Assembly of BK Butler Tube Driver in old TV-box case
I wouldn't say that I didn't believe in success, but to begin with, I decided to save on the power supply and the case. By chance, I found the ancient 1970 TV-box in my workshop, and the main joy was that this box was powered by the transformer with a 15-volt output, just like the original BK Butler. It also had a power switch with a power-on indicator, antenna inputs on the rear panel that could be used for guitar jacks, and an already built-in 10kΩ potentiometer for bias adjustment. "A ready-made case with power supply for my DIY project," I thought, and got to work.
Open the case. Out of all this variety, we only need the transformer, power on/off buttons, and slider resistor. Everything else we mercilessly unscrew, drill out, pry out, and cut off.
I place the boards and check the fit for determine the locations of the jacks, button, and knobs. The board with the tube is mounted on the standoffs in place of the original board, and one hole will need to be drilled in the board. The second board, where the power supply is located, will be screwed onto the standoffs directly to the back wall of the enclosure.
On the chassis need to drill holes. On the back where the antenna sockets were, for the guitar input and output - up to 10 mm, and for the power - 12 mm. On the top, instead of the "Fine" potentiometer, I'll set a switching button, 12 mm. I won't drill the body itself, the diameter of the holes in it is quite suitable. I place the potentiometers on the top of the body, with a diameter of 7 mm, mark and drill. We also need to make a hole for the lamp, I drilled a hole with a wood drill bit of 22 mm and then expanded it with a utility knife. The resulting hole is about 25 mm. This hole, firstly, simplifies the placement of the board in the body, and secondly, greatly simplifies the replacement of the lamp. By the way, I tried using an RFT ECC81 instead of the 12AX7, the sound is far from the original, but still very interesting.
Okay, let's remove the cover and start soldering. Usually, I solder circuits following the signal path, but this time I decided to follow the instructions and go clockwise. I started with the jumpers on the button, and then proceeded counterclockwise: the orange wire from R1, then ground from the input jack, and so on.
As a result, we got this frankenstein. I foresee comments like "the wires need to be shorter!" and "twist them into braids!", but I remind you that this is just a prototype for now. In the end, everything will be shortened and twisted, for now I just wanted to make sure that the circuit works. And it turns out that it really does work! I spent two evenings just extracting sounds that gave me goosebumps.
But the noise... To be honest, the original Tube Driver was not a great symbol of silence either, its signal-to-noise ratio was only 70dB. But here the noise was even higher. "The transformer is causing the noise," I thought, and immediately decided to make a duplicate external power supply. To make it easier to compare, I installed a military toggle switch that quickly switches the power supply from internal to external.
And to ease my conscience, I also soldered a parallel X2 capacitor to the input winding of the transformer. Do you know what changed? Nothing. When switching from the internal transformer to the external power supply, the tone of the noise changed, but not its volume. The next step is to shield the enclosure.
I am assembling and listening. When powered by the internal transformer, there is still some noise, although it is insignificant: you won't be able to play concerts with it, but it's fine for home use. And with the external power supply, the sound is absolutely wonderful. Clean, without noise or artifacts. To show off my work, I'm shipping the resulting device by post to a composer friend of mine. His name is Max, he composes music for movies and records it in his home studio.
Two days after receiving the package, Max contacted me and called me a jerk. Because instead of working, he spent two days with his guitar and my pedal. And he's never heard a more beautiful overdrive in his life. And he asked me how much this thing costs because he's not returning it. I suggested completing the project, installing the boards in the casing, painting it, and making it look nice, but Max refused. First of all, he loves old school and steampunk, secondly, the sound is more important to him in the studio than aesthetics, and finally, he has no intention of using this device for concerts. And if he ever does, it's even cooler in its current state, whoever sees it will be greatly surprised.
In general, we agreed that the trial unit will remain in the studio, and instead, Max will order another set of spare parts, a tube, and a 1590BB aluminum enclosure for me. He also promised to record a demo of my version of Tube Driver.
The attack of Russia on our homeland delayed the release of the demo a bit, but it's recorded, and all the guitar parts on the track were recorded using the gadget described in the article.
Glory to Ukraine!