Yamamoto Sound Craft HA-02 Headphone amplifier

Vintage tubes headphone amplifier

HA-02 is a vacuum tube headphone amplifier which equips speaker output for small BGM sound as well. The amplifier tube is Western electronic vintage miniature tube 408A, it has 300mW output is enough output for a headphone amplifier. 408A is superior for noise performance as well as resolution at small volume.
HA-02 is designed as a single stage amplifier circuit construction with pentode amplification factor. The transformer is similar high performance one for upper grade amplifier. The input section of the HA-02 is provided with two terminals so that a CD player or music player can be connected, and can be used by switching with the switch on the top of the chassis.
The output is 50ohms for headphone, 8ohms for speaker. The load impedance for headphones range is 8-600ohms(ideal 50ohms), corresponds  almost all headphone types. HA-02 equips a CD direct input which accept to connect portable music players like iPod with attached high quality cable.
The HA-02 input terminal adopts our original chrome copper Teflon insulated pin jack. The speaker terminals use gold-plated high-grade terminals that can connect cables up to 5 mm in diameter. The headphone jack uses a highly reliable type manufactured by Neutrik.
Vacuum tubes WE408A x2
Maximum output
300mW (50Ohms / headphone) 
240mW (8Ohms / speaker)
Frequency response 
45Hz-17,000Hz (speaker) 
Residual noise
100μV(headphone output)
70μV(speaker output)
9.5dB/50ohms (headphone)
1.5dB/8ohms (speaker)
Dimensions 150(W)325(D)125(H)mm
Weight 4.2㎏
*The power voltage is available from 100V to 240V/50,60Hz.
*Yamamoto Sound Craft amplifiers are build to order system. It takes 8-16weeks to delivery.


The HA-02 is like water - ultra-transparent and essentially absent as a playback device. How often have we heard that no audio amplifying device is as linear as a triode only to realize that once coupled to real-world loads, linearity goes to hell and back in the toilet? The only listeners to know just how linear and dynamic triodes really are will be those who use single-ended feedback-less valves in their respective entry ranges of available output power. Connecting a triode to a single tiny -- and naturally crossover-less -- driver in a headphone prompts average playback levels in the milliwatt sphere. That's where triodes rule and the Yamamoto device proves it brilliantly.
Listening sensitivity diminishes over the course of a session. That's why movie soundtracks get louder towards the end - to make up for this loss. The HA-02 compelled the opposite reaction. I kept turning it down. The music seemed to get louder as I advanced from track to track. Curious about why that would be so, I closely inspected the experience between and behind my ears. I soon realized that the reason for the unusual intensity had to do with weight. It's customary to talk of bass weight with endowed amps or speakers. We all know what's meant by that. How often has this descriptor been applied to the midrange and lower treble, however? 
Enter the HA-02. The amount of weight and density it projects on the vocal range is unusual to say the least. This is different from the unnatural energy of an elevated presence region and thus suffers none of the eventual fatigue or heat endemic to such voicings.
It's not the case that bass is lightweight or unduly shy either which could account for a perception of midrange prominence. And to be sure, it has nothing to do with prominence such as we usually understand it. Hence my choice of weight for this phenomenon.
Related to it is color temperature of tonal hues. The palette from which the Yamamoto draws is incredibly rich and saturated yet perfectly coincident with the aforementioned water-like transparency. It's the polar opposite to the deep-triode type of thickness which is actually opaque. The Yamamoto deserves its own moniker like deep triode - but pointing in a different direction.
Yamamoto Sound Craft HA-02 Headphone amplifier
Vacuum tube type headphone / speaker amplifier 
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