Hello Jimmy,
I know exactly what you're referring to, and it is not due to the KDSP2,
or the KAF2. It is there on the bare-bones K2, although it is primarily
audible when using headphones capable of very wide frequency response. I
have several pairs of various models of Grado headphones, as well as a
pair of Beyerdynamic DT-990's, and the thump is noticeable on all. In
fact, I can also hear a 'click' as well as a thump.
I've been wanting to investigate this myself, but haven't found the time
to do so yet. I've temporarily reduced it to the point where it's a lot
less noticeable by placing the series combination of a 3.3 uF cap and
220 ohm resistor in line with the headphones, and shunting across the
headphones with a .47 uF cap. The series 3.3 uF will help to reduce the
'thump' by reducing the low-frequency response, and the shut .47uF will
roll off the high frequencies, thereby reducing the 'click'. It's still
not perfect, but it's a lot better than it was. You may have to play
with these values depending upon the characteristics, and impedance of
your headphones.
Of course a much easier solution is to just use a pair of cheap
headphones, similar to the ones that come with a portable cd player,
(especially since you're ruining the response anyway by inserting the
caps and resistor) but in my case the comfort level of the Beyerdynamics
is enough of a reason to go through the little bit of extra trouble.
73, Dale / WA8SRA
Jimmy Lee wrote:
When I use headphones I have a" thumping" sound everytime I key the rig.
(seems worse on wide range headphones, lots of bass response really
shows this "thumping" sound) Is this common and what is the fix?
Thanks,
Jimmy, AE4DT
K2 #2832
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