[Elecraft] Audio interface issue.

[Jim Brown]

Hi Dick,

I suspect some sort of problem related to power wiring, and perhaps to 
equipment bonding, is causing the equipment failures. I would check 
every power outlet for wiring errors -- hot and neutral or neutral and 
green swapped, stuff like that. I would also bond every chassis to every 
other chassis with short, fat copper, including the computer, the 
dongles, etc. One of these boxes (usually the power amp or rig) should 
be bonded to the power system ground, the antenna entry ground, etc.

There are some pretty flaky dongles and sound cards in the wild. I had 
some little $35 USB POS that sort of worked, but was junk. The two I 
bought a couple of years ago work great. One, the Tascam US100, is 
discontinued, and is what I use on my main rig. I paid about $75 from 
B&H about 3 years ago. At the same time, I bought the cheapest stereo 
Numark for about $35. It also works fine, and I use it on the second 
radio for SO2R RTTY (and to a second laptop). Both are free of Pin One 
Problems, they are equally good at decoding RTTY and JT65, both go 12 dB 
farther down into the noise than the Thinkpad T4x-series built-in sound 
cards. If I were buying a USB box today, it would be the lowest cost 
Tascam replacement for a higher budget, or the Numark for low budget. 
The advantage of the Tascam is that it has more gain on the line inputs, 
so you don't have to crank the K3 as much.

73, Jim K9YC

On 4/9/2014 10:48 PM, Dick Frey wrote:
> I have blown up computer motherboard audio line inputs on three computers
> and two USB audio adapter dongles trying to run RTTY or PSK.
>
> The Line Out is set at "nor 15". There was a direct connection from Line
> out to the rear sound line in.There is a large ferrite 51 mix choke on the
> cable. There was a ~20dB pad in line going to the mic input on the
> dongles. The antennas are >150' away 75' up, and I am running 500W.
>
> The line output is transformer-coupled, right? It appears there is some
> sort of transient that's killing the input to the audio codecs.
>
> Does anyone have experience with this problem?
>