Bear Hug Fet Compressor - Too much hug

[cliffmustard]

Hi all,
I've built the later version of the Bearhug FET compressor on perf (with the diode and resistor changes).

schem: https://dl.dropboxusercontent.com/u/9878279/Jon%20Patton%27s%20layouts/Bearhug%20compressor%20schematic.pdf

perf: https://dl.dropboxusercontent.com/u/9878279/Jon%20Patton%27s%20layouts/Bearhug%20layout.pdf

Whilst my build is working, it does seem to compress too much, especially compared to the previous version (with the 1n60p diodes) that I've also built and really love.

I'm pretty sure I've made a mistake somewhere but have checked and double checked the component values and connections and can't spot a problem. If anyone could check over my voltages and offer any pointers that would be great:

Supply voltage 8.99v
q1 d 5.05         g 3.8 decreasing        s 1.2 increasing
q2 c 6.93         b 1.18           e 0.66
q3 d 0             g 0                s 0

Measuring the resistance from Q3 drain to ground, with the volume and compression on full, at idle I get about 360r and with a heavy strum it goes up to around 12k. I think this is supposed to be around 1-2k but am not sure whether that just applies to the first version.

I've attached some pics.

Any help would be much appreciated. Also a big thanks to Jon (should he see this) for sharing his great designs, all the detailed build notes and the forum responses.

Cheers.

[midwayfair]

I don't think you've made a mistake, but we can still fix the issue if you want different performance for your build.

What's it like on compression at minimum? What kind of pickups are you using?

The highest compression setting is usually pretty nuts, and it is indeed able to get much more compression than the first version. If you want to reduce the total compression, there are a bunch of ways to do so, but the easiest are either (a) lower the collector resistor (the 2.2K) on Q2 (lowers the total gain of the envelope), or (b) raise the 47R to 220R-470R or so (if you have really hot pickups; this reduces the MAXIMUM gain of the envelope) or (c) increase the 1K that's connected to the gate of Q3 (this decreases the ultimate threshold -- try 10K or you can go even higher).

However, I'd try just turning down the compression knob and flipping the switch first.

[cliffmustard]

Thanks Jon, that does explain it. I was expecting it to be similar to the earlier version so thought I'd missed something.

If I can just run a few things by you, I'm using p90s, fairly medium low output. At just under 9 o'clock on the comp knob and in the low setting I'm getting about 2k resistance from the q3 drain to ground and I can hear the compression going on.  At the most extreme compression there's almost a 2s hold before it lets go.

Think I'll have a play to see where I can get with values you mentioned.

Thanks again.

[midwayfair]

Another easy thing that ... this is actually how I do the comp knob on mine now.

Remove the 1K from the emitter of Q2 to ground.

Remove the 47uF between the 47R and the comp pot. Connect the comp pot directly to the 47R (just add a little jumper if that's easier). This should give you more "less" range.

Originally I had the gain pot set up that way because I was worried about scratching feeding back into the audio signal somehow. It was unfounded. This change will probably be on the next PCB run, but I haven't gotten around to updating my perf layout after I confirmed it in a couple working builds.