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This is short but interesting talk with Slovenian tube guru and high end manufacturer, Bojan Hajdinjak. Many think he is an eccentric individual who speaks his mind openly about what he believes are audio truths. Others just step aside and listen to what he has to say with respect. His knowledge and experiences are really something that any audio constructor wishes for. What made and continues to make him stand out is, for sure, his love for music perfection and his constant struggle to achieve non-compromised audio reproduction.

This is the first part of friendly talk we had about a project Hajdinjak was working on that lead to the creation of a unique headphone amplifier. The amplifier will be boxed in custom wooden marquetry art box, handmade by Slovenian uprising marquetry artist Ivan Krivec.

MI: Why and how did you start to work on this project?

BH: Matej Isak, an admin on our High End audio site www.hiendfi.com (and on our forums), often has light flashing ideas that simply go beyond ordinary. He is always trying to explore the borders of exotic audio. He is a headphone and headphone amp fan and he has had quite some experience with 300B amps and knows what a 300B triode base amps can offer.

Once an audiophile with that much mileage listens and hears the details and tonal nuances of the 300B design, it’s hard for him to live without such an amp because there will always be something missing :). After Matej talked to me about his vision, I had to make it come to life.

MI: What is so unique and special about this amp?

BH: This is a design without any feedback and with gain from two amplifier stages and a wide bandpass. It is an OTL design without any output transformers. It is especially hard to build such a design and to make it stable while also removing the hum and noises. Biasing is achieved with a technology called “auto bias.” In such amp it’s very hard to get the electrical impedance to match right and to derive enough power from the amp. This is the reason why there are only a few builders worldwide who can design such an amp. It’s impossible to produce such an amp in serial production, because building this amp requires careful setup, almost like building a complex music instrument. I dare to say this is electro acoustical art.

BH: 300B OTL is probably the world's first headphone amp with this particular configuration.  For me such a project is surely a challenge and that’s also a big reason why I embraced the idea.

MI: Why is 300B such a unique tube?

BH: In my opinion this tube offers possibly a 100% neutral sound with internal harmonic nuances that brings the listener as close as it gets to listening to live music. Also the internal mechanical design of this valve is unique. This is a 100% audio tube that is also very exotic and therefore very hard to get the best out of it, but it does hold enormous potential.  

MI: Many think that it's almost impossible to achieve the musicality of a 300B with any other tube or transistor amp. Why is this?

BH: On the market there are a lot of bad sounding 300B based amps. Finding a good sounding 300B is something very rare. There is not much, or if at all any power triode that is specifically designed for audio and that can compare with 300B. But people don’t know or sometimes don’t want to know that this tube demands top quality audio components. There are very few loudspeakers that can benefit from the resolution of a 300B and suddenly headphones are a very good choice for many demanding listeners.  

MI: Why are there so few 300B amps?

BH: First thing for sure is the price and second the ability to create something like this.

It is much easier to get good sound from solid state or from hybrid headphone amp.

There are many tube designs and lot of them offer lower resolution and a more euphonic sound much easier for chain setup.

MI: It's rare today that audio manufactures produce hand wired components. What is advantage of this wire wrap topology?

BH: In extreme audio applications it’s very important to match audio electronic components precisely and three dimensional wire wrap point to point design is simply the best choice to achieve this.

Such 3D point to point design is a must because its layout provides the ideal position for electronic parts. Also, there are fewer and much better junctions and the best possible wiring material can be used. Inside of this kind of top notch design (300B) every single detail is crucial.

MI: Who can and will appreciate such a headphone amplifier?

BH: The most experienced audiophiles and music lovers, I think also audio technology fans. Also this amp is for those who love listening to music with headphones but are unhappy without sonic drama that happens at present inside of headphones.

MI: Any additional words for our readers?

BH: To accomplish great things we must not only act, but also dream. Not only plan, but also believe ;)

And best regards to all on your site.

Bojan Hajdinjak

www.hajdinjaklabs.com

www.hiendfi.com