The C421 is a new headphone amplifier made by JDS Labs, housed in a brushed aluminum enclosure. Audio is inherently analog, so they spent 18 months designing a 100% analog amp around features that matter: straightforward sound and functionality.
This model is the AD8620 opamp which is better suited for higher impedance headphones or IEMs. The alternative opamp for this headphone amp is the OPA2227, which has a warmer, but less analytical sound signature.
The audio chain passes only through ultra precise 0.1% thin film resistors. Thin film parts increase cost by two orders of magnitude over consumer grade 1% thick film resistors. Why spend more? Because thick film resistors can be heard. Thin film resistors improve channel balance and reduce random noise by up to 8x. The result is transparency--enjoy your music like you're on stage.
c421 is packed with dual gain, bass boost, low battery detection, and synchronous voltage boosted +/-7V rails with low ripple, all implemented on a 4-layer PCB with dual internal ground planes for maximum signal integrity.
We created a new active-true ground topology for c421. Three opamp channels and two successive reference circuits in the power stage enable fail-safe charging while still providing the load isolation benefits of an active ground circuit. Great sound, enough said.
Too many headphone amplifiers impose functionality limitations here--not c421. The power circuit uses constant voltage boosting so that your music stays strong until the battery is empty. c421 gives low battery indication during the last 45 minutes of run-time.
Want to listen while charging c421? You can!
Want to charge from your laptop, motorcycle, or AC outlet? Great!
Only have a few hours? The battery reaches 80% capacity in about two hours.
Don't want to unplug the cord? No problem, c421 charges intelligently.
Dual Gain, 2.3x or 7.0x (+7.2dB or +16.9dB)
Bass Boost, +8dB peak
Alps Dual Analog Potentiometer
Low Battery Indication
0.1% Thin Film Resistors
1200mAh, 3.7V Li-Ion Battery
USB Powered Smart Charging
Synchronized +/-7V rails, NO power degredation!
3.5mm Input and Output Jacks
4-Layer Printed Circuit Board
Run-Time: 11+ hours
Charge Time: 2 hours to 80%, 110 dB (20-20kHz)
THD: Exceeded test equipment*,