[TenTec] 6n2 aux speaker

[Dr. Gerald N. Johnson]

On Sat, 2007-06-30 at 23:02 -0600, Richard Williams wrote:
> I recently acquired a NCS  Multi-Switcher so that I can switch my two
> mics between three different radios.  The unit also switches the speaker
> audios to one speaker.
> 
> Have had the radio for a couple of years, but for some reason I had
> failed to notice that the 6N2 is one of the few radios that does not
> have and external speaker jack.  Found that surprising, but figured
> installing one would not be a big deal;  however, after taking a quick
> look at the schematic, it looks like Ten Tec is not using a "standard"
> audio arrangement.   I.E. where one side of the speaker is grounded
> 
> Am wondering if anyone else out there has "modified" the 6n2 so that an
> external speaker can be used and one side is grounded??
> 
> Thanks
> 
> Dick K8ZTT

I don't have a 526, but if I did, I would first determine the internal
speaker impedance. Besides using a balanced or bridge amplifier the
impedance may be far from 4 or 8 ohms typical of external speakers. Then
I would select a transformer or pair of transformers to match that to 8
ohms and use a phone jack with an auxiliary SPDT switch to select the
internal speaker or the transformer(s) to the external speaker. If the
internal speaker was 32 ohms Z, I might use a 42TU120-RC using half the
primary, or if the internal speaker was 8 ohms, I'd use a pair of any
transformers with the same impedance with one driven on the 8 ohm
winding, the corresponding high impedance leads connected (two of the
three if center tapped) and the other 8 ohm to feed the speaker. It
would be also practical (though less compact) to use 25 or 70 volt line
to speaker transformers like used to be sold by RS and are still sold by
places selling parts for PA systems.

-- 
73, Jerry, K0CQ,
All content copyright Dr. Gerald N. Johnson, electrical engineer