I am completely new to electrical engineering. I have a software background and have an interest in tinkering with hardware.

I'm wondering what knowledge/engineering skill/equipment is required to add Bluetooth capability to an existing keyboard. The keyboard I own is a Roland EP-9.

I know there is something to do with analog-to-digital conversions. But in terms of what data is being sent to the internal speakers, I have zero understanding how that works. The issue is "I don't know what I don't know", so I'm probably communicating this incorrectly.

I don't expect a full solution, but any links to helpful documentation is greatly appreciated!

Edit: For clarification, I just want the audio output sent to a BT speaker or headphones. Currently it is sent to an internal speaker.

  • 1
    \$\begingroup\$ Just buy a MIDI->Bluetooth converter. \$\endgroup\$
    – Ron Beyer
    Jan 21, 2020 at 20:48
  • \$\begingroup\$ It's not clear what you intend to do. Do you want to transmit the audio output over Bluetooth? That can be done with a simple Bluetooth transmitter with a headphone plug. Do you want to transmit audio into the EP to mix with the EP output? Or do you want to transmit MIDI data over Bluetooth? \$\endgroup\$
    – Transistor
    Jan 21, 2020 at 20:49
  • 1
    \$\begingroup\$ What kind of data are you asking to send? Just the audio to some BT speaker? Then simply plug a BT transmitter into the line-out. \$\endgroup\$
    – Eugene Sh.
    Jan 21, 2020 at 20:51
  • 2
    \$\begingroup\$ amazon.ca/Bluetooth-Transmitter-Aigital-Wireless-Headphones/dp/… \$\endgroup\$
    – DKNguyen
    Jan 21, 2020 at 21:06
  • 1
    \$\begingroup\$ Then, as I said, as an experienced electrical engineer I would go to amazon and buy a BT audio transmitter :) \$\endgroup\$
    – Eugene Sh.
    Jan 21, 2020 at 21:06

1 Answer 1


The engineer method would be a mux or digital switch or output from the IC8 Synthe Chip on the schematic to a bluetooth audio IC. Proper grounding, decoupled analog and digital power etc.

A hacker way would be to tap the IC11 D/A output at TP4 and TP3 to get the audio before the filter IC, and route that to an internal bluetooth audio module.

But the simple tinkering method is seeing that the piano already provides a method for line out and that line out to bluetooth adapters are cheap and premade. Headphone output would work too. Buying one is the best idea when you already have audio outputs. Or a headphone out to bluetooth adapter that you could even buy at a retail store.

At best you could cut the muting control for the IC19 output inverter (q15 and q14) so that you can mute the internal speakers without muting the line out, as they are tied together. Of course this involves tearing your keyboard apart.

If you want to learn, first step is to find the EP-9 service manual which has the schematic and block diagrams and learn what does what and how. I found the manual with a quick google search.


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