Should compressor go before overdrive, or after overdrive? I saw many of this questions on Internet.
There is no correct answer for this, and many videos and forums explain the difference with excellent demos. In this article I will explain from more technical point of view by using some oscilloscope screenshots.
What is compressor, what is overdrive?
Before we check graphs, I want to explain what the compressor is and what the overdrive is. Basically compressor compresses the signal when input signal reaches threshold and more. Overdrive pedals do very similar thing. Actually, overdrive can be described as boost + high compression ratio compressor. So there is no wonder the fact that overdrive hides compressor result. If you give extreme gain to overdrive, there is no difference to add compressor (In perfect world. In real world, there are another factor like tone circuit gonna change the tone, so there is the difference).
1. Compressor AFTER overdrive
Here is real screenshot of oscilloscope. Blue is the result of big signal, and yellow is the result of small signal. All input signal is sine wave.
As you see, big signal is clipped by overdrive, and compressor doesn't do much for the big signal. For small signal, compressor enhance the volume. In result, this configuration keeps your picking nuance, but equalizes the volume. Other words, when you play weaker note, you will hear tone difference (less distortion), but volume will be kept.
2. Compressor BEFORE overdrive
Let's move on next. This graph shows the result of Compressor before overdrive configuration. Difference of big and small signal is much less than first configuration because compressor equalizes the volume to overdrive. This will hide signal size difference and the signal will be more equally clipped by overdrive section. Your playing will be more equalized and tone will be constant regardless how hard you pick the string. This configuration is suitable when you prefer more consistent tone and volume.
I hope this article helps to understand the difference!