Most variable compressor?

[Radamus]

I'm going to revive this almost dead post here with another couple questions.

The first: The roll off capacitor in the LA light schematic posted here - If I'm playing bass, should I use a larger value, so nothing is rolled off? I don't know how much I care about having variable roll off or anything like that. If someone could explain that a little more, that would be nice. If I don't want the roll off option, should I just omit it or replace it with a sufficiently large capacitor, such as 10uf?

Second:The resistor following the envelope control is supposed to be a pot? Johan mentioned that 470 to 1000 ohm would be a good starting point. If I want variable amounts of compression, should I go with a 1k pot? What about 2k? I just want to know what would be useful.

Third: What effect does the 100k pot at the beginning have on the sound? I'm having a hard time understanding it from just reading the schematic. I've done ten or so builds but I'm still a newbie at this.

Thanks fro all the help.

Edit: I was looking at the schematic and writing the parts down when I realized that it only says v+. Is it 9v?

[R O Tiree]

The major reason for rolling off the bass in a stomp-box compressor is that the bass (thicker, wound) strings of a guitar, having more mass, vibrate for much longer than the treble strings (thinner and plain wire). The basic compressor circuits we're considering here don't care about frequency - they just percieve total signal strength so the bass strings tend to kill the treble strings fairly quickly when playing chords. Rolling off the bass gives the treble strings more of a chance to hold their own in the mix.

For a bass guitar, I don't think this would be too much of a problem, as all the strings are fairly massive. I'd lose that roll-off cap if it were me, and construct it flat-line.

Or, if you must, use the other circuit fragment where you use a pot to select the roll-off freq.

[Radamus]

If I use the starred resistor as a sort of sensitivity pot, would it also be wise to add a 100-200Ω resistor in series? Will the output of an opamp kill an LED? Also, is a 4558 okay? I know other envelope devices can be pretty picky about their op amps.

Getting ready to build this one finally. Had to buy extra large shrink tubing.

[petemoore]

  Here's questions to ask:
  What would you use it for
1 quick note attacks and not too much 'over the top' [quick release time and not a whole lot of gain variation], not terribly noticable exept it keeps your signal up but not over the point where something else 'groans'.
2 Long slow notes that 'grow' [long recovery, lots of gain increase during that time].
  The Orange Squeezer is a 'mellow' compressor, there are offshoots and mods to offer more noticable attenuation / compressor sound.
  The Dyna and Ross can be built on the same board, one has more HF rolloff [compressors turn the volume up at the worst time, for a noise boost, when your'e not playing, there's nothing to cover it]. For bass, a comp user may have use for the LP filtering, since the only HF's passed may be only noise.
  Headroom, running at >9v increases it. Is it necessary to increase it for your comp?
  I built a DOD280 because it's simple, easy to read schematic, I had the parts, I like the way this one was made to work [LED/LDR in partray worked in there].
 

[Radamus]

I would personally like to be able to play with all of those things. I think that a lot of the quirks with attack and release times can be musical, or at least rhythmic. At this point, I have the parts for the LA light and the Orange Squeezer. I would be willing to do mods if necessary, but the previous posters thought the LA Light would suffice. If there are any mods to make the LA Light more variable, I would like to know. Also, I'd like to know just what each knob is supposed to correspond to.

Any thoughts on the questions I asked in my last post? It might be a really uninformed question, but I don't usually pick up on what I'm doing until after I've done it. Then it makes sense.

Thanks for the input again!

[oldrocker]

I would try bread boarding both the LA and the Orange Squeezer.  I haven't built the LA yet but as for the OS I love it on my bass and it's not modified at all.  Make sure you use a GE diode though as this makes a world of difference.  I will be bread boarding the LA Light to check it out.  Compressors I have built are:
DOD 280
Flatline
Orange Squeezer

[oldrocker]

Well after bread boarding the LA Light comp I have to say it sounds as good as the DOD 280 if not better.  To prevent rippling you need an LDR that is around 50k when dark.  I also used a 50k LDR in the DOD 280 which had a 200k dark (too big) which took the ripple out of it too.  I may box it up if my bass sounds good through the LA.  My bass amp is being stored so I haven't tried it on the bass yet.  If your looking for heavier compression the 280 may be a better choice though.

[Radamus]

Thanks for doing that. That sounds interesting. I think the LDR I put in the tubing with the two LEDs is going to be too big. I'll have to check and see if I have any that only max out at 50k, otherwise another order may be... in order. I haven't actually heard where anyone tested different kinds of LDRs in their units. I might have to double check that in my Meatball, too.

I can always use a normal type compressor, and thanks for the vote for the orange squeezer on that, but I want to make something that can also do all of those weird hold and release type sounds.

What do the pots correspond to on the LA Light?

Thanks again.

[Radamus]

Okay. The 2LED/LDR I put together has around 700k dark resistance, but, if I did my math, putting a 56k resistor in parallel should take it down to the right value. Will that cause any other problems? At dark, it would be just over 50k, at full light, it's zero. Do the values in between change the same way?

[oldrocker]

When you watch the LED's you will see them flickering as the input starts to fade.  Apparently when an LDR with larger resistance is used you can hear the flickering through the LDR as distortion as the guitar signal fades.  If the LDR is too large it takes too long for it to ramp back up to it's rated value.  Hence the audible ripple while the LED's are flickering.  I would think that what you're doing with the 56k should work.  Maybe Mark H. could shed more light on this. (No pun intended.)  The LA Light is more subtle IMO than the DOD 280 or the Flatline.  But if you don't mind subtle then my vote is the OS.

[Radamus]

I did the math it will wind up making the LDR a log scale. It doesn't cut in half until it gets down to 56k from 700k, which is way less than half. I thought bigger dark resistance was the way to go. Guess not. It may not even be a log scale, it's just not going to be even.

[Radamus]

I did some more math and I found that no amount of resistors in parallel will make my LDR any better. I also found that none of my usual suppliers have any LDRs that get as low as 50k in the dark. Where do you get yours?

[oldrocker]

Believe it or not they were in a variety pack of LDR's sold at Radio Shack.  You may want to try a 100k LDR since it seems to respond fairly quick.

[Radamus]

The best I have right now is 200k. I'll check and see what Radio Shack has to offer later if I get a chance.

[Radamus]

How much do you suppose minimum resistance counts? I've got an LDR on one website that maxes at 100k, but the minimum is listed at 10k. It seems to me that the schematics should have a specific value that they want, but maybe tinkering with the other knobs makes it work. Have you tested Ultra Bright LED's?