DOD FX80 compressor mods?

[rosscocean]

I've bought a DOD FX80 for £35. I bought it because I plan to build a compressor and I wanted a commercial circuit to compare it too. I've never really been into the way a compressor affects the attack and sustain of the guitar (I'm not looking for massive sustain, bloom or a squishy boost) and wasn't expecting much from the DOD. After playing with it I'm quite impressed. I can get a reasonable amount of compression without messing with the envelope too much. What I don't like so much it that it shaves off a bit of bass and it's a little noisy. Anyone know any mods?

Cheers
Ross

[rosscocean]

Here's the schematic. I hope it's ok to post this, It was originally included with the pedal.



Would increasing the input cap from .01uf to 1uf sort out the loss of low end or will I need to make other cap changes too?

Anyone else modded one of these?

Cheers
Ross

[rosscocean]

[Nasse]

Unmodified good ones go quite high somewhere. Just looked ebay last week and one was UK only (no post overseas or other countries) or was it pick only

[rosscocean]

It might have been the same one. I bought this one on ebay about a week ago.

[rosscocean]

Anyone?

[Nasse]

Sorry I was too busy and tired to answer. But I thought the schem is a bit like Ross/Dynacomp in some degree, so mods for those would give some ideas. Later model FX80b release version is most sought after, maybe you could add a mini knob and extra parts...

[rosscocean]

Cheers for your reply.

I'll have a look into the Dynacomp/Ross mods and schematics.

I'll double check against the FX80B schematic, but isn't the only different the attack knob? I don't think I need that, I like the compression amount, attack and release. The main thing is the hi pass/low end roll off thing it does.

I've also noticed that it addeds high frequencies as you turn up the compression knob. Is that normal for this type of circuit? I understand why it might do that but it's a bit much.

Cheers
Ross

[rosscocean]

I'm no expert but I'm pretty sure they're exactly the same apart for the attack pot.

[rosscocean]

I tried comparing the Dod FX80 (Above) and the dynacomp  here- http://home.comcast.net/~snmavronis/mxr77dynacomp930x624.jpg but Although I can see some similarities, I'm not sure on what it doing what. Also is the CA3094 written two different ways?

This is the first thing I've tried that isn't a boost, fuzz or overdrive and I'm not sure where to go from here. Does anyone know what I'd need to change for a flatter frequency reponse/no bass cut? or Where I could learn more about this tye of circuit?

Cheers
Ross

[petemoore]

  Letting more bass in means more current going in = the comp should kick on harder or sooner [if anything, and probably the comp knob will comp ensate for this.
  K That said, there's a .01uf at the input, and another .01uf above a 22k, both of which look to be in the signal path, before and after the input buffer.
  Making these caps larger should let more bass in.
  Pretty soon the signal path caps start to be .1 and above though, whether these roll off bass much...I'd start with the .01uf first, then maybe try the other one.
 

[rosscocean]

Hi Pete, I've already tried the first cap and it didn't make a difference. I'll try the cap above the 22k resistor and reprt back. Thanks for your help!

[rosscocean]

I tried changing the first two 0.01 caps to 0.1. The first one didn't seem to do anything and the second, parallel with the 22k resistor, seemed to add more gain/distortion but no more low end. I changed the second back to 0.01.