[Elecraft] Mic Pre-Amp

[Joe - aa4nn]

Hi Ian,

Check http://www.qsl.net/la3za/K2/modAny.html where all official and 
unofficial K2 mods are listed.

The Heil mic elements do not offer enough drive and you´re about 6-10 db 
down without a modification.  Several solutions are described, yet there is 
a simple mod you can make for using Heil mics.  We made these mods on the 
K2s we used during the Banaba DXpedition, T33C, as suggested by Frank, 
DL4KQ.

If on the mic connector you soldered a 5.6k resistor, remove it.  This is 
only needed for electret mics.  You also must jumper the K2 for the Kenwood 
mic.

Improving the sensitivity of the input needs to be done on the KSB2 board. 
Simply replace R14 with a 5.6 k resistor.

Originally the mic gain settings were:
SSBA 1 = - 6db, SSBA 2 = 0 db, SSBA 3 = + 6db
Now they are (roughly):
SSBA 1 =  0 db, SSBA 2 = + db, SSBA 3 = + 6-10db

Using the SSBA 3 setting you will now have enough level to work with the 
insensitive Heil element.  But remember when using other elements you have 
to go down in setting to avoid distortions.

73, Joe, aa4nn
----------------------------------
Hi all,
> I am currently using my K2 with a Heil HC-5 insert to good effect on
> DX.  I was wondering though if I should build a little pre-amp for the
> mic?  I notice there is a circuit on the website and I wondered if I
> would gain anything from building it?  I don't want to put too much into
> the K2 from the mic, I would just like to up the audio a little.
>
> Your thoughts appreciated.
>
> 72/73
>
> Ian