Cayin C9 Portable Headphone Amplifier

1. Choice of Timber: select between Vacuum Tube and Solid State timber on the faceplate. This is no doubt the most attractive, most discussed, and most sought after feature of C9.
- There are several portable tube headphone amplifiers in the market, most of them are low power and with limited portability (microphonic effect from shock and vibration). C9 is a truly portable headphone amplifier, you can put it in your backpack or hold it in your hand and walking around while listening to it.
- C9 is designed around the KORG Nutube. This is a new generation vacuum tube developed by KORG in Japan. It is a Direct Heated Triode (DHT) but KORG replaced the traditional filament with LED technologies. It offers some advantages that make it a very good candidate for portable audio applications (flat form factor, low power drain, generated very little heat, …), but it maintains the microphonic problem of DHT vacuum tube, so the Nutube was not widely adopted in a portable application.
- Cayin N8 DAP is the first successful implementation of the Nutube is a portable music player. We have developed a custom silicon housing and a spring-loaded suspension system to resolve the vibration, shock, and impact, C9 has incurred the technologies from N8 (with modification). On the other hand, Cayin N8 used only one piece of Nutube so you can only listen to the Nutube with 3.5mm single-ended headphone, this is an inevitable limitation of N8 given we need to operate it as a DAP, but C9 has used a pair of Nutube so the Timber selection function is available to both single-end and balanced circuit, making C9 the first fully balanced portable tube headphone amplifier, to the best of our knowledge.
- We didn’t overlook the importance of the Solid State option. We designed a discrete audio circuit around two matched pairs of Toshiba 2SK209 JFET as the alternative to Nutube in the Timber Circuit.

2. State-of-the-Art analog amplification for both earphones and headphones: C9 is probably the most sophisticated portable headphone amplifier in the market. Cayin firmly believes that when the amplifier excels in control and equipped with appropriate volume management, there is no such thing as over-powered. Even IEMs will perform at a different level when we have ample power. Unfortunately, from what we observed, most, if not all, high-end headphone amplifiers are designed with a full-size headphones in mind, portable amplifiers are mostly DAC/Amp with emphasis on digital audio technologies. Given the rapid development of high-end IEMs in recent years, Cayin believes there is a market for the ultimate portable headphone amplifier that can bring out the best of these high-end IEMs, especially when they are equipped with demanding dynamic, planar magnetic, and/or EST drivers, and yet versatile enough to cover a lot of full-size headphones in portable scenarios.
- One of the very few fully Balanced portable headphone amplifier in the market
- Dual Amplification Operation (DAO): allow users to switch between Pure Class A and Class AB
- In-house developed Amplification circuit with discrete components, not IC or Op-Amp based
- Selectable High/Low gain that is widely applicable to both input modes (LINE and PRE) and all amplification operation (Class A or Class AB), offer extra 6dB headroom when needed, and enhance paring with different earphones and headphones.
- High-precision and highly linear 99 steps volume control system that composes of a 4-channels ALPS potentiometer with a pair of MUSES72320 low noise, low distortion resistance ladder based stereo electronic volume.
- High Power portable headphone amplifier (4100mW to 2600mW per channel at 16-32ohm loading, and same rating for both Class A or Class AB) - Special attention to make sure C9 can work with most, if not all, IEMs in the market satisfactory. Design a premium high power amplifier requires engineering and experience, but is attainable in general, make it enjoyable with both IEM and headphones are way more challenging.

3. Dual input mode: on top of regular LINE input mode, C9 can also operate in PREamp input mode (or known as pure power amplifier mode), with volume control disabled and all stages operate at full capacity.
- When operating in LINE input mode, which we presume will be the primary input mode of C9, it will receive an audio signal from the line-level output of DAP, DAC, or from any reliable audio source.
- The PRE-amp input mode is designed to work with variable level inputs (e.g PRE-amp or DAC with a variable-level line out).
- Alternatively, if you have a DAP with a high-quality low distortion phone out but no line out, you can use the phone out as PRE-amp output. Switching between Line input and PRE-amp input is a unique feature, the first of its kind to the best of our knowledge.

4. Versatile input and output options: C9 supports 3.5mm single-ended and 4.4mm balanced for both input and output, the amplifier will also optimize balanced inputs to single-ended headphones, and from single-end input to balanced headphones.
- Single-ended Portable Interconnect CS-35C35 (3.5 to 3.5) and balanced Portable Interconnect CS-44C44 (4.4 to 4.4 with GND) are bundled.

5. Replaceable battery: the removable battery module houses 4 x Sony US18650VTC6 (3000mAh 3.7V) lithium batteries. You can charge the 18650 batteries while the battery module is attached to C9 or after you detached it from the amplifier. The battery module supports standard, PD, and QC3.0 battery charging through a USB-C connector.
- Users can acquire and replace the batteries conveniently to extend the battery duration when needed.
- User can acquire an extra set of battery modules.
- In case the original battery is run down after extensive use, the user can replace the battery conveniently, making sure the C9 can serve a very long time without worrying about the 500 charge cycle of the lithium battery.
- Changing to a different make and specification of 18650 battery might introduce small changes to the sound signature, audiophile can enjoy battery rolling as an additional tweak to their system.