BAJA Optical Limiter revisited - rev2  [documentation]

Original effects with schematics, layouts and instructions, freely contributed by members or found in publications. Cannot be used for commercial purposes without the consent of the owners of the copyright.
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roseblood11
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Post by roseblood11 »

Try it first, and if you need a mod, ask again... :roll:

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seedseed
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Post by seedseed »

Hi everyone, I play bass and know this would be a great limiter for bass but has anyone used if for a pa application as in betweent the preamp and the main amp for a pa as i reckon it would work great but i thought i would ask the question if anyone else has tried that with this unit. I can't see why it wouldn't respond well but i guess the only way to find out is to try it. Could someone please let me know otherwise thanks :mrgreen:

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roseblood11
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Post by roseblood11 »

Doesn´t it work with bass? Have you tried it?

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diegoribba
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Post by diegoribba »

hi!
im wondering where are the project files, because i tried to enter this page members/bajaman/Baja/Baja%20Optical%20Limiter%20rev2/
and nothing!
could you upload the files somewhere else? thanks!

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coldcraft
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Post by coldcraft »

diegoribba wrote:hi!
im wondering where are the project files, because i tried to enter this page members/bajaman/Baja/Baja%20Optical%20Limiter%20rev2/
and nothing!
could you upload the files somewhere else? thanks!

members/bajaman/Baja/Baja%20Optical%20Limiter%20rev2/

works for me
Black Dynamite wrote:you need to shut the fuck up when grown folks is talkin.

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jorri
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Post by jorri »

so its fine removing the 2sk117 buffer section? I'm running it as part of a buffered blender for a particularly unstable speaker-blowing-oscillation type soviet delay unit.

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bajaman
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Post by bajaman »

I guess so as long as it is running from a low impedance source - Pete Cornish likes double buffering though, so may be beneficial left in - you can use many other jfets as buffers though - may have to alter source load resistor to compensate - will give varying current draw which may extend or reduce high frequencies and distortion products when overdriven :wink:
bajaman
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theehman
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Post by theehman »

Is there a new link for the parts list, photos, PCB, etc?
Ron Neely II
Electro-Harmonix info: http://electroharmonix.vintageusaguitars.com
Home of RonSound effects: http://www.ronsound.com
fx schematics and repairs

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Barcode
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Post by Barcode »

maybe it got nuked in the move? I'm not sure about the state of the attachments in the second move. The first move I know a lot hand to be manually restored.

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roseblood11
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Post by roseblood11 »

Bajaman, could you upload the project files again? The link is dead...

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lietuvis
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Post by lietuvis »

are you looking for these:
Attachments
la2a Label.png
la2a Layout.png
la2a PCB.png
la2a Schematic.png

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Bastelfixx
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Post by Bastelfixx »

Thanks bajaman!
:applause:

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bajaman
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Post by bajaman »

:thumbsup
thanks lietuvis
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Ihunda
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Post by Ihunda »

Great bajaman!

Could you explain how the two 1N4148 diodes to on the last opamp before the LDR led?
Are they just here for a 1.4V reference? I am not sure if that opamp just adds gain or if it also works as a comparator?

Many many thanks in advance :)

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Ihunda
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Post by Ihunda »

Well I am answering myself :)

After looking around for info, this looks like a differential amplifier and the diodes make a up a 1.4V reference voltage that is subtracted from the control signal, which is an amplified version of the input signal.

This way, the LED/LDR lights up when the signal becomes higher than the limit...

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Intripped
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Post by Intripped »

I'm studying this circuit, trying to understand the side-chain part as well.
i've found other schems in which the signal is usually rectified in order to convert it in a DC signal and control the opto-LED lighting,
(using one of these circuits: http://sound.westhost.com/appnotes/an001.htm)
but here i don't understand exactly what is going on... ihunda could you please explain it more in detail?
is the signal rectified or not?

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Post by MacGyver »

Hi,
Just finished this proyect, and it's nice!
A lot of gain and clarity!
However I want a little more of limit. I got the Limit pot full and I think I need a little more.
What can I do? Any resistor change to get a more brightness led in the LDR?
Thanks!

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aion
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Post by aion »

http://www.alliedelec.com/images/produc ... 136790.pdf

Would this be a good optocoupler for this project? On is 60R min/150R typical, off is 25M max. Although, I am not sure what to look for with the rise time.

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scaai
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Post by scaai »

I need help, please.

Build this thing following Bajaman's layout and schem. Connected it - it's motorboating. Very loud!

Looked for mistakes. Recognized that the 1N4148 diodes are reverse polarity in the schem and the layout. Corrected and connected again - motorboating.

Drew a new schem from the layout to control the differences. Everything seems right, except the diodes.
Opened the tube of the LED and the LDR to look if the LED works. Connected - motorboating. This time I can play with it dancing in front of the LDR.

Again controlled everything, reversed the polarity of the diodes again and gave it a try without them - motorboating, even when the switch ist off.

No idea what to do anymore...

Anybody?

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scaai
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Post by scaai »

And again...

Checked everything. Changed the ICs. Measured the voltages and all components. Checked for shorts and breaks. Still the same.

It is generating a really loud signal like an oscillator depending on the LDR's resistance. If it's dark the signal ist about a few Hz; in the sunlight it goes up until about 3kHz. The LED flickers simultaneous.

Could somebody please give me a hint what to check else?

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