Фонокорректоры — Soulution Audio 757 deemphasis

The 757 deemphasis is a Soulution preamplifier for magnetic phono cartridges, tape heads and DS Audio optical pickups, with switchable equalisation curves for records and tapes made to different standards. It offers two inputs for MC, MM or tape heads on both RCA and XLR, plus a separate RCA input for an optical cartridge.

Key specs that matter

MC termination runs from 10 to 1,000 ohms. The MM setting is 47 kohms with 0 to 750 pF of capacitance, and the tape head setting covers 20 to 100 kohms with the same capacitance range. Gain can be adjusted from -40 dB up to +80 dB for MC, +60 dB for MM, +70 dB for tape and +120 dB for the optical input. Two balanced XLR outputs and one unbalanced RCA output are fitted, with output impedance of 0.8 ohm and 0.4 ohm and maximum voltage of 16 Vpp and 8 Vpp respectively, and a maximum current of 0.5 A. Frequency response at -3 dB spans 0 to 2 MHz. Soulution lists THD as not measurable, noise below -170 dBV/√Hz, CMRR above 100 dB and channel separation above 100 dB. The unit runs on 100-240 V at 50-60 Hz, uses 60 W in operation and under 0.5 W in standby, measures 480 x 167 x 450 mm and weighs about 30 kg.

Engineering and use context

For phono, the curves on offer are RIAA, DECCA, COLUMBIA, LONDON, TELDEC and NARTB, and for tape IEC2 at 30 ips, IEC1 at 15 and 7.5 ips and NAB at 15 ips. Soulution quotes accuracy of the chosen curve within plus or minus 0.05 dB from 20 Hz to 200 kHz. The input stage uses parallelised instrumentation amplifiers designed for wide bandwidth and optimal common mode rejection. A tape head calibration network compensates for the roll-off of imperfect heads, and a wideband transimpedance amplifier receives the current-based signal of DS Audio optical cartridges. Gain is set in 80 relay-switched steps of 1 dB using precision metal foil resistors. While the level changes, a secondary IC-based path carries the signal to avoid clicks, and the unit then returns to the relay path once the new gain is set. The Class A output stage is designed for speed, precision and high peak currents, with a bandwidth of 20 MHz at -3 dB. Power comes from a switched-mode intermediate supply feeding DC-DC converters and linear regulators placed next to each active component.

Pairing

The pair of XLR outputs allows two balanced destinations to be connected at once, alongside the RCA output.

Alternatives

Soulution also makes the 755 phono preamplifier in its Series 7.