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Re: simple protection for low wattage speakers?

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ehsjr <ehsjr@verizon.net> wrote:
> On 3/5/2026 11:09 PM, Jeff Liebermann wrote:
>> On Thu, 5 Mar 2026 17:34:25 -0500, ehsjr <ehsjr@verizon.net> wrote:
>> 
>>> On 3/5/2026 12:12 PM, Christopher Howard wrote:
>>>>> 
>>>>> parallel protection1    parallel protection2
>>>>> -+-[<D1]-[<D2]-+-       -+-[<D1]-[<D2]-[<D3]-[<D4]-+-
>>>>> |             |         |                         |
>>>>> -+-[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.
> 
> The limiter I described addresses the OP's application, not yours:
> "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."
> 
> 
>> 
>> Hint:  I haven't seen any commercial hi-fi amplifier schematics that
>> include such diode clipper speaker protection.
> 
> Nor I, but irrelevant to the OP.
> 
> Ed
>> 
>> 
> 
> 

Of course a series clipper would protect the speaker without shorting the
amp. Needs a bit of auxiliary power, and would cause a bit of distortion,
but nothing awful for a toy application. 

Personally I’d just crank down the LM386’s  supply voltage. 

Cheers 

Phil Hobbs 

-- 
Dr Philip C D Hobbs  Principal Consultant  ElectroOptical Innovations LLC /
Hobbs ElectroOptics  Optics, Electro-optics, Photonics, Analog Electronics 

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simple protection for low wattage speakers? Christopher Howard <christopher@librehacker.com> - 2026-03-04 08:42 -0900
  Re: simple protection for low wattage speakers? ehsjr <ehsjr@verizon.net> - 2026-03-04 16:10 -0500
    Re: simple protection for low wattage speakers? Christopher Howard <christopher@librehacker.com> - 2026-03-05 08:12 -0900
      Re: simple protection for low wattage speakers? Bill Sloman <bill.sloman@ieee.org> - 2026-03-06 05:31 +1100
        Re: simple protection for low wattage speakers? "Edward Rawde" <invalid@invalid.invalid> - 2026-03-05 13:44 -0500
          Re: simple protection for low wattage speakers? john larkin <jl@glen--canyon.com> - 2026-03-05 12:06 -0800
      Re: simple protection for low wattage speakers? ehsjr <ehsjr@verizon.net> - 2026-03-05 17:34 -0500
        Re: simple protection for low wattage speakers? Jeff Liebermann <jeffl@cruzio.com> - 2026-03-05 20:09 -0800
          Re: simple protection for low wattage speakers? Jan Panteltje <alien@comet.invalid> - 2026-03-06 05:41 +0000
          Re: simple protection for low wattage speakers? john larkin <jl@glen--canyon.com> - 2026-03-06 06:56 -0800
            Re: simple protection for low wattage speakers? ehsjr <ehsjr@verizon.net> - 2026-03-06 14:26 -0500
              Re: simple protection for low wattage speakers? john larkin <jl@glen--canyon.com> - 2026-03-06 11:43 -0800
              Re: simple protection for low wattage speakers? Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2026-03-06 19:46 +0000
                Re: simple protection for low wattage speakers? ehsjr <ehsjr@verizon.net> - 2026-03-06 17:56 -0500
          Re: simple protection for low wattage speakers? ehsjr <ehsjr@verizon.net> - 2026-03-06 14:08 -0500
            Re: simple protection for low wattage speakers? Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2026-03-06 19:43 +0000
              Re: simple protection for low wattage speakers? john larkin <jl@glen--canyon.com> - 2026-03-06 11:58 -0800
      Re: simple protection for low wattage speakers? Bill Sloman <bill.sloman@ieee.org> - 2026-03-06 16:29 +1100
  Re: simple protection for low wattage speakers? Jeremiah Jones <jj@j.j> - 2026-03-04 13:20 -0800
  Re: simple protection for low wattage speakers? john larkin <jl@glen--canyon.com> - 2026-03-04 14:17 -0800
  Re: simple protection for low wattage speakers? "Edward Rawde" <invalid@invalid.invalid> - 2026-03-04 19:58 -0500
    Re: simple protection for low wattage speakers? Martin Brown <'''newspam'''@nonad.co.uk> - 2026-03-05 10:30 +0000
  Re: simple protection for low wattage speakers? Don Y <blockedofcourse@foo.invalid> - 2026-03-04 18:58 -0700
  Re: simple protection for low wattage speakers? "Edward Rawde" <invalid@invalid.invalid> - 2026-03-04 21:55 -0500
  Re: simple protection for low wattage speakers? Jasen Betts <usenet@revmaps.no-ip.org> - 2026-03-07 02:44 +0000

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