[Elecraft] K3 Audio reports

[Jim Brown]

On Sat,1/3/2015 10:27 AM, Michael Sell wrote:
> Since buying my K3 secondhand, I have always received audio quality 
> reports from "sounds like rf in your audio" to "rough sounding audio, 
> especially at the peaks", or "your audio sound hollow or distorted"

Did you check TXEQ?  The fact that it sounds better with Compression 
suggests that TXEQ may be screwed up.

> I've been all over the place trying to fix this.  Grounding mods, 
> ferrite filters, sold the KPA500 and got a new amp, even got rid of my 
> EV RE 20 and Symetrics 528E and went with a Heil Pro 30 straight into 
> the radio.  Still the same reports!

Why would you use a 528E for a dynamic mic like the RE20 with a ham 
rig?  Virtually all dynamic mics can be connected directly to the K3 mic 
connector with a simple XLR to Foster plug adapter. One side of the 
balanced mic output goes to Mic In, the other side and the cable shield 
go to the chassis.  An outboard preamp is needed only for a pro electret 
mic, and then only to provide the phantom power.

>
> Finally got on with two other K3 owners and did some testing.  We 
> found that for two of us, we had the same problem and same audio. One 
> did not.  We found that for two of us the problem was solved by 
> advancing the compressor setting to at least 16 with 21 being the best 
> setting.

First, don't go by the numerical readout for Compression. Instead, set 
the K3 display to show ALC and Compression.  The "right" thing to watch 
is the Compression bar graph. For contesting and DX chasing, adjust the 
Compression control for about 10 dB on peaks. Do this AFTER you have set 
the TXEQ. For more general operation, you may like 6 dB better.

Communications mics are designed with a built-in peak around 3-4 kHz to 
compensate for the rolloff of the crystal filter. Pro mics don't have 
this peak (although some vocal mics like the SM58 have a peak around 
8-10 kHz), so pro mics need TXEQ boost in the two top bands of TXEQ. 6 
dB is a good starting point.  Virtually all mics need low frequency 
rolloff so that power is not wasted on LF energy that does not 
contribute to speech intelligibility. A good starting point for all mics 
is max cut of the three lowest bands, then get on the air reports for 
setting the 4th band.  The other guy listening should have his IF set 
pretty wide for this test.

I'm a retired sound and recording engineer, so I own RE16s, RE20s, 
RE27s, and lots of other mics. Before I found the CM500, the mic in my 
shack was an RE16 on a boom stand.  With both mics I get reports of 
excellent audio, but I like the CM500 because it's a boom mic attached 
to a comfy headset.

73, Jim K9YC