"Fast, friendly service. High-quality, custom built. Awesome sound/bass. Best cMoy!"


Store Home > hidden > > Item#: 28

c421 Black Edition Headphone Amplifier

c421 Black Edition Headphone Amplifier
c421 has been replaced by our new C5 Headphone Amplifier.

c421     Unassembled View of c421 v1.01

DISCONTINUED: c421 has been replaced by our new C5 Headphone Amplifier!

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.

  • Reviews
  • Headfonia - Flyin’ High: JDSLabs C421

  • 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 degradation!
  • 3.5mm Input and Output Jacks, Gold Plated
  • 4-Layer Printed Circuit Board
  • Aluminum Enclosure

  • Run-Time: 11+ hours
  • Charge Time: 2 hours to 80%, <5 hours to 100%
  • Frequency Response: +0.01, -0.41 dB (20Hz-20kHz)
  • SNR: Exceeded test equipment*, > 110 dB (20-20kHz)
  • THD: Exceeded test equipment*, < 0.0041%
  • Crosstalk: Exceeded test equipment*, < -57dB
  • Volume Potentiometer Taper: 3B
  • Enclosure Size: 97.5 x 14.0 x 62.5mm
  • Weight: 4 oz

    *Test Configuration: RMAA 6.2.3 Loopback on c421 at low gain w/AD8620 via external engineering reference 24-bit, 192kHz Asynchronous, bit-perfect USB ADC+DAC (not sound card!)

  • c421 v1.01 Headphone Amplifier
  • USB 2.0 Mini B Cable
  • Rubber Bumpers/Feet
  • Instructions Sheet

  • c421's dual gain switch and active-true ground topology enable it to drive headphones of all types and impedances. No customization is necessary.

    Two options are available for the primary stage opamp: AD8620, or OPA2227. Our #1 recommendation for c421 is the OPA2227, which gives smooth, refined output and an excellent soundstage. If you cannot decide, it's safest to choose OPA2227. This chip receives excellent feedback from c421 owners.

    We also greatly enjoy the AD8620. Some users love the AD8620, but feedback is admittedly mixed (either loved or hated). Choose AD8620 if you've heard the chip before, or if you certainly prefer an analytical sound signature over the "warmer" characteristic output of the OPA2227.

    All opamps are soldered to the 4-layer PCB for maximum IC performance.