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Thread: Vacuum tube amp story (some pics too!)

  1. #1
    Join Date
    Nov 2012

    Vacuum tube amp story (some pics too!)

    And now for something a little different…

    About 2 years ago, I was looking around Akihabara and saw these cool vacuum tube amps. They were not the type you would find in your grandparents living room, but a hybrid of old and new. Gone are the big-box VCR cases that used to hide the tubes, not they are prominently displayed as the pieces of art they really are. We tend to forget that the technology of the past can and do the same tasks of the present (just a little differently).

    I was struck by the soothing glow of the tubes as they warmed up and the great look the glass tubes gave off with varying personalities from the tube shapes themselves. I was also struck at how expensive they are! What I thought looked like simple designs were well above $1000 and the more robust juggernauts hovering around $4000-8000. Woah!! Some of this is due to construction, even more is due to the tubes themselves. Having old, rare tubes are the pinnacle of bragging that your classic car still has original rubber. Also, many tubes are just not made anymore since their usefulness went from daily use in many products to audiophile .

    I went back home with a spark but without the cash or justification of spending good money on something I knew nothing about. I researched more about what it was that made them sound better (subjective) and why some preferred them to solid state. Ultimately, I realized that my artistic eye was skewing my judgement. I liked the look of them but really did not need an amp in my small Japanese apartment. I decided that if I could get something on the cheap, I would give it a try.

    I spent a solid month online and finally found a seller with amps made in China of decent quality and price. The list price for one in particular was around $300 but every once in a while, the seller puts just a penny (really a yen) and let bidders duke it out. Many of those auctions would creep around $250 or so, a little more/little less.

    As luck would have it, one auction was barely moving. This was around the time of Obon, a holiday for families to come together to recognize their deceased. I guess that meant not many people were watching the auction cause I scored this amp for $100!!!

    When it arrived, the first thing I noticed was that it was HEAVY. The copper coil packs were solid and ready for storing huge amounts of juice for a big sound. All the internal bits were old school. No chips or new tech to be found (a must for audiophiles). I made my own speakers as well by getting a pair of car speakers and making the speaker boxes out of corkboard.

    Since the amp was seen as a “starter” amp, something for newbs to get into, many of the connections were simple/cheap. I hit Akihabara again and started to upgrade the amp; putting in better connectors, bolts, knobs, etc. The amp lasted 1 year.

    Last year, the amp just kinda gave up. I would turn it on and was greeted with an amplifying hum that got louder and louder despite the volume turned off. I tried to look at the guts but had literally no idea on what I was doing or what to look for. I shelved it since taking it to a repair shop would definitely cost me more than what I paid into it.

    Last month, I decided to take it back out. I was either going to fix it or toss it. I didn’t need it taking more space in my closet area. Poking around a little more, I discovered that one tube in particular was being nasty. It was throwing sparks and snapping inside the glass. If I took it out of the loop, I still got the loud feedback, though. So it could be the tube or something else. Vacuum tubes are picky little things. It is always best to buy them in pairs since no tube is alike. For the best sound, you need to have matching tubes that display similar resistances and power consumption/output. Getting matching tubes is also expensive. Buying those in Japan get expensive real quick. As luck would have it, I had been using a site for a while that sold stuff from China and I found the same tubes that came with my amp. I ordered 4 since I could not be guaranteed 1 would match the good tube it paired with.

    One month later, the tubes arrived. I was super excited to finally get the amp working again! I put the good tube in, turned on the amp, and was disappointed. The amp was working, but the sound was lacking volume and deep tones. It sounded like the music you hear when waiting on the phone for a call center operator. Lame. I thought it was my plug: nope. I switched all the other spare tubes: nope. Checked all tubes if they were broken: nope. Finally, I opened up the bottom again and started inspecting the board. What I found, was a very tiny ground that had lost its grip. Actually, the ground was made up of less than 10 strands of wire. Cheap indeed. Space was cramped and in trying to solder the wire back on, another ground gave up. I unbolted the board from the case and 2 more broke off. What the hell!!!

    It was one of those 2 steps forward, 10 steps back situations. I gave up trying to solder the existing wires and instead ripped it all out. All of it. I had some proper thick gauge wire that I used on my bike and instead soldered those in. It was a struggle between the size of the ground point, the wire size, and my basic skill of soldering. After some choice words and a sore back leaning over, everything was soldered back together. I plugged everything back in, crossed my fingers, and turned it on.

    Beautiful sound once again began to pour out of my speakers as the tubes warmed up. Everything seems to be quite happy. The tubes are paired, the grounds are proper, and everything is functioning as they should. All in all, I am happy. I catch myself just staring at the tubes glowing and have since routed some wire to include a connection to my PC for watching movies. And now, some pics:

    Inside guts:

    Grounds on the input connectors:

    Wire that broke off (grey) supplying a ground to the outer tube:

    All ground wires (black wire) soldered in using thicker gauge wire:

    Functioning amp!

  2. #2
    Senior Member
    Join Date
    Feb 2010
    Williston SC

    Re: Vacuum tube amp story (some pics too!)


  3. #3
    Join Date
    Oct 2009
    Nagoya, Japan

    Re: Vacuum tube amp story (some pics too!)

    Very nice!

    And very well done with the repair job! It's always difficult diving into something new, but you knocked it out like a pro.

    Makes me want to buy some vacuum tube stuff, haha.
    1967 LT23 Mitsubishi 360 // 1967 L10A Cosmo Sports // 1971 S30 Fairlady Z // 1973 PR95 Bellett 1800 GT // 1978 PA95 Isuzu 117 Coupe // 1988 Z31 300 ZX SS // 1996 EK11 March 1.3 // 1997 AC15 Dream 50
    Homepage: Hidden Content

  4. #4
    Join Date
    Nov 2012

    Re: Vacuum tube amp story (some pics too!)

    I had a pic of the original ground wire but photobucket ate it. I will post that up tonight. There's something about the amp that I just like. You might think its the tubes glowing, or the satisfying throw of the on/off switch, or the big volume knob that allows pinpoint volume accuracy; No! It is that although it is a tool, it does not have the same presence as other "tools" in my entertainment home center. It is a piece of art in every way. The whole design of the amp is centered around making it pleasing to the eye. I can appreciate that. :tu:

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