Pre/Power Amplifiers

With no phono stage or integrated DAC on board – Constellation offers the Revelation 2 Phono preamp to service vinyl fans – the Revelation 2 Preamp remains a fully analogue, balanced line preamplifier. The volume control ‘number’ reflects attenuation rather than gain, so ‘0.0dB’ is full volume (a very high +26.6dB gain) and ‘6.0dB’ is half the output – if ‘0.0dB’ yielded 2V then ‘6.0dB’ would give 1V, for example. In practice the ±0.5dB steps are less precisely calibrated over the top of the preamp’s range where there’s a ±0.2dB variation in accuracy with each increment. Over the top 12 steps (0 down to 6dB) the resulting level is actually –6.5dB, ‘10dB’ is –10.6dB but the error reduces at ‘20dB’ to deliver –20.2dB, etc. Over the top 60dB of its range the cumulative error is just +0.05dB and over a full 90dB range (180 steps of 0.5dB) the error falls to an insignificant +0.01dB. The Revelation 2 Preamp’s maximum balanced output is a very healthy 24V from a 113ohm source impedance (rising to 127ohm at 100kHz) while the input overload threshold is >14V.

The frequency response is only minutely affected by volume position, being flat to within ±0.05dB from 2Hz to 100kHz at ‘0.0dB’ but falling to –0.21dB/100kHz at volume ‘6.0dB’ [see Graph 1, below]. The A-wtd S/N clocks-in at 90.8dB (re. 0dBV) while distortion beats the 0.001% specification with a very low 0.00025-0.00055% (20Hz-20kHz, re. 0dBV), rising fractionally to just 0.001%/40kHz [see Graph 2, below]. Channel balance is a tight 0.01dB and stereo separation better than 90dB from 100Hz-20kHz. Finally, and intriguingly, the impact of the display is measurable here – spurious peaks at 1.75kHz (–98dB re. 0dBV), 3.5kHz, 5.25kHz, 7kHz. 8.75kHz, etc, disappear once the touch-sensitive display times out and goes dark... PM