[Elecraft] K3 transmit and receive audio response

[Joe Subich, W4TV]

> The low end response of the stock K3 is limited by coupling 
> capacitor impedance in the audio stage.

Only in regard to the headphone amplifier when used with low 
impedance (8 Ohm) headphones.  With the stock 10 uF caps the 
-3dB point (corner frequency) for 8 Ohm headphones is 2 KHz.  
However, with professional (600 Ohms) headphones the corner 
frequency is 25 Hz and with a Heil Proset (200 Ohms) the corner 
frequency is 80 Hz.  

For reference, the corner frequency (-3 dB) of the speaker 
amplifier using the stock coupling capacitors is about 17 Hz. 
The audio response of speakers will be much more heavily 
influenced by the speaker enclosure than the coupling caps 
in the stock audio amplifier. 

73, 

   ... Joe, W4TV 
 






> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net 
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Barry N1EU
> Sent: Wednesday, June 17, 2009 8:13 AM
> To: elecraft at mailman.qth.net
> Subject: Re: [Elecraft] K3 transmit and receive audio response
> 
> 
> 
> The low end response of the stock K3 is limited by coupling 
> capacitor impedance in the audio stage.
> 
> 73,
> Barry N1EU
> 
> 
> 
> Lyle Johnson wrote:
> > 
> >> What I would like to know is just what the ACTUAL response 
> curves of
> >> the K3 transmit and receive audio are (when all EQ 
> settings are set to 
> >> '0',
> > 
> > Flat means the EQ does not add or subtract to the filter response 
> > dialed
> > in by the operator with the SHIFT/WIDTH/HIGH CUT/LOW CUT 
> controls.  The 
> > high end and low end response will be dictated by those 
> settings,  This 
> > will be modified by the impedances in the path from the 
> radio to the 
> > headphones or speaker and the impedance of the headphones 
> or speaker, or 
> > the characteristics of the transformers and the overall 
> impedances in 
> > the LINE OUT case.
> > 
> > Finally, the edges of the selected passband will be rolled 
> off by the
> > action of the FIR filter windowing function applied to the filter 
> > coefficients.
> > 
> > 73,
> > 
> > Lyle KK7P
> >