BOSS - ME 70 “Extended”

The ME - 70 is a multiple guitar effects pedal which I happen to own. I was trying to go through the whole thing by playing through it and guessing through various modes.

Before I go ahead with the writeup, just a few things to mention about my setup. The GUI is the best way through my plugin. RackAFX sliders might be a little too confusing considering there were way too many things to play around with. The GUI has two issues. There seems to be a bug in integrating the Alpha to the LCD control. I have linked it correctly, but it does nothing. Secondly, the SOS mode is much easier to use in the RackAFX GUI. The rest of the plugin works fine.

General Signal Flow :

The signal flow is as the same as the original effects pedal. The SOS was also a part of the original pedal. The reason for putting the SOS at the last was to have the loop with every effect that was used to make the patch. Each of the blocks mentioned below have several sub blocks and also can be turned off and turned on individually. So the user has a lot of room to play around with.

Interface :

The GUI which I built is shown below. I tried to keep the look of the original board intact so that when someone who has previously used it tries to use the plugin, it should be really easy for them. Photoshop, GIMP and Lightroom helped me create it.

Compressor :

The dynamic compressor from the book was implemented here.

The main parts of this part of the plugin are the types of processor

Comp : This produced an effect that sustains the second without distortion.

Limiter : Suppress the loud peaks in the Input signal

Expand : The expander increases signal presence and energy

Gate : It produces a little lesser musical compression when compared to those above.

Attack, Release, Level, Time Constants are all Envelope Follower related terms that help the compressor to do its functions.

OD/DS : This entire block are wave different wave shapers. I have personally played around different names on the pedal board and tried to arrive at the most reasonable seeming wave shapers possible. You can see the various equations used below. The drive Atan+ and Atan- operate according to the equations mentioned and the knobs needn’t necessarily work for every wave shaper.

Modulation Block :

Rate Depth Resonance hep in obtaining the desired kind of effects. There are 4 LFO’s (which is an addition to the original board) to play along with.

Delay :

The delay block is self explanatory. The original just had several limitations of the Delay times, but i thought this would actually give the user a lot of room to play around with.

Pre-Amp :

The pre-amp block is a set of parametric EQ’s set at different cutoff’s. The frequency response is shown. These were constant Q=2 parametric EQ filters implemented allowing the used to change the cutoff’s over a reasonable range of frequencies. The reason for choosing the value of Q to be 2 was that it mapped the original response of the pedal really close. A rough picture of the frequency response is shown below.

Reverb :

I changed this part and implemented Will Pirkle’s reverb algorithm from his Designing Audio Effect Plugins in C++ book. The most commonly required RT60 and the Wet/Dry mix are left on the GUI for the user to be able to manipulate them. The rest of the controls of the reverb also can be found in the LCD control through the Alpha wheel. The user is free to change any of those parameters and

play around with the reverb algorithm ( which is usually a hit and trial one ) to make a better sounding reverb. The reverb algorithm is shown below.

SOS - Sound on Sound

This part of the plugin is easier to use with the RackAFX GUI and not the custom GUI. I implemented the Loop controls as buttons. Would be perfect if I would’ve used the assignable buttons. The way the SOS is setup right now, is that it is capable of taking a 15 second loop and sound on sound can be performed only once. You can add another loop to it without erasing the old one, but you will not be able to hear the original loop playback when you are recording the new one.The wet/dry mix is another addition just to listen to the actual sound on sound being looped.