Category Archive: FET Overdrive


All MI Effects overdrive pedals are op-amp based circuits - either using the LM833 or JRC4558 depending on the circuit. It wasn't until my experiments (with relative success) with capturing the tone and response of the Megalith amps in a FET based pedal format, that got me thinking about extending this to other 'amp-like' overdrive sounds.

The initial idea was to try to make an overdrive as smooth as possible, but after tinkering with it a bit, it's morphed into something else altogether. This isn't modelled on anything in particular but we were shooting for a few things:
1) A very natural response, both in terms of tonal balance and overdrive feel.
2) Unlike opamp based pedals, I wanted something that when you roll back on the volume, the sound is virtually clean, but also balanced.
3) Touch response.
4) high gain sounds to have a big footprint, but with a vintage vibe to them,... what I've heard referred to as the 1000lb violin

At its lowest gain, it is a boost/enhancer adding some extra sparkle to your guitar tone. Mid gain mode gives some nice, complex, tube-like overdrive but allows clean-up of your signal via the guitar's volume knob that A/Bs well against your standard clean. Crank the gain and you have a smooth, harmonic-rich, sustaining lead sound from 70's rock to jazz-fusion.

Here is a demo we made with a Les Paul > FET Overdrive > MI Amplification Iron Duke...

This demo with two Strats > FET Overdrive > MI Amplification Iron Duke...

It is always great when a prototype delivers what you want to hear, and this one did. We were undecided on whether this would be a pedal we would put into production, but due to the positive feedback we have received from the demos, we will be continuing with it.

However there are a few tweaks needed before a production-ready pedal can be made:

  • The tone control is the standard MI mixing tone control. I felt it needed it just so that you could adjust the top end as the gain goes up (as clipping increases, so does the higher frequency content). Having it at a fixed setting would mean either that the low gain sounds were too dark, or that the higher gain sounds were too bright. I'm experimenting with taming the top end with a three-position toggle (as in the Neo Fuzz/GI Fuzz) so that it can be matched no matter the guitar/amp set-up.
  • The gain control sweep needs fine-tuning so that at minimum settings it is clean and a more gradual increase in gain from there. At the moment, all of the sweep is from 9 o'clock to 2 o'clock.

Keep posted on the blog for the next prototype iteration with the new tweaks, and a new demo.

- Michael I.