Lehmann Audio Linear II
Hi-fi headphone amplifier with a Class A output stage, featuring adjustable gain and a pre-out output, for headphone listening as well as preamplification.
Description
The Linear II is a hi-fi headphone amplifier built around a Class A output stage. It is intended for headphone listening in a desktop or living room setup, but also features a pre-out output that allows it to be used as a preamplifier, for example to feed active speakers or a power amplifier.
The unit offers adjustable gain across four levels (0 dB, 10 dB, 18 dB and 20 dB) selectable via DIP switches, allowing the output level to be matched to the sensitivity of the headphones used, from the easiest to drive models to high-impedance headphones. Its frequency response extends from 10 Hz to 35 kHz, with a signal-to-noise ratio above 100 dB at 0 dB gain and total harmonic distortion below 0.001% measured at 6 mW into 300 ohms, figures that reflect clean reproduction even at high listening levels. Channel separation exceeds 70 dB at 10 kHz. Output power reaches 200 mW into 300 ohms, with an output impedance of 5 ohms on the headphone output.
This type of amplifier is aimed at a listener equipped with demanding hi-fi headphones, wishing to benefit from dedicated electronics rather than the headphone output of a DAC or integrated amplifier. The presence of a pre-out output also makes it a sensible choice for anyone wanting to centralise their source around a single unit, switching between headphones and active speakers.
Technical specifications
| Input impedance | 47 kohms |
| Maximum gain | 0 dB, 10 dB, 18 dB, 20 dB (selection via DIP switches) |
| Frequency response | 10 Hz (-0.3 dB) to 35 kHz (-1 dB) |
| Signal to noise ratio | > 100 dB at Gain 0 dB |
| Total harmonic distortion | < 0.001% at 6 mW/300 ohms |
| Channel separation | > 70 dB at 10 kHz |
| Output power | 200 mW/300 ohms |
| Output impedance | Phones out 5 ohms |
| Weight | 1.5 kg |
What to check before buying used
The volume potentiometer is the most sensitive point on this headphone amplifier: crackling or a channel imbalance at the start of the travel indicates a dirty track. Also check that the gain-selection DIP switches work properly, as their contacts can oxidise over time and cause intermittent contact or channel loss. Checking the headphone output at different gain levels helps confirm the absence of background noise or hum related to the ageing of the internal capacitors.
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