Предусилители — Cayin Soul 170C

The Soul 170C is a two-channel valve preamplifier from Cayin, the Chinese valve amplifier maker, designed as the partner for the Soul 170P valve power amplifier. It is priced at EUR 4,480 in Germany. It uses eight valves, including valve rectification and valve voltage regulation, and offers switchable negative feedback. The Soul 170 line also includes the Soul 170HA headphone and speaker amplifier.

Key specs that matter

Line gain comes from two ECC83 and two 6SN7GTB valves, two 6CA7 regulate the voltage for each channel, and two 17AX4GT handle rectification. Gain is 17.5 dB with low feedback and 16 dB with high feedback. Connections comprise four RCA inputs and one XLR input, with a single output of each type. The inputs present 47 kOhm on RCA and 25 kOhm on XLR, while the outputs have a source impedance of 380 ohm on RCA and 700 ohm on XLR. Maximum output is 8 V RMS on RCA and 16 V RMS on XLR. Frequency response reaches 8 Hz to 100 kHz on RCA and 8 Hz to 35 kHz on XLR at -3 dB. THD is 0.02% at 2 V RMS, signal to noise ratio 100 dB A-weighted and channel separation 90 dB. The preamplifier measures 430 x 212 x 445 mm, weighs 20 kg and consumes up to 75 W.

Engineering and use context

The 6CA7 is a power pentode, and using one per channel as a voltage regulator gives each channel a stable supply that does not follow changes in the mains. The 17AX4GT damper diodes rectify the supply and bring the high voltage up slowly, together with a soft start of about 60 seconds. Switching the negative feedback between low and high changes both the gain and the amount of correction applied around the circuit. The preamplifier is wired point-to-point by hand with silver-plated wire, the volume control is a motorised ALPS potentiometer that can be adjusted from the remote, and the transformer is wound by hand. The anodised aluminium front comes in two colours, black or silver, framed by side panels of North American black walnut. A valve cage is supplied, and the infrared remote controls input, feedback and volume. Because the feedback switch is on the remote, both settings can be compared from the listening seat.

Pairing

The Soul 170P valve power amplifier is the intended partner, and the higher-voltage XLR output also drives balanced solid-state power amplifiers. Four RCA inputs and one XLR input cover a phono stage, DAC and other line sources.

Alternatives

The Cayin Soul 170HA combines a valve headphone and speaker amplifier in the same Soul 170 line.