The over-whole MT2 tone (and the bass variation)

This entry is part 1 of 13 in the series Analog modelling

In the last blog post, we saw the individual effect of each stage of the Boss MT2 pedal. But with all these effects impacting each other, what is the final find of spectrum that we get?

The MT2 sound

Let’s start with the spectrogram of the pedal, with an oversampling of x8 for the non linear sections:

MT2 spectrogram
MT2 spectrogram

We see here that we have lots of odd harmonics, which is what we expect, but also a good amount of even harmonics. The drawback with this is that we do have lots of noise in the low frequencies, and we see that we do have lots of signal above 20kHz, despite the low pass filter before the decimation.

The amplitude response has a reminder of the post distortion tone: shaping stage

MT2 amplitude response
MT2 amplitude response

We also see there the lasting effect of the band pass before the distortion stage, and these two graphs combined show the complex processing that the pedal does and probably explains why the pedal is so effective.

Adapting the pedal for the bass

I wanted also to adapt the pedal for the bass. One of the reasons is that the MT2 is really a guitar pedal, although the bass works well on it despite the input high pass filter. It still creates too many high frequencies harmonics for my taste, which is why MTB exists as well.

So I decided to move all the cut frequencies down. The high pass filter would cut around 40Hz, the pre distortion tone shaping peak frequency would be lowered, etc. One of the drawbacks is that the amplification on some filters was lower due to the resistors and capacitors used, but I still think that the overwhelm result is interesting: 

MTB spectrogram

Obviously, we have a far lower amount of harmonics int he high frequencies, as was required, but also a lower amount of noise, due to amplifying more of the low frequencies.

The global amplitude response is also very interesting:

MTB amplitude response
MTB amplitude response

It’s very similar to the MT2 version with a lower bump on the post distortion. I’m very curious about what people will think about this variation!


The characteristic sound of the MT2 is, according to me, due to the combination of so many non linear and linear filters. The bottom end of the spectrum is there, no matter what, and the higher frequencies can be shaped better than with a SD1 or a warm preamplifier.

A dedicated bass version is tough to create because of the very deep lower end of the pedal, but I think MTB does a good job while being less present int he higher frequencies, leaving more space for other instruments.

I will make a small video in the future comparing the sounds of the MT2 with my SD1 as well as the guitar preamp, and I will do the same for the MTB variation and my bass preamp. Stay tuned!


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