The Music Issue!

Announcing I had received my new headphone amplifier just before my birthday raised the level of curiosity surrounding my hobby. Directly never making mention of it again was wrong. In an effort to reverse this deficiency, I henceforth offer an excess of numbers, statistics and details. I will describe my new headphone unit while strictly ignoring questions about why one needs a dedicated headphone amplifier.


Wide angle view of the Yamamoto HA-02. (Click to enlarge)

The Yamamoto HA-02 is a singularly beautiful piece of audio equipment. Hand-made by Shige Yamamoto in Hyogo prefecture outside Tokyo, it uses two type of exotic woods, a hand-wound transformer, gold-plated tube guards and a life time of experience in electrical engineering. Asking “why tubes?” opens a topic that threatens to overtake my blog. The short of it is is that there must be some type of inherent value in a technology that perseveres even though it was far surpassed by modern offerings by any scientific measurement 50 years ago. At risk of ignoring large parts of the topic, like the clipping characteristics of tubes or impedance curves, I will start at the point I find most interesting having to do with the different types of harmonic distortion found in audio circuits (feel free to jump to the pictures at this point); odd order harmonic distortion versus second order harmonic distortion. Smarter people than I have put it better:

…tubes have more measured distortion. However this distortion is primarily 2nd order, lessening greatly as we go through the higher harmonics. Distortion characteristics for solid-state however, tend towards higher odd order harmonics (5th 7th etc), albeit in smaller amounts.

Scientific studies have shown that humans perceive even order distortion as being musically consonant while odd order distortion is perceived as musically dissonant. Anecdotal evidence shows that while up to -5% of 2nd order distortion is audibly tolerable, only -0.5% of 5th order distortion is audibly tolerable.[thanks head-fi.org!]

Staying on the topic of harmonic distortion, the harmonic distortion found in audio circuits is what allows the human brain to distinguish between a recording and a real instrument. Because such low levels of odd order harmonic distortion are audible to the human ear, solid state manufactures have gone the very edge of material science in a quest to lower harmonic distortion. On the other hand, second order harmonic distortion is the type associated with the decay of a note in space and time or a chord being struck. Called “musically consonant” in the quote above. A tube amplifier’s high levels of 2nd order harmonic distortion in effect accentuates the decay of notes and creates a sonic glow around harmonies, though the exact mechanisms of such are lost in the workings of the brain. One could almost say that tube circuits sound “hyper-realistic.” This is the characteristic euphony that many listeners describe ultimately leading to a more musical presentation at the expense of accuracy.

My Yammy, as it has been coyly named on the internet, uses two Western Electric 408As tubes. The WE408A themselves have an interesting history that prove it did not find its way into the Yamamoto HA-02 by chance. The tube was initially used in underwater telephony applications in the early 60s. This gives the tubes excellent reliably and longevity compared to other tubes. Most tubes are designed for higher output levels than needed for headphones amplification, meaning they are not working within their optimum range. However, the WE408A’s optimum working specs sit exactly in the micro current range needed for headphone amplification. Coupled to the tube circuit is a transformer output stage. Glossing over volumes of electrical engineering theory, a quality transformer is essential and this is where lesser amps fail. Shige-san guarantees quality by providing an in-house built, hand wound design. If you are familiar with what goes into hand winding a transformer, than you know this means serious dedication, and ultimately, along with the circuit design and tube selection, defines the sound of the Yamamoto HA-02; which is transparency, coherence and musicality. The Yamamoto HA-02 has a life-like flowing midrange. Over the years, I have read comments from the hi-fi community that music lives in the midrange. My Yammy has certainly turned me into a believer. (Upper Left: "Pilot Lump"? Just to prove it's a product from Japan, there's an English error included on the front.)

My description has probably raised questions in the reader as to why one would ever need anything beyond an iPod with those white things. Again at great risk of ignoring large swaths of the discussion, I can touch on two major positives for myself. Headphone listening in my opinion, offers a great value, even in light of the law of diminishing returns that defines hi-end audio. I could probably never afford a tube amplifier for a stereo rig but because of the lower power requirements of headphones it offers a possible solution. Top-shelf headphone gear can offer surprisingly high sound quality. Consider, for example, the stereo system needed to distinguish between a $1000 CD player, $3000 CD player, $10,000 CD player and a $50,000 CD player; it would take speakers in the $20,000 range to say nothing of ancillaries. A headphone system can do the same trick at a fraction of the cost. Secondly, a stereo system deserves a home. Hi-fi hobbyists are not a condo association’s best friend. Because home ownership is far off for me, headphone listening offers the perfect balance between sound quality and the ability not to drive roommates or neighbors crazy.

I probably didn’t change too many people’s opinion about my hobby. However, I offer this warning: if any reader feels a slight tickle in their brain to try, please do yourself the favor of first giving a trusted friend or family member your wallet.


Macro shot of a Western Electric 408A out of it's socket. (Click to enlarge)


The Yamamoto HA-02 at work. One can see the headed cathodes and the blue plasmas created by the electrons jumping the vacuum. I believe Tchaikovsky's Violin Concerto in D Major was playing.