Internal Noise

Whitehall

Super Member
I don't mean your tummy rumbling, I mean background noise from a FM tuner.

Most manufacturers will offer a specification for tuner noise. The best are over 90 dB while most decent units are in the low 80's.

This is not noise coming down the antenna lead, its just noise generated within the tuner or tuner section.

Where does this noise come from and what can be down to lower it?

The reason I ask is that my Marantz 4300 has the best sound so far but has noticably more background hiss than my other units. Is this a maintenance issue or would specific modifications help?

Others have scoffed at my earlier suggestion that lower noise FETs in the RF front end and in the IF amp might be useful.
 
recapping might help?

There has been discussion in various threads about the benefits of replacing old electrolytic capacitors, and I have noticed suggestions that aging electrolytics can contribute to background noise.

I am not an authority on this topic, so please consider this comment merely as something worthy of further investigation.
 
I changed the caps in a cheap alarm clock radio the other day that was making that kind of noise (to see if it would help). I doubled the capacitance of the 4 or so electrolytics. It reduced that sound a bit, but the problem is still there. I think the main problem affecting background noise is the need for a tuner adjustment.
 
The power supply capacitors, if failing, would pass additional 120 Hz hum. I'm not hearing that, rather, it's a static llike background.

The sources could be two places: design or maintenance. On the design side, one can shield internal cables and components and add lower impedance grounding. I did notice that Marantz never published a figure for tuner S/N ratios for this model like most manufacturers. Maybe they have something to hide.

I had it in for alignment right after I got in about 18 months ago. Of course, I came away with a very poor opinion of the ethics of the shop.

How do some tuners (the Sony ST-730ES comes to mind) achieve such low S/N figures? Are ICs the secret?
 
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