Orange Squeezer

[erick4x4]

Sorry if this is a repeat question, but I can't search anything.

So I just built my second orange squeezer, and I have a couple quick questions about mods and parts, so I can make more intelligent decisions.If someone could help me that would be great.

First many people talk about changing the output cap to 1uf, which I did.  What exactly is this doing, and what does changing this value correspond with?

Second people talk about changing the 4.7uf cap near the transistors to a higher value. I tried 10uf. As I understand this should slow down the attack and the decay? How high can I go, and can someone help me understand this. I think I am thinking of it backwards. If its slower, than it takes longer for the compressor to kick in? And if the 1.5k and 2.4k resistors also control this, can I put it pots for this? If so how big can I go, and do I need to put a resistor in series to stop it from going to close to zero?

Lastly, the other 2 4.7uf caps that are side by side. I only had 2x 3.3uf caps around, so I used them instead. It sounds fine, what did that do?

Thanks so much!!

[markm]

I think it would be helpful to know which layout was used to build your OS.
Maybe.....
Real nice simple comp though. I love mine!!
   MM

[Mark Hammer]

The output cap limits the low-frequency rolloff both of the audio output, and of the signal being used to control the FET.  Depending on the instument in question, this can be a good thing.  Understand that different string thicknesses result in different output levels.  Ideally, you want the unwound strings to result in as much compression as the wound ones.  Should one use a heavy bottom on the guitar, or if the pickups deliver mucho basso, then shaving off a little bass amplitude in the sidechain (the portion of the circuit that tracks playing strength and controls the compressor) can result in better balance in the extent of compression across the fingerboard.  Just note that in many cases itmay take a big change in cap value to do that.

I'm not exactlysure what C3 does here: http://www.generalguitargadgets.com/diagrams/orangesqueezer_sc.gif
...but C7 is the one which dictates the timing of the compression effect.  As it gets larger, it takes a little longer for the signal coming off D1 to charge the cap up and start to affect the gate of Q2.  Not only does it take a little longer to charge up, but it takes a little longer to discharge as well, so the drain/source resistance of Q2 is held low for a little longer (which, in conjunction with R2 and R7, acts like a volume control that has suddenly runed down the input to the op-amp).  It isn't held low for THAT long, because R12 lets the cap discharge to ground through it.

Making C7 larger, then slows down the response, and making R12 larger can slow the second part of that (the decay, but not the attack time) down even more.  Part of the big difference between the OS and the Dynacomp is that the OS's action is extremely brief, due to: a) the size of C7, b) the presence of R12, and c) the absence of any resistor between D1 and C7 to slow down chargeup.  The Dynacomp prolongs the decay portion such that a sudden transient will force the circuit to take longer to allow the gain to come back up to normal.  IN the case of the OS, that transition from normal, to reduced level, to back-to-normal, happens very very quickly.  This is what leadspeople to describe it as sounding more "invisible" or transparent as compressors go.