Sp3 a/b switch

[RICHH]

Hi
    I was wondering if there is a problem using the A/B switch   on the SP3
as a  on / off   switch for audio from the k3.  The k3 would be on.
It seems like this would be ok but I am checking with the experts here.
Thanks Richard
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[Elecraft mailing list]

Doing so would mean outputting the K3 into an open load
I would at a minimum turn down the volume on the K3

      From: Richard Donner <[hidden email]>
 To: "[hidden email]" <[hidden email]>
 Sent: Saturday, February 18, 2017 10:32 AM
 Subject: [Elecraft] Sp3 a/b switch
   
Hi
    I was wondering if there is a problem using the A/B switch  on the SP3
as a  on / off  switch for audio from the k3.  The k3 would be on.
It seems like this would be ok but I am checking with the experts here.
Thanks Richard
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[Don Wilhelm]

Richard,

If your K3 has all the audio amplifier mods installed, there should be
no problem.  If you have an early K3 without those mods, you could
damage the speaker audio amplifier by driving it into an open or shorted
load.  Yes, the A/B switch will make the load to the K3 an open circuit
when switched to the non-K3 position.

See the listing of K3 mods to determine whether your K3 has the mods
installed when you bought it or if they should be added.

Adding the mods is not difficult and can prevent a trip to Elecraft for
your K3 should the audio amp fail.

73,
Don W3FPR

On 2/18/2017 10:32 AM, Richard Donner wrote:
> Hi
>     I was wondering if there is a problem using the A/B switch   on the SP3
> as a  on / off   switch for audio from the k3.  The k3 would be on.
> It seems like this would be ok but I am checking with the experts here.
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[ab2tc]

Hi,

Why would the amplifier be damaged from driving an open circuit? Transformerless solid state audio amplifiers typically are perfectly happy driving an open circuit.

AB2TC - Knut

Don Wilhelm wrote

Richard,

If your K3 has all the audio amplifier mods installed, there should be
no problem.  If you have an early K3 without those mods, you could
damage the speaker audio amplifier by driving it into an open or shorted
load.  Yes, the A/B switch will make the load to the K3 an open circuit
when switched to the non-K3 position.

<snip>