[R-390] Better BA sound

[Charles Steinmetz]

By far the easiest way to get good sound out of the 390A is to tap 
line-level audio from "Diode Load" Terminal TB103 - 14 at the back of 
the radio and send it to the audio amplifier and speaker of your choice 
(see attached image for tap details).  This applies to all BAs, but in 
some cases you may need to go inside to tap the audio and bring it out 
of the box.  One trick is to take a feed from the headphone jack, if you 
don't want to mess around inside the radio.  But the 390A makes this 
easy with the "Diode Load" terminal.

The amplifier needs to have a volume control, and it can be handy to 
have at least rudimentary tone controls.  An old hi-fi preamp and amp, 
or integrated amplifier, is ideal.  I assume most of us have one or more 
suitable candidates buried in a closet or the garage.  If not, a trip to 
the local thrift store should find one.

In my case, I feed line level audio from all of the radios to the 
various inputs of an old NAD hi-fi integrated amplifier (I bypassed the 
phono preamp to get one more line input).  It has its own tone controls, 
plus I installed an Ashly seven-band parametric equalizer in the tape 
loop.  This allows greater tone control flexibility, but its main 
contribution is to add notch filters to the audio chain for radios (like 
the 390A) that don't have them.  I find this an incredibly valuable tool 
even with radios that *do* have their own notch filters, because there 
are often two or more heterodynes I want to remove.  You'll never 
realize just exactly how irritating and fatiguing all of those birdies 
are until you've lived without them!

Best regards,

Charles


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