K2: Audio hiss in headphones w/ KDSP2...

[Steve Kallal]

I posted this question before and never got any response.
 
I have a K2/100 SN 2289 w/ the KDSP2. There is a definite soft hiss in the headphone output. It disappears completely when putting the KDSP2 into bypass mode. So I know it is from the DSP and not from QRN. I use the K2/100 almost exclusively for CW. The hiss often covers a weak signal particularly when the RF gain is turned down. The hiss doesn't seem to be a problem through the speaker. I rarely listen wo/ headphones. Switching headphones has not made any difference.
 
A search of this reflector's archives has produced an older thread on the topic. But there was not a definite fix for the problem. One suggestion was to put a shunt capacitor across the headphone audio line too act as a low pass filter. That might be OK for CW, but could be a problem w/ SSB.
 
Please let me know if someone has this problem or has resolved it.
73,
Steve N6VL
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[KK7P]

> Please let me know if someone has this problem or has resolved it.

< URL:http://www.qslnet.de/member/la3za/K2/modAny.html#KDSP2 > and look
up the link for Hiss Reduction by adding the KAF2 LC-filter.

73,

Lyle KK7P

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[Steve Kallal]

Tnx Lyle,
I've seen that link before. It links to http://www.ac6rm.net/mailarchive/html/elecraft-list/2003-10/msg00581.html which is broken. Maybe I can browse the old archives 2003-10 from a different archive.
73,
Steve N6VL


----- Original Message ----
From: Lyle Johnson <[hidden email]>
To: Steve Kallal <[hidden email]>
Cc: [hidden email]
Sent: Thursday, July 10, 2008 4:32:09 PM
Subject: Re: [Elecraft] K2: Audio hiss in headphones w/ KDSP2...

> Please let me know if someone has this problem or has resolved it.

< URL:http://www.qslnet.de/member/la3za/K2/modAny.html#KDSP2 > and look
up the link for Hiss Reduction by adding the KAF2 LC-filter.

73,

Lyle KK7P
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[Steve Kallal]

Thanks to all those who help with the the hiss problem. I was able to
find a comment in the original thread by WA8SRA. Dale's solution is at
http://mailman.qth.net/pipermail/elecraft/2003-October/024744.html.
However I found a reply to Dale at
http://mailman.qth.net/pipermail/elecraft/2003-October/024746.html 
<http://mailman.qth.net/pipermail/elecraft/2003-October/024744.html>
that mentions success doing the AF-Gain-Control Mod instead. My K2 is
dated, sn 2289. All the new K2s already have this mod.

I did the mod. It took me about 2 hours and is well worth the effort. I
am amazed at the quality of audio in my headphones. I don't feel the
need to do the WA8SRA, at least not right away. The soft audio hiss only
appears in my headphones when the volume is at 3/4 max now, rather than
at min as before. It feels like a whole new K2.

I had long suspected something wasn't quite right with my K2. That is
the problem w/ buying an older K2 as I did a year ago.

Thanks to all those who helped!

73,

Steve N6VL


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