Most opamps have a minimum allowed load of 2 thousand ohms.
I am not arguing- just interested. Where does that requirement come from?
Data sheets typically show 2k when specifying the output drive. In reality there is no set minimum load impedance requirement. It's determined by the op-amp's maximum output current and the desired voltage swing. If the op-amp can drive 10mA peak, then it'll be able drive a 600Ohm load with a peak voltage of 6V.
Hello,
I have tried out the circuit from AudioGuru and unfortunately it still doesn't work.
The OPA134 will not drive a speaker directly either.
You need to connect the output of the MAX9814 or OPA134 to a power amplifier such as the LM386 to drive a speaker.
OK, I will be ordering some LM386s. I think using the LM386 directly won't be possible because of its low gain (x20), right ? I have found a post of someone using the LM386 to connect an electret mic to a speaker : https://circuitdigest.com/electronic-circuits/lm386-audio-amplifier-circuit

It seems like this works but I think the gain is really low here. If I connect the LM386 to the OPA134, which changes should I make to the circuits please ? Would the one I've attached work pleas ?
How much gain do you want? The LM368 configuration you linked to has a gain of 200, not 20, because C1 bypasses an emitter resistor inside the IC. The data sheet provides lots of information about configuring the LM386 for different gains.
http://www.ti.com/lit/ds/sbos869/sbos869.pdfThe circuit you've posted with the op-amp and LM386 stages cascaded has a total gain of 200 000, which is far too high.
The single stage LM386 circuit, with a gain of 200, will probably have enough gain to drive a small speaker, form an electrect mic.