Really Cheap Compressor. New with LDR + compression led indicator

[nonost]

 Hi! I'm going to build a Really Cheap Compressor as a part of a large build. It's my first time with LDR+led. I'm following this layout:

http://tagboardeffects.blogspot.com.es/2012/03/really-cheap-compressor.html

 Some people recommend to test some LDR and use the best that fits the needings, should I get 3 or 4 LDR and test them? what should I exactly test? I'm ordering a 8k-20k (light), 1M (dark) one.

 For this layout  3mm green leds are needed, I'm going to order them to Musikding. They also offer a bright 3mm green led. What do you think that will work best? I know that I can get both and try them but since I have to put the LDR+leds in the heatshrink and all that stuff...it would be a PITA.

 The other subject it's about adding a compression led indicator. I've seen some builds of this compressor with it, but the owners don't say how to achieve that. I guess that I should use one of the LDR+led rows but I don't know exactly which one.

 Any help is very welcome :)

[Ciaran Haslett]

The problem with "home rolled" vactrols (a separate LDR and LED heatshrinked together) is that it opens up the number of variables that can introduce problems.  The specific LDR specs, the amount of light from the LED, the LED beam angle, the ambient light isolation etc etc.  That's why its always best to get as much variety as you can when ordering these kind of parts.

I wouldn't heat shrink until AFTER I've tested a combination...either with some electrical tape or simply in a dark room with a box or something over the whole build.  When I've found a combination I'm happy with...then I heat shrink it move on.

As for the compression indicator...just add another LED in parallel with one of the 2 on the board.  You may need to add a small value resistor in series with this new LED to isolate it from the others but as they are rectifying the guitar signal I don't think that's necessary.

Good luck

[Boba7]

I found that adding a parallel LED produced more distortion with higher compression settings.

I used this little circuit to add an indicator led : http://www.madbeanpedals.com/forum/index.php?action=dlattach;topic=24296.0;attach=14856;image

[nonost]

Thanks man! I will order a few of them and use sockets in that case. Testing in a dark room sounds nice! I will post here how it goes.

[nonost]

Ey Boba7 thanks! I think I can put that circuit in a vero without problems. In the RCC, the 'A' red dot of your schematic would be right before Sustain 3?

This is the layout I'm using: http://tagboardeffects.blogspot.com.es/2012/03/really-cheap-compressor.html

[Boba7]

Yeah exactly, pin 7 of the opamp / pin 2&3 of the compression pot

Glad to help! Post some pics when it's done! :)

[nonost]

Built it! Great compressor, it's addictive! The LDR 1M 5mm from Musikiding seems to work pretty nice. At first I tried a couple of bright green leds and it distorted and sounded awful. Even if both leds were pointing in the opposite directions to the LDR, it sounded bad. Then I swap the bright green led close to the LDR for a common green led and the result was the same. So I think I can say that you should take into account both leds, even if you use one of them as led indicator. At last I put two green leds and they are settled in.

BTW, for those who are planning to use Mark's layout, the sustain pot is wired backwards. As it goes clockwise you get less compression. In order to get more compression as the pot is turned clockwise, sustain 1&2 becomes sustain 2&3 and sustain 3 becomes sustain 1.

I've buit it with the bright mod posted here: http://www.freestompboxes.org/download/file.php?id=20729&sid=e45e1d97ad7999d0e93e39ca2d066350&mode=view

and used the little circuit posted by Boba7 above for the indicator led. The only problem I', having is the indicator led not blinking in both modes.

As others said, it distorts at high comp settings if the level/volume pot is set high as well. But it's not a problem since this compressor has a lot of volume IMO.

[induction]

nonost wrote

I tried a couple of bright green leds and it distorted and sounded awful. Even if both leds were pointing in the opposite directions to the LDR, it sounded bad. Then I swap the bright green led close to the LDR for a common green led and the result was the same. So I think I can say that you should take into account both leds, even if you use one of them as led indicator. At last I put two green leds and they are settled in.

I got some nasty distortion on mine, and found that it was coming from the ldr, not the led. I swapped the ldr out with one I got from Radio Shack, and it worked great. That may or may not be the case for you, but it's worth looking into. If you want to test it before buying a new ldr, maybe replace the existing ldr with a fixed resistor and see if you still get distortion from the leds.

I've buit it with the bright mod posted here: http://www.freestompboxes.org/download/file.php?id=20729&sid=e45e1d97ad7999d0e93e39ca2d066350&mode=view

Ha! That's my layout.

I didn't bother heatshrinking my led/ldr and it works great. Bear in mind, though, if you use a status led (either for on/off or for compression indication) and you don't heatshrink the led/ldr, you should make sure that the back of the indicator led isn't leaking light into the enclosure or it will screw up the compression.

[nonost]

Ey induction! Your bright mode works great! I've put a Pitch Pirate Deluxe after the RCC and it's perfect for those dark settings of the PPD.

Yours doesn't distort at high settings? I'm not so bother because it's only when the volume is far away from unity. But if I order parts to some other place I will try another LDR.

I'm using two leds actually, one for each effect. I've checked them and they don't affect the compression so far, but I think the best thing would be to heatshrink the LDR+LEDs.

The only thing that bothers me is that the indicator led only works with the stock mode. With the bright mode it turns on and stay that way like a common status led. I guess I did something wrong with the little board for the led indicator...

Thanks for your tips!!!