Is it possible to add a phaser circuit to a Korg SP170S digital piano ?

[eh la bas ma]

Hello,

I would like to know if it's possible to take a phaser circuit from a stompbox, and put it into a big Korg SP-170S keyboard.
I think this would be really hard to do, because both circuits power supplies don't match, but I don't really know for sure...

here are the schems :

https://www.manualslib.com/manual/1313552/Korg-Sp-170s.html

https://www.pedalpcb.com/docs/PhaseII.pdf

The phaser is just my first idea, I am looking to give some singularity to the keyboard'sound. It features a chorus and a reverb, maybe there is something to be done with these... a distorsion before the reverb would be great too.

Finally, if someone can see something doable with this Korg, any suggestion would be welcome !

Thank you for your help.

[bluebunny]

A quick glance at that manual tells us that there's a 12V supply in there.  It's not bipolar (I can see a "V/2" designation, just like we'd have in a pedal).  So I think you ought to be able to put a phaser in there somewhere, perhaps with some adjustments for the slightly higher power supply.

[Ben N]

The phaser is powered by a TC1044SCPA configured to provide +-9v, but that assumes a +9v supply. Per the datasheet, the TC1044 is designed for an input of up to +12v, but can handle up to +13v. If the Korg PS is regulated at 12v (those schem are too hard on my old eyes to figure that out), you should be fine as is running the phaser as is, just make sure your caps are all rated for >=16v. If the phaser isn't happy at +-12v for some reason, or the 12Vin is not regulated, it's trivial to add a 9v regulator (& heat sink) to drop it down.

[eh la bas ma]

Thanks for your replies.

9v voltage regulator ?

like this ? https://www.musikding.de/7809CKC_1

Should it be soldered between the phaser pcb's +9v pad and the korg's DC power jack's + lug ?

On Korg schematics page 9 : can I connect the phaser between Q1 et Q2 outputs and both HP ? Is it the easiest way ?

[Ben N]

Yup. This is how it's used.

[anotherjim]

The keyboard 12v seems to be entirely dependent on an external PSU. There is soft electronic power switching from that but I'd be tempted to fit a 7809 running off the incoming  12v socket to avoid damaging the keyboards circuits.

The sounds are entirely digital. If you can find the DAC board it has opamp output buffers and the output from them can be cut and diverted through DPDT bypass switching for the added fx.
The keyboard is stereo, most pedal fx are going to be mono. How do you want to deal with that?

[ElectricDruid]

Rather than add a phaser into the piano, what I'd do would be to wire an effects loop in after the post-DAC filter and before the power amp. Since those are on different boards, that shouldn't be too hard to do. Then you'd be able to easily experiment with phasers, distortions, whatever you like, and you're not limited to just the effect you have now.

Since the outputs from that 5532 already have 10uF DC blocking caps, it's all pretty much done for you (no need for extra buffers or anything). I think it could be as simple as a pair of jacks, with the NC connections normalled so the sound still goes through from one jack to the other when nothing is plugged in.

However, there's one twist that Jim mentioned, which is it's in stereo! So you'll need to start building two of everything!

[eh la bas ma]

The keyboard is stereo, most pedal fx are going to be mono. How do you want to deal with that?

I guess it can't be as simple as doubling the wiring and have both R and L channels going and coming out of the effect ?

Edit: I like ElectricDruid's idea about an fx loop out of the NE5532DR (schematics p.6).

I built a Processor (and it's a great tool, it was a good surprise).

https://diy.thcustom.com/download/pro-cessor-v4-2-build-instructions/

maybe I can use a similar circuit to mix the signals ?

[PRR]

Because this thing is stereo, also not made for hacking, I'd ask if you have a guitar/keyboard amp on hand? Tap signal from ahead of the Korg's power amp, mix and attenuate, go out to phaser/fuzz/ottotune, then to a guitar/keyboard amp.

We ought to mute the power amp, and there is a pin for that, but more study needed.