[Elecraft] KDSP2 Problem

[Lyle Johnson]

Hello Paul!

> The distortion is just as bad in bypass mode, so I think it is much more
> than me being critical about the sound of DSP.
>
> Replcaing the KDSP2 with the KAF2 returns the audio to normal clean
> sounding.
>
> Any ideas where I should start looking please?

There are two possibilities for distortion that I am aware of.

1) AGC is off and a strong signal is present.  This is caused by the limiter
diodes (D5 and D6) on the KDSP2 board being driven to clipping.

2) Oscillation of the +1.8V supply on the DSPx board.  This usually causes a
"crackling" kind of sound.  If this is happening, and if you have access to
an oscilloscope, you can verify it by probing the striped (+) end of C3 on
the DSPx module.  C3 is the tan rectangular capacitor next to the Flash
memory socket.  Normally this will be quiet, with 10 to 20 mV or so of
noise.  If the regulator is oscilalting, the noise will typically be around
200 kHz and several hundred mV peak-to-peak.

if this is the problem, I can send you a repalcememtn capacitor.  This is a
surface mount part.  Otherwise, if you send me the DSPx, I can repair it for
you.

Let me know...

73,

Lyle KK7P