[Elecraft] My K3's hissy and noisy audio

[Stewart Baker]

Audio response seems to be a difficult area for Elecraft.
SSB from the K2 often received poor reports because of the 
excessive LF response in the TX audio stages. 
It could be cured by reducing coupling capacitor values.
The K3 RX audio appears to need the opposite approach.

Stewart G3RXQ

On Mon, 6 Apr 2009 06:54:21 -0400, Paul Christensen wrote:
>> Perhaps the band noise is more obvious in the K3 because the 
low frequency
>> audio is restricted causing the noise to be distributed over a 
more narrow
>> range. This lack of bass tends to induce for ear fatigue.
>> Steve Ellington
>
> I agree with Steve on this one.  Once more low-end was rolled 
into my audio
> hardware changes, I noticed a significant reduction in my own 
listener
> fatigue.
>
> Others have noted the K3's audio frequency response variance 
across
> different headphone models, most notably the Heil product.  The 
K3's
> headphone circuit uses 10 uF of series capacitance from the 
headphone amp to
> each of the headphone coils.
>
> For the moment, assume that your headphones are 32-ohms (ref 
100Hz).  What
> is the best possible low-end response from the K3?  The answer 
is 500 Hz
> @ -3dB.  That part of the circuit needs some help.  With a 
headphone Z even
> lower toward 8-ohms, the attenuation of bass response is worse.
>
> Now upgrade the series caps to 330 uF and re-run the 
calculation.  With
> 32-ohm phones (ref 100 Hz), the frequency response improves to 
15 Hz.  Now
> that's t real Hi-Fi on par with what Icom delivers and the 
difference is
> immediately noticeable to anyone -- not just the folks with 
"golden ears."
>
> Finally, compare the result of the modified K3 with the Icom 
'7700 or '7800.
>
> Paul, W9AC
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: 
http://www.qsl.net/donate.html