K3 Audio reports

[k0com]

New to the list, looking for some input on Audio Quality and a discovery
made by myself and another owner.  This may be old hat, but hope to find
out the cause.

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"

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!

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.  
The audio in both our K3's smoothed out and now sounded excellent.  
Below a 16 setting the audio issue began and progressively got worse
down to 0.

My questions is why?  I have never been a proponent of running
compression.  I'm doing it and since I started, I'm now getting
excellent audio reports.  The other odd thing is that the 3rd ham in
this test did not experience bad audio with the compressor turned down
or off.  We are all running the same firmware version.  Could it be
something in the set up of the ALC in the audio section or is this a
known bug?

Thanks for listening...
73
K0COM
Mike
Bloomington, MN



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[Don Wilhelm-4]

Mike,

If you turn compression off and talk into the microphone (you can do
that in TX TEST and no RF will be generated) how much deflection do you
have on the ALC meter.
It should be 5 to 7 bars for proper audio drive and power control (which
can affect the audio quality).  After setting the Mic Gain to achieve
that level, you can add in some compression - about 10 dB is right for
most operation.

If you have the DVR option, you have a good tool to evaluate your audio
signal.
Record some audio and then play it back.  That way you avoid the bone
conduction problem of listening to yourself live in the monitor and
eliminate the subjective element of on-the-air reports which are
dependent on the other ops receiver and his personal opinion of how you
"should" sound.

73,
Don W3FPR

On 1/3/2015 1:27 PM, Michael Sell wrote:

> New to the list, looking for some input on Audio Quality and a
> discovery made by myself and another owner.  This may be old hat, but
> hope to find out the cause.
>
> 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"
>
> 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!
>
> 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.  The audio in both our K3's smoothed out and now sounded
> excellent.  Below a 16 setting the audio issue began and progressively
> got worse down to 0.
>
> My questions is why?  I have never been a proponent of running
> compression.  I'm doing it and since I started, I'm now getting
> excellent audio reports.  The other odd thing is that the 3rd ham in
> this test did not experience bad audio with the compressor turned down
> or off.  We are all running the same firmware version.  Could it be
> something in the set up of the ALC in the audio section or is this a
> known bug?
>

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[Jim Brown-10]

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

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