K1EL
K45 Audio Splitter Board
K45-SPLT
Introduction
The K45 has a great CW reader but one thing that slows most folks down is connecting audio
from their receiver to the K45's audio input. K1EL recommends using audio from the receiver's
audio line output jack which, in most cases, is located on the back of the radio. Usually it's in a
multi-pin DIN accessory connector, which is certainly not very convenient. The reason the line out
works so well is that it is a high impedance output, which matches the K45 audio input, and it is
unaffected by the radio's AF gain control. You can turn the AF gain control up and down and K45
copy is unaffected.
The next best option is to plug into the radio's external speaker jack. There are two problems with
this, the first is that it is a low impedance output, usually 8 ohms. The second is as soon as you
plug something into the external speaker jack, the radio's internal speaker is muted. Our
recommendation, up to now, has been to make up a Y cable but that doesn't solve the impedance
mismatch. To solve this once and for all, we designed an audio splitter board which takes the
place of a Y cable and also solves the impedance mismatch problem. Unfortunately, it doesn't
solve the AF gain adjustment issue but it's a good compromise.
The K45 Splitter board has three 1/8 inch jacks, one jack goes to your radio's external speaker
jack, a second one goes to you exernal speaker, and a third goes to the K45's audio input jack.
The K45 splitter is shipped with one 1/8” cable assuming you already have an 1/8” cable from a
K45 cable set.
Features
1/8 inch (3.5mm) audio input jack. Connect this to your radio's external speaker jack.
1/8 inch (3.5mm) speaker audio output jack. Connect this to your external speaker.
1/8 inch (3.5mm) Hi-Z audio output jack. Connect this to the K45's audio input jack.
K45 audio is coupled through a low level impedance transformer
4 - 16 ohm audio input, 4 - 16 ohm speaker output and 4.7K ohm output impedance to K45.
Audio attenuator to prevent K45 audio overload.
Negligible effect on external speaker volume or tone.
Mono/Stereo switch
External power is not required.
Assembled and ready to use.
Figure 1 – K45 Audio Splitter board
K45-SPLT Manual A.1
4/27/2023
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