Adding a mix control to an Ibanez CS-9 chorus

[Headshot]

Hey all,

Anyone know how I might go about adding a mix control to an Ibanez CS-9 chorus?  I really like the chorus sound, but sometimes it's a little too much.

Thanks,

Head

[Mark Hammer]

I haven't got the schem handy, but here's an educated guess.  

With most choruses, there will be an op-amp mixing stage just before the output.  The FET used for bypass switching will actually be a kind of controllable barrier between the wet signal and this mixing stage.  There will be usually a pair of equal-value resistors for combining the dry and wet in equal proportions at the mixer input.  If you prelace the resistor in the wet path with a) the next standard value below it, and b) a pot with the closest standard value about 5 times larger/higher, you'll be able to do what you want.

For example, if the mixing stage used a pair of 47k resistors to combine wet and dry in equal measure, replace the 47k wet resistor with one that is either 43k (sort of standard) or 39k (more standard), and a 250k pot, wired as a variable resistor.  As the series resistance of the 39k+pot increases, the wet signal will fade into the background more and the chorus effect will be subtler.  The reason why I recommend the 39k in this instance is that most major manufacturer pedals will use 5% resistors.  The wet mixing resistor could be a bit lower within that tolerance than the dry one, or vice versa.  You don't know, and Ibanez probably doesn,T either.  

Maximum chorus effect is achieved when the wet and dry are combined in precise 50/50 fashion.  With 5% resistors, your unit may well be currently 49/51, or some other combination that yields a bit less than the maximum chorus effect attainable.  From your request, that may actually be preferable for you, but allowing yourself a slightly lower resistance for the wet signal, incombination with the capacity to increase resistance (via the pot) give you the option to nail a perfect 50/50 balance when you want, and achieve subtler effects when you want.  The 250k pot in this example won' *completely* cancel the chorus effect, but of course that's what the footswitch is for, isn't it?

[bwanasonic]

Have you tried using the trimmers inside the pedal? I believe one of them is a *bias* control that you can use to fine tune the amount of chorus effect. If it is the same as my CS505 (the predecessor to the CS9), there should be two trimmers - one labeled "clock", and one labeled "bias". The clock control acts as a depth control, allowing for a range from chorus to more flanger like sounds. You can also get some strange noises by handling the edges of the clock trimmer while playing :twisted: .

BTW- Just realized I have a somewhat legible CS9 schem (116k gif, yes there is a bias control). If you look around you ahould be able to find the same one I did, but I can email it to you if you like - PM me.

Kerry M

[Headshot]

I found a copy of the schematic, and am looking it over.  Thanks for the help guys!

H

[Mark Hammer]

Have you tried using the trimmers inside the pedal? I believe one of them is a *bias* control that you can use to fine tune the amount of chorus effect. If it is the same as my CS505 (the predecessor to the CS9), there should be two trimmers - one labeled "clock", and one labeled "bias". The clock control acts as a depth control, allowing for a range from chorus to more flanger like sounds. You can also get some strange noises by handling the edges of the clock trimmer while playing :twisted: .

BTW- Just realized I have a somewhat legible CS9 schem (116k gif, yes there is a bias control). If you look around you ahould be able to find the same one I did, but I can email it to you if you like - PM me.

Kerry M

Whoa there, camel!!!

The bias control adjusts the DC voltage that the audio sits on, going into the delay chip.  This needs to be optimized or the signal drops markedly in quality, and if set wrong the delay signal disappears.  Feel free to monkey around with it to get optimal tone, but do not use it for adjust effect intensity.

One way, seldom discussed, for achieving a subtler chorus sound is to roll off the low end of the delay signal higher up, such that there is little chorussed fundamental, but mostly an "animated" group of harmonics.

To do this, identify the last cap in the delay signal path before the dry and wet are mixed, and simply drop its value to 1/5 the original or even a bit less.  So, if the wet signal went to the mixer via a 1uf cap, you could replace that with a .1uf to .22uf cap.  That proportion would depend on the original rolloff point.  If the original cap rolls off bass at 5hz, then a .1uf cap would roll it off around 50hz, which is still not enough to make a difference.  There, I would suggest .01uf instead.  I did it to my Zombie, and it makes a heckuva difference.

[domenico]

http://www.generalguitargadgets.com/diagrams/IbanezCS9.gif

this is the schematic , can someone help me adding a mix control to an Ibanez CS-9 chorus?
thanks
domenico

[Mark Hammer]

R126 and R133 set the amount of delay signal mixed in with the dry signal.  Increasing the value of either will decrease the intensity of the chorus effect.

Depending on your taste you may wish to do such a mod to one of the two outputs (the easier mod to do) or to both.  In general, a 250k pot wired up as a variable resistor in series with the 82k component, should provide the degree of subtlety needed.

[sandro]

Hi everyone, I read all the post with attention and I understood what kind of mod to do on the wet-mixing resistor. Now, I'd like to locate the same resistor in the ARION SCH-1, because I like the pedal but in some cases I find the chorus too present. Thankyou guys!