Flatline capacitor 100uF or 100nF ?

[flo]

In the Flatline compressor of John Hollis (http://www.hollis.co.uk/john/flatline.jpg), there is a capacitor parallel to the LED of the LED-LDR combo. It is not clear to me if this should be 100uF or 100nF even after reading all Flatline posts here (for instance http://www.diystompboxes.com/smfforum/index.php?topic=36485.0). 

Mark Hammer for instance states it is 100nF while some others state 100uF. The schematic drawn by John Hollis clearly shows a elco with a + and - side. This leads me to a 100uF value. Some people state that using 100uF leads to a much too slow compressor response while others state that using 100nF gives them almost no compression.

Does anyone know what it should be: 100uF or 100nF?
Perhaps I should just try both (or something in between)... 

If it depends on the kind of optocoupler, I'm using a VTL5C9 (http://optoelectronics.perkinelmer.com/content/Datasheets/DTS_vtl5c9c10.pdf)

Regards,
Flo.

[pjwhite]

Looks 100uF (microfarads) to me.  This would make sense also, as a smoothing filter for the signal driving the LED, that 100uF would smooth the signal better than a 0.1uF (100nF) capacitor.

[balance]

I'm sure I used 100uF in mine and it works just fine. The schematic really looks like uF to me (note John's "n" in "Flatline"). I would try both and see what they sound like. It may even be worth making it switchable so you can have a variety of decay times.

Brian

[moro]

I asked this a while back and I'm positive it's 100uF.

http://www.diystompboxes.com/smfforum/index.php?topic=60951.0

While the "u" there is a little ambiguous on its own, if you compare it to the "1n" input cap and the "10uF" capacitors in the power supply, it's pretty clear that it's meant to be 100uF. I used a 100uF cap there and it worked fine.

That having been said, people have reported using 100nF there with no problems.

[Mark Hammer]

1) John's initial schematics that he posted were all hand-drawn, sometimes leading to squinting readers mistaking values.  Look here: http://www.hollis.co.uk/john/flatline.jpg  and tell me the way John writes "u" (mu for micro) doesn't look like the way he draws his N (see 1n input cap in the upper left hand corner).

2) Even folks who you think know something make typos.

[MartyMart]

It's been a while but my initial "mistaken" 100n cap resulted in no compression and general "wierdness" with
my particular LDR.
100uf looks like the correct value to me and I had the same "Bad" sound/comp with anything under 47uf
so the opto-coupler type will make a difference.
MM.

[flo]

... Look here: http://www.hollis.co.uk/john/flatline.jpg  and tell me the way John writes "u" (mu for micro) doesn't look like the way he draws his N (see 1n input cap in the upper left hand corner)...

It really looks like a "n" and then again it also really looks like a "u". While looking at the value of that cap in John's schematic it looks to me like it can be both. I'm not able to come to a descision just looking at the value of that cap. I'm glad to have some people report their experiences with what they percieve to be correct or (even better) have actually tried these values and came to a conclusion. Thanks for your responses. Very helpfull.

Flo.

[slacker]

If you look at all John's schematics he consistently writes uF for where he means micro and just n where he means nano. So the fact that it has an F following the unreadable letter points to it being 100uF. It's also shown as a polarised cap which makes it more likely that it's 100uF.
Having said that this might be the exception that proves the rule

[aron]

I'm right in the middle of compressors right now. How does the LDR compressor affect the signal as opposed to something like the Orange Squeezer or Dynacomp?

[MartyMart]

I'm right in the middle of compressors right now. How does the LDR compressor affect the signal as opposed to something like the Orange Squeezer or Dynacomp?

Technically I have no idea, but the Flatline and other "opto" compressors just seem to be superior to me and perform
much more like pieces of studio hardware than guitar stompers.
I'm a BIG fan, using the Flatline and the LA-Light a lot.
I would just say it's a "smooth" and expensive sounding comp .. given the small parts count !! - Flatline has a wicked volume boost also - BONUS!!
MM.

[aron]

How would you compare the Flatline vs LA-light?

[balance]

From what I understand, optical compressors rely on the reaction time of both the lamp (or led) and the LDR to create the shape of the compression, especially the attack and the decay, ultimately requiring fewer components in the signal path to achieve a musical result. This is normally at the expense of flexibility.

In my experience opticals are slower to respond and slower to release, but its more about the shape of each of those. Transients, like those from a snare, may not benefit from optical compression, but you may like that "pumping" sound it creates. Opticals are awesome on bass and voice though, but everything is a matter of taste. Guitar is sort of in the middle. Depending on the song, guitar may benefit from one or the other. My Flatline sounds perfect for slide, but its a little too slow for chicken pickin'.

[moro]

I'm by no means an expert, by my experience with the Ross, Squeezer, and Flatline colloborates balance's technical description above. The Flatline reacts a bit more slowly and preserves the attack more than the other two compressors. This is both good and bad, imo.

I find that I use the Squeezer the most. I really like the simplicity of the one knob.

[aron]

>but you may like that "pumping" sound it creates.

Jack's Q&D compressor has a bit of pumping like you describe. I'm not an expert by any means with compressors. I've never really used them other than my really old Soul Preacher and my Orange Squeezer.

Thanks!