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it would be better to understand what you are trying to achieve and also it would help you achieve your goal if you understood how compression works and where to use it.
Think of the guitar signal in terms of aptitude (a wave) with the high point being loud and the low point being quiet or even silent.
What a compressor will do is squash that wave or more to the point the upper part of that wave so that you can then feed more of it into the following device/circuit and it 'seems' louder and thicker with possibly the impression of more sustain.
The point at which you start squeezing or compressing the wave is called the threshold. The ratio of compression (none being 1:1) is called the ratio. There is make up gain because once you squash the top of the signal you amplify it back up. This thickens the sound but also raises the noise floor when everything that was quite before is now louder. It is manifested among other things by louder hiss when you're not playing, some people incorporate a noise gate to overcome this.
You would do well to google 'audio compression 101' and read up some more. Compression is a useful tool and subtle where you don't notice it going on but you notice it being turned off if that makes sense.
If you play distorted lead lines they will sing with sustain, if you play funk chops they will pop out in your face. Country licks become more in your face too.
Best to go to a website called prosoundweb.com which is a forum of professional sound engineers. On there are guides and questions in all levels of detail with no BS or sales tat. Straight talking techs. Understanding the tool will help you incorporate it into your sound.
Hope that helps in some way.
many thanks for the above post, a big help already, I play pink Floyd stuff and buying gear to match that sound/tone etc. I know Gilmour uses compressors, so getting input from you guys all helps me learn,
all the best, bluesfloyd.