The MT2 pedal sections: analysis

In the previous entry in this series, we saw the effect of the gyrator in a circuit. Now we can analyse each stage individually.

I will not show the individual circuit for each stage, but you can go on Github to download each circuit. I will use perfect opamp according to what I said previously in this series as well, so you will have to adapt the circuit to your LTSpice, or you can just use ATK filters as well and use the C++ code.

High pass

The first stage is a simple high pass and filters around 100Hz:

High pass
High pass

It’s very straightforward and only impacts notes on the first string of the guitar.

Pre-distortion tone-shaping

We now have a first non linear stage, as can be seen on a spectrogram:

Pre-distortion tone-shaping spectrogram
Pre-distortion tone-shaping spectrogram

The distortion is quite low but noticeable. The amplitude response shows a clear affinity for frequencies just below 1kHz, which is the meaty part of a guitar sound.

Pre-distortion tone-shaping amplitude response
Pre-distortion tone-shaping amplitude response

Band pass

The next stage is another linear one that slowly removes all frequencies above 100Hz:

Band pass
Band pass

Distortion level

The distortion level is a very aggressive amplifier with a small high frequency attenuation:

Distortion level
Distortion level

Distortion

Now we have the actual distortion stage. It has a small shelving effect:

Distortion amplitude response
Distortion amplitude response

And of course generates lots of odd harmonics:

Distortion spectrogram
Distortion spectrogram

Of course this stage is driven with the previous stage that has a huge amplification factor, so the effect will be more important that the one here with an input amplitude of 1.

Post-distortion tone-shaping

Now, we have the last stage that consists of a dual filter section:

Post-distortion tone-shaping amplitude
Post-distortion tone-shaping amplitude

This stage emphasizes frequencies around 100Hz and around 1kHz, which is very different from the SD1 and TS9 tone section (see previous entries in this series).

The spectrogram also shows additional harmonics generated by this stage:

Post-distortion tone-shaping spectrogram
Post-distortion tone-shaping spectrogram

Contrary to the first gyrator filter that was very quiet, this one generates far more harmonics, probably due to the higher Q factor of the low band pass section.

Conclusion

All things considered, there are three stages that generate distortion, almost all stages are filtering some frequencies one way or another and this can be heard in the pedal sound itself.

Of course, looking at each stage individually doesn’t tell us the full story. This is an investigation for next entry.

 

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Series Navigation<< The over-whole MT2 tone (and the bass variation)Analysis of the Boss MT2 Metal Zone pedal (2) >>

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