Ever wonder exactly what people mean by hard clipping and soft clipping? What exactly is modulation? How measurable are the differences between say, a Big Muff and a RAT? One of the neat things about multi-effect devices is they bundle many different effects into a single package, and with a few additional tools we can use them to visualize the difference between the effects. This can lead to a better understanding of how the different devices work and impact tone.
You’ll need some sort of effects modeling device for this, unless you happen to have all the actual effects pedals you want to test available; in which case, you can use those. Using a modeling device makes the process a little simpler as it’s easy to add and remove devices to the signal chain without impacting the signal level. I used a Line 6 HX Effects and I’ll describe how I did it using that. You may have to modify the steps slightly if you use something else.
First, you need to generate a tone. Something that can at least create a sine wave in the audible frequency spectrum will do. If you can change the frequency and generate other signals such as noise, you can experiment more, but a simple sine wave will be fine to start. You can get low cost tone generators online, or you can use some computer software. Just a recording of a continuous test tone from Youtube will do if that’s all you have. Connect the test tone generator to the input of your multi effects device. Since I have access to a lab function generator I used that, and I connected its output to the input of the HX Effects.
Next, you need to be able to listen to the test signal. Test tones through a guitar amp and speaker can get pretty unpleasant to listen to, especially for those around you. Some devices can also generate high power signals that can damage the gear and/or your hearing so be careful with this. The HX Effects does not have a headphone output, so I connected the left and right line outs to a small mixer and used that as a headphone monitor. If you are using computer-based effects, or a modeling amp with a headphone out, you can use that. Turn the volume right down and keep headphones off your ears at first. Once everything is working, you can gradually bring up the volume to a safe monitoring level.
Now you need something to visualize the audio signal. An oscilloscope is perfect for this, and that’s what I used as I have access to them, but there are other ways to do it. There are software-based systems that run on a computer or a smart device. If you connect the output of your effects to an amp and speaker, you can use a microphone. I sometimes use an IOS app called Signalscope. It uses the phone mic, and I can just position it next to the speaker to visualize the tone on the iPhone screen. There are also PC based oscilloscope applications, and again, if you output to a speaker cab, you can use a microphone connected to your computer as the input. Then when you play the tone through the speaker it will be picked up by the microphone and displayed in the computer program. I often use a program called TrueRTA.
Since I have a hardware oscilloscope, for this test I enabled one of the sends on the HX Effects and connected that to the oscilloscope input. With that done I could generate a tone on the generator, send it through the HX Effects, monitor it via headphones, and visualize the signal on the ‘scope. First I created a new preset with no effects. I enabled a 1KHz tone at 1V and made sure that when the tone was played I could hear it through the headphones and see the 1K sine wave displayed on the scope.
Now the fun starts. Add a few distortion effects to the preset and then turn them on and off one by one. You’ll be able to see and hear the difference at the same time. Try some other effects like reverb, delay, modulation and pitch and you’ll be able to see how the effect impacts the frequency and amplitude of the signal. Using a simple sine wave is not representative of what happens with a complex signal like a note played on a guitar, but it will let you visualize the basic differences between how the effects work which can be very informative. After that, try recording a note from your guitar and then replaying that through the input. With the HX Effects, I can use the looper as the source. Visualizing the output is more complicated here and depends on what you are using to do the measurement. Some of the computer software apps can do sophisticated processing such as FFT and waterfall displays which are useful when analyzing the more subtle effects of the different devices.