Here is one of those virtually unheard of "web find" products that reach my e-mail inbox from time to time. While some of these finds are home-brew turned company, others are from well-established companies in parts of the world where they have not ventured outside their home country. As an example, the world's first outside Germany review of the Lehmann Audio Black Cube by yours truly was one of those great finds. Great sound on the cheap is always a joy! Only weeks after my initial review did word on the street reach a feverish pitch. Eventually the Black Cube found its way into the homes of many thousands of audiophiles. The rest, as they say, is HIStory. If i was a betting man, the Dubiel Accoustics (was called Skorpion) HV-1 OTL headphone amplifier will also garnish such praise.
Based in Poland, Dubiel Accoustics was officially formed and began manufacturing electronics since 1979. Maybe we need to back up a bit as in 1969 their first tube amplifier, based on ECL 86, was designed for vinyl replay. After some years manufacturing silicone-based amplifier (solid-state), they decided to offer a line of tube amplifiers. This includes everything from tubes phono stage to amplifiers. As my home is chock full of equipment, the one component that could use an improvement was in acquiring a headphone amplifier. Enter the Dubiel Accoustics HV-1 at only $750!
Features include two standard stereo headphone jacks, a power switch (plus power LED) and volume control on the front. On the rear are quite solid gold plated RCA inputs, paralleled RCA outputs, standard IEC power receptacle, and fuse holder. Wood side panels round out the visual beauty of this unit. While there is a single power transformer centrally located, notice there is no sign of output transformers as this is an OTL design. Each channel uses a single 6AQ8/ECC85 for pre-amplification and 6080 for amplification. This design is said to provide a very wide frequency response from 5Hz to 70kHz (+0/-3dB). While output power is rated at 300 mW with a 40 ohm impedance, i found it more than enough for my power hungry Sennheiser HD600 setup (as reviewed here).
Using good quality parts and construction techniques, the HV-1 lends itself to greatness through the ability of not just eliminating the costly output transformers, but in also benefiting from using no output transformer at all. OTL is an abbreviation for Output Transformer Less and there is a huge audiophile cult that feels the best output transformer is none at all. Less = more. Hmmm... i detect a pattern forming as the Royal Reference 3A MM De Capo-i (reviewed this month by yours truly) also follows this technique within their crossovers.
Tonally, the HV-1 is on the accurate side of the fence over tube warmth or "lush". It is not a cold and sterile unit and to further clarify, harmonics seems quite good and precise over the rose-colored glasses variety. If you are looking to have added warmth to your headphone's sound, then i would suggest looking elsewhere. The Dubiel Accoustics HV-1 seems to be more akin to the proverbial "straight wire with gain" versus a "tone control". While the lowish signal to noise ratio of 86dB initially concerned me as headphones are like audio microscopes seeing into the sound, the 86dB rating may be very pessimistic. Using my Sennheiser HD600 headphones i could detect a very slight buzz, yet it was very low and appears to be undetectable once the music begins (with the exception of the quietest of passages). While we could all wish for perfection, at only $750 for an OTL tubed headphone amplifier perfection may be unreachable.
Be forewarned, this unit inverts the phase. This means that the plus and minus needs to be reversed within your earphones or use the reverse phase switch on your CD/DAC (provided it offers this feature). Vinyl lovers may be left out of luck, though fortunately (for me) the Sennheiser HD600's ear pieces have a removable cord that can be reversed to effectively reverse phase at the "speaker".
Summing It All Up
The Dubiel Accoustics HV-1 does so much right that it would be hard to not recommend this unit at this low pricing ($750). While i would prefer a bit more lush, the stock 6AQ8/ECC85 and 6080 seems to come from ??? so tube tweaking could benefit greatly in this department. Regardless, those who desire a good quality headphone amplifier on the cheap and with tubes can rejoice! Perfection may not come in at $750, though the HV-1 does so much right that it can't be wrong. As they say "If loving you is wrong, i don't want to be right." As always, in the end what really matters is that you...
Enjoy the Music,
Steven R. Rochlin