Upgrading a CS-9

[Bernardduur]

Hello all!

I have a friends Ibanez CS-9; he is kinda a audiophile and wants to get rid of the (tiny) amount of hiss the unit produces.....

When I opened up the pedal I spotted three TL022's  and one LM741 (next to the normal components ) so I guess it will sound better if I replace these IC's. Also some caps can be upgraded

Any thoughts on this? Can I just swap the 022's with, for example, 072's?

Schematic of the Ibanez CS-9

One thing I spotted (dunno if it is a great thing); C126 is not on the board, R144 is 10M instead of 22M

[MartyMart]

Yup, TL072's and an NE5534 for the single opamp should help

MM.

[Mark Hammer]

Um, before anybody gets their soldering iron heated up, IC101 is the only op-amp always (EDIT) in the audio path.  Everything else is involved with either modulation circuitry or, irony of ironies, noise reduction.

That's right, folks.  The 741 is for purposes of noise reduction.  "But, but, but...but", you say "that simply can't be!  How could a lowly 741, known for its inferior sonic qualities, be part of the noise reduction?"

Simple.  Look at the schematic for the CS-9, and the schematic for the venerable A/DA Flanger and the similarly venerable Boss CE-1, and you will see that IC106 is actually an envelope follower (note the two diodes on its output?) that controls FET Q104.  When there is no input signal present, Q104 gets turned on (resistance goes low) such that any residual clock noise and hiss from the delay chip is severely attenuated.  When the input signal is resumed, Q104 gets turned off (resistance goes high), such that there is no attenuation of the delay path and you hear the full delay signal.  It is a noise gate specific to the delay path.  Because the dry signal is on all the time and is unaffected by this gate, you won't hear any choppiness at the start or end of notes, merely a sudden appearance and disappearance of the effect....if you listen REALLY closely.

So, if you want to, you can replace IC101 with a TL072, an NE5532 or an LM833 to reduce that particular source of hiss, and you can also do the same for IC105 if you use the pedal in stereo all the time (ignore IC105 if you're a mono-only sorta player) but leave everything else exactly where it is.

[Bernardduur]

Thanks man!

This is why I rather make questions then go and solder

[MartyMart]

Sorry Mark, I jumped in with opamp choices before looking at the schem !!

Probably due to recently removing the TL022's in my GE-7 thread ...

MM.

[Mark Hammer]

No problem.  With over 8000 postings, I  have probably logged as many "shoulda-just-kept-my-mouth-shut-and-waited" postings as any 50 people here.