Path: csiph.com!eternal-september.org!feeder.eternal-september.org!nntp.eternal-september.org!.POSTED!not-for-mail From: Christopher Howard Newsgroups: sci.electronics.design Subject: simple protection for low wattage speakers? Date: Wed, 04 Mar 2026 08:42:33 -0900 Organization: A noiseless patient Spider Lines: 21 Message-ID: <87fr6fcwza.fsf@librehacker.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Injection-Date: Wed, 04 Mar 2026 17:42:34 +0000 (UTC) Injection-Info: dont-email.me; posting-host="547f1d62d365f72a14d3137df4b3e632"; logging-data="3277551"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18b4ZNyI9f1pb3TFvXsF7JhRslfk9jFsUY=" User-Agent: Gnus/5.13 (Gnus v5.13) Cancel-Lock: sha1:stfhydXuss1JLB7DAWh+Okq0UfA= sha1:My3vhxAEx8PFmM4Zvct9ZZXUUE0= Xref: csiph.com sci.electronics.design:741219 Hi, lately I've been playing around with making sounds on tiny 8-ohm speakers — whatever units I could get for free, which included a 3W speaker and also some 0.5 Watt and 0.25 Watt speakers. I feed in a small signal, from my signal generator or from my analog computer, into my LM386 amplifier (20x gain) and then to the speaker. However, several times now I have accidentally pressed the wrong button on my signal generator, or turned the knob too much on my analog computer, and blown out the speaker. For example, the 3W-8ohm speaker should only see 5V but I accidental drove it up over 10V. So I was wondering about adding some kind of limiting circuit right before the speaker. My understanding is that one way to do this is to have back-to-back zener diodes, shunting excess voltage to GND. I am unclear if that by itself is sufficient, or if I need resistors or something to keep the diodes or amplifier from getting damaged. I suppose another idea would be to have some kind of limiting right before the amp, but I am not sure of the simplest way to go about that, with voltage input being in the 100s of millivolts or less. -- Christopher Howard