Single ended Class A pentode tube amplifier using 408A tubes. HA-02 is the headphone amplifier...

Yamamoto HA-02

  • Single ended Class A pentode tube amplifier using 408A tubes.

    HA-02 is the headphone amplifier which uses a vacuum tube as an amplification element. Although output power is small, it has the output terminal for speakers and it can also sound a speaker with small volume as BGM.
    Only one right and left are using each the miniature vacuum tube 408A of a Western Electric for an amplification tube. Although this WE408A is a vacuum tube of a vintage, it is one of the produced vacuum tubes, and since it was used abundantly for telefon equipment, there are no worries about a spare tube even now. It seems that it was used for various uses in order to often tend to use characteristics, although this vacuum tube is originally designed as an object for high frequency amplification. When it was used for the data of a Western Electric as a small output tube, there was description that about 300mW output power was obtained. When we manufactured the amplifier for headphone based on this description, we decided to produce commercially, since the good result was obtained. (...)

    HA-02 specifications: Use vacuum tube: Only WE408A 2 tubes / Circuit system: Single stage amplification, pentode connection, and non-feedback system / Maximum output : 300mW (at the time of 50ohm load) of headphone terminals, 240mW (at the time of 8-ohm load) of speaker terminals/ Frequency characteristic: 30-21,000Hz (headphone terminal) 45-17,000Hz (speaker terminal) / Gain: Headphone output power 9.5dB (at the time of 50-ohm load) Speaker output power: 1.5dB (at time of 8-ohm load) / Remains noise: 100 microvolts of headphone output power 70 microvolts of speaker output power / Outside dimension: 150 (W) 325 (D) 125 (H) / Weight: 3.5kg

Recent Reviews

  1. alexdemaet
    Yamamoto HA-02
    Written by alexdemaet
    Published Dec 16, 2011
    I tried this amp with a Sennheiser HD650 and I was not very impressed (I remember I was not very impressed when I tried it a couple of years ago). Maybe the tubes were not in good condition).
    But I did not try this amp as a speaker amp because I did not have them yet and neither an AKG K1000.
    An advantage is that you can use the amp both as speaker amp and phone amp.
    Anyway I shouldn't have started this review because it is more then 2 years ago since I owned it.
    If I could I would delete this all.
      LinuxmasterD and asuperpower like this.
    1. View previous replies...
    2. Balisarda
      But it's an informative comment! Unless it includes frequency-response graphs and such, all reviews are subjective.
      Balisarda, Dec 17, 2011
    3. jazzgene
      I find the HD650 to match well with the HA-02.  
      jazzgene, Oct 23, 2013
    4. asuperpower
      I actually agree. I thought I was the only one to feel this way, but I listened to this the other day and the HD-650 sounds really muddy with these.
      asuperpower, Mar 5, 2015
  2. akabane@drjackel
    Superb Amp
    Written by akabane@drjackel
    Published May 18, 2011
    Pros - Good For Audio Technica Woodies Headphone
    Cons - Event stated can support high impedance headphone but still has a limitation.
    This is a Amp that make a lot my Audio Technica Woodies Headphone sing and this is make me no more worried about choosing an amp anymore. That at last i manage to find this Yamamoto HA-02 is the most suitable for my current collection that i owned. Anyway this is just a reference make from me based on Audio Technica Woodies headphone that i owned. 
    Equipment using during the test : Yamamoto HA-02, Audio Technica ATH-W2002, Audio Technica ATH-W11JPN, Audio Technica ATH-W1000 & Modded Ipod 4g
    Classical Music
    This is the one of the most hard way to test in different various instrument during the test especially in classical music. This the part where my 40th Year Anniversary Headphone (W2002) is tested during this genre. I'm listening Ein Straussfest-An der schönen, blauen Donau (On the Beautiful, Blue Danube), waltz for orchestra (with chorus ad lib), Op. 314 (RV 314) conducted by Erich Kunzel. This is the best ever i listen to based on my headphone with a type of amp. What i able to listen to this amp such as the Decay is much longer compare to my old custom built class A amp. Transparency is much improved. Detailed of every single orchestra instrument that i can feel and know which is the position of is play-off. Accuracy/speed is a +1 for me. This is a remarkable sound for me. is just perfect to the amp + headphone.
    Female Vocal
    As much prefer to Female voices and this test i'm listening to Celine Dion - All by Myself. Headphone that i'm using is the W11JPN which is much high coloration headphone for me and this is a killer for the best combination for this Amp for vocal. What surprise me is this amp is really make this W11JPN coloration headphone more beautiful sound. The emotional of the Celine voice and i can touch her feeling too. I cannot denied that Celine voice is too perfect for this setup and i did listen over and over again is that is very touching to you heart. This is the best combination for vocal i ever heard. Celine voice has a very powerful message with this amp, it produce the best/deliver to the headphone and to the listener. 
    This genre i would prefer to use my W1000 which this field is the best for this headphone and the amp as well. During the test i listening to Kenny G - In The Rain & Rodrigo y Gabriela -Tamacun/Orion. If you like a musical this combination is always be in you mind then. The Speed/Detailed/Transparency/Decay is the position that i'm looking. Is a very enjoyable sound and is really make you day happy. Kenny G sax is really gave a good emotional of fantasy which you really can relax when you are in tense or frustration. The message is playing in your heart and mind. Rodrigo y Gabriela is much to fun for me. Is enjoy and the feeling is you want more and more. you mind will keep ask faster and faster and more and more outcome. This is a great combination.
    This short review is much to my personal view and is does not criticize to anyone here. But i would say every single cent that you pay for this amp is really worth it if you do see the package of the amp come with a nice Audio Technica cable which is suitable for PMP/CDP. I guess this is just some few aspect that i want to say here that some genre might also suitable but i think i only touch more to this three aspect. But i pretty much concern on Female Vocal at sense that i do listen daily after i back from a busy day at work. 


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