[Elecraft] AF gain pot mod

[Ron D'Eau Claire]

No. There is no other source of noise, but it changes the behavior of =
the
audio gain control to act like audio gain controls on other equipment, =
and
so the rate of change in volume (and noise since we're usually listening =
to
a noisy band background) is different after the mod.=20

The original circuit uses the pot as a shunt to literally short out the
audio going into the amplifier. When the pot is all the way 'down' =
(CCW),
its low resistance shorts the two audio lines together. These pots were =
not
designed to insure a very consistent low resistance with fully CCW, and =
so
over time some of them start to sound scratchy or noisy when the volume =
is
turned way down. Also, the way the circuit changes gain when turned up =
is
nearly linear.=20

The modification changes the pot to work like most audio gain controls =
with
what is called a "logarithmic" response that better matches the way our =
ears
respond to changes in volumes. This gives the gain control more of the
"feel" of other gain controls AND it removes the need for the control to
have a very low resistance at the "down" or CCW position.=20

Ron AC7AC

-----Original Message-----

I have never done this mod to # 700 because my AF pot is not noisy when =
it
is turned.  But the other day I saw a posting that suggested to me that
there may be more to it than that, sounded like there is audio noise
introduced that the mod removes regardless of whether the pot itself is
noisy.

Is this a mod that should be done regardless of whether the pot is noisy
when turned or not???

tnx

Fred
K2 # 700