[Elecraft] Re: K3 Audio

[Mike Harris]

Hi Dave,

In the presentation the TX element was not necessarily TX audio quality, 
rather the less than stellar intermod figure, however, I believe this has 
been accepted as typical of a low voltage 100W output PA.

The RX audio issue, which is probably more important, comes up in the last 
eight minutes and relates to high levels of distortion in the audio amp, 
up to and beyond an 11th harmonic at 7kHz. on a CW signal and a 9th order 
product on two tones only -40dB down.

Maybe this explains why, to my ear, even after cropping the high end of 
passband in DSP at 2400Hz on SSB it still sounds harsh.  The junk is 
apparently being generated post DSP by the af amp.  One can only speculate 
on the consequences of a CW pile-up.

The good news is, according to Rob Sherwood, that it is fixable once the 
cause has been identified.  The good news is that the good folks at 
elecraft are aware of the problem and are presumably on the case.  The bad 
news is it's probably hardware not code.

Didn't someone also mention that line output above a certain figure was 
also distorted.  I think the speculation there pointed to the af 
transformers.

Regards,

Mike VP8NO


----- Original Message ----- 
From: "Dave G4AON" <elecraft at astromag.co.uk>
To: <elecraft at mailman.qth.net>
Sent: Tuesday, August 05, 2008 4:55 PM
Subject: [Elecraft] Re: K3 Audio


|I use TX equalisation with my K3 to improve on my deep gravelly voice.
| It sounds far better than my TS-480 with a similar microphone on both
| transceivers (Kenwood MC-43S on the K3, stock mic on the '480), the
| TS-480 has limited equalisation on TX but even with that it's well below
| the quality of the K3 audio which sounds to my ears close to as good as
| it's going to get from my voice. Unsolicited reports on the quality of
| my K3 TX audio are commonplace and I've never received reports such as
| those at any time in my 37 years of operating... I don't think there is
| anything wrong with the K3 TX audio.
|
| On receive the only "quality" receiver I have for comparison is a Drake
| R4A and the K3 sounds better than that, and the R4A isn't at all
| unpleasant to listen to... The Drake meets specification and has new
| smoothing capacitors... The K3 receiver has an open sound which can
| sound harsh when combined with a lot of background hash in the form of
| white noise from a typical domestic situation where you are surrounded
| by houses with computers, switched mode PSUs, etc. Under clean band
| conditions that openness sounds great when listening to SSB with the
| same DSP bandwidth as the roofing filter (2.8 KHz in my case). I use no
| equalisation on receive.
|
| Bottom line to me is the K3's audio is fine. And no, I'm not on
| commission from Elecraft!
|
| 73 Dave, G4AON
| K3/100 #80
|
| "Wouldn't something like this be affected by equalization?"