[Elecraft] K2 Audio issue

[John Magliacane]

--- Don Wilhelm <w3fpr at earthlink.net> wrote:

> As stated many times by Wayne B., the K2 design criteria was for low
> receive current consumption and that is one reason that the K2 has
> limited audio power output.  The current consumed by a higher powered
> audio stage could likely take more current than the rest of the receiver.

For a linear, class AB audio amplifier, I would agree.  However, there are some
very efficient Class D audio amplifiers on the market now that deliver an
amazing amount of audio power from very tiny packages.

Check out:

         http://monolithicpower.com/prd_05_classd_amp.htm

They have a 20-watt amplifier in an 8-pin DIP package.  It's rated at 24 volts,
and can operate down to 9.5.  The quiescent current at 24 volts is a whopping
1.5 mA, and efficiency is 93% at 20-watts!  (I'd assume the power output at 12
volts into 4 ohms is 20/4, or 5 watts.)

The challenge, of course, will be in preventing the switching noise from the
amplifier from destroying the noise-floor of an already very quiet receiver.

As far as getting more volume from an 8-ohm speaker, there may be small 4-to-8
ohm matching transformers available that can do the trick.  An old audio output
transformer with 4 and 8-ohm taps on its secondary can be wired as an
autotransformer to achieve a similar effect.


73, de John, KD2BD


Visit John on the Web at:

	http://kd2bd.ham.org/
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