DiSCO - Dirty compressor and overdrive

[samhay]

https://dl.dropboxusercontent.com/u/11996927/DiSCO_audio1.mp3

Recording setup is behaving itself today, so make a quick direct recording while twiddling pots. The link above is now to the newer recording.

My apologies for the poor metering, but the volume pot is not very accessible on the breadboard and this was all recorded with the level set to the same place.

[sajy_ho]

https://dl.dropboxusercontent.com/u/11996927/DiSCO_audio1.mp3

Recording setup is behaving itself today, so make a quick direct recording while twiddling pots. The link above is now to the newer recording.

My apologies for the poor metering, but the volume pot is not very accessible on the breadboard and this was all recorded with the level set to the same place.

Nice demo! I breadboarded your circuit and I'm getting some neat tone out of it, Also I tried jfets as diode pair in the feedback loop and got interesting results.

[samhay]

Thanks for breadboarding - it is always nice to have multiple sets of ears to audition things with.

There are still a few things I would like to tweak with the circuit and the feedback clipping in the first op-amp is one of them. I'm still trying to decide whether a tone control is necessary, but also wondering if it would be useful to have variable release times too (make it more of a real compressor). Other than that, it seems to be doing everything I set out for it to do, so will start working on a layout soon - probably vero.

[antonis]

so will start working on a layout soon - probably vero.

Some of us would be grateful to you..!!!

[samhay]

I haven't built anything on vero for quite a while, and my recent reverb build on perf has sated my desire to work with that medium for a while, so will put the layout at the top of my list (once I have settled on a final design).

[Cozybuilder]

Hi Sam-
Is the schematic in the first posting (version 1.2) correct?

[samhay]

I think that is what I have on the breadboard at the moment, so it is correct in the sense that it works. However, I have some final tweaking to do, so there may be a few changes before I build it.

[Cozybuilder]

5 pots, it'll have to go in a big box, that would be a nice change of pace. It sounds nice, looking forward to whatever improvements you have in mind.

[Freppo]

Great job! I like the demo.

Maybe a bit early, but I took the liberty of doing a vero layout


Full Size version

It's not verified, but it should match the schematic.
Here is the file for DIY Layout Creator (version 3.28.0)
So you can do any changes to the layout yourself.
But I will make changes to your upcoming tweaks aswell.

Thanks for sharing your project!

cheers
Freppo

[samhay]

Nice one Freppo.
I tend to leave things on the breadboard for quite a while before deciding whether to build them. In this case, I had another play with the circuit last night and added a release control, which was quite useful. I think I might refine the side chain a little too, and then have to decide whether to leave the SYMMETRY pot as-is, or make it switchable...

Anyway. It might take a while before I settle on a final version, but I will leave the current version of the schematic here for reference, and continue to undpate the schematic on the 1st page until I settle on a 'final' version.

Freppo's layout version:

[samhay]

Have updated the schematic in the first post to a probably-final version.
Freppo - I noticed that C4 should be 220p rather than 1n, which I have updated on the legacy schematic above too.

The latest design iteration has a slightly tweaked envelope detector with added release control and faster attack.
I have also replaced the symmetry pot - I tended to only use either extreme - with an on-off-on toggle switch that can also switch in asymmetric clipping in the first gain stage (edit - have re-oriented these in the updated schematic to emphasise even-order distortion). The 3 different clipping options are fairly subtle, but give a little more range/flexibility.
I have also added a Millennium bypass option that uses the compression indicator as the status indicator (the LED doesn't tend to go completely off under max compression). I haven't tested this, but would be surprised if it doesn't work.

For a final test, I need to put new strings on my guitar. Will put something brighter on and see whether we can get away without having a tone control.

For reference, the simulated frequency response looks like this. Different traces are simulated with the gain pot settings. Input signal is at 1dB.

[Cozybuilder]

Hi Sam-
Thanks for posting, I look forward to breadboarding V1.3 this evening.

One thing on the Compression Sag monitor- you might want to move the LED and its parallel resistor to the drain side of the MOSFET. I had problems with your arrangement in the past, and subsequently found the Millennium bypass works best with the source wired to ground.

Cheers, Russ

[samhay]

OK, sounds like I had better give the bypass a test - thanks.

Happy breadboarding.

[samhay]

Gave it a test with new much brighter strings. Still sounds ok without any need to tweak the EQ, so happy to go sans tone control.
It works as a pretty decent compressor - can do a reasonable job with chicken pickin' through to smooth sustain. There is some pumping and breathing with some settings, but this could be seen as part of the charm.

Tested the bypass with the first random 2N7000 I could find. Worked fine once I got the pinout right.

I think the 1.3 version in the first post can be considered 'final' and is likely to be the version I box up.

[Cozybuilder]

Hi Sam-
I've got it on the breadboard, and it has a good range from clean to crunch. I'm with you, it doesn't need a tone control. Not too much time to play with it yet, but I think its a winner, worthy of boxing up  Hmm, wonder what it'll fit in?

[samhay]

Russ - glad you like it.
I guess you could replace the attack and release controls with trimmers or switches, which should allow one such as yourself to squeeze it into a 1590a. I feel like spreading out a bit, so will aim for 1590b.

[Cozybuilder]

Can't decide wether to paint the box pink (distortion) or neon lime (compressor). Decisions decisions

[duck_arse]

Can't decide wether to paint the box pink (distortion) or neon lime (compressor). Decisions decisions

perfect combination of colours for stripes, in my colour palette.

[sajy_ho]

I added Big muff's tone control to this but ended up omitting it, so I have to say you're right about no need for tone control.
Right now I'm working on a PCB for this circuit and will post it as soon as possible. It deffinitly takes a place on my pedalboard.
Thank you Sam.

[Freppo]

I made the changes to my vero layout.

I had to compromise alittle to keep the size 1590B friendly,
so I didn't include the millenium switching and kept the comp LED as the 1.2 version.


Full Size version

cheers / Freppo