AussieComp / AussieMart Compressor - any oppinons?

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I have been looking for a comp circuit simpler/needing less tuning than an OS or Ross/Dyna, and I happened to trip upon the AussieComp and it's derivative the AussieMart in the search, and a layout in the gallery. From what people said, it is a little more dramatic than the OS (good in my opinion), and seems to be pretty adjustable, and above all is an extremely simple circuit.

Any opinions on it? In the original threads, it looked like people were getting good results out of it, but not much info on it since then.

I'll probably try breadboarding it based on the layout (no schems around anymore), but wondering if anyone else has anything to say about it as I have to buy a couple parts to even breadboard it.

[superferrite]

I'm bumping this for purely altruistic reasons.  And I just found the layout and need to build it!

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Thank you for your altruism...

and *BUMP*

[markeebee]

**BUMP**

That makes three of us.  For the love of God, somebody please help before more innocent souls are lost.

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Funny you bumped this. I was going to breadboard it last night but didn't have the mosfet.

[Tonemonger]

Any compressor that does'nt use near obsolete ICs has got my attention.

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So I breadboarded it...

I can't tell if I am getting any compression. Compared to bypassed, it is a lot brighter sounding, but I can't hear any obvious compression.

Something must be wrong because also, with the comp knob up all the way, sound cuts out, and it gets very distorted just a hair before that.

I do not get any sound at all if I have the release knob anywhere but almost all the way down.

I checked my connections vs. the layout and could not find anything that is obviously wrong.

One thing that was not clear from the layout was where pin 1 of the release knob goes to. I assumed it was to ground as it is not marked otherwise in the PCB layout.

The other thing I notice is that compared to a vero that someone drew up for the aussie comp, the above layout for aussiemart (which is just a modified aussiecomp) has some very noticeable differences.

It is a shame in general that the schem itself is not around anymore.

Any ideas/input welcome...

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well... I kept going. I noticed that in this vero layout, 7 has NC rather than 8. I switched the cap from pin 7 to pin 8.




Now I am getting more of an effect... still can't say it is obvious compression. What it seems more like is variable pickup loading or something... at certain settings, my neck humbucker can sound either stiff and chimey, relatively bright, (more like I would normally expect, but brighter even), or at other settings, it sounds rubbery and heavily "tone sucked"... I think this may be the "compression," but it is certainly is different from the kind of dynamics processing that I would expect out of a comp.

[.Mike]

It is a shame in general that the schem itself is not around anymore.

I went through the original topic and looked for posts that had the schematic embedded in them. Then, I went over to the web archive with the URLs of the missing images. Here's what I came up with:







I hope that helps!

Mike

[Brymus]

It looks like to me,which Im am not sure, but its not tracking the voltage so much rather its just using negative feedback to tame the signal.
Maybe someone else can offer a better interpetation.

[dschwartz]

well... I kept going. I noticed that in this vero layout, 7 has NC rather than 8. I switched the cap from pin 7 to pin 8.




Now I am getting more of an effect... still can't say it is obvious compression. What it seems more like is variable pickup loading or something... at certain settings, my neck humbucker can sound either stiff and chimey, relatively bright, (more like I would normally expect, but brighter even), or at other settings, it sounds rubbery and heavily "tone sucked"... I think this may be the "compression," but it is certainly is different from the kind of dynamics processing that I would expect out of a comp.

for what i see, the guitar pickup is directly connected to the mosfet through a simple capacitor..The mosfet acts as a variable resistor, and is in parallel with the IC input, so, basically, it IS a variable input impedance device, and not a compressor..even more, if the capacitor is small enough it may become an envelope controled HP filter..

the mosfet should create a variable resistor voltage divider to get attenuation..for this, the guitar signal should go something like this:
guitar-->buffer-->big cap-->resistor-->mosfet-->ic input

the value of the resistor will also define the amount of compression..since the input impedance of a lm386 is not very large, this resistor should not be too big..use a trim..

[Brymus]

So DShwartz your saying the signal should be taken from the source of the Jfet instead of the drain in the Aussie II ?

[dschwartz]

either..
i suppose in the latter desigbn they use the drain because it´s higher impedance makes the effect more noticeable that using the source..
what i´m proposing is using a resistor in series with the 0.1 cap, so the mosfet can make a more effective voltage divider.

[NPrescott]

Something must be wrong because also, with the comp knob up all the way, sound cuts out, and it gets very distorted just a hair before that.

Not that it helps anything but I breadboarded it and got the same based on the same layout. It was a pretty ugly distortion and I didn't notice any compression either.

Daniel's suggestions are next I guess.