AcousTech Electronics PH-1 phono preamplifier Measurements
The AcousTech PH-1 was reasonably quiet in both modes, its A-weighted S/N Ratio measuring 61.8dB (MC) and 83.8dB (MM). Under the more taxing unweighted, wide-bandwidth conditions, these figures reduced to 53dB and 74.5dB, respectively. The voltage gain at 1kHz measured 41.8dB (MM) and 57.7dB (MC).
The PH-1's output impedance measured a low 220 ohms at all frequencies, meaning that it will have no compatibility problems with any line preamplifiers with which it will be used. Its input impedance at 1kHz measured 49.9k ohms (MM) and 125 ohms (MC).
The RIAA error with the AcousTech set to its MM condition is shown in fig.1. There is a very slight and probably inaudible saddle in the midrange, but with then a 0.1dB (left) or 0.25dB (right) positive error in the top two octaves. This might just be audible as a little added "air." Set to the MC mode (not shown), the response appeared to roll off to -2.0dB or so at 20kHz. However, this measured rolloff is most likely due to the Audio Precision's 25 ohm source impedance. I note that WP did not find the sound to be mellow. As with the Linto, the channel separation was better at high frequencies than at low, varying from 40dB at 100Hz to 86dB at 20kHz. This is fine performance.
Fig.1 AcousTech PH-1, RIAA error into 100k ohms, at 10mV/1kHz, MM (right channel dashed, 0.5dB/vertical div.).
With its slightly lower gain in MC mode than the Linn preamplifier, the AcousTech offered excellent overload margins. These varied from 26dB at 20Hz to 18.7dB at 20kHz (all ref. 500µV at 1kHz). In MM mode, the overload margin reduced slightly, to 22.9dB at 20Hz, 22.3dB at 1kHz, and 14.3dB at 20kHz. The latter is only just acceptable, implying that really high-output MM cartridges should be avoided, particularly if they have a rising top end.
Both these phono preamps offer generally excellent measured performance. I could recommend either.—John Atkinson