The Cayin Soul 170C succeeds the A-845Pro model launched in 2018 for the brand’s 25th anniversary. This 20 kg preamplifier relies on eight carefully selected tubes (Tung-Sol and Mullard) and a fully balanced Class A circuit. Its adjustable negative feedback system lets you tailor the sonic character from the listening chair. The chassis combines anodized aluminum and North American black walnut, while mixed RCA and XLR connectivity ensures integration into most setups.
The Soul 170C uses eight tubes distributed according to their functions. The two 17AX4GT tubes handle AC rectification and are renowned for their low internal resistance. Two 6CA7 tubes manage voltage regulation independently for each channel, contributing to 90 dB stereo separation.
Line amplification is based on an unusual combination: two ECC83 tubes (Mullard CV4004/12AX7 variant) and two Tung-Sol 6SN7GTB tubes. The ECC83 tubes provide high gain and linearity, while the 6SN7GTB tubes handle higher currents while maintaining low distortion. This eight-tube configuration for a preamplifier is rare and reflects Cayin’s choice to entrust each critical stage to tube technology.
Each Soul 170C is hand-assembled using point-to-point wiring, which avoids printed circuit boards. Connections are made with heavy-gauge silver-plated cables, minimizing signal loss. This time-consuming method ensures the purity of the audio path.
The toroidal power transformer and EI output transformer are designed and hand-wound in Cayin’s workshops. The oversized design of these components allows the tubes’ full potential to be exploited. The motorized volume potentiometer comes from Japanese manufacturer ALPS, renowned for its precision. Ceramic tube sockets offer better thermal insulation than plastic models.
A soft-start circuit delays voltage ramp-up by one minute at power-on, protecting the tubes from thermal shock. A removable cage covers the tubes to prevent accidental contact.
The negative feedback (NFB) system can be set to two positions via the infrared remote control. In Low NFB mode, gain reaches 17.5 dB and the sound presentation remains open and fluid, favoring naturalness. In High NFB mode, gain drops to 16 dB and the circuit tightens linearity, reducing distortion for a more precise and analytical presentation.
This function allows the preamplifier to be adapted to the character of the power amplifier, the room acoustics, or the type of music. Being able to switch from one mode to the other from the listening chair turns this technical adjustment into a genuine comparative listening tool.
Five line inputs equip the Soul 170C: four RCA pairs and one XLR pair. On the output side, one RCA pair and one XLR pair allow amplifiers to be driven in unbalanced or balanced configurations. The outputs deliver up to 8 V RMS via RCA and 16 V RMS via XLR, providing comfortable headroom even for sensitive amplifiers.
The infrared remote control manages all functions: input selection, volume, and NFB mode. The unit remembers the last settings before shutdown. Its dimensions (430 × 445 × 239 mm) and 20 kg weight require a stable piece of furniture. The solid anodized aluminum front panel and black walnut side panels require handcrafted work for each unit.
Frequency response extends from 8 Hz to 100 kHz (±3 dB) via RCA, but is limited to 35 kHz via XLR. This choice affects the reproduction of the highest harmonics depending on the output used. Total harmonic distortion (THD) reaches 0.02% at 2 V RMS, a respectable figure for a tube preamplifier. The 100 dB signal-to-noise ratio (A-weighted) ensures a quiet noise floor. Power consumption of 75 W remains reasonable, although the unit runs continuously warm like all tube equipment.
Replacement is possible, but Cayin strongly recommends using matched and tested tubes, ideally supplied by the manufacturer. The 6CA7 and 17AX4GT tubes require careful selection to avoid any imbalance in the power supply. Poor matching can damage the circuit.
Like all tube devices, the Soul 170C requires a stabilization period. The soft-start circuit already imposes a one-minute delay, but it is recommended to wait 15 to 30 minutes before critical listening. This time allows the tubes to reach their optimum temperature.
The XLR output delivers twice the voltage of the RCA output (16 V versus 8 V RMS), which is useful for less sensitive amplifiers. However, its frequency response is limited to 35 kHz, compared with 100 kHz via RCA. The choice depends on the power amplifier and tonal preferences.
The Soul 170C drives both tube and solid-state amplifiers. Its adjustable negative feedback system makes it possible to adapt its behavior to the character of the amplifier. Low NFB mode is often suitable for sensitive tube amplifiers, while High NFB mode may pair well with more analytical solid-state amplifiers. The choice depends on the overall system and personal preferences.
Absolutely. The Soul 170C accepts any source delivering an analog line-level signal: DAC, network player, CD player, turntable with a phono preamplifier. The five inputs allow several sources to be connected simultaneously and switched between using the remote control. Its XLR inputs make it a good match for high-end DACs equipped with balanced outputs.
Detlef
Very fast delivery !!!!!!! very good product !!!!!! Perfect thank you very much !!!!!!
Comment from 7 April 2026 — Experience from 26 March 2026
Rob
Really beautiful and already sounds amazing, and over time it will only get better as the tubes burn in/break in.
Comment from 14 January 2026
