Really Cheap Compressor

Gabe_ · Post by **Gabe_** » 12 Mar 2016, 17:21

Well you could just have changed the 100k log sustain pot for a 1M log to get more sustain range. It would have allowed for dialing it down if necessary...

reneshelle · Post by **reneshelle** » 13 Mar 2016, 09:06

Here is a perfboard layout that with some carefull planing fits in an A-size box.

Thanks to Mictester for sharing this fine compressor.

I build mine with a ne5532 and a bright switch (as discussed by others earlier in this threat). I used a ldr called GL5528 found dirt cheap on ebay.

mictester · Post by **mictester** » 13 Mar 2016, 14:16

That's a neat little layout, but I don't like "standing" components - I usually try to fit them close to the board.

reneshelle · Post by **reneshelle** » 13 Mar 2016, 14:49

I agree that it is generaly a better solution to have the resistors all flat to the board. I never make pedals for anyone but myself and I don't mind standing resistors that much. I make sure that they don't touch the aluminum box though!

Gobi · Post by **Gobi** » 21 Mar 2016, 21:09

Hey Folks, this is what I get, seems to be final for me:

There is more ampification in the first OPAmp and the LED Part is changed. If the Sustain is set to low , the trimmer is needed to let the LEDs glow just a litte bit (dark room!) to make it a little bit more muted. If Sustain is set to high, you get some more.
The intake condensers ould be modified of course - be shure to get no distortion!
I use 12V, works better - but runs also on 9V

phatt · Post by **phatt** » 28 Mar 2016, 09:54

Gobi wrote:Hey Folks, this is what I get, seems to be final for me:
[ Image ]
There is more ampification in the first OPAmp and the LED Part is changed. If the Sustain is set to low , the trimmer is needed to let the LEDs glow just a litte bit (dark room!) to make it a little bit more muted. If Sustain is set to high, you get some more.
The intake condensers ould be modified of course - be shure to get no distortion!
I use 12V, works better - but runs also on 9V

Hey Gobi, Yes you have more gain at front end but you have also lowered the input z by quite a bit so it may not work as well depending what is in front of the circuit.

Just thought I'd mention it for the sake of everyone who may get caught out

BTW,, I love this compressor simply because It Actually does what very few Compressor circuits can do,,, it Distorts while compressing.
Fantastic little circuit,, I have dreamed about this idea for years but never found one that works right,,,love it.

Phil

ppluis0 · Post by **ppluis0** » 29 Mar 2016, 01:47

Hi folks,

In the previous diagram the red led, due a lower junction voltage, turn on rather the green one that are pointed in the same direction. So that led (green) remains always off.

So the another green led is unable to drive the LDR appropiately, IMHO

What do you think ?

Cheers,
Jose

Gobi · Post by **Gobi** » 29 Mar 2016, 06:16

Hm, yes - this could be. I simply needed the other LED to check whats going on inside and for the trimming. There is no need for a red LED. I will check this in the evenig - but on the other hand: it works perfect as it is....

Gobi · Post by **Gobi** » 29 Mar 2016, 20:18

Hey Jose,
well, it's not a bug, it's a feature!
You are right, the red LED steals some power from the green LED's. But that works ok for me - one can figure out different caracteristics with different LED's or none, canging the direction of the red one, adjusting the trimmer.
Thanks for this good thought!

ppluis0 · Post by **ppluis0** » 30 Mar 2016, 00:31

Gobi wrote:Hey Jose,
Thanks for this good thought!

Sometimes I remember how to think...

Perhaps you can place a small resistor (say 390 ohms) in series with the red led to avoid alter the function of the couple of grren ones

Cheers,
Josè

Rolbista · Post by **Rolbista** » 03 Apr 2016, 19:50

anyone tried making a "matched" pair and use them on a stereo drum bus?

mictester · Post by **mictester** » 03 Apr 2016, 22:38

You could do that, but you'd have to match everything and the chances of finding two opto-couplers with exactly the same characteristics and matching LEDs and so on are very small!

Also, this compressor wouldn't be too good for drums, as the attack is too slow. People like the "sound" of this effect because it largely leaves the attack of the guitar notes alone, and just extends the decay.

A much better compressor (for drum tracks) is to use a feed-forward, delay-line based compressor. You do the level sensing at the input, then pass the audio to be processed down a delay line that is the same as the compressor attack. I've used BBD ICs with very fast clocks to do this - effectively you end up with a compressor / limiter with zero attack time! For radio audio processing, I've used delays of 3 - 4 ms, but try to get shorter times for live musical use, so that the delay is imperceptible.

Jamdog · Post by **Jamdog** » 06 Apr 2016, 03:05

Greetings.

I am attempting to build this circuit. I do have audio out. However, to my newbie ears, it doesn't work. I don't see a difference between bypass and the compressor, and the sustain knob has no effect whatsoever. I can manage to get some clipping if the input is loud enough.

How do I know if it actually works?

Gobi · Post by **Gobi** » 06 Apr 2016, 06:58

Are the LEDs lighting up?
Circuit just works if its absolute dark inside! Any light from outside will destroy the effect.

Jamdog · Post by **Jamdog** » 06 Apr 2016, 11:55

I placed the leds and ldr inside a heatshrink tube that I tested before building the rest of the circuit. Powering the leds did lower the resistance, that was otherwise huge.
The only way to know for sure if the leds light up would be to Crack open that seal.

I was thinking like you that if there's no effect, the leds/ldr combo must be flawed so I guess I'll do that and see from there.

Thanks for helping out!

How are the leds supposed to light up? Brighter with increased amplitude, and dark with no sound?

Gobi · Post by **Gobi** » 06 Apr 2016, 16:24

Best just relpace them with a normal LED , to see if its working.
"Brighter with increased amplitude, and dark with no sound?" is correct!

induction · Post by **induction** » 06 Apr 2016, 16:51

There's a video in a post on the previous page that should give you some idea of what to expect. The led's won't light up steadily, they will flicker as you play.

Jamdog · Post by **Jamdog** » 06 Apr 2016, 21:23

induction wrote:There's a video in a post on the previous page that should give you some idea of what to expect. The led's won't light up steadily, they will flicker as you play.

I see the pictures and get to wonder if I actually placed my leds too close to the ldr, I got them almost touching. Perhaps it's always kicking in too strong?
(would I notice?)

Tonight I am working on the enclosure, and will test the leds as time permits. Thanks a lot guys for the help! This is a fun project, but having some guidance only make it more fun

(I am actually new to guitar, and this is my first ever effects pedal!! I think the next one will be a fuzz)

Jamdog · Post by **Jamdog** » 07 Apr 2016, 01:15

I checked, the leds wont light up. At all. I also can confirm the LDR has effect on the circuit, as hiding it from light change the tone, and putting it in direct full light muffle the signal completely. That's a good sign on that end

I wonder if its the LED resistors that are not properly valued for the specific leds, or the second up amp that isn't outputting anything. I'll try and probe that to see where it leads. Anyone has hints on probable cause?

Thanks!!

Jamdog · Post by **Jamdog** » 07 Apr 2016, 02:20

turns out the leds are toast. I pulled them to test and nothing goes out. I dont get it, I tested them before assembly.

I do not have much in term of replacement at this moment (go figure, I tought I had like tons of leds in here, but I don't!)
I placed a pair of those rectangular green leds

They do light (but very dim) - I have a hard time comparing to what's in the video.

how do I know its bright enough? I placed them directly to the LDR, and can't say for sure if it does anything

Remember I am still new to the guitar...

Is there a sure way to know it actually works?

Really Cheap Compressor [documentation]