[Boatanchors] Re: Hi FI amp as speech amp

[WA5CAB at cs.com]

I think this thread went off on a tangent, with most recent respondents maybe 
not knowing how a BC-610 is actually built.  If someone is going to use a "hi 
fi amp" instead of a BC-614-(*) to drive the audio in a BC-610 (any model), 
it only needs to put out a watt or less into 500 ohms because you are driving 
the grids of a pair of push-pull 2A3's, not the grids of Class B 100TH's.  The 
output stage of the BC-614-(*) Speech Amplifier is only a push-pull 6SN7GT.  
So if you are going to use a civilian amp, you should probably pull the 6V6 or 
6AQ5 output tubes and match the driver to 500 ohms.

Nothing was said in the original post by the 610 owner about  extensive 
modifications having been made to his transmitter.  An easy test of the BC-614 can 
be done by temporarily connecting an LS-166 or LS-454 Loudspeaker to the 
output.  Both contain a 500 ohm to voice coil matching transformer.


> As *** mentioned, you can use an external amplifier as a driver for the 
> BC-610 modulator tubes without worrying too much about the amps' output 
> impedance so long as you have a suitable transformer to somewhat match the amp's 
> output to the modulator tube grids.  You need to ...
> 

Robert Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480
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