[Elecraft] Optimizing K3 Mini Speaker Gain with RemoteRig

[Paul Christensen]

Since last May, I've been using a K3 Mini with RemoteRig.  Apart from one
anomaly, operating the K3 Mini has been a great experience.  However, when
using RemoteRig, K3 mini speaker audio is extremely loud and the CW
side-tone is even louder.  However, receive audio and side-tone level in
headphones is excellent.  If one tries to reduce CODEC gain in the
RemoteRig, then headphone audio suffers and low-level digital artifacts
start becoming detectable.  

The fix inside the K3 Mini involves replacement of two (2) "603" size SMT
resistors at R39 and R40.  The stock values are 15K.  I changed these to
100K.  This results in a computed gain close to zero (Av = 1) for the
speaker amp and allows it to be used as a current driver for the speakers.
After the modification, speaker audio approximates headphone level without
excessively loud receive audio and side-tone.  This change may affect
operation of the K3 Mini when a RemoteRig is not used in some applications.
However, probably most K3 Mini owners use theirs with a RemoteRig.

Suggestion to Elecraft:  if there was a design reason for so much speaker
gain, consider placing 0.100" headers on a future PCB revision to allow
jumper selection of either the 15K resistors or 100K.  

Many thanks for a great product.

Paul, W9AC