Re: [Elecraft_K3] K3 - background hiss (noisy K3) - update


Mel Farrer <farrerfolks@...>
 

Might I ask if you have tried to isolate the source?  In the tube days a gentle hiss was attributed to the electron bombardment of the plate from the cathode and was never "completely" eliminated.  While we are now in the days of SS, that issue is mute.  However, I suggest as mentioned earlier, that you might have a external source of the "hiss".

I would connect a scope to the audio output through a 1:1 audio isolation transformer and determine the frequency bandwidth and characteristics of the "hiss".  Then start isolating the K3 from all connections down to running it on a floating battery. 

I do not have your "hiss" and I am totally battery powered from solar.  That includes shorting the antenna terminals after reading your thread.  Hope you find the source,

Mel, K6KBE



From: "mikerodgerske5gbc@... [Elecraft_K3]" <Elecraft_K3@...>
To: "Elecraft_K3@..."
Sent: Thursday, October 1, 2015 8:22 PM
Subject: Re: [Elecraft_K3] K3 - background hiss (noisy K3) - update

 
I tried this on k3 5047 using some cheap earbuds and I plugged in my dusty cm500's. 

I can barely detect anything, even less so with the cm500. Plugged into the external speaker jack. 

Is it possible you are picking up something through a ground loop condition?

73
Mike R

Find me on "Zello", a walkie talkie or handi talkie type app. I'm listed as KE5GBC. I'm mostly on late at night. 

On Sep 29, 2015, at 6:45 AM, "bozidarms@... [Elecraft_K3]" <Elecraft_K3@...> wrote:

 

Hi,
i have studied all the posts about this topic.
Seems, that is still, huge confusion about that, so i will try to formulate a problem on simply way:

With low impedance earphones plugged into the audio jack on the K3, you can hear a really annoying noise (hiss) even with the AF and RF volume set to zero(CCW). This audio hiss has a constant level, is added to the audible RF noise and can prevent one from hearing weak  signals on an otherwise quiet band.

That hiss has nothing to do with K3 receiver or settings - simply is permanent present.
This indicate that something must be wrong with earphones amplifier LM4811MM, and that is
odd, because LM4811MM seems to be an high quality chip, designed exactly to work with low impedance earphones , with a minimal amount of external components?
My question is:
is, in the mean time, known any hardware (or anything else) modification for that issue?

best regards,
Bozidar



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