After butchering the poor old Telefunken reel-to-reel I wanted to build a Deacy-style using the salvaged transistors and transformers and give it a new life. For the most part, I used Mullard’s amp schematic from below and tweaked few component values to match with some of the Deacy schematics I found around. Few other changes were made to accommodate the parts I had available.


Comparing the Mullard schematic to various Deacy schematics that are floating around, I made the following changes to the Mullard amp:

  • Used AC117P output transistors that came from the Telefunken. They seem to be a bit more powerful than AC128 and can output over 1W in push-pull configuration.
  • Used AC150 for input transistor and AC122 for driver transistor, also pulled from the Telefunken. AC150 is commonly used as the first gain stage in many Telefunken devices from that era,
    so I guess it’s good for that purpose.
  • Instead of a 39 ohm resistor that biases the output stage, I used a 56 ohm resistor in parallel with the 350 ohm thermistor that was originally mounted on the Telefunken transformer. It will provide temperature compensation and make the amp run more stable.
  • Instead of two 10uF coupling capacitors in the signal path I used 1uF cap at the input and 2.2uF poly film cap to couple the first and the second stage. There’s no need for such a large capacitors for guitars, we don’t want to go that deep.
  • Omitted the 390K input resistor and input volume pot.
  • Added a 2.2K resistor downstream from the first coupling capacitor. I saw this resistor on few Deacy schematics.
  • Omitted input volume pot.

I ended up with something like this.


I’ve had a cool looking, compact tag board for years and couldn’t find a good use for it, as it’s often too small for tube projects. But it turned out to be perfect size for this project. All components fit on the board (except for the output transistors that are mounted on the transformer) and it fits perfectly inside the aluminum project box I got from Radio Shack years ago. To make it possible to try other transistors, I used individual IC socket pins soldered on the board.

Fast forward to the completed board. I didn’t have a 220nF capacitor for the output transformer zobel network, so I replaced it with two Panasonic 100nF capacitors in parallel. I did not have any axial electrolytic capacitors, so I faked them using radial capacitors mounted horizontally. At this stage, only the transistors are missing from the board. For them I left the tiny gold-plated IC pin sockets making it possible to experiment with different transistors. You can spot them where the transistor legs should go.


I wanted to do something unique with the finish that would be unique and in spirit of the 50s when germanium transistor radios and reel-to-reels were popular. I had some leftover pieces of tolex from other projects so I came up with the idea to cover the boring aluminum chassis cover with a retro cool two-tone red and cream tolex. Here’s the step by step how I did it. In terms of supplies, the only tools needed is a metal ruler, a sharp knife and some contact cement adhesive.

I started with marking the width of the chassis on the bigger piece of red tolex.

Then I drew a line roughly where I planned to put the cream stripe and applied contact cement on the chassis and the cream piece of tolex. The cream strip is not cut to size exactly. Note that I only applied it along the center, not fully. We don’t want to glue the whole piece yet because we still need to cut it to size so it meets the red piece perfectly.

Then I did the same thing with the red tolex. Cut two larger pieces and glued them to the either side of the cream strip. I didn’t put any glue around the lines where they meet and there’s some extra material to leave them overlapping.

The next step is cutting both materials at the same time, to ensure they meet perfectly. Only after we create a perfect seam can we glue the ends of all pieces to the chassis.

Once the big areas are covered we can move on to the corners. In this case, getting the corners done is easy because the corner is not rounded. It’s just a matter of making a straight cut in the material where the two sides meet, overlapping the two pieces and making a 45 degree cut. That will give us perfect seams on the corners.

Finally, I applied the original Telefunken logo to complete the look.

And here’s the complete amp.

5 Responses to “Deacyfunken”
  1. BROU says:

    what are the tranformers? do you have values for them? thank you!

  2. Jimm Zorn says:

    @bancika thanks i’ll give it a try.

  3. Jimm Zorn says:

    I’m having unbelievable oscillation from my build, pure sine wave tones. Any ideas on what might be the problem. Thank you in advance!

    • bancika says:

      Maybe you flipped the leads on the interstage transformer secondary? That would make positive instead of negative feedback loop though the 560K resistor and would definitely cause oscillations.

  4. Carl says:

    Never worked with a thermistor before. my local guy only supplies NTE components? Will 02−P331−1 work?
    It is 330 ohm with a trip of 75 mA the pdf sheet is
    I have all other parts including transformers and raytheon ge substitutes. What is the amperage on power transformer? I rebuild ever-ready #266 nine volt batteries and would like to try one.

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    The idea behind this site is to share my experience with Do It Yourself approach to guitars, amplifiers and pedals. Whether you want to save a couple of bucks by performing a mod or upgrade yourself instead of paying a tech, or want to build your own piece of gear from scratch, I'm sure you will find something interesting here. Also, this is the home of DIY Layout Creator, a free piece of software for drawing circuit layouts and schematics, written with DIY enthusiasts in mind.