[R-390] What have I done?

[dog]

Yes indeedee. I've been using the diode load for a long time. I just put 
a cheap LM380 type amp on the thing through a cap, the 380 won't even 
see the 455 near as I can tell. Sounds much better than the filtered AF 
amps. Thanks for that circuit though Charles.

Dave N3DT

On 5/10/2019 23:14, Charles Steinmetz wrote:
> John wrote:
>
>> I tried the diode load AF amplifier hi-fi method tonight and was stunned
>> over how much better the R390A sounds that way.  If you haven't tried it
>> with yours, do it!!!!  AC couple the diode load output through a
>> electrolytic capacitor to a good AF amplifier and a hi-fi speaker.  
>> Wow!  I
>> won't say it's FM quality, but it's really, really good.
>
> An electrolytic capacitor at this location is not a good choice, 
> because it gets no DC to keep the electrolyte layer biased.  Also, a 
> shunt capacitor is a good idea to filter out the residual 455kHz (and 
> harmonics) that appear at the diode load terminal, so your audio 
> amplifier doesn't have to deal with them.
>
> I posted a recommended circuit for a diode load tap some while back:
>
> <http://www.ko4bb.com/getsimple/index.php?id=download&file=05_Misc_Ham_Equipment/Collins/R390_R390A_diode_load_line_level_audio_tap_schematic_STEINMETZ.pdf> 
>
>
> Best regards,
>
> Charles
>
>
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