[Elecraft] K3 DSP Upgrade Correction

[Jim Brown]

On 3/22/2011 7:24 PM, Edward Dickinson III wrote:
> The matching network is a $20 item from an auto sound store and is
> used to cut speaker level down to line level.

You just spent $20 on something that you could have done equally well 
with two 5-cent resistors, AND that probably was not needed in the first 
place.

Study the part of http://audiosystemsgroup.com/HamInterfacing.pdf that 
talks about audio levels.  Also see the Appendix on audio that is part 
of http://audiosystemsgroup.com/RFI-Ham.pdf

The executive summary -- most computer sound cards clip at about 1 volt 
sine wave. A 2-watt power amp, typical for ham gear, would clip at about 
2 volts, and that only occurs on very loud audio peaks. All that's 
required to prevent clipping of the sound card input is to turn the 
speaker output gain down a bit.

A simple voltage divider (the two resistors) IS needed to drive a MIC 
level input.

73, Jim K9YC