[Elecraft] My K3's hissy and noisy audio

[Paul Christensen]

> We used my K3 on the running station and a Icom IC-7700 on the multiplier
> station. This was actually the first time I could compare the K3 to a high
> end transceiver such as the IC-7700. I was surprised to find out that the
> 7700 sounded much better.

Maarten,

At my station, the K3, '7700, and '7800 are side-by-side.  Of all three 
transceivers, the K3 produces the least amount of residual hiss.  In fact. 
when the AF control is turned full CCW on the Icom's, a slight degree of 
hiss remains.  Zero hiss with the K3.  If you look at the audio structure of 
the K3's headphone circuit, it would be pretty difficult to improve upon 
when using a single-ended power supply.  When bi-polar power supplies are 
used, it's possible to eliminate intra-stage coupling capacitors with 
servo-controlled op-amps, thereby eliminating DC offsets.  Larger voltage 
swings are possible with bi-polar supplies and overall distortions are 
generally lower with these circuits.  You tend to find these techniques used 
in Hi-Fi audio and broadcast equipment, but not in communications-grade 
audio systems.

One important point is that the stock K3 has less low-end audio response 
than that of the two Icoms.  But that's a personal choice.  Some 
well-respected ops here detest the presence of low-end audio below ~ 200 Hz. 
Others (myself included), like to hear the entire passband while 
operating -- right down to 50 Hz or so.  It's not right, it's not wrong - 
it's just a personal preference one way or the other.   My personal choice 
is to open up the audio response, then limit low-end and high-end response 
through the K3's DSP filtering.  I get the best of both worlds that way...

In order to attain a richer low-end response on the K3, you may wish to 
review my mods on the N1EU website.  After modification, the K3 is capable 
of sounding just as rich and smooth as the two Icoms.  My guess is that when 
you use the adjective "sharp," you're likely hearing a lack of low-end 
balance as both transceivers are capable of extremely sharp low-pass 
response.

If you do invoke the mods, I would suggest first looking at the revision of 
your Main DSP Board as some of components I've changed may have now gone 
into production at Elecraft.  It may also turn out that Elecraft eventually 
scales the audio R values rather than C values to accomplish the same end 
result.  I changed C values since fewer components are changed that way.

Paul, W9AC