flatline compressor...... HELP!!!!!

[Br4d13y]

i jst built the flatline compressor using ulysses vero layout. i made my own LED/LDR using a yellow led and a radioshack photoresistor(the biggest one in the pack)

im also using a tl082 but have a 072,

now, when i play through it it distorts very.... yuckily. and gates relatively quickly   and sometimes it will just get very quiet and i have to play hard for it to register again


anybody had these symptoms or knows how to fix its help is greatly appreciated

[ppatchmods]

can you post some parts values of the photo cell and maybe a pic. also some voltage measurements would help. i built one of these a couple of weeks ago.

[Br4d13y]

idk the value of the photocell, it was jst the biggest one in the pack   and were shud i take voltage readings?

[BAARON]

The value of the photocell is going to make a big difference in the effectiveness of your compressor.  It's not only the resistive value that's going to have an effect, but also the speed the photocell reacts at.

Personally, I'd recommend using a photocoupler instead, so you know that part of the circuit works.  It's pretty rare that a VTL5C2 ends up causing problems in a Flatline, but I've seen more than a few Flatline threads where a large part of the problem was homemade LED/LDRs.  Sure, they might cost $8-9, but if it fixes the problem, it's worth the few dollars.

Also, the cap in the middle of the diode bridge: are you using 100µF, or 100nF (aka 0.1µF)?

[Br4d13y]

ok  i guess i will have to grab the photocoupler from smallbear. i am using a 100uf electrolytic i believe

[flo]

... and sometimes it will just get very quiet and i have to play hard for it to register again

If it behaves in this erratic manner, something is wrong in the circuit which is not due to the optocoupler itself. If it was only the optocoupler that is the problem, the behavior would be consistently the same.

Put the "sustain" pot to minimal, how does it sound now? It now should work as a buffer/booster with very little compression.
Does the "volume" pot work correctly?

Check the soldering, the wiring and all components.
Measure the voltages on the pins of the opamp and post them.
Take pictures of the circuit and post them.
Follow:
DEBUGGING - What to do when it doesn't work
http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

[nosamiam]

I had the same problem. Which layout are you trying to build? I tried one that did the same thing and realized after a LOT of trying to troubleshoot that the layout itself was most likely the problem. I gave up and decided I would try again later after reading some build reports of one of the layouts that actually worked.

There's this:

http://www.hollis.co.uk/john/flatline.jpg (original schem)

and this:

http://i17.photobucket.com/albums/b72/mmarkmm/Flatline_Compressor_LAYOUT.png

It's too early in the morning for me to remember where the inconsistencies were, but I think I found some a long time ago.

[oldrocker]

I would agree that your problem is not the optocouple but either a build or layout error.   The problems you're having doesn't sound like optocouple issues IMHO.