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 Post subject: What is the 'best sounding' simple solid state AM detector?
PostPosted: Dec Tue 05, 2017 2:18 am 
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Joined: Sep Sun 04, 2016 9:26 am
Posts: 32
Location: North Queensland, Australia.
G'day all, please forgive my hi fi AM indulgences for a moment. I'm always looking for the nicest sounding/lowest distortion AM detectors that I can build and I'm trying to arrive at a definitive answer purely on the basis of listening.

All my DIY AM detectors sound good patched into a good audio system including my various diode and infinite impedance designs but trying to find the best sounding is a bit like 'splitting hairs'! So far I put my 'voltage doubler' two diode detector as the best sounding in terms of general clarity, but there isn't much between all of them! Any thoughts or comments. Regards, Felix.


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 Post subject: Re: What is the 'best sounding' simple solid state AM detect
PostPosted: Dec Tue 05, 2017 6:40 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 25759
Location: SoCal, 91387
What Diodes are you using? I've found the best to be a 1N64.

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 Post subject: Re: What is the 'best sounding' simple solid state AM detect
PostPosted: Dec Tue 05, 2017 10:06 am 
Member

Joined: Sep Sun 04, 2016 9:26 am
Posts: 32
Location: North Queensland, Australia.
G'day mate, mostly BAT-46 Schottky diode 'germanium diode equivalents'. Regards, Felix.


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 Post subject: Re: What is the 'best sounding' simple solid state AM detect
PostPosted: Dec Thu 07, 2017 7:04 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2074
Location: Saskatoon
There is a whole range of linear detectors from simple passive circuits at the low end, to precision rectifiers, to synchronous detectors at the high end. Since you specified simple, here's a diode linearization scheme that uses two diodes and two resistors.

Attachment:
LinearDetector.png
LinearDetector.png [ 23.29 KiB | Viewed 141 times ]


It forms a voltage divider with identical components on each leg. Since the components are identical (assuming the diodes are matched), the output must be exactly half of the input voltage when forward biased. Thus the diode nonlinearities cancel out. So you get linearity at the expense of having the signal attenuated by half. For this to work properly, the output impedance of the IF should be much lower than the 4.7k resistors, and the input impedance of the audio amplifier stage should be much higher than the 4.7 k resistors.


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