HA-2 Headphone Amplifier Specifications

Note: Specifications listed are typical, and are derived from measurements on actual amplifiers.  There will be some variation from one amplifier to the next.  Specifications are subject to change without notice. 

Anyway, you should believe your ears!  


Single-ended, OTL, class-A  triode amplifier

Single voltage amplifier stage, single cathode follower stage 

DC-coupled input; capacitor-coupled output. 

Tube complement

1 - 6SN7GT voltage amplifier  (one section used for each channel)

1 - 7236 (premium) or 6080 cathode follower (one section used for each channel)

1 - GZ37 (premium) or 5U4G rectifier

Power supply

Full-wave tube rectifier

Capacitor-input filter with choke, using electrolytic and polypropylene capacitors

AC filament supply

Dimensions and Weight

13 wide  x 8.5 deep x ~8 tall (including tubes)

15 pounds

Power requirements

120VAC 60Hz only

100 Watts 

Fuse type

AGC-type, slow-blow, 1.5A 250V

Output Impedance

100 Ohms

Maximum output level

(1kHz, 5% THD)

620 ohm load: 13V RMS / 36V P-P

270 ohm load: 10.5V RMS / 30V P-P

Rated Maximum continuous output power

(1kHz, 5% THD)

620 ohm load: 270mW

270 ohm load: 400mW

Total Harmonic Distortion

(1kHz, 1V RMS out)

620 ohm load: < TBD %

270 ohm load: < TBD %

We're not trying to hide anything here.... we just don't have a clean enough audio source to provide an accurate number.  The THD we measure on the amplifier output is the same as what we measure directly from our (tube, of course) test oscillator - around 0.1%.  Until we can get a really, really clean oscillator, you'll just have to assume that the HA-2's THD is really, really low!

Voltage Gain

620 ohm load: 17dB

270 ohm load: 15dB

Frequency Response

(+/- 3dB)

620 ohm load: ~10Hz 75kHz

270 ohm load: ~15Hz 75kHz

Ripple and Noise

< 3.5mV RMS