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Meurthe-et-Moselle.mw-parser-output .entete.map{background-image:url("//upload.wikimedia.org/wikipedia/commons/7/7a/Picto_infobox_map.png")} Administration Pays   France Région Grand Est Création du département 7 septembre 1871 Chef-lieu (Préfecture) Nancy Sous-préfectures Lunéville Toul Briey Président du conseil départemental Mathieu Klein Préfet Éric Freysselinard [ 1 ] Code Insee 54 Code ISO 3166-2 FR-54 Code Eurostat NUTS-3 FR411 Démographie Gentilé Meurthe-et-Mosellans, Meurthois Population 734 403  hab. (2015) Densité 140  hab./km 2 Géographie Superficie 5 246  km 2 Subdivisions Arrondissements 4 Circonscriptions législatives 6 Cantons 23 Intercommunalités 18 Communes 592 modifier   La Meurthe-et-Moselle .mw-parser-output .prononciation>a{background:url("//upload.wikimedia.org/wikipedia/commo

4 I'm building a simple amplifier around a LM386. The circuit I'm using is this: The input is on pin 1 of the connector and is a square wave coming from a digital pin on a NodeMCU devboard. When I turn the circuit on, I can hear a low frequency oscilation on the speakers (not a constant tone, but as if the speaker was turned on and off a few times a second). I tried adding a capacitor between the signal and ground as it seemed to work in this related question but I needed a fairly big capacitor (220uF) to get any result at all, and it only decreased the volume of the noise (not to mention it is filtering my input, if I understand it correctly). What did get rid of the noise completely was adding a 1K resistor between pin 7 and ground (in parallel with the existing capacitor): I have no idea why this