I understand the function of a compressor pedal. For now, i don’t need one. (or i think i don’t need one. Wait untill the next gas attack happens… 
)
But what i don’t understand is why anybody would stack 3 of them, like the guy in this video.
It seems David Gilmour used this technique, but i don’t get it.
You can’t compress a signal any more than it already is with pedal nr 1, right?
I’m certainly no expert where guitar is concerned and have not experimented with this. I have been a systems engineer for a while and my job was to consider each element in a signal chain so I can see what he is trying to do.
He did not mention the order his chain is in except for once on his Big Muff. This means we cannot look at what he did, and can only analyze all the options.
I noticed he did not stack all three except for an experiment. The levels and tone controls would really need to be fine tuned to get useful differences in compression levels.
You can acheive some tailored compression with use of the tone controls and setting the levels. If you had the first compressor only working on a narrow range, then a second working on a wide range, you’d be able to hear everything when soft, but start to cut out the narrow range as you played harder, eventually compressing everything.
The thing here is to think through the order the compression is in, making sure that the following compressor has something specific to control. You don’t need to think that a single compressor will be working on the whole frequency range.
The other thing would be the mixing level of the compression. By tuning this and selecting the order that compressor happened in the chain you can do something similar to the above - highly or lightly compress or highlight some range of frequency. at a particuar volume coming out of the guitar.
Does that make sense?
To be honest it never occured to me to stack them.
Being able to use ONE compressor for what you want to achieve and knowing when to use one…or not use one… is hard enough for me to master.
After reading up on it, it seems that most of the applications have various uses for the first compressor but the second seems to be added often for the usecase: add sustain?
I seldom use one but I was considering for the acoustic because of the picking and strumming (mixed styled). Not the easiest of tools but definitely one thats can add “professional quality” to your sound IF used well…
Eeehm, not really, but that probably stems from my very limited understanding of how they work.
Which is based on this explanation:
If you look a the picture he’s drawn, i can understand that the frequency the guitar makes, can be cut of at certain levels.
What i don’t understand is how this affects other compressors down the line.
It isn’t so much guitar output frequency nor pickup frequency response, but the frequency you want to control with the compressor. He mentions this in the first video. It is also mentioned that he wants to limit the aggressiveness of the compression so you don’t notice it so much when it moves from boost to compress and back again.
By stacking, you can get the compression set up for setting the level you want - he mentions a level he likes for the amp input to get the amount of distortion he wants to hear. Then, in one case, he uses the tone control on a first compressor to limit a frequency range so he can highlight the solo or blend the strumming. He can use a second compressor to smooth out the first so the boost is not so obvious when it kicks in.
I can see a handful of ways to use this, but they do seem like I’d need better control of my picking/strumming aggressiveness. So far, I’ve only used a single compressor to either give me a more consistent volume for finger style or a more consistent level for a distortion I want to get out of an amp.
Ok. So one compressor has the “start” level set, and another one goes from there? Something like that? The first one sets the amount of compression that’s needed, and the other ones get to “play” around with the amount set by the first?
it is a balancing act between the two. That goes for whatever goal you have in mind.
My current personal opinion is that it should be done for artistic reasons, once enough prowess at playing is achieved. I may never get there!
I’m not seeing a compressor on my board in the near future. I might also never get anywhere to whatever “enough prowess” is in playing.
Having fun and understanding what it is i’m having fun with, is the main goal…
lol, yeah! I get that!
I have a fancy-dancy Helix. I really enjoy it, but I mostly use just the basics - noise gate, amp, reverb, speaker model. That is it on 80% of my saved signal chains.
So, the basic function of a compressor is to reduced the dynamic range of the signal. That is, to reduce the difference between quiet sounds and loud sounds. It may do this by boosting the level of quiet sounds, reducing the level of loud sounds, or both.
But you are right that, in principle, if you’ve already reduced the dynamic range with one compressor a second “stacked” compressor can only act within that new dynamic range and can only really reduce the dynamic range further.
The argument then becomes: why not just use one compressor and change the setting?
The problem is, this assumes all compressors do the same thing and impact the signal the same way, and across the whole frequency range. And in practice, they don’t.
Compressors, especially analog compressors, are electronic circuits and electronic circuits almost always have compromises. In the case of compressors, this means that a given compressor circuit can compress unevenly across the frequency spectrum.
This means that the compressor settings (threshold, ratio, make-up gain) may act differently at different frequencies. You may, for example, get a different ratio at 1kHz than you do at 10kHz. It may be the case that the compressor responds quickly to signals at 2kHz but no so quickly to signals at 12kHz, and so on.
Different circuits will have different characteristics. So, by combining them, you can shape the tone more carefully.
Note that the audible impact of compressors can be quite subtle and so this really can be seen as tweaking things at the edges.
And, as has been pointed out, the main use of having multiple compressors seems to be to use them one at a time with different settings for different songs, or different parts of a song. If you have a multifx system, then you would do this with a patch or a “scene”, etc. which swapped out the compressor, or even just changed the compressor settings.
Personally, I think this level of tone-tweaking is a bit beyond most of the people on this forum and if you are still at the stage of trying to understand what a compressor does for you, then it’s certainly not worth bothering with.
But it’s an interesting discussion to have.
Cheers,
Keith
Hah. Interresting.
It isn’t something i’m going to buy soon, as i don’t see a scenario (yet) where i would need one.
I just like to understand how things work and how they are used.
With so many other fun pedals to explore, it will be some time before i start looking into these types…
Thank you all for the usefull explanations!