Tiny Guitar Amp Rebuilt with Tiny Tubes

[Blackcorvo] wrote in to tell us how he took a cheap “retro” guitar amplifier and rebuilt it with sub-miniature vacuum tubes. The end result is a tiny portable amplifier that not only looks the part, but sounds it to. He’s helpfully provided wiring schematics, build images, and even a video of the amplifier doing it’s thing.

Detail from the circuit diagram

The original Honeytone amplifier goes for about $26, and while it certainly looks old-school, the internals are anything but. [Blackcorvo] is too much of a gentleman to provide “before” pictures of the internals, but we looked it up and let’s just say it doesn’t exactly scream high quality audio. Reviews online seem to indicate it works about as well as could be expected for an amplifier that costs less than $30, but this is definitely no audiophile gear.

Powering up the miniature vacuum tubes takes a bit of modern support electronics, including a buck converter to provide the high voltage for the tubes as well as a 6V regulator. The plus side is that the new circuit can power the tubes from an input voltage between 12 and 30 volts, meaning the amplifier can still be powered by batteries if you want to take it on the go.

We’ve seen some fantastic tube amplifier builds over the years, proving that some things never go out of style. If you’d like to learn more about the magic that lets these little tubes of hot pixies make beautiful music, the US Army has you covered.

25 thoughts on “Tiny Guitar Amp Rebuilt with Tiny Tubes

    1. Yeah, wow. The original guts were numbingly pedestrian compared to the gorgeous old-fashioned components and construction style it has now!

      Thanks for the comparison, that makes the project even more interesting.

    1. While those KORG NuTubes look neat, the circuit is more complicated than traditional tube circuits, as each triode requires a buffer at their grids since they have very low input inpedance. Also, they’re a tad expensive at the moment if compared to subminiature tubes. But I do love this new tech they came up with, and I hope to someday get my hands on one of those to try out myself!

    1. Here you go:

      Parts List

      Resistors (all rated at 2w, because of size rather than heat dissipation):

      1x 330R
      1x 1k
      2x 1k5
      1x 3k3
      3x 68k
      1x 100k
      1x 220k
      2x 1M


      2x 500kA (Gain and Volume)
      1x 500kB (Tone)


      1x 100p 50v
      2x 4,7n 250v
      2x 10nF 250v
      1x 0.47u 50v
      1x 22uF 50v (6N21B b cathode)
      2x 22uF 250v (B+ nodes)
      1x 220uF 50v

      Output Transformer: 3K:4R/8R, 1 Watt, 120Hz low-end cutoff (custom-made for this project by http://schatz.eng.br

      Voltage Conversion Boards:
      B+ https://m.ebay.com/itm/263382388214
      6V https://m.ebay.com/itm/183032224901

    1. I wouldn’t know how much such a kit could cost, considering the tubes aren’t produced anymore. They’re not expensive or hard to find by any means, but they’re not too widely available either.
      And the output transformer would need to be custom made.
      And I’m in Brazil, which would make shipping it to overseas customers a nightmare because:

      1. The Brazilian mail service is slow;
      2. They often “lose” packages;
      3. They also often mishandle packages;
      4. Shipping might be more expensive than people are willing to pay for.

      If it weren’t for that, I’d get right on making kits of this. I’d love to see people making them!

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