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Has anybody done a DIY audio in? I own Kawai ES-110 and it needs this hack. Thanks.

I can imagine two slightly different approaches
- Just make the sound go to the speakers. (Easier? Less risky? Just tap into the speaker cables?)
- Make the sound to mix with the signal that goes into the headphone sockets too. (More intimate soldering on the PCB perhaps?)

I guess you'd be happy with the first one.

And no, I haven't done it myself.

Basically, you'd need to find the line signal and insert an audio mixer circuit. A simple passive mixer circuit with just a couple of resistors might work, but that'd depend on the compatibility of the external source you'd want to mix in.

Nobody who can do this would bother. Get an external mixer and speakers.


Specifically the spot between the DACs generating the signal, and the audio amplifiers/routing. Which is going to be 2-3 traces on a PCB somewhere. They'd have to be cut, and an appropriate mixer inserted.


Almost certainly not. Anyone doing this should plan on putting in at least an op amp mixer, as that will be sufficiently high impedance to work with anything.


You'd have to supply your own amplifier for the speakers, and put in controls to ensure that your amplifier, and the built-in amplifier don't both attempt to drive the speakers simultaneously. (Required to prevent the amps from destroying each other.)

Sell your keyboard and get a better one. You'll save in two ways:

1- You saved in buying hardware for your DIY that most likely will be a cheapo solution and will look extremely ugly.
2- You will save money when you are going to sell your keyboard because I'm 200% sure if you DIY anything you'll ruin it aesthetically.

So do yourself a favor and just simply change your keyboard. It'll be cheaper than getting a mixer and speakers! Much cheaper!

Abdol, you're not considering the fun factor.

I understand SSS likes ES110 for more than one reason and intends keeping it. So modding is definetly an option as long as he manages doing it without burning the instrument. If he is handy with electronics, then it is doable.

I would start by dowloading the service manual and looking at the block diagram. With it, it is possible to identify the key components, power amplifier included. Probably Kawai uses some standard IC which data sheet can be obtained and from that, it may be possible to guess what to do next. It may be as simple as adding some passives (resistors/capacitors/protection diodes) or it may require assembling an small op amp amplifier to mix the audio sources. Its not a no-risk operation but, who knows?

I don't think the service manual is necessary. The wires that go to speakers can be directly fed into a dead-simple mixer module like this:

https://www.instructables.com/Making-an-Audio-Mixer/

You lost me here. My understanding is the OP wants to add an line-in input, so that he may mix piano sound with an external audio source. Sou he will need to add the line-in connector and, at a minimum, two resistors that are connected to ES110 audio amplifier. That is where the block diagram in the service manual (easily found and dowloaded from the internet) may help.

The service manual is indeed available.
https://www.manualslib.com/manual/1249306/Kawai-Es110.html?page=16#manual
Not sure from the block diagram if the relevant line signal before the "Power AMP" is easily accessible. And if the dead-simple mixer module Abdol suggested would work with no issues, depends a lot on luck with signal levels and impedances and such. More elaborate op-amp based mixers are beyond a simple hack.

That "dead-simple mixer" may be suitable as a line-level mixer. But the suggestion that it be connected to the speakers is absurd.

The service manual has only a block diagram of the piano ... so it's no help in finding the audio amplifier on the PC board.
All that can be said is that the mixing point is here at the blue dot ...

^^^This.



I suggested the block diagram as a guide to help to visually inspect the main board (which in ES110 carries the audio amplifier) for the point where the external input could be mixed. I did not mean it is necessarily easy, most likely it will require adequate electronics skills.

OK, now I understand Abdol's post. However, my undestanding from other threads is SSS wants to play an external source (e.g. song played by a smartphone) through ES110's speakers. If I misunderstood it (and/or memory failed me), then I agree that is a good suggestion.

Maybe first practice with some $10 thrift store keyboard. 😉

> However, my undestanding from other threads is SSS wants to play an external source (e.g. song played by a smartphone) through ES110's speakers.

I guess this is the main point why such a hack would be useful, on a tight budget, with the mixer circuit inserted at the blue point. Otherwise it is a much easier hack to connect an external mixer+speakers at the line-out, if the aim is a mixed output signal for recording etc.

Sure electronics skills are required, otherwise sth gets fried easily.

> Maybe first practice with some $10 thrift store keyboard.

Due to different circuits, "dead-simple mixer" experience with different keyboards may be irrelevant.

My bad then, I rushed and forgot that to drive speakers we need an amp. If the line-in signal is not loud enough, it can be installed before the amp module (if it's modular).

So "keyboard out"+"line-in" -> mixer's out

How about a ES520 instead?

I'm amused to see everyone coming around to what I described in the fourth post (without even having to see the diagram, because there's only one way to design this kind of thing).


A line level signal is never enough to drive speakers. Kawai wouldn't have included the relatively expensive power amplifier and the heatsink(s) that go with it for giggles.


It's going to be a PCB trace kept as short as possible so it doesn't pick up noise from all of the other digital circuitry on the same board. Since you've got to pull the signal off, and run it into something else before it hits the power amp, you're going to have to scrape solder mask off the PCB without damaging the underlying copper in at least one spot. If you're lucky the power amp will be through hole parts and you'll have an easy target for connecting the signals back up to it.

I believe you didn't read my post properly then. I clearly said, "before the AMP".

This entire thing isn't worth trying though.

Connecting the speakers to an outside source is easy. Anything else will be extremely difficult, even if you are very experienced. Modern surface mount circuit boards aren't easy to mess with.

I think it is already too heavy for him. He is using public transportation so the lighter the better. From memory, if Casio PXS-?000 (not sure if he tried 1000 or 3000) action were not so awkward (to him), he would keep it (small and light).

Somebody seems to have hacked the Korg C1 air... https://www.youtube.com/watch?v=OWDHCuWeMEI