Immerse Yourself in the Sumptuous Sonic Feast of the Powerful and Authoritative Cayin Soul 170HA Flagship Speaker / Headphone Tube Amp

Premium, powerful vacuum tube-based amp for headphones or home speakers
Features 1st implementation of matched pair of Tung-Sol KT170 tubes in a single-ended architecture Class A headphone amp
Authoritative 18W per channel speaker output at 8Ω and max 18W headphone output via XLR Balanced
6.3mm (3.5mm), 4.4mm Balanced, and 4-pin XLR Balanced headphone out
3 level impedance matching
Separate power supply chassis for cleaner, low-noise power
Ultra-premium, heavy-weighted umbilical power supply cables with quick release connectors

Bloom's Take

The Cayin Soul 170HA is a masterful blend of vintage tube warmth and modern engineering, delivering a rich, organic sound with exceptional clarity and detail. Its fully balanced circuit and meticulously designed output transformers ensure a pure, distortion-free signal, bringing out the full emotional depth of your music. With a powerful yet refined presentation, the Soul effortlessly drives a wide range of headphones, from low-impedance dynamics to high-sensitivity planars, making it a versatile centerpiece for any high-end audio setup.

From its premium build quality to the nuanced, lifelike sound it produces, the Soul embodies Cayin’s commitment to audiophile excellence. Whether you’re seeking the lush textures of classic tube amplification or the precision of a modern reference system, the 170HA delivers an immersive listening experience that truly lives up to its name.

Read the full review here.

The Fascinating KT170

Tung-Sol KT170 is an octal-based beam tetrode vacuum tube. It is the 2021 newly released flagship of the KT (kinkless tetrode) tube family.

Audiophiles love the KT family, and the KT88 has maintained a center role since 1956. There were multiple attempts to develop a new vacuum tube for high-end audio, that rivaled the sonic performance of KT88 with higher power.

The KT170 is the latest attempt from Tung-Sol and by far the best attempt based on Cayin's experience with all the KT vacuum tubes currently available.

It features a high-efficiency outboard power supply circuit with substantial power reserves, delivering an authoritative headphone output of up to 18WPC, ushering headphones into a new realm of personal listening experience.

Immersive Enjoyment

The driver tubes amplify signal voltage so that the rest of the amplification circuit can operate at a very linear condition.

The KT170 output tubes, operating in single-ended Class A, will produce completed amplified output without splitting the musical signal into parts.

Cayin engineers meticulously designed the gain circuit, independently adjusting the working current of each stage of the vacuum tubes, to allow the Soul 170HA to fully display the unique rich tones of single-ended Class A design.

The Soul 170HA provides users with an immersive audio experience, maximizing musicality without scarifying on technicality.

Cayin Soul 170HA headphone amplifier closeup of KT170 vacuum tube under warm yellow glow

Single-ended Voltage Amplification

After carefully evaluating different alternatives, Cayin decided to use two indirectly heated dual triode 6SN7 to take care of the voltage amplification given its medium (amplification factor) and low internal resistance.

The JJ 6SN7 is impressive for its low noise and balanced tonal balance across the audible frequency ranges. The sound performance is dynamic, with rich details, and offers excellent musical expressiveness.

Outboard Power Supply Design Empowering with Ample Energy

Physically separated 2 box design, the outboard power supply delivers clean, low-noise electrical power to the amplification circuit in a separated chassis independently. It also provides better heat dissipation even when stacked up, allowing the users to place the amplifiers with flexibility.

Dual power supply transformers deliver high and low voltage separately, minimize electrical interference, and safeguard clean power to the amplifier.

Multi-stage tube-regulated power supply circuit feeds power to different amplification stages independently. It can minimize ripple effect, eliminate circuit interference, and enhance circuit performance of both the voltage and current amplification.

The separated high-rigidity chassis and damping mounts absorb shock and vibrations effectively, isolating noise interference caused by transformer vibrations and magnetic leakage to achieve a higher SNR.

The Indispensable Power Supply Link

Heavy-weighted Umbilical Cable

Custom designed silver-plated 6N copper wire to connect between the outboard power supply and main amplification chassis. Separate high and low voltage transmission, with a total of two cables.

6N copper offers excellent electrical conductivity, the high level of purity reduces the presence of impurities that can interfere with signal transmission, and it also ensures consistent performance and longevity of the cables.

Independent shielded to minimize external interference as well as interference between independent transmission of multi-stage power supply circuit.

Fool-proof Quick Release Connection

Quick-release connectors from the aviation industry are used at both ends of the cables for connection.

8-pin for high voltage power transmission, and 12-pin for low voltage, making sure the output from multi-stage power supply will feed to different amplification stages independently.

Connect and disconnect in seconds, and you'll always get it right.

Tube Regulated Power Supply

Multi-stage tube-regulated power supply circuit feeds power to different amplification stages independently.

Soul 170HA employs 2x GZ34S rectifier tube from JJ to handle the driver stage high-voltage supply, providing a tube presentation that is more euphonic and nuanced.

The rectifier tube converts the incoming power source to DC, providing clean power with minimum interference for the circuit.

Unlike output tubes or driver tubes, the rectifier tubes convert signals without a heavy lifted load and can last for years without deterioration.

Since they are not involved in audio amplification directly, there are no matching requirements and they can be replaced on a per-piece basis.

The Flesh and Blood of Tube Amplifier

Transformer Coupled Balance Driven

Soul 170HA is a transformer-coupled single-ended Class A amplifier. The output from the KT170 will drive a pair of output transformers that support both headphone and speaker outputs.

The vacuum tube amplification circuit of Soul 170HA is operated in a single-ended, the output transformers provide an alternative phase and compose a balanced output, enabling a balanced driven from a single-ended vacuum tube circuit.

Custom Designed Audio Grade Transformers

Transformers play a vital role in Cayin's amplifiers. The choice of transformer core, specification of copper wire in different parts of winding, and the winding instruction affect the performance and sound signature of their amplifiers.

Cayin designs and winds all the power supply and output transformers in-house. This becomes their critical core competence and it allows the engineers to have total freedom in specifying the transformers for the circuitry they developed.

They consistently use high-purity copper enameled wire in the design of toroidal power supply transformers to reduce magnetic noise effectively.

The custom-designed wide-frequency response EI-type output transformer uses a high-quality Z11 silicon steel core, to minimize signal loss and enhance fidelity.

Cayin's shielding packaging technology and circuit protection measures further protect the machine from noise interference and extend the product's lifespan.

Dual Operation Mode

Triode Mode
KT170 screen grid connected directly to the anode. Tender, smooth and elegant. Holography with sharp image, suitable for vocals, string music and mid-range focused genre.

Ultralinear Mode
A tap is added to the primary winding of the output transformers and connected to the KT170 screen grid, providing higher voltage and changing the operating state of the power tubes. Open, bold, with great momentum. The soundstage will open up, suitable for orchestral, OST, and music with wide dynamic range.

Dual Tonality

Adjust the operating current of the two KT170 tubes synchronously

Dynamic
Dense, fast and authoritative, prominent dynamic with contrast. Forceful and exciting quality.

Soft
Relaxing, delicate and peaceful, revealing low-level details. Engaging and involving quality.

Impedance Matched Headphone Output

In-house designed output transformers provides three sets of impedance matched outputs to handle different headphone loadings accordingly:

Low (L): 8Ω-64Ω
Mid (M): 65Ω-250Ω
High (H): 251Ω-600Ω

Matching headphone impedance should produce a natural sound with well-defined bass reproduction. Planar headphones are more sensitive to impedance matching than dynamic headphones. Users can try out different settings after they are familiar with the sound signature of properly matched output.

A higher impedance setting will deliver higher output power because they are driving a harder load. It is completely different from gain control of a solid-state amplifier.

Application Oriented Output

The 4-pin XLR output is a full-fetched balanced output but the 4.4mm headphone output is optimized for wider range of applications, including high-sensitivity portable headphones and IEMs:

4-pin XLR (Balanced): 12WPC- 18WPC
4.4mm (Balanced): 2WPC - 4WPC
6.35mm (Single-ended): 7WPC - 17WPC

The 4.4mm phone out optimization has taken low-impedance high-sensitive headphones and IEMs into consideration. Cayin reduced the output and improved the S/N ratio, making sure the Soul 170HA is relevant to a very wide range of personal audio applications.

The lower output of 4.4mm phone out can also serve as a fallback when the system suffers from unidentified hum and interference.

Dynamic Auto Bias

The Soul 170HA adopts an integrated bias servo circuit design. When replacing vacuum tubes, there is no need for manual adjustment, as the Dynamic Auto Bias servo circuit handles it.

It precisely controls the power tubes, ensuring better compatibility with the amplifier. The innovative circuit design enhances safety and prolongs the lifespan of the vacuum tubes.

0dB Gain Difference

The volume control circuit comprises a custom ALPS carbon film potentiometer and a JRC MUSES72320V electronic volume chips.

The ALPS volume potentiometer acts as a physical motion sampler, and the MCU controls the two low-noise low-distortion electronic controlled resistor ladder analogue volume chips to achieve 128 levels of high precision volume control, making it more stable and reliable than traditional potentiometers. The 170HA's high-precision volume control circuit ensures a 0dB gain difference between the two channels.

Cayin potentiometer thumbnail closeup with JRC volume chips

Comprehensive Protection for Ideal Performance

The Soul 170HA uses an MCU to manage the entire headphone amplifier, incorporating multiple protection circuits and startup sequences to provide comprehensive protection from power on, playback, to power off. This safeguards the vacuum tubes while ensuring the amplifier always operates in an optimal state.

Performance Driven Design, Top of the Line Configuration

Hand-matched Vacuum Tubes

The vacuum tubes used in the Soul 170HA are manually tested and matched. They undergo strict performance testing, a 48-hour aging process, final measurements after installed on amplifier, and listening test to ensure high standards of channel uniformity.

Classic Point-to-Point Wielding

The entire circuitry is hand-wired using point-to-point wielding, this is time-consuming but ensures the shortest signal path with low signal loss. It also isolates audio signal, grounding, and high voltage power from cross-infecting each other, preventing mutual interference and ensuring the performance and reliability of the Soul 170HA.

High-end AudioCapX PPFXS Coupling Capacitors effectively isolate DC, improve the accuracy and stability of audio transmission, and enhance overall sound quality.

Elegant and Majestic Design

The front panel of Soul 170HA is made of aerospace aluminum with a matte black anodized finish. The side panels are crafted from North American black walnut wood with unique grain and texture, enhanced by hand polishing for a more sophisticated feel.

Luxurious and exquisite VU meter design, combining high aesthetics with functionality, allowing you to appreciate the charm of details while listening.

Theatrically designed tube cage protect the vacuum tubes and prevents accidental contact with the hot tubes during operation.

Specifications

Tubes:
- Output: TUNG-SOL KT170 x2
- Driver: JJ 6SN7 x2
- Rectifier: JJ GZ34S x2
Analog Inputs: XLR (x1 pair), RCA (x1 pair)
Output Power:
- 3.5mm Single-ended
  - Ultralinear: 11W (L); 13.5W (M); 17W (H)
  - Triode: 7W (L); 8.5W (M); 11W (H)
- 4-pin XLR
  - Ultralinear: 15W (L); 17W (M); 18W (H)
  - Triode: 12W (L); 14W (M);15W (H)
- 4.4mm Balanced
  - Ultralinear: 2.5W (L); 3.5W (M); 4W (H)
  - Triode: 2W (L); 2.4W (M); 3W (H)
- Speaker: Ultralinear: 18W (8Ω); TR: 10W (8Ω)
THD: 1% (1kHz, 7W/UL, <5% Rated Output)
S/N Ratio: 109dB (A-Weighted)
Weight (Amplifier): 23.3kg
Weight (Power Supply): 17.2kg
Dimensions (Amplifier): 330mm x 400mm x 231 mm
Dimensions (Power Supply): 330mm x 363mm x 114mm
Power Consumption: 240W (Max)