"QuadraPuss" -- Educational Journey into Compressors

[Transmogrifox]

A few weeks ago I started with this quick design/build idea:
http://www.diystompboxes.com/smfforum/index.php?topic=110146.msg1009817#msg1009817

Never got around to recording audio samples direct to PC before I started modding and then broke it.  Compression on the camera was enough to obscure the difference, so in the videos it just sounded like a booster.  
EDIT *** Demo of updated circuit linked at bottom of post. ***

So.. I decided my perf had too much solder and mess on it so I spent a good bit of time thinking how to simplify it and came up with this:


Then I tried the SMT thing and ended up with this:



Heres the educational part:

At lunch break at work I decided I would hook it up to a signal generator and scope and watch it do its work:


Attack Time Measurement (time settling to within 3 dB of final value):


Release Time (settle to within 3 dB of final value):


Attack time is depended upon the input level.  It attacks faster with higher level inputs, so this is a nice feature.

What does it sound like?  ***EDIT***
https://soundcloud.com/transmogrifox/compressor-demo

I'll leave it to the listener to decide whether you can tell when the compressor is on and off.  At the end it is apparent because you can hear some of the distortion from setting the compressor on max gain and getting some clipping on attack.

The circuit is a bit of a "me too" on the Bearhug compressor.  The Bearhug is subtle, but this circuit is even more subtle -- partly because the compression control is hard-wired to a relatively moderate value and the threshold is also moderately set.  

Something I'm not set up to capture well (I just don't have a good quality microphone) is where this pedal really does it's work, and that is going into my tube amp.  It might be better viewed as a booster that does some compression than a compressor.  Because it has the ~30 ms to ~75 ms attack, it can be set to push the tube amp right on the edge of breaking up, and the attack gives a nice little breakup while the sustain works with the effect already part of the tube compression to make a sound that feels much more responsive and alive.  Definitely good for a dynamic booster.

On the dirty channel it adds a sweetness I haven't heard from my amp before.  I recently made some mods to really improve my dirty channel, but this circuit is a perfect complement to this.  I had some sounds this afternoon that reminded me a lot of guitar sound I heard coming from Ty Tabor in King's X early '90's albums.  If only the right equipment was the only thing needed to sound like Ty
***/EDIT***

Anyway, I hope this has proved somewhat educational for some of you as well.

I decided to call it "QuadraPuss" because the the "quad" part refers to 4 transistors used in the circuit, and the "Puss" part just because it compresses softly like a cat sitting in your lap.