From: Garey Barrell 
Subject: Re: [drakelist] R4B hum - 99.9% solved


Ron -

Another biggest problem is the sensitivity of phones 
versus speaker.  Phones often require running the AF 
Gain control near zero for the desired volume.  Since 
the AF preamp and output stages in these receivers run 
"wide-open" and the volume is set by varying the input 
signal to these stages, the S/N (hum) ratio is worst at 
the lowest Gain setting.  A series resistor chosen so 
that the Gain has to be set nearer to 10 - 11  O'clock 
(EST, you DID remember didn't you?) for suitable volume 
levels will help considerably.

73, Garey - K4OAH
Atlanta

Ron Wagner wrote:
> John,
> Not sure that changing filter caps will help theheadphone hum.  Biggest 
> problem is that new headphones respond to very low freq.  I played with my 
> R4B for a long time before I threw in the towel and built an audio filter.  
> Best I can tell, it will be more a function of headphones then your power 
> supply filters.
> 73,
> Ron
> 
> 
>>won't be happy until I change out those filter caps...  :)
>>

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