Elevating the Humble Electra Distortion

[Aleph Null]

I've built quite a few dirt boxes, but I keep coming back to the Electra Distortion circuit. Recently, I discovered a roll of magical 1N34A germanium diodes at my local electronics shops, so I decided to build one more Electra, this time with some extra mojo.



I wanted to keep the circuit simple and avoid adding unnecessary features, but I wanted to tune it and refine it a little bit. I kept it to one knob: a gain/bias control



The board is mounted to the potentiometer. This leaves enough height for full-size electrolytics.



The gain range is limited to a modest 5–26dB—the sweet spot for this circuit. Much more that 30dB gain tends to get farty anyway. Magical 1N34A diodes provide just the right amount of clipping with a forward voltage around 450mV. The 220nF capacitor in parallel with the 510 ohm resistor creates a 2dB shelf at 1.4kHz. This adds just a little bit more clarity and articulation without making it sound bright. The 68nF output capacitor trims off just enough bass to keep things tight, especially when using the Electra to push another overdrive. The 1nF capacitor rolls off the "fizz" above 16kHz. This is much more subtle than a typical tone control. It's unnoticeable at lower gain settings, but tames the harsh harmonics at higher settings.

These are all small changes, but I think it takes the circuit from simple to elegant. This almost certainly isn't the last overdrive I'll build, but it's probably the one that will stay on my board.

[cooder]

Great build and explanation about the wee changes, good stuff to a classic.

[Aleph Null]

Thanks!

I spent most of 2020 and 2021 experimenting with various kinds of clipping and circuit architectures. After all that, I've learned that the little EQ choices that are made along the way contribute much more to the sound of a pedal than the clipping method.

[nzCdog]

Very tidy work 

[dirkvandoesburg]

Hey, awesome looking layout! What's the value of the gain/bias pot? Is it LOG or LIN?

[LaceSensor]

Hey, awesome looking layout! What's the value of the gain/bias pot? Is it LOG or LIN?

it says c5k
so reverse log, 5k ohm

[dirkvandoesburg]

Thanks! The reverse log is something new for me. I see it now. I appreciate your help!

[Aleph Null]

Hey, awesome looking layout! What's the value of the gain/bias pot? Is it LOG or LIN?

Just saw this. Reverse log works best. Linear will work in a pinch too.

[szukalski]

Great one! I built one tonight and really enjoy it. Thanks for sharing.

[Aleph Null]

Great one! I built one tonight and really enjoy it. Thanks for sharing.

Yay! I'm glad you like it. What diodes did you end up using?

[szukalski]

Yay! I'm glad you like it. What diodes did you end up using?

I just cranked it out with Si 1N34A which measured the same Vf as you mentioned. Nothing magic there.
I hadn't built an Electra so it was a quick and dirty build.

Got me smiling enough that I'm going to breadboard it and test out the Ge diodes I have (mainly Russian D9's) to get a bit more magic.

It pairs really well with a Jackson Op Amp boost (what doesn't?).

[Aleph Null]

Yay! I'm glad you like it. What diodes did you end up using?

I just cranked it out with Si 1N34A which measured the same Vf as you mentioned. Nothing magic there.
I hadn't built an Electra so it was a quick and dirty build.

Got me smiling enough that I'm going to breadboard it and test out the Ge diodes I have (mainly Russian D9's) to get a bit more magic.

It pairs really well with a Jackson Op Amp boost (what doesn't?).

The diode selection definitely isn't magical. I ask because the forward voltage directly effects the total output—there's no volume knob. I tried a few different diodes before I found the right ratio of boost to drive for me. 1N60s felt a little quiet and compressed. 1N914 was punishingly loud into a clean amp before breakup.

[culturejam]

Very nice, and well done.