[Elecraft] [K3] K3 and noise with external speakers

[Thomas Horsten]

Hi,

I like to alternate between operating with headset and speakers and find
the K3's built-in speaker inadequate (plus I want stereo). So I purchased a
pair of Audioengine A2 speakers (black, and with the corresponding desk
stands, wonderful little speakers I must say and they look GREAT next to
the K3 - judge for yourself: http://goo.gl/KErTo)

Now the problem is that I have been running with AGC=LOW since it gives me
a comfortable range in the headset. The speakers have a volume control on
the back, so I thought I could adjust that to get a volume that was similar
in the headset. The problem is that with a low enough AF volume setting on
the K3 that the headset isn't blasting my ears out, and the speakers volume
set to give a similar level to that of the headphones (about 66% of their
max), the speakers give a very noticable very low frequency bassy "click"
once a second anytime the K3 is turned on.

It's like "thump, thump, thump" at one second intervals. This is loud
enough to be noticeable when the speakers and the headphones are at about
the same level for the real audio. If I turn the speakers' gain down and
turn the K3's AF knob up, I get FB loud enough audio without hearing this
problem, but with a low enough volume in the headset for it to be
comfortable, I have to turn the speakers up where the "thump" gets
noticable to get rid of it again.

I'm powering my K3 from a car battery that is in turn hooked up to a smart
charger. This has never caused me any problems in the past, but it would
seem that this artifact comes from the smart charger somehow, as soon as I
disconnect it the problem goes away and I can have the speaker volume all
the way up to max without hearing it.

As I said I've never had any audio (or other) problems before from having
that battery charger connected. Any suggestions for what to try next would
be appreciated.

73, Thomas M0TRN