[Elecraft] EV664

[Jim Brown]

On Sat, 27 Aug 2005 10:26:57 -0500, Jim Brown wrote:

>The mods are quite simple. First, change R14 from 1K to 2K. Second, 
>change C34 to 0.22 uF. Third, add 2.2uF in series with R15.

A correction to one of my suggested mods by Don, W3FPR, who understands the K2 
in far more detail than I do, and emailed me to discuss it. The cap in series 
with R15 is a bad idea, for several reasons, based on the control logic for 
the compressor. If a cap were to be added there, it ought to be in parallel 
with R15, not in series, and it ought to be smaller -- perhaps about 1 uF. 

What both caps do is reduce modulation from breath pops and low frequency 
noise in your shack. Popping and low frequency boost is a common problem with 
directional mics used close up. Even in pro applications, we use a lot of low 
cut on these mics, and it is even more important to do so in communications 
circuits. 

Jim