Planning to build a compressor. Can someone please comment on this circuit?

[nguitar12]

Just find this compressor circuit which look pretty simple.



http://freecircuitdiagram.com/2010/05/19/audio-speech-compressor/

Just wonder if this compressor can be used directly on guitar? Do I need a input buffer? Can someone please tell if this is a good compressor by looking at its topology. Thanks

[GGBB]

The input stage looks like it has quite low impedance which wouldn't play well with electric guitar, so yes you'd need an input buffer, which then makes this less simple. I can't tell if this would make for a "good" guitar compressor or not - depends on what you are looking for and depends on how this sounds - but if simple is your goal, there are better choices like the Orange Squeezer or Orange Smoothie, and others even more simple.

[anotherjim]

+1,
In principle, it will do something. I don't know, it looks as though a fair bit of ripple could get to the FET gate.

It's inverting, so input buffer should be inverting too if you want true polarity  - a JFET common source stage built for unity gain would do it.
At 9v power, the x10 (oops, I mean x100! edit) gain in the opamps would probably clip strong playing.

[PRR]

You can do better.

[nguitar12]

The input stage looks like it has quite low impedance which wouldn't play well with electric guitar, so yes you'd need an input buffer, which then makes this less simple. I can't tell if this would make for a "good" guitar compressor or not - depends on what you are looking for and depends on how this sounds - but if simple is your goal, there are better choices like the Orange Squeezer or Orange Smoothie, and others even more simple.

How about Orange Squeezer compare to Orange Smoothie?
Orange Squeezer look very simple which is good to me. However I would like the compressor to at least have a ratio and threshold control. Can it be added?

[GGBB]

How about Orange Squeezer compare to Orange Smoothie?
Orange Squeezer look very simple which is good to me. However I would like the compressor to at least have a ratio and threshold control. Can it be added?

True ratio controls are at least rare if not non-existent in guitar compressor pedals. The one in the smoothie is sort-of ratio, but in all practicality it is only marginally useful. On the other hand the threshold control is quite useful. Everything you ever wanted to know about the smoothie (and more) is in the build guide found here: http://www.diystompboxes.com/smfforum/index.php?topic=105342.0. If you compare the smoothie schematic with the squeezer schematic, you'll see how to add the smoothie's features to a squeezer.