Review: Lab12 hpa Headphone amplifier – Embers from Greece

Review: Lab12 hpa Headphone amplifier is a reproduction with little tonal discoloration with a tiny touch of warmth.

The tube amplifier market is enjoying steady, if not growing, popularity. Here, attention is not simply paid to pure performance, the special sound character and vintage charm play the decisive roles. In 2012, the resourceful Greeks from Lab12  jumped on the trend, since then they have been producing high-quality audio electronics using tube technology. As a headphone enthusiast, their headphone amplifier “hpa” made me especially happy.


Externally, the headphone amplifier Lab12 hpa (price: 1,260 euros), available with a silver and black front, is reminiscent of tube devices from the 1970s. With dimensions of 32 x 11x 29 cm (WxHxD) it is between full and half rack size and weighs six kilograms – it fits well into the existing playback chain in the hi-fi rack. The matt lacquered aluminum front looks quite simple and clear due to the few elements. In addition to the 6.3 millimeter headphone output, there is an analog, yellowish VU meter from Nissei. The volume control is located on the right-hand side of the sand-blasted, five-millimeter-thick aluminum front. A precise Blue Velvet potentiometer from Alps is supposed to ensure even volume control with high channel synchronization.

Der Volume-Knopf auf der rechten Seite des Lab12 hpa bewegt ein Alps-Blue-Velvet-Potenziometer

The back looks just as tidy as the front, even if Lab12 doesn’t save on connections. In addition to a USB-B input , the hpa has two analog cinch input pairs and an adjustable preamplifier output, for example to operate a power amplifier or active loudspeakers. Switching to a fixed-level line-out is not possible. The coaxial output below is used to loop through the digital input signal via USB to S / PDIF, for example to feed a DAC without a USB socket with songs from the computer. Unusual: The input selection is controlled with a rotary knob on the back of the device.

Ungewöhnlicherweise befindet sich der Eingangswahlschalter auf der Rückseite desLab12 hpa - und nicht auf der Front


At the hpa, Lab12 relies on a hand-selected selection of audio components. The amplifier structure (OTL = Output Transformer Less), which does not have an output transformer, integrates three matched double triodes of the 6n1p type made in Russia and, together with a powerful power supply with five separate power supply sections, should ensure a transparent and emotionally rousing sound. The five-year manufacturer’s guarantee, among other things, proves that the manufacturer has complete confidence in its circuit concept. The recommended headphone impedance is from 32 to 600 ohms. This leads to the assumption that the amplifier will not exactly be a fan of low-resistance in-ears, but also that it offers enough power reserves for drive-hungry cars such as the Beyerdynamic DT880 600 Ohm.

The USB input of the DAC accepts PCM signals with a data rate of up to 16 bits and 48 kHz. Lovers of high-resolution audio streams will probably be disappointed, but the test showed that it is not always the high data rate that determines the musicality of a KH amplifier. If you want to feed the Lab12 hpa with high-res material, you have to take the detour via an external D / A converter. Unfortunately, it is also not possible to use voltage decoupling on the USB port (I like to use the SBooster VBus² isolator for this), which with some DACs audibly brings more calm to the sound. The chip in the Lab12 hpa seems to need direct current supply via USB, with the SBooster adapter in the signal path, the USB input remains muted.

Lab12 hpa: sound & comparisons

The switch-on phase of the Lab12 hpa lasts about ten seconds, during which the tubes are brought to operating temperature. In my experience, the amplifier should ideally be allowed around five minutes to “start” after a long period of inactivity, in order to be able to enjoy the full sound potential from the first note. Regardless of this, the manufacturer recommends that you give your audio components a warm-up phase of around 150 hours after the initial use. To what extent the break-in time pays off, more on that later.

Fine overtone

After a short warm-up phase, I was particularly impressed by the very sensitive tweeter. In Avishai Cohen’s “Chutzpan”  the cymbal and the hi-hat attack are not only reproduced in detail, they also by no means drop in the super high frequency . A comparison with the Burson Soloist SL Mk2, which is also quite high-resolution regardless of price(around 600 euros) confirms the consistently positive impression. Here the Greeks are noticeably behind the Australians. There can be no question of “Greek cosiness”, rather the joy of life of the inhabitants of the Peloponnesian peninsula can be heard. The highly detailed reproduction makes the highs a pleasure even with lighter albums. The tube amplifier also reproduces the overtones of the piano and the reverberation of the steel strings of the double bass very accurately. In comparison, a benchmark DAC1 USB (approx. 1,000 euros) that is a little bit old has noticeably fewer subtleties to offer, especially in the super high range.

It seems to be irrelevant for the Lab12 hpa at what volume the music is played. I have seldom noticed such a complete performance even at the lowest levels. In addition to the excellent synchronization behavior of the Alps Blue Velvet, the background noise, which has been reduced to a minimum, which can only be heard without music playback and with very sensitive headphones or in-ears at a higher volume level, probably also contributes to this.

Im Lab12 hpa arbeiten drei Doppeltrioden vom Typ 6n1p

The high level of synchronization with a low level setting also benefits efficient in-ears. A Soundmagic E80, for example, looks a bit lost next to the Lab12 hpa, but musically the small earphone on the tube feels surprisingly comfortable. Fortunately, the feared drop in level in the treble due to a possibly too high output resistance at the headphone connection does not occur, at least with in-ears with dynamic drivers. However, multi-driver systems in balanced armature technology are not quite as unaffected.

Middle positions

The mid-range reproduction is also very successful with the Lab12 hpa. A high level of detail in the presence area and above guarantees excellent speech intelligibility, as “Movers and Shakers by the American singer / songwriter project Lemolo confirms. Unpleasant sibilants are just as bad as a level of the mids that is too low. The nymph-like voice of Seattle-born Meagan Grandall blends in perfectly with the other instruments and adjacent frequency ranges .

This very musical characteristic seems to continue up to the root note. In the lower mid-range, the Lab12 hpa suggests slightly more volume than the sterile-sounding benchmark DAC1 USB, which gives the general sound character a slightly warm note, not unlike that of the Burson Soloist. Despite the above-average performance in terms of resolution in the mid-range, it cannot hold a candle to the Lab12 hpa. The Lab12 does not have to shy away from pairing it with a warmer Audeze LCD-2 . The Audeze is by no means driven to a muffled sound due to the almost linearly rising highs into the super high frequency and not noticeably decreasing there.

Lab12 hpa: Klares Design mit Vintage-Anleihen

Stage talent

Another strength of the headphone amplifier is the almost holographic stage display. The individual instruments in “Boj sie Boogie” by Felix Kubin and Mitch & Mitch in the 2013 album bacteria and batteries are conjured up very precisely into the headphones. The size of the stage is neither supernatural in terms of depth nor width. Yes, you can imagine the dimensions of the stage on which the band is playing almost to the last centimeter. If you really want to go crazy to the psychedelic-jazzy sounds of the Polish-Hamburg music combination, you can do so with the Lab12 hpa without annoying distortions and other loss of sound quality even at high levels. The Greek has enough reserves to let it rip properly with power-hungry headphones such as an AKG K702 or the Beyerdynamik DT880 600 Ohm.

Bass or not bass?

If I had to describe the bass range at the beginning of the test phase, the assessment of this frequency range would have been less flattering. After a long warm-up phase, however, the rather mixed first impression turned almost 180 degrees.

After the first few hours of operation, the bass range opens up both qualitatively and quantitatively. Not only that the level in the deep bass range corrects itself upwards by a few decibels and now plays at the level of the Burson Soloist and Benchmark DAC1. The kickbass comes on, as in “Berg & Tal” by Mia  is much crisper. Even in the deep bass, the Lab12 hpa now goes much further down than after the “cold start” straight out of the box. The tube amplifier cannot quite keep up with the gnarled, dry bass of my personal bass reference Nuprime HPA-9 (around 800 euros), but it plays at a high level in terms of quality. The double bass of jazz formations is given enough time to fade away without it becoming spongy. Overall, the Lab12 hpa is fun even on tracks with excessively used bass lines.

Even with the dynamic in-ear Soundmagic E80, there is no noticeable reduction in quality at the 6.3 millimeter headphone output. Unfortunately, this does not apply to every representative of this headphone class: Both the Audiofly AF-160 and the Fabs Fabulous Ears Dual Basic – both in-ears with highly sensitive BA drivers – do not feel quite as comfortable on the Lab12. A level drop can be heard here, especially in the deep bass, which somewhat diminishes the otherwise excellent sound impression. Other driver concepts, such as the magnetostatic principle in the Audeze LCD-2, were able to exude their charm without restriction on the Lab12.

Conclusion: Lab12 hpa

The tube-equipped headphone amplifier Lab12 hpa scores with a tonally balanced, minimally warmer reproduction, high resolution and a vivid stage representation. He is also very stable dynamically.

Lab12 hpa - schwebend

At most, I see two minor weaknesses: The built-in D / A converter seems a bit old-fashioned in terms of format, it only accepts PCM data rates up to a maximum of 16 bit / 48 kHz – and playback via in-ears with balanced armature drivers is not as convincing as it is with other driver concepts. If you can live with it, this tube headphone amplifier is a sonically very convincing all-rounder.

The Lab12 hpa is characterized by …

  • a reproduction with little tonal discoloration with a tiny touch of warmth.
  • a very detailed and not noticeably falling high tone even in the upper frequency range.
  • Mids harmonize very well with the other frequency bands, including great speech intelligibility.
  • a slightly stronger bass range that extends into the basement, which can certainly compete with transistor colleagues.
  • a very plastic stage representation with very good locating ability of the instruments and voices. The stage size is drawn realistically.
  • a realistic decay behavior of the instruments, which is still topped in the bass range by some amplifier specialists.
  • very good fine dynamic properties. Power reserves for power-hungry headphones are in abundance. Impedance-sensitive BA in-ears often feel more comfortable on other amplifiers.
  • a distortion-free and uncompressed way of playing, even at higher volume levels. The very high channel synchronization, even with the smallest potentiometer settings, pays off when listening quietly.

Facts Lab12 hpa:

  • Model: Lab12 hpa
  • Concept: tube headphone amplifier / pre-amp with integrated D / A converter
  • Price: 1,260 euros
  • Inputs: analog: 2 x RCA; digital: 1 x USB-B (PCM 16 bit / 48 kHz)
  • Outputs: analog: 1 x headphones (6.3 millimeter jack); 1 x RCA (pre-out); digital: 1 x S / PDIF coaxial
  • Dimensions & weight: 32x11x29 cm (WxHxD), 6 kg
  • Power consumption: approx. 60 watts
  • Guarantee: 5 years

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