Ibanez - CP-9 Compressor/Limiter  [schematic]

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
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The Rotagilla
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Post by The Rotagilla »

If you have a factory schematic I would be most appreciative. Thanks.
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MoreCowbell
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Post by MoreCowbell »

well...its not the factory schematic, but tonepad has a cp9 project...maybe the schemo there could be of some help ?

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The Rotagilla
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Post by The Rotagilla »

Saw that one and I'm sure it's correct. I just try to grab factory when I can. I'm a little obssessive that way. :D
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Post by estragon »

Though it is not the same, you might be interested in a (supposedly) factory scan of Ibanez CP-10 Compressor.

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Post by The Rotagilla »

estragon wrote:Though it is not the same, you might be interested in a (supposedly) factory scan of Ibanez CP-10 Compressor.
If you have one that would be great!
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Post by Dirk_Hendrik »

Something like this? (and do study the differences between a 9 and a 10)
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CP9.pdf
I don't recall where I got this either ;)
(278.64 KiB) Downloaded 1413 times
Sorry. Plain out of planes.

http://www.dirk-hendrik.com

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Post by moshe_dol »

im looking for a mod for the cp9 do you know a mod to reduce the high end trable or to make an eq on the cp9

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Post by The Rotagilla »

A belated thanks for both.
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Post by moshe_dol »

hi i got an ibanez cp-9 compressor i want to remove the high pass in the input . remove R101 and C101, does it possible ?? and i want to increase the amount of compression

thank :popcorn: :horsey:

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Post by analogguru »

The search button can be found on the top-right corner - even for new members.

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Post by moshe_dol »

i have searched but didnt found answer to my quastion.
can anybody help me ?

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Post by gght »

Guess no one had an answer to this old thread???

I recently picked up a CP10 dirt cheap on the bay, and in some ways like the sound. BUT, I realized quickly why I have always quit using any compressor. They all seem to rob the low frequencies out of the signal, leaving a thin sound (at least to me). I am guessing this is because the lower strings/frequencies are a hotter signal than higher frequencies, so the output to the control input (pin 4, ba6110) is a relatively hotter signal causing the compressor to compress lows more than higher frequency signals. I hope this thinking is correct!!!

So, I am wondering if someone can tell me, would it be possible to add a simple highpass filter to ONLY the signal to pin 4, causing the compressor to react more to highs and less to lows??? If this would work, can you suggest the values for a filter??

Or, have I TOTALLY LOST MY aching old brain??

Any help would be much appreciated!

Dave
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Post by gght »

No one????? Hmmmm??? Must be a bad idea.

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Post by rocklander »

I built the tonepad version, and am not sure about what I set the trim in relation to.

I tried the 150K that comes off pin 10 (and 12, on the 47uF side [near the trimmer] - cos this is what was suggested in the ibanez PDF in this thread), but no joy, however it does make a difference on the 150K on the trimmer side of pin 13.. is that where I should reference the trim to?
if so, should I trim it to 0V with all other pots set at full? cos I can't.. best I can get with the 10KTR is low 1.(something)V.. that's at full trim.. less trim the volts go up till rail voltage.

anyone got some suggestions for me?
cheers in advance
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Post by Liquids »

gght wrote:No one????? Hmmmm??? Must be a bad idea.
I had one bread boarded recently--similar to the tonepad version of the CP9/Ross, etc. They're all pretty similar, however You'd want to verify the similarity between yours and the schematic since you're working off a PCB.

I didn't go to far with it, but I here's my theory, since no one else more versed chimed in....

Apart from input cap thing to control the bass (I don't see why you need to shave frequencies much at the input or output, personally)... The OTA feeds a darlington buffer built onto the same chip. From this, the output signal is taken off the emitter of the buffer, AND the phase splitter input is fed off it as well. This is superior to the Ross, in my opinion, and allows for some more potential tweaking than the Ross, etc. My impression is that the phase splitter is what feeds the 'sidechain' that goes back to the OTA etc and compresses....I'm thinking that if you reduce the two caps that feed off the collector and emitter of that transistor, it will reduce bass in the sidechain....give it a go and tweak to taste, see if it helps. May need to go small to really get somewhere given the 1M resistors....not sure of the impedance. Tweak by ear. I liked the CP9 it better even in a simplified version on the breadboard than I did my old compROSSer, in fact. The proper buffering of the inputs and outputs goes a long way in this pedal. Not sure how your version compares to the tonepad, however.

Also, don't be afraid to compare the Boss CS-2, the Marshall ED, Saffron Squeeze, and of course the dynacomps and the Ross to the to the Ibanez CP schematics, etc. They're all working off about the same core circuitry/concept. May give you ideas. Breadboarding and A/Bing may help you figure out what you want and what values and mods sound good to you before you do too much work on the actual board.

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Post by bluesmansway »

I stumbled accross this thread and felt compelled to join and give input. I've been doing this a long time and keep finding I still have a lot to learn. I played hard out of Nashville for about 20yrs (blues/jazz/soul) and had to learn to work on my own gear as well as being a tone junky. Now I have three children and am in recovery from tone addiction. Ok, so now I'm a closet junky with socker dad van and only get to play every now and then when I'm not rollin with the kids whom I love to death. I'm sure there may be better or other ways to do this. This is just what I came up with.
I have conquered the CP 9 tone issue with a mod that is inexpensive and pritty basic. The mod does not have to be perminent and can easily be removed.
The boss cs 2 (vintage) was always what I used because if anything it was slightly dark (blues, jazz). When I bought a cp-9 I noticed the mid/treble and not so much the bass. I decided to make an adjustable low pass filter for it. It's a common circuit but I made a creative application that makes it very conveninent. I found that when I rolled the treble off it was not as loud and as I turned it up, ahhh there's the bass. The CP 9 with this mod blows the boss out of the water. Why? Cause for some reason no one ever put a tone knob on any of them. I was able to match my compressed tone with the tone when I wasn't using it and that's exactly what I was looking for. Now when I press the compressor, it doesn't change my tone.
Here's how I did it. They make some real small pots (PC mounted) that you turn with a screwdriver. These are made to go inside electronic equipment and to ocasionally be adjusted. You will find that once you get the tone right, you will not want to adjust it anyway. I have a pile of junk circuit boards from thrift stores/ect laying around and pulled a 10K variable resister pot out of one and then attached it to a .01uf cap = Instant low pass.
Here's the installation.
I wanted to access the pot without taking the back off all the time so I attached one end of a wire to the volume lug of the compressor and then attached the other end of the wire to the lug on the pot (you need a long enough wire to reach into the battery compartment of the compressor so that you can pull the pot out of the compartment to adjust the tone). Next I came off of the other lug on the 10K pot and attached it to one leg of the cap and the other leg of the cap to ground. This puts a low pass filter in your battery compartment. You will notice that there is not much room in there. I took a piece of shrink rap that would slide over the pot and just used it as an insulated sleeve to keep the contacts from touching the battery or the chassis. I slide the pot down at the non contact end of the battery in the compartment. You will also want to make sure to use short legs on your cap and use more wire so your leads don't touch anything it's not supposed to. I used a little piece of electrical tape to insulate the cap and leads from everything else.
To dial it in, open the battery compartment, pull it out, take the boot off and you can push your bypass button on your compressor on and off and listen to the tone as you dial the tone in with a little screwdriver. The little pots I use look like little tires and I have been calling it the spare tire mod.
Now just dial in the tone with the compressor on, with the compressor off. Cool.
Here is my personal take on dialing in guitar compressors.
First put them near the begainning of the effects chain if not first. Definitely before the drive.
I personally do not like to squish my attack so I have the attack knob turned all the way down so the compression comes in more slowly and doesn't squash my attack. To me this sounds more natural. I adjust my sustain knob next and toggle the compressor on and off and hit notes and let them ring. I do not go past doubling the natural sustain of my guitar or the tone sounds very squashed. I try to just inhance the sustain. I know when I crank up my amp on stage it will have extra sustain on its own as the guitar and amp interact. At low volumes you may want more sustain. Then I adjust the volume to be just a hair higher than the bypassed volume. This will give you natural attack, realistic compression and sustain and strong volume. The idea is to inhance your natural volume not to try to fix a poor sounding amp or guitar.
I hope this helps. It's an expensive thing to learn all the lessons of tone. I have spent a fortune and continue to go back to simplicity. I believe true tone is in your hands. Good gear helps that tone to be heard for what it is.
If you can't work out the room to fit it into the battery compartment, I'm sure you can find room inside somewhere for the tone control. Be creative. Have fun. All you gurus let me know if I have misstated anything here. I think I included everything. Have a great day!

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Post by danickd »

Hey, Man
Here's Ibanez CP-9 Original Schematic ...
Enjoy!
Danick,
Denver CO, USA
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Ibanez 80's CP9 Schematic .pdf
Ibanez CP-9 Original Schematic
(219.42 KiB) Downloaded 678 times

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Post by phatt »

moshe_dol wrote:hi i got an ibanez cp-9 compressor i want to remove the high pass in the input . remove R101 and C101, does it possible ?? and i want to increase the amount of compression thank :popcorn: :horsey:
Do you mean longer sustain? As more compression would sound horrabillas. :?
If anything most of the stomp box circuits actually LACK any control over compression depth.

On some circuits you can back off the depth a little by adding series string of diodes or just swap them for Leds.
I found that had a positive effect,, i.e. sounding less like a compressor but still retaining a fair amout of sustain.
Cheers, Phil.

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skydragster
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Post by skydragster »

Hi Bluesmansway.
I like the idea of your mod and Im in the process of doing this to my CP9.

One question, which lug on the CP9 volume pot did you attach the lowpass filter to?

Thanks

Skydragster

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