From: jl@glen--canyon.com
On Thu, 05 Mar 2026 20:09:35 -0800, Jeff Liebermann
wrote:
>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.
A bridge rectifier has 4 diodes in one can.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
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