[Elecraft] New K3 DSP Board

[Paul Christensen]

> "If the new DSP board does not improve the low frequency response in 
> receive audio unless the bandpass is adjusted as some have suggested, I 
> wonder what it is intended to do.   Is it supposed to improve the low 
> frequency transmitted audio?  What can the new DSP board do that the TX EQ 
> and RX EQ in the MAIN menu not do?   Roy Morris  W4WFB"

Here's a summary:  The Main DSP Board (Rev. D) does three things that are 
independent of EQ settings and contrary to other opinions, do in fact make 
measured improvements to Tx and Rx audio response:

1) The new low-pass audio filter in the Rx path attenuates undesirable 
artifacts above approximately 4 kHz;

2) The headphone low frequency response is improved when using low Z 
headphone types (e.g., older 4 or 8-ohm) through a 10X increase in coupling 
capacitor value; and

3) Mic and Line-In low audio response is improved through the re-scaling of 
several components.

Paul, W9AC