freestompboxes.org

http://www.futurlec.com have a miniature photocell that works okay in this circuit - it is listed as photocell1 in their online catalog
bajaman

Yeah thanks, but resistivity is between 5k to 500k.

PHOTOCELL1 Miniature Photocell 5k 500k Yes 1 $0.25

http://www.futurlec.com/Photocells.shtml

It will work - trust me
bajaman

OK. So why not use this cell?
http://www.banzaieffects.com/Photo-Cell ... 17338.html

try it and see
bajaman

Hey and what about this?
http://www.banzaieffects.com/Audio-Opto ... 17349.html

yes - try it and let us know
bajaman

Hello all,

First post here . Long(ish) time looking, finally think i may have something to contribute.

I was recently called into action playing bass (not my first instrument) and was looking around for a limiter/compressor. Being aware of the fabled LA2A from studio work i thought this would be an interesting one to try... So, I've had a go at a stripbpard/vero layout for this.

- I've not included the buffer section (I use a simple buffer at the start of my chain, my assumption is that this would remove the need for this section?)
- The input point is taken after the buffer-out cap and resistor, essentially where the signal splits.
- Not sure if the 68k (pre signal split) should have been retained for this but thats obviously an easy fix.
- I've only left a little space for the LDR components - not sure how much space i needed.

OK caveats over with. Oh, and the last one.

THIS IS NOT VERIFIED YET. PLEASE FEEL FREE TO COMMENT.

I have attached a notated version of Bajaman's schematic for the component references.

Cheers,

Ian

Finished building mine with the Banzai 'Photo Cell 1,2k/500k' and it works well!

I used 5mm red LEDs (cause I didn't have yellow ones laying around) that I taped to the photo cell with electrical tape. I used a 10k log pot for limit as this gives me much better control for setting the limiting. The level allows for a nice amount of make-up gain as well.

Thanks Bajaman!

Hi Baja.
I built finally your opto limiter, but a took layout form DimebuGG here https://www.freestompboxes.org/download/file.php?id=1777 .
I have used audio optocoupler from banzai http://www.banzaieffects.com/Audio-Opto ... 17349.html
I think there is too much compression and usable range for "comp" knob is between 8 and 10 o'clock. When i turn knob above this range, signal is totally crushed.

How can I tune overall treshold?

If you build it to my design you won't have these problems - or use a VTL5C10 optocoupler and omit the status light
bajaman

Yeah! I solved it!

I measured LED in optocoupler and compared value on multimeter (Diode measuring - value probably respond to resistivity) with value from status LED.
It must be closest as possible and status LED should have lower value than LED in optocoupler = more current thru LED = more light = lower current thru optocoupler = not too much limiting.
For example:
LED in VTL5C10 shows about 1600 units so I've used orange LED with 1450. Yellow LED is also possible with their 1650 but orange lights nicer and stronger.
Optocoupler from Banzai have got about 1300 units = too low for my LEDs

choudy wrote:Yeah! I solved it!

I measured LED in optocoupler and compared value on multimeter (Diode measuring - value probably respond to resistivity) with value from status LED.
It must be closest as possible and status LED should have lower value than LED in optocoupler = more current thru LED = more light = lower current thru optocoupler = not too much limiting.
For example:
LED in VTL5C10 shows about 1600 units so I've used orange LED with 1450. Yellow LED is also possible with their 1650 but orange lights nicer and stronger.
Optocoupler from Banzai have got about 1300 units = too low for my LEDs

also you can buffer the second LED (indicator) with a transistor, like i draw before in this thread. It also works presumably well

Glad to see you got it working
Now try it AFTER a fuzz or distortion unit to fatten up the sound and get you closer to tube amplifier output stage feel - you cannot put how it feels to play in an MP3
bajaman

I found that combination of orange LED and VTL5C10 is just perfect! There is right range of compression and signal LED blinks optimally.
VTL without signal LED is unusable for me. It has too wide range of signal reduction.
I've tried yellow LED with VTL and it doesn't work well. LED doesn't lights only if there is strong signal peak from guitar. So in this case LED flashs and signal is in this moment totally sqashed.

choudy wrote:Hi Baja.
I built finally your opto limiter, but a took layout form DimebuGG here https://www.freestompboxes.org/download/file.php?id=1777 .
I have used audio optocoupler from banzai http://www.banzaieffects.com/Audio-Opto ... 17349.html
I think there is too much compression and usable range for "comp" knob is between 8 and 10 o'clock. When i turn knob above this range, signal is totally crushed.

How can I tune overall treshold?

I have no problems with that layout. It's all working fine.

DimebuGG wrote:

choudy wrote:Hi Baja.
I built finally your opto limiter, but a took layout form DimebuGG here https://www.freestompboxes.org/download/file.php?id=1777 .
I have used audio optocoupler from banzai http://www.banzaieffects.com/Audio-Opto ... 17349.html
I think there is too much compression and usable range for "comp" knob is between 8 and 10 o'clock. When i turn knob above this range, signal is totally crushed.

How can I tune overall treshold?

I have no problems with that layout. It's all working fine.

Yeah, layout is OK. But I'm still trying right combination of LED and optocoupler. 5C10 and orange seem to be ok. I have to try version with two LEDs and photocell.

No, VTL5C10 is not right combination.
I've finally ripped photocell from optocoupler ordered from Banzai and put him with yellow LED into shrink tubing.
Now it works perfect.

bajaman

OK. Limiter is now limiting, but for higer amount of limitation I can hear noticable distortion. SWR wrote about this behavior at the beginnig of thread. I've tried many types of opamps but this problem is still here. I'm using 3mm yellow LEDs and LDR riped from banzai audio optocoupler.