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 Post subject: Magnavox CR-192 FM tuner question
PostPosted: Nov Tue 28, 2017 1:49 pm 
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Location: Warner Robins, GA
I have a Magnavox CR-192 FM tuner I restored to working condition including adding an AFC circuit and getting the alignment pretty much perfect so that the IF has enough bandwidth to feed a MPX decoder and it gives pretty good stereo separation.

The problem with it is the audio seems a bit bass heavy when feeding the MPX decoder and also when directly feeding an amp with a high impedance input both without the de-emphasis circuit connected.

Any idea what could cause that?

One would think based on how it sounds that the treble is being cut, but that doesn't seem to be the case.


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 Post subject: Re: Magnavox CR-192 FM tuner question
PostPosted: Dec Sat 02, 2017 3:35 pm 
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Could it be something that is reducing the treble some as I go higher in frequency while still allowing for decent stereo separation?

Maybe it is a problem with the MPX decoder.

I did find the solid state MPX decoder I made several years ago. I might try that one with a buffer between the high impedance output of the tuner and the lower input impedance of the MPX decoder and see if it sounds any better.


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 Post subject: Re: Magnavox CR-192 FM tuner question
PostPosted: Dec Sat 02, 2017 4:24 pm 
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How does the tuner sound with its original mono output circuit connect to your amplifier?

Dave


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 Post subject: Re: Magnavox CR-192 FM tuner question
PostPosted: Dec Sat 02, 2017 4:43 pm 
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Location: Warner Robins, GA
I think it sounds a bit heavy in the bass using the mono output, but I cannot remember as it's been several months since I've used the tuner.

This was originally meant to connect to a Magnavox CR-198C console which had no tweeters so it wouldn't have much mattered if the sound was a bit on the bassy side and might have even made the console sound better.

Here's the discriminator circuit.

Attachment:
Discriminator.jpg
Discriminator.jpg [ 68.7 KiB | Viewed 127 times ]


I don't see anything that would bwe causing the apparent overly bassy sound.

If needed I can email you the full schematic.

I don't think I have a buffer amp I can use to connect the tuner's output to my McIntosh C-24 preamp unless one isn't needed for that preamp. I woudl also have to make up a proper de-emphasis filter.

When getting the alignment perfected for stereo I did replace the shielded audio wire with a good quality low capacitance shielded cable to ensure there was minimal cutting of the highs by the cable given the tuner needed to pass up to a 53KHz signal for proper stereo decoding.


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