A Cake Tin Makes A Great Tube Amp Chassis

If you have ever had a go at building a tube-based project you will probably be familiar with the amount of metalwork required to provide support structures for the tubes themselves and the various heavy transformers and large electrolytic capacitors. Electronic construction sixty years ago was as much about building the chassis of a project as it was about building the project itself, and it was thus not uncommon to see creative re-use of a chassis salvaged from another piece of equipment.

This morning we stumbled upon a rather nice solution to some of the metalwork woes facing the tube constructor courtesy of [Bruce], who built his tube audio amplifier on a chassis made from a cake tin and with its transformers housed in decorative display tins.

The circuit itself is a straightforward single-ended design using an ECL82 triode-pentode on each stereo channel, and comes courtesy of [Nitin William]. The power supply is on-board, and uses a pair of silicon diodes rather than another tube as the rectifier.

It’s true that [Bruce] has not entirely escaped metalwork, he’s still had to create the holes for his tubes and various mountings for other components. But a lot of the hard work in making a tube chassis is taken care of with the cake tin design, and the result looks rather professional.

We have something of a personal interest in single-ended tube amplifiers here at Hackaday, as more than one of us have one in our constructional past, present, or immediate futures. They are a great way to dip your toe in the water of tube amplifier design, being fairly simple and easy to make without breaking the bank. We’ve certainly featured our share of tube projects here over the years, for example our “Groove tube” round-up, or our look at some alternative audio amplifiers.

44 thoughts on “A Cake Tin Makes A Great Tube Amp Chassis

    1. Came here to say the same. What was once old is now new again…

      Excuse me while I get back to work on my motion sensing turret lawn sprinkler; may be it will keep those darn kids off my lawn!

      1. Sure not. They’ll love it and make big fun out of running on your lawn and trying to “ecape” the sprinkler.
        They’re kids – not cats. They do not fear a bit of water.

      2. In my mind you are actually building this and you are doing so using vacuum tube electronics mounted on cake tins. Maybe you have an old tool-shed (shack) in a corner of your yard that is mostly occupied by them all!

    1. in the 70’s, there was a QST (or equiv) article on building a 2 transistor xtal ham transmitter. it was called the ‘tuna tin 2’ and with a name like that, I could not forget it. I really did use a tuna tin, as the pcb was laid out for that round shape. (the receiver was a sardine can 5 but I never got the receiver board working. transmitter worked, though, qrp as it was).

      1. I found it! Very sweet looking rigs. Search for:

        tuna tin “transmitter”

        Quotation marks can make or break a search. There are a lot of great examples of what you described, thanks!

      1. It’s a coil, made of wound (hence the pattern) wire. Today’s inductors are quite a bit smaller, but in an RF tuning circuit, the purpose is identical.

        Often older receiver circuits (technically, the picture shown above is a TRF receiver, which was one generation newer) would have a second coil mounted inside the first. By carefully rotating the inner one about its axis, its changing position relative to the larger (outer) one would perform a variable tuning function. Google “regenerative receiver” and you’ll see some pictures of this type of design.

    1. Whatever you think of the arguments pro/anti tube.

      They give me a warm fuzzy feeling.

      Music is art. The value of the result relies heavily on how you get there.

      A photo of the Mona Lisa would portray her much better than that shitty portrait. But it would be valueless and not priceless.

      1. I love tubes. Digital is great for calculations, but tubes work just fine for audio and they look great. It COULD be just my imagination, but vacuum tubes just seem to sound better!
        I’m 30 BTW, not someone who lived with tubes for half their lifetime.

        1. A tube amp sounds like a tube amp, if you like that sound it is ‘better’ – it is ultimately a matter of taste, and that makes the whole argument stale and pointless.

    2. tubes: even order harmonics. solid state (most, iirc) is odd order. even order sounds more pleasing.

      but now, the thd levels are so low, its really academic. solid state can be as good as you need it to be. its solid state that is mixing and recording your music, not tubes.

      1. Why care? If that is what some folk like, let them have it. There are whole genres of music that I can’t stand listening to regardless of the fidelity of the recording/playback, but have a following and a market. Just because I don’t like it doesn’t mean it should not exist. Vinyl, tube amps, bagpipe music: à chacun son goût.

  1. the hum you get if that is happening whenever you connect to your computer out or video game out or tv out it could be a ground loop.

    you may want to try isolating with an audio transformer on the input.

    it should also protect the outputs of the other devices if the tube should melt down and short internally

  2. Working with a sheet of aluminum as a top plate is really not that difficult once you’ve collected a few of the right kind of drill bits and files.

    Here’s my method:

    Mitering the box is a little more time consuming, but the end result looks good (IMO). Material cost for the chassis above is under $20 ($6 aluminum, $14 for the mahogany). Could be even cheaper with scrap or cheaper wood species.

  3. Hi,

    When I was living in Japan I couldn’t speak Japanese so to keep myself busy I thought what is a cheap easy way to make a base to build on, I was at Notori a local department store and I handed over some yen and I owned a cake tin. I then bought the wood/stain heyuckle yen (100 yen shop) and made the we wooden plinth. The amp now sits in my office at work in New Zealand. Glad you guys liked my amp but the idea I believe is nothing new, people have been building tube amps on all sorts of things! Cake tins, oven dishes, just be creative and think outside the square :)

    Thanks
    Bruce

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