[Elecraft] K3 Harmonic Distortion

[Jim Brown]

On Tue, 02 Sep 2008 11:53:23 -0400, Jack Smith wrote:

>The solution of choice in my opinion for the 
>Softrock receivers turns out to be a MILSPEC Triad transformer, SP-70, 
>with excellent frequency response and quite low distortion. In single 
>lot prices, an SD-70 costs about four times as much as a TTC-108.

You should look at Jensen (www.jensen-transformers.com) 

and Lundahl (www.lundahl.se) 

which are pretty much THE standard in the pro audio world. 

Jensen is well known for excellent applicactions engineering support, 
with real engineers (not salesmen) answering the questions. Bill 
Whitlock, the owner, is a Fellow of the AES. The guys who work for him 
are also very good. 

Both companies make "good, better, and best" products, depending on the 
needs of the installation, but Jensen's best is significantly better 
than Lundahl's best. 

The old line mfrs like Triad and UTC are dead meat in the world of pro 
audio. 

BTW -- there's another problem with the transformers in the K3 -- 
they're unshielded, so they pick up whatever magnetic fields surround 
them. Like the fields from the power transformer(s) for your power amp!  
This can be either a small problem (hum about -35dB carrier) or hum 
that regenerates to full transmit power! I have the small problem, my 
neighbor has the big problem. If you have this problem, you can hear 
the hum with nothing connected to the line input (if the line input is 
on). 

IMO, the transformers need to go away. My Ham Interfacing tutorial 
shows convincingly why they are completely un-necessary if all the gear 
in your station is properly bonded together.

Leigh Klotz said, 

>It may be, as Jim K9YC has hinted, related to core saturation 

The most important difference between the Line Out and the Headphone 
Out IS the transformer and the 600 ohm resistors, and it IS the cause 
of the much higher distortion on the Line Out. BTW -- 600 ohms has not 
been good engineering practice in audio for at least 40 years (since 
the days of TUBES). Modern audio stages have LOW source impedances and 
HIGH input impedances. 

73,

Jim Brown K9YC