freestompboxes.org

Here's my board I did with ExpressPCB. 2-sided with all resistors and non-electrolytic caps in SMD. The pcb fits easily into a 1290NS box.

Nice! You did the solder work? Looks more than pro!

Duckman wrote: Nice! You did the solder work? Looks more than pro!

Thanks. I do this stuff all the time at work.
Here's my work site where you can see other examples: http://www.polyphasemicrowave.com

I knew it!

OK question for someone with a little more experience than me.... How to convert circuit to Bipolar supply.

If I wanted to run this circuit from a bipolar supply (+12V -0- -12V) is it just a case of all the 1/2V connection points on the schematic going to ground and the ground (Black bars) being tied to the negative rail?

It just that I would like to include it in a unit I am putting together and the other circuit has a bipolar supply...

Any advice greatly appreciated
regards

Kevin

Just to be clear on what I was thinking...

here is a schematic of what I was proposing...

as I will have a single opamp unused, I was thinking to drop the fet input buffer and use the opamp configured as a buffer...

Regards

Kevin

Hi,

I was wondering the same as KB. My intention is to build a rack-mount stereo version, minus the JFET buffer, with an opamp buffer and using symmetrical -9 / +9 volts. In that case, would it be safe to just use GND for everything labeled "1/2v" in the schematic? Would it be necessary to add some more diodes to the existing two? Also, probably the LED resistor should be adjusted as well.
Thanks in advance,

David

Hi Everybody!

I did that pedal and i have only one problem - sometimes it distort the sound ( espessialy with the bass guitar ) or it almost no effect at all depend of leds/optocouplers/photocell.
I tryed all types of leds that i have , a lot of different photocell, few optocouplers and i cant get rid of distortion or i cant get evident effect of limiting.

Something is wrong in that project?

My Question Is : did someone found perfect combination of leds/photocel/optocoupler that have no distortion and you can hear limiter is working and if it hard limiting you can gradually decrease it?

Im not professional pedal maker like some guys from here , so i can not say what is wrong in schematcs, i just take schematics from here and i trust to engineer who did that project that everything is correct, i start building my exact copy, but after hours of soldering, drilling box and spending money ( almost 70 euros in Banzai shop ) project does not work as it should - so it is quite sad.
Sorry guys, but it is very upset sharing project with others that is not 100% fine working it is just waisting money and time.

Inside of the pedal

a bit off track but i think i can get some help here/
i build the rev 1...the file with BAJA OPTICAL LIMIT label on the pcb layout.
Fix the reverse polarity on the diode....all 3 diodes.
Using VTL5C10 and 2n5457 with leg bended for input buffer.
When engaged, it sounded very dimmed, lower than unity gain and the limiter knob is not really doing much.

May i know where do i start troubleshooting?

I finally fixed all dead links in the first post, sorry it took so long...

KB wrote: ↑12 Dec 2012, 20:38 Just to be clear on what I was thinking... here is a schematic of what I was proposing...
as I will have a single opamp unused, I was thinking to drop the fet input buffer and use the opamp configured as a buffer...

Sorry to play thread necromancer here, KB, but did you ever have any luck with this? I'd like to add this to a larger +-15V build I have as well.

I think the easy part is replacing the power rails: +9V with +15V, +4.5V (Vb) with GND, and 0V with -15V. I am not so sure about the LED driver circuitry:
- Will the LEDs survive the much higher voltage?
- Do I need to re-calibrate the driver circuitry to account for the much larger headroom in the signal path?

The LED driver circuitry also has that strange circuitry w/2x diodes + 4.7K resistor, which PaulC said is to bias the LEDs so they don't "cold start" the LDR:
"Putting a DC offset in will allow the LED to have a little "soft glow" at quiescence. This will get them started early so you don't have a dead spot in the curve while you're waiting for enough signal to get the leds to start lighting up. Gets everything in a nice working range at the start."

Hello, sorry taking my time replying, I don't get as much time to play as I used to.

Short answer. I gave up.

I ended up running one on 18V, not sure if it is any better than 9V as I have never tried it. To be honest I wasn't that impressed with the effect - but that is probably down to LDR / LED combination I used - I rolled my own photocell.
Your question has sparked my interest again, maybe I will have another go.

Seasons Greetings.

Kevin

So after about 30LDR turning up …

The recommended LRD1 from futurlec are the same as this from musikding https://www.musikding.de/LDR-30k-90k-5M
And some from eBay labelled GL5516

Obviously I could be wrong but might be useful!!

I think I'm wrong

maybe. I've got the distortion when the thing comes on thing happening. And reading the two posts no idea how to fix it!

Right it works

As a mod I added a switch that bypasses the 2k7 resistor … mainly as I saw that that’s what the comp/limit switch on a real LA-2A does - it changes the sound but I need to experiment a bit to find out what what it’s really doing…

Comparing it to the LA2A sim in my HX stomp it’s the same ballpark

I’m possibly going to need to do some modding as all the comp setting is at one end of the comp pot and it would be nice if it could be a bit more extream at the end of the pot if that makes sense…