So, this is my first design. I’ve spent all week tweaking and testing it, and I am super excited to share it here. It works great, and the sound can go from a good tube saturation all the way up to absolute madness.
I’m still not sure what to call it exactly, and I am not an engineer so I would be lying if I knew exactly what was going on in the circuit. From looking at the waves on the scope, it adds some crazy harmonics and folds in the waveforms when you flip the Mutate switch and goes into insane self-oscillation extremely easily.
I’ll post some audio examples shortly, but for now here is the schematic - I tried to make it as easily understandable as I could (I work on industrial equipment for a living and I hate how vague some of the schematics can be):
This is a slightly odd notation. 104 means 10x10^4 picofarad, i.e 100,000 pF, which is the same as 100 nF or 0.1 uF. I’d use either 100n or possibly 104 in the schematics, not both.
Hey very cool!
I’ve never seen dual plate pentodes before.
But since the plates are tied together, do you think a normal pentode can be used?
Seems to me that the only requirement is that g3 is not connected to the cathode.
EDIT: Never mind, it does need the two supressor grids i think. Maybe i’ll try it with two pentodes
So, things got SUPER interesting when I put a jack on the third grid (pin 2 on the schematic) and fed audio signals into it along with audio in the main input… that’s going to be a CV input for sure
With that huge current draw, maybe there could be some way to get the module running on positive voltage only? Then the module could have a dedicated off-the-shelf 12v supply instead of using a whole eurorack power supply by itself? Can’t wait to hear how it sounds
No doubt the design could be improved as I’m just a dumb hobbyist. I’m sure someone with experience could vastly improve the efficiency of the circuit. The 15v heater version of this tube (15LE8) takes 300ma for the heater.
You could get a separate dedicated 6.3v transformer for the heater circuit and use the 6LE8.
When I was putting this together the overall amp draw wasn’t much of a concern for me because I have a fairly beefy linear power supply but we will see how it all holds up.
So I’m having some issues. I got the module actually built, but the heater is causing some humming that’s driving me insane. It’s not 60hz and it happens whether I run the heater through a dropping resistor in series, or off of the LM350 regulator. There was no hum when I made it on the breadboard. I’m so confused and after messing with it all weekend I’m trying to fight the urge to throw it in the garbage.
Once I figure the kinks out I’ll post up an updated schematic as well as a strip board layout I’ve been working on.
edit: i might look up a different dual control pentode that’ll run off of 12v natively because all of this finagling with the 10V heater is holding the whole damn thing up…
Edit edit: apparently the xLE8 series is pretty damn unique. Hmph. I have 6VAC transformers. Maybe I’ll get the 6LE8 and use a dedicated heater supply. I think the problem is from the power supply for my case.
