BAJA LA2A Style Optical Limiter [documentation]
- johnk
- Resistor Ronker
how would i go about making the limit knob have a better sweep range?i used a 3mm diffused yellow LED and it works great, but the B10K limit knob has a very narrow range at the beginning of it's sweep. i tried it with both red and green opto leds but other than the amount of limiting, it still comes on too quickly.
Just fyi for you diy'ers pot curves can be logified (i.e. audio tapered) by adding fixed resistors, as detailed in this excellent article by Rod Elliot at ESP: http://sound.whsites.net/project01.htm
I've done this when audio taper pots are difficult to find in the configurations I want, and with very good results. Cheers!
I've done this when audio taper pots are difficult to find in the configurations I want, and with very good results. Cheers!
- bajaman
- Old Solderhand
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Because photfuckit (photobucket) changed their free viewer status, the original schematic, and layout views are now unreadable to most of us, SO - here is a readable version for you all!
cheers bajaman
cheers bajaman
be kind to all animals - especially human beings
- bajaman
- Old Solderhand
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In the above post schematic, I found it a good idea to reduce the 68k source to ground resistor on the input jfet buffer to 10k
cheers
bajaman
cheers
bajaman
be kind to all animals - especially human beings
- bajaman
- Old Solderhand
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be kind to all animals - especially human beings
- Dingleberry
- Breadboard Brother
Anyone tried this with NSL-32 optoisolator?
At first glance it looks like the parameters would match well.
At first glance it looks like the parameters would match well.
Simplify before you amplify.
Finally got it built this thing is freaking awesome.I have never been into limiters or compressors or anything but what this limiter does to the sound is incredible.It makes the clean sound really come out thick and meaty thanks baha awesome design.
I'm having problems with this - once it starts limiting, it also starts distorting the sound. Tried different optos, and NSL32 sounds the best, although it also distorts a little. What could be the cause? Which optocouplers did you, people, used?
I tested all the vactrols I have with this circuit and this is the conclusion:
- the best is NSL32, almost no distortion
- the second placed is LCR-0202
- the third is some VTL5C10, marked with those letters and PRC, so I'm not sure if it is the original Perkin Elmer one or some kind of a copy.
All the others (I tested 5 more) distort the sound a lot, and I actually don't like those "best" 2nd and 3rd either. Strange circuit.
I tested all the vactrols I have with this circuit and this is the conclusion:
- the best is NSL32, almost no distortion
- the second placed is LCR-0202
- the third is some VTL5C10, marked with those letters and PRC, so I'm not sure if it is the original Perkin Elmer one or some kind of a copy.
All the others (I tested 5 more) distort the sound a lot, and I actually don't like those "best" 2nd and 3rd either. Strange circuit.
- bajaman
- Old Solderhand
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you are doing something wrong if it distorts
be kind to all animals - especially human beings
- Frank_NH
- Solder Soldier
I built the LA-2A style limiter circuit recently on my breadboard and used the lcr-0202 opto coupler. The limiter works great as does the lcr-0202. I modified the circuit to use a split supply (+/- 9V) which didn't introduce any complications. I also used an op amp for the input buffer (didn't need the extra op amp for the reference voltage circuit), but will also try the jfet eventually. I plan to use the limiter at the end of a preamp, and my experiments so far indicate it should work fine, although one might want some additional make-up gain if the input signal is hot.