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audioguru
 Post subject: Op Amp swap.
PostPosted: Fri Aug 27, 2010 8:07 am 
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I have changed my OptiComp Op Amp for a Burr Brown OPA2604 and it made all the difference in the world!!!!!!

I have lots of high and definition that I couldn't get with the cheap 4558.

Just want to let you know.

Pascal Sauvageau.

P.S.: I've read about all the mods you guys came up with and I ordered a new case and all the parts to mod my compressor, can't wait to try it!!!

http://www.oftsmusic.com
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khekwenyes
PostPosted: Mon Jan 03, 2011 3:32 pm 
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Shot in the dark here, but...
In reading the mods for the delay, there is mention of an effects loop so that the delayed signal could be modulated of phased or what have you...
Image

Is there a way to use this same principal on the 5 knob to achieve sort of a side-chain kinda deal?

Say, for example, a 5knob with a parmetric eq (or any old boss eq pedal) in the loop to boost/cut certain freq's of the compressed signal automatically, like a de-esser would work.

make a slap bass more punchy and less muddy in the lows, that sort of thing?

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coolhand
PostPosted: Wed Jan 05, 2011 2:45 pm 
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I think what you are doing is possible. After some assistance from some of the others mods we have come up with some ideas. I haven't really ever tried it or even thought of doing it myself.

Image

Image

It really depends on if you want the loop to be pre or post compression? R30 (post compression) looks like a good place to start since that is last place the wet signal goes before the blend knob mixes the signals.

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Wilkie1
PostPosted: Fri Aug 05, 2011 11:22 am 
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Coolhand mentioned a mod for the opticomp that adds an LED that shows compression taking place. Can this be done on the 5-knob? WHere would you insert the LED? Would you need a CLR as well?

I'm just starting assembly on a 5-knob.
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coolhand
PostPosted: Fri Aug 05, 2011 11:51 am 
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The compression indicator for the opticomp is based off the extra leg of the vactrol that controls the compression. I don't have any idea how you would incorporate that idea into the 5-knob design.

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Wutz
PostPosted: Sat May 05, 2012 2:01 am 
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coolhand wrote:
Opticomp adding LED to indicate compression:

I have figured out a way to add the compression indicator LED to the design. This is an additional LED and not the bypass/on LED. To add it you will need to drill another hole in your enclosure. The bypass LED still functions the same but the new LED will indicate when the pedal is compressing your signal.

It is pretty simple, on the new board all you have to do is connect the positive side of the LED to bottom leg (closest to the footswitch) of the octocoupler on the side with 3 leads. (on the old board - the rightmost leg on the side of the octocoupler with 3 leads). This lead has no connection to anything else on the board. It is only connected internally in the octocoupler. I then attached the other leg of the LED to ground on the outlet jack or anywhere that is grounded.

When you strum a string the light lights up completely but it fades as the compression fades. The more the compression is turned up the longer it stays fully lit up before it starts to fade. Notes that are picked gently don't fully light up but the indicator works just like it is supposed to.


My opticomp came with the four-leg optocoupler - is there any way to do this "led to indicate compression" mod with it? I'm planning on doing the release mod at the same time if I can do the led mod, too. What's the best way to keep a floating pot from shorting on the leads on the solder side of the board?

So far the attack mod and a swapped resister value have helped this thing be more up my alley, now I just need to get the release time to speak to my playing style...
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Tark
PostPosted: Sat May 05, 2012 10:34 am 
If I understand this correctly - the vactrol with five leads has two Light Dependant Resistors inside it, both illuminated by the same internal LED. The compressor circuit only uses one of these LDRs so if you put an external LED in series with the unused LDR that LED will illuminate in synch with the vactrols internal LED. This cannot be done with the 4 lead vactrol.

But you can get the same effect by connecting a high impedance FET stage (to drive an LED) to the time constant cap.
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Bassman
PostPosted: Sat May 12, 2012 7:27 pm 
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coolhand wrote:
Adding Release Pot: Remove R10 (4k7) and replace with a 1k resistor and a 50k pot in series to be able to adjust the release time.

Connect one leg of the 1k resistor to one of the empty spaces from the 4k7 resistor. Now connect the other leg of the 1k resistor to lug 1 of the 50k pot. Lastly, connect lug 2 of the pot to the other empty hole from the 4k7 resistor.


Is there any way to use a 100k pot with this mod? I only ask because I have a ton of those on hand and no 50k's atm. I am about ready to box up my opticomp build and am considering this mod but don't really want to wait for items to be shipped if I can use what I have on hand.

If not no biggie I can live without the release mod. Thanks in advance.
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coolhand
PostPosted: Sun May 13, 2012 11:06 am 
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Bassman wrote:
coolhand wrote:
Adding Release Pot: Remove R10 (4k7) and replace with a 1k resistor and a 50k pot in series to be able to adjust the release time.

Connect one leg of the 1k resistor to one of the empty spaces from the 4k7 resistor. Now connect the other leg of the 1k resistor to lug 1 of the 50k pot. Lastly, connect lug 2 of the pot to the other empty hole from the 4k7 resistor.


Is there any way to use a 100k pot with this mod? I only ask because I have a ton of those on hand and no 50k's atm. I am about ready to box up my opticomp build and am considering this mod but don't really want to wait for items to be shipped if I can use what I have on hand.

If not no biggie I can live without the release mod. Thanks in advance.


That will still work. The usable range of the pot will probably become smaller but it will still work.

You could add a 100k resistor across both outside lugs of the pot to bring that value down closer to 50k.

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Bassman
PostPosted: Sun May 13, 2012 1:12 pm 
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coolhand wrote:

That will still work. The usable range of the pot will probably become smaller but it will still work.

You could add a 100k resistor across both outside lugs of the pot to bring that value down closer to 50k.


That is good to know! Thanks!
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willembad
PostPosted: Sat May 26, 2012 9:01 am 
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Did the attack and release mod to the Opticomp and figured I'd post pics. This is a great compressor!

Image
Image
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thedetroit88
PostPosted: Fri Dec 28, 2012 7:35 pm 
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coolhand wrote:
Opticomp Mods:

Adding Release Pot: Remove R10 (4k7) and replace with a 1k resistor and a 50k pot in series to be able to adjust the release time.

Connect one leg of the 1k resistor to one of the empty spaces from the 4k7 resistor. Now connect the other leg of the 1k resistor to lug 1 of the 50k pot. Lastly, connect lug 2 of the pot to the other empty hole from the 4k7 resistor.


Would this be a linear taper or an audio taper? Thanks.
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Tark
PostPosted: Sat Dec 29, 2012 10:32 am 
Well the pot shown in the example pic is a B law, a linear pot.

I guess we do perceive 2 seconds as twice as long as 1 second and 3 seconds as three times as long, so a linear pot seems appropriate.
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desire
PostPosted: Thu Oct 16, 2014 7:05 am 
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Just wondering if anyone has any results to share in regards to modding the 5 Knob for bass? I've just a bought a bunch of resistors and capacitors to experiment with but I'd like to minimise the time spent desoldering.

If not I'll post my results here. I've built a 'stock' 5 Knob already so I'll be able to compare the two pretty accurately.
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duhvoodooman
PostPosted: Thu Oct 16, 2014 7:56 am 
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Just a thought, but if your intent is to purchase a second 5-knob comp kit to modify for bass, why not just buy a kit that's designed for use with a bass?

http://buildyourownclone.com/bassfx/paracomp.html

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desire
PostPosted: Sun Oct 19, 2014 1:20 am 
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duhvoodooman wrote:
Just a thought, but if your intent is to purchase a second 5-knob comp kit to modify for bass, why not just buy a kit that's designed for use with a bass?

http://buildyourownclone.com/bassfx/paracomp.html


Definitely good advice! Unfortunately, I don't play bass and I already own two 5-knobs. I built one for my girlfriend and in the interests of not building the same circuit twice, I thought I'd try my hand at modding the second.
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slayer666
PostPosted: Sun Dec 07, 2014 12:36 pm 
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I ended up installing a VTL5C4/2 (5 leads) and installing the compression status LED with that. I have the Attack Mod installed too. When the pedal is set to fast attack the status LED flickers as the compression gets lower. It doesn't do that in medium or slow attack. Can I do anything about the flickering?

I also noticed that I have some unwanted distortion when I plug in my Music Man Stingray 4. It dissappears when I turn the pedal off or lower the output of the bass. Will 18V to the optical compressor fix that or can I make the input padded somehow.

Help please!
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bjfly17
 Post subject: Re: Mods for 5-knob comp
PostPosted: Sat Apr 25, 2015 3:25 pm 
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coolhand wrote:
Possible Mods to increase bass for 5-knob

C6 - increase size, possibly .001uf, .0022uf, .047uF
R8 - increase if C6 increase is causing clipping or if active bass has too much output.


I tried these out with the following results shown in this picture. I ran my amp through Ableton and monitored the frequency output of an open E chord.

In summary, .001uF sounds great and I highly recommend this mod to retrieve your guitar's natural bass response.


Attachments:
5 knkob comparison.png
5 knkob comparison.png [ 156.16 KiB | Viewed 15190 times ]
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douglas_fir
PostPosted: Mon Sep 02, 2019 8:46 pm 
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Does anyone know which one C6 was? The image in Coolhand's post (from Thu Oct 01, 2009) is broken. I'd like to try changing it to .001uF on my 5-knob.

Thanks,


Last edited by douglas_fir on Tue Sep 03, 2019 9:40 am, edited 1 time in total.

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duhvoodooman
PostPosted: Tue Sep 03, 2019 8:02 am 
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Assuming that you're referring to the current rev.2.0 version of the 5-knob comp, it's the small ceramic cap at the bottom left side of the PCB:

Attachment:
5-knob_C6.gif
5-knob_C6.gif [ 120.01 KiB | Viewed 7238 times ]

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douglas_fir
PostPosted: Tue Sep 03, 2019 9:45 am 
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Hi duhvoodooman,

I appreciate your time and efforts. I believe that the discussion in this thread is so old that it does not use the numbering from the current schematic. For example when coolhand said "C13/R17 - Try a larger cap/smaller resistor" - these two components do not form a high-pass filter on the current schematic. Perhaps I could start fiddling with the circuit myself, but bjfly17 actually went through the efforts of swapping components and I would like to take advantage of what he learned.

Thanks much,
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coolhand
PostPosted: Tue Sep 03, 2019 11:42 am 
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I uploaded a new pic to replace the old pic. Somehow I still had that pic from 2009!

These pics were courtesy of Stephen.

Attachment:
5-knob.jpg
5-knob.jpg [ 143.99 KiB | Viewed 7221 times ]

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douglas_fir
PostPosted: Tue Sep 03, 2019 11:08 pm 
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Cool, thanks coolhand. I'm actually working on a current board but I was digging around looking for information on increasing bass response. I took a look on Archive.org and found the schematic from 2009, thinking it would have different numbering, but it turns out it hasn't changed much. I don't understand these things well enough to see how the other mods you described would effect the bass response, but I will start by changing C6 to see if it has the desired effect.


Attachments:
File comment: 5KnobComp_Rev_1.3
5KnobComp_Rev_1.3.png
5KnobComp_Rev_1.3.png [ 406.96 KiB | Viewed 7207 times ]
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