[Elecraft] Fwd: Speakers audio is gone

[Joe Subich, W4TV]

The main board already has capacitors between the audio amplifier and
speaker switching on the KIO3 board.  The capacitors - C2 and C3, 470
uF each - don't prevent accidental overload of the audio amplifier if
the output is shorted.  With an impedance of less than 0 - j0.5 Ohms
at 1 KHz, they simply can't do the job.

The smart thing to do would be to replace L14 and L16 on the KIO3 Audio
IO Board with 1.2 Ohm to 2.2 Ohm resistors.  Although 2.2 Ohms would
result roughly 2dB less maximum output (with 4 Ohm speakers), the
slight decrease would certainly be worthwhile to protect the audio
amplifier.

73,

    ... Joe, W4TV


On 12/23/2013 6:33 PM, Mel Farrer wrote:
> Next rev of the DSP PCB should have the same series caps that all of the other audio output have!!!!!.  Sized of course to the impedance, DUH.
>
> Mel, K6KBE
>
>
>
>
>
> On Sunday, December 22, 2013 11:14 PM, Don Wilhelm <w3fpr at embarqmail.com> wrote:
>
> Gary,
>
> It seems that that is one adapter that 'does it right'.  Many do not and
> connect the ring of the stereo plug to the sleeve when a mono jack is
> inserted, thus grounding the right channel.  That is typical of the 1/8
> inch to 1/4 inch adapters.
>
> 73,
> Don W3FPR
>
> On 12/22/2013 10:17 PM, Gary NL7Y wrote:
>> Another mono/stereo speaker comment and question. Fred KE7X covers this topic
>> well in his reference, as does Elecraft in their Owner's manual...to some
>> extent.
>>
>> Above noted earlier " I have a Radio Shack P/N 274-0374 1/8" Mono Jack to
>> 1/8 Stereo Plug Adapter stuck in the back of my K3. It feeds the mono plug
>> to my ICOM SP 20." That particular adapter shorts the tip (left speaker
>> feed) and the ring (next up the plug; right speaker feed) when a monaural
>> plug is inserted.
>>
>> When OHM'd out the sleeve (third up the plug and metal body) sees 8 ohms
>> between either the tip or ring when connected to the single monaural speaker
>> (because they're shorted).
>>
>> Question for those that better understand the Elecraft's audio wiring: Will
>> shorting the left and right speaker channels cause harm when they see the
>> same 8 ohm source?
>>
>> 73, Gary NL7Y
>>
>> PS: Alternatively I can install a Radio Shack 274-375 dual mono to stereo
>> adapter, or a simple stereo plug on my mono cord.
>>
>>
>>
>>
>> --
>> View this message in context: http://elecraft.365791.n2.nabble.com/Speakers-audio-is-gone-tp7581916p7581946.html
>> Sent from the Elecraft mailing list archive at Nabble.com.
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