model S501 "air"
Smart Headphones/Line Amplifier

In switching signal systems, adopting a long life, high reliability reed switch (contact: ruthenium) in which an inert gas is sealed in the glass tube, the deterioration of freshness is very low. The sound with a sense of high speed, warm and relaxed does not feel sluggish seems to have been driven almost in the air. In addition to the conventional voltage-mode type (S501v), we have a type for current-mode audio interface (S501i).


Smart Size ― Easy to wiring from rear panel.

Since the depth is narrow, it does not get in the way routing of the wiring from the rear panel.

Japanese Taste ― The texture of Japan.

Elegant and cool, finished with a timeless design. The color of the handmade Japanese paper is by hope, you can choose from below color variations. You can also choose gray-smoke monotone or clea-transparent panel without Japanese paper.

Large Front Panel ― Easy to operate.

Operation is the power switch, input switching, volume control knob, the mute only and does not need complicated settings.

Works As Line Amplifier ― Can easily drive power amplifier.

When you do not connect the headphones, you can also be used as a line amplifier.

Sophisticated Internal Structure ― Fully discrete amplifier.

Amplifier section adopts a little configuration of simple amplifier stage as much as possible, was the highest priority on freshness of the sound more than anything. Sound quality with open and natural sounding and a sense of speed, you will forget the existence of the amplifier and headphones.



  • Power Supply: Worldwide, depend on market (IEC 3 pin AC inlet), AC110~120V, AC220~240V (factory assembled)
  • Selector: inert gas sealed reed switch (contact: ruthenium)
  • Mute: Play/Mute
  • Amplifier: Fully discrete, 8 BJT transistors, high slew-rate design
  • Voltage Gain: about +15.5dB (×6) or equivalent
  • DC Offset: < 10mV
  • S/N: very quiet (under measurement limit)
  • Frequency Response: DC~500kHz (-3dB)
  • Load Impedance: 16~600Ω
  • Max Power: 600mW (@16Ω), 70mW (@600Ω), 16Vp-p
  • Output: standard phone jack (φ6.3mm), RCA pin jack (unbalanced) ×1 - voltage-mode
  • Size: W300×H46×D100mm
  • Weight: 1.6kg (without power cable)
  • Accessories: power cable for IEC 3 pin AC inlet, alternate fuse, userʹs manual

model S501v ― for voltage-mode signaling

  • Input: RCA jack (unbalanced), voltage-mode (20kΩ) ×3
  • Volume Control: ALPS RK27 high quality potentiometer, impedance 20kΩ

model S501i ― for current-mode signaling

  • Input: RCA jack (unbalanced), current-mode (0Ω) ×2, voltage-mode (20kΩ) ×1
  • Volume Control: mechanical potentiometer, impedance 0Ω

Top Panel

Color variations of handmade Japanese paper

From left to right: 1.white, 2.cream, 3.plum,, 5.purple, 6.olive, 7.beige. Please choose your favorite color for top panel when you purchase order of this product.

Monotone Panel

You can also choose gray-smoke monotone, or clear-transparent panel without Japanese paper.

Retail Price

model S501v ― for voltage-mode signaling

model S501i ― for current-mode signaling

Ask our authorized distributors/dealers.