3-Knob Tube Driver Build.

[DrNomis_44]

Hey Everyone,


Seeing as I started a thread about doing a 4-Knob Tube Driver build, I thought that it would be cool to do a 3-Knob Tube Driver build thread as well, the 3-Knob Tube Driver is basically the cheaper version out of all the Tube Drivers manufactured by Chandler in the US, it has a different tone compared to the 4-Knob version.

Anyway, after the success I got from building the Doctor Overdrive pedal circuitry on a piece of perf board, I thought that I would try the same basic construction technique of laying out all the 3-Knob Tube Driver circuitry components on the perf board and joining them up point-to-point with tinned copper-wire and insulated stranded wire, I've built the 3-Knob Tube Driver circuit a few times in the past, once on a proper etched PCB, and a few times on vero-board, so I thought it would be cool to try a point-to-point version this time around.

I'm going to be documenting the build process in this thread so that any one else interested can build one for themselves if they like, I'll also post a layout diagram, pics of the build process, an audio demo of the finished pedal so you can hear what it sounds like, and also details of all the components I used to build it and their Jaycar Electronics catalogue number as well so that you can find them at your local Jaycar Electronics shop.

Note that Jaycar Electronics no longer stock valves/tubes, you can order them online together with valve/tube sockets from Evatco.


Stay tuned for more info...

[DrNomis_44]

Update:

Last year I bought a Grab Bag of bits and pieces from Jaycar Electronics, and inside it I found two packs of 8-way Tagboards in it which look like this:




Each pack contains two 8-way Tagboards in it, anyway, been doing some thinking about what I would use to mount all the parts, minus the valve socket, pots, etc on and thought that it would be cool to try something different and go for a Tagboard/point-to-point construction method for the 3-Knob Tube Driver pedal.


Here's a hand-drawn circuit-diagram that I'm going to be working from while designing a suitable layout of parts on the 8-way Tagboards:

[Marcel]

Here's a hand-drawn circuit-diagram that I'm going to be working from while designing a suitable layout of parts on the 8-way Tagboards:

Looks a lot like a Valvecaster circuit with a 4558 drive... maybe as an alternative you could look at the dual tube designs in the linked pdf... also has lots of interesting info to add

https://cdn.instructables.com/ORIG/F...6HIK1FLK5B.pdf

[DrNomis_44]

Looks a lot like a Valvecaster circuit with a 4558 drive... maybe as an alternative you could look at the dual tube designs in the linked pdf... also has lots of interesting info to add

https://cdn.instructables.com/ORIG/F...6HIK1FLK5B.pdf

Cheers for that Marcel, I downloaded a copy of that pdf, I've experimented with the Valvecaster circuit in the past but wasn't able to get it working at it's best, maybe the valves I was using were getting a bit worn out, the circuit tended to be a bit hummy, I'm thinking of building a circuit that uses two 12AX7 valves, but with a higher HT supply that's produced by a square-wave oscillator made from a CD4049 IC that drives a Voltage Multiplier circuit consisting of some 1N4007 (or similar) diodes and some 1uF/100V, or 2u2/100V (can even be some 47uF/100V caps too) electrolytic caps, I found that using the circuit I can easily generate up to something like +90V from a 15V DC supply.


Here's the Voltage Multiplier circuit:




The 10k resistor on the output of the Voltage Multiplier is there just to limit the output current a bit, the square-wave oscillator consisting of the CD4049 IC, 33k resistors, and 220pF cap runs at about 60kHz.

The CD4049 IC has six Inverters in it, three of them are used to form the 60kHz square-wave oscillator and the other three are used as inverting-buffers so that there is enough current drive to drive the Voltage Multiplier section.

I definitely need to get to it and do some breadboarding soon.

[Marcel]

Cheers for that Marcel, I downloaded a copy of that pdf, I've experimented with the Valvecaster circuit in the past but wasn't able to get it working at it's best, maybe the valves I was using were getting a bit worn out, the circuit tended to be a bit hummy, I'm thinking of building a circuit that uses two 12AX7 valves, but with a higher HT supply that's produced by a square-wave oscillator made from a CD4049 IC that drives a Voltage Multiplier circuit consisting of some 1N4007 (or similar) diodes and some 1uF/100V, or 2u2/100V (can even be some 47uF/100V caps too) electrolytic caps, I found that using the circuit I can easily generate up to something like +90V from a 15V DC supply.


Here's the Voltage Multiplier circuit:




The 10k resistor on the output of the Voltage Multiplier is there just to limit the output current a bit, the square-wave oscillator consisting of the CD4049 IC, 33k resistors, and 220pF cap runs at about 60kHz.

The CD4049 IC has six Inverters in it, three of them are used to form the 60kHz square-wave oscillator and the other three are used as inverting-buffers so that there is enough current drive to drive the Voltage Multiplier section.

I definitely need to get to it and do some breadboarding soon.

If it were me I'd be increasing the size of the cap on the oscillator circuit to lower the frequency to just out of earshot range. The charge caps in the multiplier will work and hold charge better at 20kHz than at 60kHz.
There won't be much power coming out of the IC, so if there is a voltage sag issue on the tube's plate resistor then I'd consider using the output of the IC to drive a transistor switcher so that more power (wattage) can get put into the multiplier so that the multiplied voltage is "stronger"....

[DrNomis_44]

If it were me I'd be increasing the size of the cap on the oscillator circuit to lower the frequency to just out of earshot range. The charge caps in the multiplier will work and hold charge better at 20kHz than at 60kHz.
There won't be much power coming out of the IC, so if there is a voltage sag issue on the tube's plate resistor then I'd consider using the output of the IC to drive a transistor switcher so that more power (wattage) can get put into the multiplier so that the multiplied voltage is "stronger"....

So maybe increase the 220pF cap to maybe something like 1nF, or 2n2?

[JohnH]

Woaaaah that hurts my brain. Super interested to watch this Doc - I've got so much to learn about electronics

[DrNomis_44]

Woaaaah that hurts my brain. Super interested to watch this Doc - I've got so much to learn about electronics

There are some mini-tutorial threads I started that you can find in the "How To Build Your Pitbull Guitars Kit" section, feel free to check them out.

[JohnH]

There are some mini-tutorial threads I started that you can find in the "How To Build Your Pitbull Guitars Kit" section, feel free to check them out.

Shall do! Thanks Doc

[DrNomis_44]

It's actually not as complicated as you might think it is, I've managed to get most of the Tagboard layouting done, just got a bit more to do and then it's ready for the next stage in the build-process.