vibrotron clone

[R.G.]

Hmmmm... MOSFET oscillator and submini modulator tube... tiny case, low power ...

[Kagliostro]

Many thanks for the answer maxkracht

Franco

[Balticnoiseforge]

Like most of these projects, this one was intended to be quick and dirty but got out of hand. My main design constraint was to fit everything on that predrilled board, which I mostly succeeded. This made it harder to put each stage’s filter cap close to that stage. It probably doesn’t matter much, but that is how Merlin did it, and is usually good practice. I didn’t spend too much time thinking about the grounding scheme, so that could be improved. I assumed if I kept the preamp quiet, everything else would be fine. Not exactly layout, but I wish I would have shielded the under board signal wires to eliminate a variable when looking for sources of noise. This likely isn’t necessary, but couldn’t hurt. I’m sure there are other improvements that more experienced people on this forum would be able to point out, but it is hard to change one thing on a layout without changing the whole thing.



I designed the faceplate without thinking of clearance between the board and the input and output jacks. Once I had the board built, I realized it needed to be pushed back farther to make room. This also pushed the tube sockets back, requiring them to be rotated to leave room for the mounting screws. My layout, on paper, put each triode half at a right angle to the board, allowing shorter wire lengths and easier heater routing to the corner of the chassis. I used floating heaters because I ran out of room.



I thought about placing the tube sockets where you suggested, but opted for what I thought would be a more compact cabinet design. I also find it oddly satisfying when the transformers in an amp are just taller than the tubes. This is purely aesthetic when there is only one transformer. Your way makes more sense in the cabinet I ended up with.



I did all of the electronics first, then looked around for scrap wood. I found a piece of decorative trim and a leaf from a beat up table that the previous occupants left in my house. Those dictated the cabinet dimensions. The width was about right, so I didn’t have to bother with ripping anything down to size, just cut to length, glued and screwed. I used a broken, wood, coat hanger as a dowel to cover the screws. I initially planned to cover it with vinyl, so I didn't bother sanding the interior before gluing together. This is why the outside finish doesn't match the inside.

The trem/vibe mix pot is just a variable resistor between the node marked “A” on my layout and ground. You could eliminate the selector switch entirely, if you used a pot with a switch connecting the node marked “B” to ground when it is in the off position. To put it more simply, when “A” or “B” are grounded you have tremolo. When “A” and “B” are not grounded you have vibrato. When “A” and “B” are grounded the effect is bypassed.

Just ressurecting the old thread, that mix sounds interesting - if you are still here i have some basic question.

So it is basically wiring a 1m linear pot between A and ground? So with some rewiring of the switch with vibrato/bypass/tremelo it could be rewired for a vibrato/mix/tremelo? Ie introducing the 1m pot?

[Balticnoiseforge]

Many thanks for the answer maxkracht

Franco

Hey! If you are still active - did you understand fully what he ment with the mix pot?

About to build one for fun, but changing some things - more voltage, 12ax7 for tremelo together with 3mC pot and such, but otherwise similiar circuit.

Having a mix setting instead of bypass sounds interesting.

[maxkracht]

Just ressurecting the old thread, that mix sounds interesting - if you are still here i have some basic question.

So it is basically wiring a 1m linear pot between A and ground? So with some rewiring of the switch with vibrato/bypass/tremelo it could be rewired for a vibrato/mix/tremelo? Ie introducing the 1m pot?

Audio taper is probably better, also not sure why I wired it as a variable resistor instead of voltage divider, was probably feeling lazy at the time. Cut the wire going between junction A and the grid, put a volume pot where the wire was. On the vibrato switch setting, the pot will gradually transition between tremolo and vibrato.