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I'm trying to convert an old analog synth into a digital one. I'd like to bypass the speaker and read the values of the speaker with my arduino. But I don't know how to do itenter image description here

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    \$\begingroup\$ An analogue synth isn't converted to a digital synth by bypassing the speaker. It still remains an analogue synth but with the speaker disconnected. BTW, do you have a specific question? \$\endgroup\$
    – Andy aka
    Commented Jul 31, 2018 at 13:32
  • \$\begingroup\$ I know, I'd like to know how to convert the signal into a digital one \$\endgroup\$ Commented Jul 31, 2018 at 13:33
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    \$\begingroup\$ I'd use the line-out from the synth rather than the speaker output and use an ADC capable of sampling at over 40k samples per second. Is the arduino capable of interfacing with an ADC running this fast? \$\endgroup\$
    – Andy aka
    Commented Jul 31, 2018 at 13:36
  • \$\begingroup\$ i think i might need an audio dedicated chip. anyway there are too many wires and i don't know which one pick up \$\endgroup\$ Commented Jul 31, 2018 at 13:39
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    \$\begingroup\$ I would use the sound input of a PC. \$\endgroup\$
    – Oldfart
    Commented Jul 31, 2018 at 13:54

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It sounds like you're wanting to create a hybrid analog/digital synth. For a pure digital synth the only part you really need from your old synth is the keyboard (and perhaps power supply).

The Arduino Uno doesn't make a very good choice for a digital synth because of the limited memory, limited processing power, and no DAC. You can make a DAC from the Arduino's digital I/O outputs using a resistor ladder or use a couple outputs in PWM mode to drive an OpAmp (which I've found to be a very noisy solution).

The Arduino Due might be a better choice since it has much more memory and processing power. Whichever flavor of Arduino you use though, you'll need a circuit to shape the input to the Arduino's ADC from the AC speaker or line level output of your synth to a DC (0-5v) analog input that the ADC expects.

If you go with a digital only design then you'll only need to read the keyboard keys and have the Arduino play an appropriate tone based on the key pressed.

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  • \$\begingroup\$ Yes, this is exactly what I wanna do. An hybrid analog/digital. From the all things in the photo I want to save only the keyboard. But the problem is that i can't understand how to read the keyboard keys with arduino. Do you have any idea? \$\endgroup\$ Commented Aug 1, 2018 at 17:11
  • \$\begingroup\$ any idea to read the keyboard keys? \$\endgroup\$ Commented Aug 2, 2018 at 23:03
  • \$\begingroup\$ The keys may be simple on/off switches but they could be more complex if they sense velocity. Assuming they are just on/off switch they will either be pulled high or low when pressed. A schematic would really help here. They are likely arranged in a matrix format (similar to a computer keyboard) because this reduces the number of digital input pins you need to decode which key is pressed. Use a continuity tester to determine which wires correspond to an individual keypress. These wires can be connected to the Arduino's digital inputs so that you can determine which key is being pressed. \$\endgroup\$ Commented Aug 3, 2018 at 16:51
  • \$\begingroup\$ I don't think this website is the proper forum for this discussion. It is about a specific question and answer here. You really need to find a discussion forum for this project. \$\endgroup\$ Commented Aug 3, 2018 at 16:53

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