Tweeter hiss - source with scope?

[TheMonkey]

RCA input to amp unplugged, car not running, tweeters have audible hiss. Amp->Xover->tweeter.

QUESTION: Can I see if it's the speaker wiring or power source by using my oscilliscope? Pretty good PC based scope I can sample up to 100k Hz and get very good look. Just not sure what to look for.

DETAILS:

Amp = Rockford Fosgate P300X2

Component speakers = Rockford Fosgate T1650S

Crossovers directly next to amp.

Gain on amp was set with a scope.

Tech support at Rockford Fosgate said either power supply or speaker wiring is routed by noise.

Power supply: 8awg direct to battery.

Speaker wires are 16awg.

Ground is big lug and star washer bolted to wire wheeled steel of truck body next to amp. Wire connections I feel very good about. Everything is soldered well except wire clamps in/out amps, crossovers, and power fuse junction, but they are all tight and proper.

I did my best to avoid running near anything that might cause EFI, but if I can figure whether speaker wire or power line, I can chase it down.

Thanks.

Click to read more...

 

[keep_hope_alive Premium Member]

Some amps are noisier than others.  you'll have to turn the amp gain down.  That will make the hiss inaudible.  Getting to the same power output will require more signal into the amp. 

 

[DRBOOM]

Some amps are noisier than others.  you'll have to turn the amp gain down.  That will make the hiss inaudible.  Getting to the same power output will require more signal into the amp. 

Agree, its call signal to noise ratio on the amplifiers.  I have notices the newer products now days don't seem to take this important factor into consideration when selling their products.   I say, if you have access to another amplifier from a mate, take your amp out and run that to see if the problem persists.   Most likely it is your amplifier that is causing the hiss but by turning the gains down, you can reduce the hiss to non-audible levels so if you are not happy with the sound with the gains down, then it may be a good point to consider buying another amplifier with a higher power rating and a better signal to noise ratio. :veryhapp: