Hi, I'm trying to build a high gain distortion pedal, so I tried to analyze distortion pedals like metal mulff or metal zone. Both of them has similar schematics.

Here's metal zone's

There is a gaining stage with 4b OP amp which amplifies at 33Hz and 5kHz,

Since even at drop A tuning you have lowest possible note at 55Hz, perhaps someone knows why such thing is needed?
Double gyrator filter.png
I don't know but at 33hz. I think the only thing that can be heard is earthquake rumble.
Hi. Been a while since I worked with transistor gyrator circuits but tried my own calcs and I get a different response to what you get with the circuit.

Looking at the transistor gyrators I calc a peak at 5Khz for one of the stages (same as you) but my other peak is at around 100Hz for the other stage. These are roughly at opposite ends of a guitars full response (including overtones and harmonics) at standard tuning. The peak at 5Khz and the Q factor is slight (Q ~ 2, not like the pic you have attached which shows it as very high and sharp peak with very high Q). The peak at 100Hz is more pronounced with a higher Q.

When these responses are combined I would interpret it as being an overall response which lifts the outer end of the bass response and slightly raises the treble response and leaves the mids slightly scooped in between, which would be reasonable in a pedal like a metal zone. Drop tuning would really come through using the 100Hz gyrator. I've used a metal zone and this makes sense. The amount of bass sludge you can get from it when it's cranked is inordinate

The remaining stages etc just play around with the gain levels and the basic shape.

That's my take on it anyway.
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Last edited by Phoenix V at Jan 12, 2015,