Lehmannaudio

Linear II

Headphone Amplifier

£1,399

Once upon a time, just about every integrated amplifier had a socket for headphones. It used to be a boringly common feature. Then, one by one, manufacturers quietly dropped it. However, in recent years it's become more popular again, but not all headphone sockets are born equal…

The best of these feature a dedicated amplifier specifically designed to drive headphones, but others simply employ a resistive pad from the main amplifier's output stage. The latter solution is cheap and works fairly well but does not deliver maximum sound quality.

Lehmannaudio's Linear is a compact, mains-powered dedicated headphone amplifier that doubles as a line-level preamp. It can be driven directly from sources such as a CD player, streamer, an outboard phono stage, or the fixed line-level output of your preamplifier or amplifier. It's designed to partner all kinds of dynamic and isodynamic headphones, regardless of impedance or sensitivity. The company also offers more expensive versions with USB inputs, but the basic Linear model does not have this feature.

There's a choice of finishes – the front panel is available in silver or black, and there's also a bright chrome option available as a special order. So far as features and facilities go, the Linear is about as simple as it gets.

There's just a volume control and rear-mounted mains on/off switch. On the back are a set of gold-plated Neutrik line-level RCA phono inputs, plus outputs to drive a power amp. For those wanting to use it as a preamp, a few more inputs would have been useful, but there you go! On the base of the unit are two sets of DIP switches to adjust gain/sensitivity in 10dB steps from 0dB to +10dB or +20dB. The Linear's casework is made from aluminium rather than steel and is non-magnetic. The unit sits on three broad cork-tipped support feet.

A high-quality ALPS volume control is used, and left/right tracking between channels is very accurate. Even setting the volume to its lowest point, both channels always remain audible. Build quality is very good, and a large magnetically-shielded toroidal power transformer is used. High-quality components are employed throughout, including Mundorf capacitors in the power supply. The twin 1/4-inch (6.35cm) headphone sockets are Neutrik gold-plated types.

In use, it is extremely quiet. There's no hum, even at full volume, and hiss levels are completely inaudible during normal operation. Physically, the unit is quiet, too – there's no buzz from the mains transformer. However, the unit gets mildly warm to the touch after a while. Power consumption is around 10W, and the preamp measures 280x110x44mm and weighs 1.5kg.

Incidentally, there's no remote control with this device. If you're using the Linear with headphones, then there's arguably no need for a remote handset as you'll be sitting quite close to the unit – but the lack of a remote might be a drawback if you're using it as a line-level preamp.

THE LISTENING

Compared to even the best loudspeakers, good headphones tend to be very revealing. You can often hear all matter of tiny details on headphones that are barely discernible on speakers. If you prefer a highly detailed, analytical sound, then phones are difficult to beat. For this reason, Lehmannaudio's headphone amp is popular with sound engineers in recording studios who need to hear exactly what's happening in order to get things like microphone placement or the balance between voices and instruments precisely right.

Recording studio professionals require kit that sounds extremely clear and detailed and very neutral in terms of tonal balance. If you're mixing or remastering a recording, you need to listen using equipment that renders audible even the smallest subtlest detail. As a result, Lehmannaudio's Linear headphone amp has found favour with demanding recording engineers who need monitoring gear that offers the utmost clarity and accuracy. It certainly sounds very crisp and detailed.

Indeed, this is a highly revealing, very clean, truthful piece of kit. But while there's nothing warm or 'romantic' about its musical presentation, neither is it cold or antiseptic. Instead, it's a very faithful neutral component – quite literally, the proverbial 'straight wire with gain'! I noticed this when partnering the Linear with a Consonance M100S/Plus tube amp using 300Bs. The sound barely changed when I added it as a preamp. The tonal balance remained precisely the same, and there was no softening of transient detail or smearing.

Used with some inefficient, hard-to-drive AKG headphones, the Lehmannaudio sounded crisp and open with excellent detail. The sound was beautifully clear, open, and focused on a CD of the Oscar Peterson Trio playing excerpts from West Side Story.

Taped in January 1962 in New York City, Peterson's recording is very immediate and tactile. As was often the case with early stereo recordings, the instruments are balanced closely, with drums placed left, bass on the right, and piano in the centre. The separation between the three instruments was wide, yet (on loudspeakers) the result wasn't too compartmentalised. However, had producer Jim Davis or engineer Bob Simpson been using a set of headphones driven by a Linear, they might have gone for a less extreme mix!

Thankfully, the top end didn't sound too pronounced. It was undoubtedly sharp but not bright or edgy. The bottom end was full and extended. I made comparisons to the dedicated headphone amp in my Auralic Altair G2 streamer and found the Linear sounded a wee bit fuller and richer. The Altair was a tad sharper, giving a more immediate presentation. The Linear seemed as detailed and analytical as the Altair but just a bit smoother and friendlier. However, there wasn't a lot in it; both were extremely good.

Playing a compilation CD of Supertramp's hits, headphone listening truly revealed lots of subtle, sophisticated production details. The care taken over stereo-soundstaging to create a sense of width and depth was very noticeable. Not all pop recordings were/are this well-produced. But, particularly on some of the earlier songs – from 1974's Crime of the Century, for example, probably done using 16 tracks – you could tell there were times when producer and engineer didn't have quite as many tracks as they'd have liked.

So, while some instruments might be recorded in genuine stereo over a pair of tracks, others would have to make do with mono from a single-track source that's pan-potted into the soundstage. Even speakers that image very precisely don't always make this distinction as clear as headphones. Keeping with Supertramp, I tried streaming the album Crime of the Century at 192kHz/24-bit via the Auralic and was surprised that the CD (using a Heed transport though the Auralic's DAC) sounded noticeably more vivid and detailed, with wider stereo separation and greater immediacy.

Again, headphone listening made the differences very noticeable. All those clever left/right/centre placements of voices and instruments in the soundstage weren't nearly as apparent on the hi-res 24-bit 192kHz stream compared to the humble 16bit 44.1kHz CD… Interesting!

Something very different was Edgar Varese's Ionisation for 37 (count 'em!) percussion instruments – the recording on Erato with Kent Nagano. Everything was reproduced with great immediacy, while the soundstage was broad with natural perspectives. The Linear had more power than the Auralic and could drive my AKG 'phones about 6dB louder. But both went as loud as I'd ever want – loud enough to risk damaging your hearing with extended listening. It's easy to play headphones too loudly and not realise, so take care.

Quoted output impedance is 5 ohms, and it is designed to accommodate headphones with high or low impedance. Lehmannaudio claims a maximum power output of 400mW with 60 ohm headphones and 200mW output with 300 ohm headphones. Partnered with a CD player offering the usual output of 2V, it should be possible to play music with the volume control on the Linear set to maximum without clipping distortion. Of course, I'm not saying you should do this – only that you can…

So, is the Lehmannaudio Linear about as good as it gets for a reasonably-priced headphone amp? If your main requirement is something that sounds very lucid and highly detailed, then yes, it's outstandingly good. The only way you might get an even better sound is if you owned headphones capable of being used balanced and partnered them with a headphone amp offering balanced output. This results in a bigger sound with improved clarity and dynamics.

I recently tried Topping Audio's A30 Pro balanced headphone amp with a set of Ether open-back 'phones from MrSpeakers - now Dan Clark Audio. Here I noticed a sizeable improvement when swapping the standard unbalanced cable to a balanced type to allow the Ether headphones to operate in balanced mode. While that's tempting, many headphones have fixed cables and don't allow balanced operation. Indeed, if you're using standard unbalanced headphones, then the Lehmannaudio sets the bar very high considering its modest price and offers excellent results that wouldn't be easy to better.

THE VERDICT

Overall then, the Linear is beautifully made, looks good and offers excellent value for money. Everything is of the highest quality, both inside and out, and beyond any reasonable criticism. So, whether you're after a serious-sounding headphone amp or a nice simple line-level preamp, this little Lehmannaudio box should definitely be high on your list.

Visit Lehmannaudio for more information