[Elecraft] K3 Speaker buzz - But which external speaker ?

[Tim Tucker]

Or, one can simply choose to pay an extra $20-$30 and bypass all of the
fooling around by trying to find the right combination and just buy
something that others have proven that works.  Sacrificing the Line Out for
external speakers is a pretty lousy solution, IMO.

You originally replied that the COMspkr wouldn't work any better than the
internal speaker, however I know from personal experience that it does
exactly that.  Take off your engineer hat and put on your consumer hat.
For some of us, spending an extra couple of bucks to just be done with the
whole problem (that shouldn't exist in the first place) is worth it.  I
don't need or want to go execute an algorithm to figure out which speaker
will allow me to hear the rig at an acceptable volume.  If you like doing
that, no one is going to criticize you, however, not all of us feel like
going through that exercise.

My own experience is that I tried a bunch of external speakers with the K3
and the results sucked - in fact they were worse than other Icom and Yaesu
rigs sitting on the bench at the same time using the same speakers.  I got
tired of fooling around with it and decided to purchase the powered COMspkr
and was satisfied. Are there better solutions?  Perhaps.  Do I care?  No.
My problem is solved and I spend time enjoying the radio instead of cursing
at the volume output of the K3.



> *IF* one feels the need for an external amplifier, bypass the internal
> amplifier by using the Line Out and high cut filter to drive a better
> amplifier - something capable of 10W per channel at 0.01% THD instead
> of 3W per channel at 1% THD like the COMSpkr.  Alternatively, set up
> the external amplifier with a 16 - 32 Ohm input impedance, set the K3
> to low AF gain to keep the LM4950 in the cleanest part of its design
> range and use the external amplifier to provide the power gain.
>
> Just like RF power amplifiers, audio amplifiers are all about selecting
> the right devices, using proper design and bypassing, then matching to
> the right load.
>



On Tue, Nov 6, 2012 at 10:31 PM, Joe Subich, W4TV <lists at subich.com> wrote:

> *IF* one feels the need for an external amplifier, bypass the internal
> amplifier by using the Line Out and high cut filter to drive a better
> amplifier - something capable of 10W per channel at 0.01% THD instead
> of 3W per channel at 1% THD like the COMSpkr.  Alternatively, set up
> the external amplifier with a 16 - 32 Ohm input impedance, set the K3
> to low AF gain to keep the LM4950 in the cleanest part of its design
> range and use the external amplifier to provide the power gain.
>
> Just like RF power amplifiers, audio amplifiers are all about selecting
> the right devices, using proper design and bypassing, then matching to
> the right load.  An audio amplifier needs to be able to source enough
> current to drive the speaker without saturation or clipping.  The audio
> chip used in COMspkr and other 3W per channel computer speakers is
> simply no better or cleaner than the LM4950 used in the K3 - they all
> show high THD when operated at maximum output level because they just
> can not source the current without driving the outputs into saturation.
> That is nothing more or less than simple physics.
>



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