Build Report: J. Hollis's Flatline + M. Hammer's Punchline

[aaronkessman]

Well, built these more or less stock. a couple notes:

Used a 2k-~1M LDR (thanks Hal!), a 0.01uF input cap, no safety resistors like RG recommends, and a 0.1uF cap in the diode section. I first had a 100uF in there (misread the schematic) and the attack was too slow. The 0.1 evens it out perfectly. That's about it. A switch was added to convert it to a punchline with no further mods. I *did* use a trimmer pot to adjust the 220k range resistor in parallel with the LDR. It's a 500k and right now it's set for max. Looks like the usable range is about 200k-500k.

Sounds good. at high compression it breaks up a little, but not unpleasantly, and this is fine with me. gives me nice feedbacky sustain at higher volumes, which is exactly what I wanted it for.

The Punchline version actually works *quite* well, perhaps if the LDR had a slower decay it would be better, but it's certainly fast enough on the attack (and the decay isnt too big a problem, I just wont be able to use it on slow lines, but whateva).

Overall I'm quite satisfied, it was easy to build and sounds great. Thanks John and Mark!

Aaron

[MartyMart]

Hey, the flatline is great isn't it ? I'm using mine all the time right now
I went for a 390k across the LDR, tried up to 560k and this seemed good.
I called mine "Mr Squeeze"  !!

EDIT: The cap across diodes isn't 100UF  !! oops, that's what I have in there since I built it, are you sure it's 100 n ??
I used the vero/schematic that was posted it's hard to read ... !

Marty.

[MartyMart]

Are we talking about the cap that "links" across the diode section ?
I just tried a much smaller cap and got almost "zero" compression and
some "wierd" noise added to the signal !!
With the 100uf in there, its "clear as a bell" again and has a real "spank"
to the compression.
Attack is quite pronounced with the 100uf and non existant with a 1uf or
smaller !!
I'm convinced that 100uf is correct .... anyone else ??

Marty.

[aaronkessman]

the 100uF definitely got too slow of an attack. the note would begin as normal, then a few ms in, the compression would hit and make a very weird effect.

I've seen it listed as both 100n and 100u. I think on RG's layout it's listed at nano.

[MartyMart]

the 100uF definitely got too slow of an attack. the note would begin as normal, then a few ms in, the compression would hit and make a very weird effect.

I've seen it listed as both 100n and 100u. I think on RG's layout it's listed at nano.

OK, the "LDR" used must have a large effect on this, mine is not usable
with anything smaller than 47uf ....
If your's is operating the way you like, then thats fine

Marty.

[slacker]

I've just finished my flatline, and it's a really nice compressor.
For me it's fine with the 100uf cap across the LED. If I compare it to my old Aria compressor, which has variable attack, then the  attack of the flatline is similar to the slower Aria settings. I like it like that, at maximum sustain it gives a nice squelch to the sound.

[aaronkessman]

been using this and it's really great. i was wondering if there are any components that can be made switchable or adjustable to tune the attack and release times? Or are these kind of limited/inherent properties of the optocoupler?

[Mark Hammer]

The 100nf cap smoothes out the envelope to reduce ripple.  You can see that there is nothing in the design to permit an easy adjustment of attack time, which is normally how quickly the cap is allowed to charge up.  As such, the attack time is set largely by the LDR properties.  The cap itself, though, can be varied to adjust the decay time.  Not having built one of these, I have no idea if it is more of a fast transition sound like the Orange Squeezer, or a slow decay sound like a Dynacomp.

All that aside, you will note that the cap doesn't really have any path to discharge that isn't a diode.  So, I,m wondering if it might not be possible to stick a resistor in parallel with the cap to drain it faster.  If it IS possible, then that might suggest some possibilities by sticking in a larger cap (say, .22uf) and using some sort of pot/fixed-resistor combo in parallel with the cap to vary the drain-off time.