[Elecraft] Mic and headphone

[Don Wilhelm]

Allen,

Most modern audio output stages are low impedance sources, and there is 
no need to "match impedances".
Do you think about matching impedances when you plug something into a 
power mains wall receptacle?  Likely not, because the AC mains is a low 
impedance source and will deliver whatever the device needs. Your 
headphones are similar - with a low source impedance driver, you don't 
have to worry about it, just adjust the AF gain to a comfortable level.  
More power will be delivered to a low impedance device, but headphones 
do not require much power.

The microphone is similar.  It is a relatively low impedance source, and 
it is operating into a relatively high impedance device (1k to 10k for 
modern transceivers) and the voltage produced is the important 
parameter.  Yes, high impedance microphones may not give the proper 
frequency response curve, but other than that, no impedance matching is 
normally required.  Modern microphones are in the range of 200 to 600 
ohms driving impedance.  I suspect yours is also in that range.

73,
Don W3FPR

On 3/4/2014 7:12 PM, N5AG wrote:
> Has anyone wired up a Plantronics CS50 Telephone headset system to the K3?
> The Plantronics CS50 system is composed of a base unit that transmits and
> receives in full duplex to a small headset that is worn and gives the
> capability to transmit and receive up to 300 feet.  The system uses 900 mhz
> to communicate between the base and the headset.
>
> The base unit normally would plug in to a land line base telephone using the
> standard four wire (two pair) found in most home telephone installs. I need
> recommendations on wiring the Plantronics CS50 base unit to the back panel
> mic and phone connections with the standard four wire line from the
> Plantronics base.
>
> Does the K3 have the ability via menu selection to match impedances for the
> mic and audio hook up stated above or must the matching be done in the
> interface between the Plantronics base and the K3?
>
>