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December 2013
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LAB12 HPA OTL Headphone Amplifier / USB DAC
An audio revolution with high fidelity OTL headphone amplifier and basic USB DAC.
Review By Matej Isak


LAB12 HPA OTL Headphone Amplifier / USB DAC  The now enormous headphone revolution began intensifying within the high-end audio world a few years back. Almost by surprise to some and it is now marching to an outstanding pace in audio society. Head-fi as the prime leading working model is followed by quite few dedicated headphone high-quality listening sites. Head-fi started as an enthusiastic discussion board and idea grew into one of the most interesting recent movements in high-end audio society. And funny enough it's based firmly on headphone listening.

Many great things came from this quiet revolution. Friendly meetings, group tests, borderless connections etc. Most importantly, the new breed of audio designers came into life. Small boutique manufacturers, that serves the specific and general needs of "can" listening became the new fresh wind breezing through the established grounds. With the advancement of social medias and one globally connected world the good or bad word spreads around in no time. This gives a unique benefit of protecting the customers from frauds and boosting the honest one-man or small team handcraft ventures. There are few dozen of such audio designers and companies that make their living based only on headphone market oriented products.

Large following and ever increasing interest in headphone listening connects people to music in much broader way. The communication between manufacturers and end customers become a real interaction, that helps build stronger tides and evoke products that are desired and ready to sell once going into production. Another most important thing that transcended all the mentioned is a new breed of audiophiles and music lovers coming into high-end society. I speak about younger crowd, which finally got in touch with music in best possible and often uncluttered way. With the globalization impact, prices of high quality audio products were cut down not only to half, but sometimes even to 1/10th of what we once paid. A good thing is that actual quality didn't suffer with the mass production, but as the market showed, for example with affordable DAC units (digital to analog converters) manufacturers are brining each year the better sound, increased performance and as a rule lower prices.

It was, and remains to this day, never a better time to be in high fidelity audio. Being an audiophile presently feels great and right as high performance gear finally becomes available to the masses and younger generation. These days even on entry level you'll receive the performance, that once you need to pay few times more. Its almost funny how for example products like i-Fi brings the roughly $2500 valued performance to the $350 price range in the eyes of this writer.


LAB12 is a brain child of Stratos Vichos and marks his second product. His passion for headphone listening and music brought him to the creation of tube based gear. I've visit shortly Stratos and this year Munich high-end show and he was pleasantly surprised by the interest for his products. As mentioned above, headphone listening passed way over the trend like nature a long time ago. LAB12’s vision and urge to produce HPA came from more needs of the people in enjoying a high-quality, audiophile sound in intimate surroundings, that won't disturb others around. The fact is not everyone has the luxury of a dedicated listening room or space, and this is precisely where high-quality headphone listening becomes not only interesting, but for many a must. In the absence of the room reflections, a well-balanced headphone listening system can bring the purity and personal undisturbed musical enjoyment that very few two channel based speaker systems can. Stratos wanted to design a headphone amplifier that would suit both budget and high-end headphones and could upgrade the listening experience of dedicated high performance headphone amplifier with a noticeable impact.

LAB12 HPA OTL Headphone Amplifier / USB DACStratos is passionate not only about headphones, but also about the tubes and his first product materialized in an OTL headphone amplifier. HPA extend its use as a preamplifier with one line stage and offers two analog inputs. Additionally digital audio can be fed directly via USB input. This makes HPA a versatile device with headphone amplifier, line preamplifier and DAC under one chassis. Every LAB12 HPA comes as and handcrafted device with a choice of luxury car paint finishes. This gives an extra stylish feeling and unique appearance. The main point as with many recent devices is quick and clutter free operation.


Based on my experience with OTL on speakers and some headphones, I already have a good idea what to expect. The main feature of any good OTL design is a purity and stressless presentation of the music. Something special happens with the music reproduction in the absence of the output transformers. Tracy Chapman’s debut album Tracy Chapman on vinyl gives a quick and nice insight into the performance of any component. It is not an audiophile album by default, yet is music I truly enjoy. The variety of arrangements and masterful recording brings not only great music, but one heck of the audio recording quality we all desire. Growing up with Tracy’s melodic, raw and sadly realistic music takes on life, society and relationships. I've practically memorized the whole album! I know how it should sound regardless a medium, but admit enjoying it on vinyl brings the best. HPA and vinyl matched nicely and the HPA’s speed in sound resolution gave the often needed consistency. When it comes to the testing of vocals and energy combined I always reach for two albums. One is Harry Belafonte Sings The Blues and Muddy Waters's Folk Singer. Both Harry and Muddy burst in roarings and sometimes the energy exchange almost meets the dynamic of a classical orchestra when they emerge out on nowhere up in almost inhuman crescendo way.

Both Folk Singer and Sings The Blues show the capability of any component without fail. Especially with headphones, were all the room acoustic problems are removed and the sense of energy should reach out to you directly. The three dimensional presence of Muddy Waters is quickly smitten with an amplifier or preamplifier of lesser potency. He was a large man of huge presence and portraying his "mojo" is not an easy task. Many preamplifiers and amplifiers are easily brought to the knees with the lightning strike of his vocal power. But, this album is not just about energy. Delicate subtle playing of the very young Buddy Guy is another highlight. His guitar virtuoso was already put at spot quite early of his career and if you want to experience the true expert playing with all the little nuances of blues guitar this is an album to behold for its purity and directness.

LAB12 HPA’s ability to create an illusion of portraying those two legendary artists was very good. I often write that when high-end products are designed in right way, there is an instant ‘click’. It either connects you to the music or fails. Of course things can get more subtle and elaborate, but some components share the ability to ignite the interaction between listener and performer more than others. HPA is on the positive side of those two. HPA’s OTL nature brought familiar insights with both AKG 701 and Beyerdynamic T-1 headphones. The AKG K-701 can quickly become tiresome and un-involving, but with HPA it draws you into music with ease. The unforgiving nature of T-1 quickly reveals the flaws of any headphone amplifier. This is further quickly highlighted with Franz Schubert, Dietrich Fischer-Dieskau, Gerald Moore album. This recording from Deutsche Grammophon might come as simple at the quick glens, but the interplay and quality of recording sets the standard for the generations to com. HPA ability to recreate this duo was spot on. Sense of space and atmosphere were of intimate nature and i could immerse into the music without over thinking.

LAB12 HPA OTL Headphone Amplifier / USB DACThe speed of the vocal, regardless of genre, was in favor of HPA. Of note is that cables that may highlight micro and macro dynamics and add a bit of a bloom works best with HPA. LAB 12 HPA is very open, lifelike and airy, with the inherited OTL nature of the unit opening up a bit darkish nature of Sennheisers. HPA also guides AKG studio-like character and make them a bit easier to enjoy.  In my opinion, solid-state headphones amplifiers might give a bit more linear feeling across the frequency range, yet the HPA’s OTL impact brings that feeling of directness. And to conclude with voices. Opera vocals are on the heavenly side.


Three In One
LAB12 HPA was primarily designed as a headphone amplifier. Designer Mr. Stratos told me that a preamplifier and DAC were a later decision and implementation to the unit. They do perform fine, but especially with outboard DAC the performance boost is large. I wouldn't call preamplifier section of HPA mediocre. It packs enough bloom, potency and atmospheric impact to let it function even in bigger more demanding systems, but still the main highlight is HPA's headphone amplifier. When using preamplifiers and digital sources it is my usual routine to pick up the LessLoss Firewall and DFPC power cables as reference tools. They act as tools in the sense that they quickly and effectively show how prone a device is to the quality of incoming electricity. For now, the only device that didn't benefit from the power cord or external power filter was Robert Koda Takumi K-10 preamplifier. With all others, the well-designed DFPC makes all the difference. With the Firewall, all the more so.

It was the same with HPA. With the LessLossDFPC Reference under review the difference and benefit was instantly evident. The dynamic impact and the nature of transients changed at once with the DFPC Reference inserted. The LessLoss Firewall has the unique ability to lessen the digitalis effect of DACs. It brings about a more natural and stable presentation to the music. The same thing happened when used with HPA internal DAC. The edginess was reduced at once while keeping the dynamics intact. The LessLoss combination showed that the HPA has a "hidden" potency that can be evoked with the right combination of power cord/filter.


LAB12 HPA OTL Headphone Amplifier / USB DACLAB12 HPA comes in time when headphone listening is in a full bloom. With integrated USB DAC it offers a quick, no nonsense voyage into your music collection. The HPA reveals itself in layers. Since it can function as a well-balanced preamplifier and workable DAC, it shines when used as sole dedicated headphone amplifier. It was designed from ground up as an audiophile grade OTL "cans" amplifier and it sound performance proves it. While we can dream about stable OTL amplifier for loudspeakers in down to earth pricing, OTL headphone amplifiers are at least more affordable and much less complicated than those having to drive power hungry loudspeakers.

One feature that repeatedly came up in my notes was flexibility and ability to bring life even to more entry level headphones like AKG-K701 and lower series of Sennheiser HD line. This makes HPA a versatile headphone amplifier for those who enjoy the larger collection of different headphones. It shows that Stratos took their time with LAB12's HPA and designed something that brings joy to his personal listening and translated to others as well. Their HPA is unique enough in its design and appearance that it will draw not only many dedicated headphone listeners, but also music lovers.



Sub-bass (10Hz - 60Hz)

Mid-bass (80Hz - 200Hz)

Midrange (200Hz - 3,000Hz)

High Frequencies (3,000Hz On Up)



Inner Resolution

Soundscape Width Front


Fit And Finish

Self Noise

Value For The Money


Type: OTL tube headphone amplifier
Frequency Response: 5 Hz to 100 kHz (-3dB)
Tube Compliment: Three 6N1P tubes (matched output pair)
Volume Adjustment: Blue Velvet ALPS Potentiometer
Transformers: Handcrafted audio grade transformers (T.GIATRAS)
Power Supply: Five regulated with SRSG implementation
Connectors: Gold plated Teflon RCA connectors, gold plated tube sockets, etc.
Analog Input: Two pair gold plated RCA line inputs
Analog Pre-Out: Gold plated RCAs
Digital Input: USB capable of 48kHz/16-bit
Digital Output: Coax S/PDIF RCA
Input impedance 50 kOhm
Output impedance 32 to 600 Ohm
Preamp out impedance 4 kOhm
Headphone impedance selector (hi-low)
Faceplate: 5mm aluminum panel with luxury painting (Pearl white, Etna black or orange)
Warranty: Five years parts and labor
Dimension: 32cm x 11cm x 29cm (WxHxD)
Weight: 13.2 lbs.
Price: €990 ($1340 USD)


Company Information
Lachana 12 Street, Neo Iraklio
Athens, Attiki 

E-mail: str858@yahoo.gr 
Website: www.LAB12.gr












































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