LA-Light / Fat 'n' Pretty

[moosapotamus]

I think I'm (finally) done tweaking this really sweet compressor/overdrive. It sounds great on everything, from vocals to guitar, and especially on bass!

Johan, I know you suggested a different name, since it's not exactly a functional representation of the LA2A anymore. But, I think I'm going to call mine Fat 'n' Pretty.

I really only made a few minor changes since I posted it on the old forum. Most notably, added switching to select between either the compressor (Fat) output or the overdrive (Pretty) output. Both clean and overdriven tones are available from the Fat side as well as the Pretty side. In fact,  this little circuit pumps out a huge range of fuzz/OD tones. I think I've actually been spending more time playing through my breadboard than tweaking the circuit. :mrgreen:

Here's the scheme and a PCB layout, too. The dimensions of the PCB are 3.0" x 3.575", sized to fit nicely into a 1590BB enclosure. I used a 5532 dual opamp, and a VTL5C3 optoisolator. The PCB layout contains a current limiting resistor (R14) that's not shown on the schematic. It's there for adding a on/off status LED. And, the pads for the pots are arranged so that, with short extensions, you can mount the pots right on the PCB.

http://www.moosapotamus.com/Fat-n-PrettySCH.gif

http://www.moosapotamus.com/Fat-n-PrettyLYT.gif

http://www.moosapotamus.com/Fat-n-PrettyPCB.gif

Please let me know if anyone sees any mistakes in the files. Thanks!
~ Charlie

[petemoore59]

That is Charlie/Moosapotamus's latest post.
 It's contents include: :idea:  
 A well drawn schematic, pcb layout, and related text
 A First build report
 An exciting new project with promise of great versatility, including great optocompression and more from a fairly simple looking ckt.
 Very nicely and concicely written..it looks real good.. Yummm....!
 This week I had the finance pump working for three days [better than nothing] got called back and laid off...lol :shock:  It was a real drag for about 3 weeks there with the finances all deflated and the pump broken [no work]...I'm expecting next week will be more productive and things will become more stabilized in the near future!!!
 Hopfully then I can get parts & start to work up a couple 'top of the list' projects!!

[Johan]

Nice one, Charlie.. :lol:

please tell me...with the input gain set low and the ratio in the old comp-mode ( pot shorted ) and playing in distortion-mode ( pretty ? )..what is the caracter like?....I mean, everytime the led is turned on, the ldr goes down in value and reduses the input. and when the signal gets weaker the led leds go off and the input increases again... :roll:  ...should result in a really soft clipping with lots of attac...depending offcourse on how fast the ldr is...or is it more like a dirty hard limiting, maby?. Am I totaly off here, or is that what is hapening?...maby I should just get my old LA-light out and try it... :?

Johan

[Nasse]

                 
                 

[moosapotamus]

Thanks, Johan!

No matter how the gain and ratio controls are set, the Pretty output (from the LEDs) doesn't sound like it has any compression, to me. Which, I think, ought to make sense because that output is coming off of the side-chain, which is not effected by the LDR (compresion) side of the circuit.

With the gain set low (~unity) and the ratio low as well, the Pretty output sounds clean with light picking/strumming, and starts to overdrive (in a nice way) when you play harder. My guess is that the threshold LED indicates how much clipping is ocurring on the Pretty side.

NOTE: On the power supply that I used, a heat-sink is needed on the LM7805 regulator. I used Mouser part # 532-530614B00. On the PCB layout, the heat-sink is shown as the rectangular outline around the regulator and the convertor, which both fit neatly underneath it.

~ Charlie

[neil411]

Charlie,

I had some much fun building the AD/A Flanger, I think I will try this one next. And then maybe the Funny Cat...

[neil411]

Charlie,

I have a couple of questions about the schematic that I can't find answers to in the posts about this pedal.

• Am I correct in assuming the C1 should be 47pF?
• Am I also correct that C4 should be 0.2uF film type and that C5 should be a 4.7uF polar electrolytic?
• Did you ever have a chance to figure out why the Bright/Warm switch didn't work in your build?

Thanks

[petemoore]

  I could only find the site and all the 'effects' 'guitar effects' page.
  When clicking on say 'compressor' or 'effects', I get a listing for MF, Amazon for compressors etc...nothing very interesting. Perhaps I'm not navigating well, I think I tried pretty good though.

[neil411]

The links are wrong, they should be .NET, not .COM

Here is the page for the whole thing...

http://www.moosapotamus.net/THINGS/fatNpretty.htm

[blue_lu]

Charlie,

I have a couple of questions about the schematic that I can't find answers to in the posts about this pedal.

• Am I correct in assuming the C1 should be 47pF?
• Am I also correct that C4 should be 0.2uF film type and that C5 should be a 4.7uF polar electrolytic?
• Did you ever have a chance to figure out why the Bright/Warm switch didn't work in your build?

Thanks

any conclusion on this ? sorry to bother again, but I am going to build one of these soon! thanks for posting the layouts, charlie!

[neil411]

I never got any answer on these, and I never got the pedal to work.  Thanks.

[blue_lu]

for your questions:



1.) C1 -> 47pF for treble roll off sounds abound right, no?!

2.) well, c4 looks like a classic poly cap... compare the pic and the shem:






C5 does not look like anything polar to me...