audio in due

hi all,

i am doing a project to convert an input signal (audio) into digital and then converted back to analog and hear it via speaker.

i am using this website as my reference.

in step 4, there is external electronic circuit. in the amplifier stage, there is Vcc connected to positive of the battery. and GND is connected to the negative of another battery.
to baes an amplifier, i should connect vcc to + and vdd to - not to the GND.
my question here is , the negative of the battery is it connected to GND or vdd?

best wishes,


Hello m_lab85,

The tutorial makes reference to the TL0xx (see step 3). Those opamps do not have GND pin but Vcc-.

Thus, I believe the GND in the OP-AMP symbol of Amanda’s schematics should be Vcc-.

Also, there are two 9V batteries connected in series to power the OP-AMP.

  • The positive of the top battery supplies +9V and is your +Vcc for the opamp.
  • The negative of the bottom battery has -9V and is your -Vcc for the opamp.
  • The negative of the top battery (or the positive of the bottom battery) is your OV reference (float ground) for the Arduino.

I hope this helps. Regards!

In that circuit there's a very suspicious looking 47nF capacitor to ground that seems
very large for a TL0XX opamp to drive directly. I'd add a 330 ohm resistor between
the output of the opamp and the 10uF blocking cap to give a real LPF stage (roll
off about 10kHz with the 47nF).

hello guys,

that is really helpful.

many thanks,


Another piece of advice.
In general instructables are crap, try some place else.

hi all,

In general instructables are crap, try some place else.

i used the same circuit on instructables website. i connected the DC offset circuit to 3.3v not as it shown in the web because i am using Due board (max input 3.3v). the due board got overheated then blow up.

could someone provide me with a reliable circuit ,



Post how you connected it up and we can suggest modifications.