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K3(s) Headphone Splitter

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Rich-4

K3(s) Headphone Splitter

I am planning to build a headphone splitter/switch so I can listen to
one K3 in the left ear and the other radio in the right ear or turn off
the audio from either radio.

Two questions:

Is there a commercial item for this purpose?

I know I will need an audio isolation transformer between each radio and
the splitter/switch. Any suggestions on what a good impedance value
would be for those transformers?

Thanks

Rich

K3RWN

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Jim Brown-10

Re: K3(s) Headphone Splitter

On 4/25/2018 10:54 AM, Rich wrote:
> Is there a commercial item for this purpose?

Yes, the RANE HC-6 would work. And they make several other small mixers
that make it easy to switch and route audio. While the mixers may not
have a stereo headphone output, you could easily make a cable adapter
from the outputs to a cable-mounted stereo jack. I would study their
catalog and look for the products used on ebay.

There's also a discontinued Shure product that does what you want. It's
the model FP22 headphone amplifier. Runs on internal batteries or 12VDC.
Very nice.

>
> I know I will need an audio isolation transformer between each radio
> and the splitter/switch. Any suggestions on what a good impedance
> value would be for those transformers?

No, a transformer is NOT needed. All that is needed is proper bonding
between all equipment in your station, including audio gear like the
HC-6 or FP22. Study
http://k9yc.com/GroundingAndAudio.pdf

73, Jim K9YC
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Josh Fiden

Re: K3(s) Headphone Splitter

In reply to this post by Rich-4

You don't necessarily need transformers. If grounds from both radios bonded together it should be fine, depending on extent of "pin 1" problem internal to radio.

Two SPDT toggle switches would accomplish this. One switch for each ear which selects between the two radios. That's assuming you only care about mono sources.

If you need isolation transformers use 1:1 or close to that. I can suggest an inexpensive transformer from Mouser/Digi if needed. You'll also need a headphone amp.

I would certainly try the trivial solution first and if noisy, try to correct the grounding issue before throwing hardware at it.

73
Josh W6XU

Sent from my mobile device

> On Apr 25, 2018, at 10:54 AM, Rich <[hidden email]> wrote:
>
> I am planning to build a headphone splitter/switch so I can listen to one K3 in the left ear and the other radio in the right ear or turn off the audio from either radio.
>
> Two questions:
>
> Is there a commercial item for this purpose?
>
> I know I will need an audio isolation transformer between each radio and the splitter/switch. Any suggestions on what a good impedance value would be for those transformers?
>
> Thanks
>
> Rich
>
> K3RWN
>
> ______________________________________________________________
>

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Josh Fiden

Re: K3(s) Headphone Splitter

In reply to this post by Jim Brown-10

Good answer!! Fast, too. Hihi

Sent from my mobile device

> On Apr 25, 2018, at 11:12 AM, Jim Brown <[hidden email]> wrote:
>
>> On 4/25/2018 10:54 AM, Rich wrote:
>> Is there a commercial item for this purpose?
>
> Yes, the RANE HC-6 would work. And they make several other small mixers that make it easy to switch and route audio. While the mixers may not have a stereo headphone output, you could easily make a cable adapter from the outputs to a cable-mounted stereo jack. I would study their catalog and look for the products used on ebay.
>
> There's also a discontinued Shure product that does what you want. It's the model FP22 headphone amplifier. Runs on internal batteries or 12VDC. Very nice.
>
>>
>> I know I will need an audio isolation transformer between each radio and the splitter/switch. Any suggestions on what a good impedance value would be for those transformers?
>
> No, a transformer is NOT needed. All that is needed is proper bonding between all equipment in your station, including audio gear like the HC-6 or FP22. Study
> http://k9yc.com/GroundingAndAudio.pdf
>
> 73, Jim K9YC
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]