003%/0.0002-0.0074%
Power consumption (idle/rated o/p) 124W/1.35kW (28W, preamp)
Dimensions (WHD, Pre/Power) 457x146x389/457x236x565mm
Prices £22,500 (pre)/£30,000 (power)

Boulder Amplifiers Inc
Louisville, CO, USA
Supplied by: Padood, Cambridge, UK
01223 653199