I want to build the flatline compressor, ? about making the LDR

[jimmybjj]

I'm still learning, I've looked but couldn't find the answer. all of the layouts simply say LDR with no specifications. looking on futurlec.com there are several differnt types and resistances of photocells. how do I know which one and which resistance to use? I understand the construction technique as that is simple, or at least appears to be.

[.Mike]

I haven't actually built-n-boxed the Flatline, but I had it on my breadboard for a few weeks last fall.

I used Futurlec #photocell1 and a 100mcd / 640nm (red) LED, and it worked well. Different photocells respond differently to different color light, so buy a selection of LEDs.



Mike

[maarten]

In my experience it does not matter; the first LDR's I bought were just the ones I could lay my hands on in electronic components stores (this was before the internet, when we still had such stores locally...) - whatever was available. Note that the LDR's are not specified either. You can experiment with their colors, distance from led to the LDR, the current going into the led if needed. Be sure to isolate the LDR from other sources of light than the led.
Have fun,
Maarten

[petemoore]

  LDR's arent as fast as Jfets or Ca3080 type envelope detectors.
  There are faster ones [change resistance value where it matters more quickly].
  But it's a bit of different effect, to clip even the very first part of the attack, LDR's are a bit slow, the natural delay of gain turn-down effect is:
  Easy to work with, and can be made to compress a lot, duck down and slowly rise or other ramp rate adjustments within a limited range, just won't cut down the first portion of the initial attack...which is nice to have in left there in some instances.
  One of those instances is 'sustain' or slow ramp up of ever dying signal. Say for Distortion, can make for more pronounced initial attack, then as signal rises up later [after the 'ducking' or gain reduction portion of the envelop/ramp sequence..sounds like sustain...or even rising of increasing harmonics [like someone is turning up the gain..go figure, the gain gets turned up slowly].
  So...basically fine compressing as long as there isn't that particular portion of the initial attack that you want to supress.

[CynicalMan]

I used these:
www.smallbearelec.com/Detail.bok?no=332
www.smallbearelec.com/Detail.bok?no=711 (the 9203)

If you want to order at futurlec, PHOTOCELL1 would work.

[jimmybjj]

so it sounds like all of the ldr/led combos will work just varying degrees, right or wrong? if this is the case what combo would give the originally intended design called for or even better how could i figure it out on my own.

Pete, I'm still to young in my electronics experience to understand what your saying, if in fact you are actually saying anything at all 

[CynicalMan]

Anything in the Miniature Photocell range should work, but I would go with one with a lower light resistance. That way, you get a higher compression ratio. You can always reduce the ratio by adding resistance in series with the LDR, but it's difficult to increase it.

[Slade]

I made mine with a VTL5C3 and works perfectly.

Some guys said that using a VTL5C2 was a better choice for its very slow decay, but I haven't had any trouble with my build with 5C3.

The cap across the diodes is very important to control the decay of the effect, values like 10uF make the decay unstable and begins to distort. You should search for the "isildur100" version of the pedal, he modified it a bit and added a "comp level" control that I think actually acts like a Ratio control, I took his schematic and made some minor changes to make mine.

[petemoore]

Anything in the Miniature Photocell range should work, but I would go with one with a lower light resistance. That way, you get a higher compression ratio. You can always reduce the ratio by adding resistance in series with the LDR, but it's difficult to increase it.
  Seems like 2 LDR's with one LED would decrease the resistance / low light resistance, still probably goes over 250k or 470k in dark...measure, or try the mileage.
  What does the compressor expect is the other side of the coin.
 

[askwho69]

BUMP on this! i have a question.. i want to build flatline too but i was confused what LED should i choose? i bought a super bright blue LED as the local guy store said that they usually use superbright white LED for it.. thanks in advance