Cayin has incorporated mini-lamps called Korg Nutube in their products, starting with portable players and now in amplifiers. The Cayin C9 portable amplifier uses a balanced circuit design with two Nutube direct-heated triodes. These lamps are visible through windows on the housing.
To mitigate the impact of microphonic effects from the lamps, Cayin engineers have encased them in silicone and added a spring suspension. This technology was first introduced in the N8 player and has now been modified for the C9.
Users have the option to select their preferred sound profile by switching between the tube and transistor amplification circuits. The tube circuit is available in both balanced and unbalanced connections, while the transistor circuit features carefully matched Toshiba 2SK209 transistors.
The C9 offers two gain levels: low and high (+6 dB), catering to a wide range of headphones. Its high-precision volume control, with 99 steps, uses a 4-channel Alps potentiometer with low-noise MUSES72320 resistor arrays.
There are two modes for connecting sources to the C9: line-level and non-attenuation. In non-attenuation mode, which can be considered pure power amplifier mode, the volume control is bypassed. The device is equipped with 3.5mm and 4.4mm inputs and outputs. In addition to the amplifier, the package includes an unbalanced interconnect cable with a 3.5mm plug and a balanced cable with 4.4mm plugs.
The battery compartment is removable and consists of four Sony US18650VTC6 cells. These batteries can be charged both inside the amplifier or separately. According to the developers, this design not only extends the amplifier's lifespan but also allows owners to customize the sound, as the sound characteristics may vary slightly when using batteries from different manufacturers.
The package includes:
- Amplifier
- USB Type-C cable
- 4.4mm cable
- 3.5mm cable
- Tool and screws
- Documentation