From: jeffl@cruzio.com
On Thu, 5 Mar 2026 17:34:25 -0500, ehsjr wrote:
>On 3/5/2026 12:12 PM, Christopher Howard wrote:
>>>
>>> parallel protection1 parallel protection2
>>> -+-[>> | | | |
>>> -+-[D3>]-[D4>]-+- -+-[D5>]-[D6>]-[D7>]-[D8>]-+-
>>>
>>
>> Thank you, would you mind please explaining a little more about these
>> parallel protection circuits, i.e., how the protection works?
>>
>
>Sure. The diodes act as simple voltage limiters.
>
>General purpose diodes conduct when the voltage across them rises
>to about .7 volts. 2 diodes in series will conduct when the voltage
>across the series pair is about 1.4 volts. Therefore a speaker with
>a series pair of diodes across it won't be exposed to more than
>roughly 1.4 volts, provided of course, that the diodes are installed
>in the "right direction". Since a speaker usually is exposed to
>an AC voltage, you need two diodes in one direction and two in
>the other direction, so no matter what polarity signal is applied
>to the speaker one or the other pair of diodes will limit the voltage.
>1A rated diodes can easily handle all the current a 386 is able
>to provide.
>Ed
Two pairs of Si diodes will limit the audio (sine wave) to the speaker
to 1.4 V peak to peak or 1.0 V RMS. Into an 8 ohm loudspeaker, that's
a fabulous:
Power = E^2 / 8 = 0.13 watts RMS
My home entertainment system claims it can deliver 50 watts[1], which
will probably vaporize a simple diode voltage limiter.
Hint: I haven't seen any commercial hi-fi amplifier schematics that
include such diode clipper speaker protection.
--
Jeff Liebermann jeffl@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272 AE6KS 831-336-2558
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