[ARC5] Reverse engineeing the BC 456

[Chris Bowne]

Many years back someone had a simple circuit published in ER of an electret element mic and I believe a source follower low impedance  output stage with appropriate gain ahead of it to provide more than ample drive for the various WW2 sets that were designed to be used with a T-17 carbon mic, maybe someone can supply the particular issue to look for it in.  If you can't fit all the components in the T-17 case, why not just have them in an in-line tube of appropriate size on the mic cable?

Sent from my iPhone

> On Mar 18, 2017, at 13:46, J Mcvey via ARC5 <arc5 at mailman.qth.net> wrote:
> 
> My idea to to modulate the bc456 with a 'level shifted" electret mike hit a snag.
> 
> The mike input transformer has ratio of 1:10 primary to secondary which is terminated with about 3000 ohms which means that the primary is looking to match a 30 ohm device?
> 
> That explains why the modulation is so poor. My T-17 likes to be around 2K.
> It also precludes using the electret output directly because the internal fet needs a drain resistor of 2- 5k to provide the gain, requiring a medium Z to match.
> Bummer...
> Nothing is ever simple...
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