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<blockquote data-quote="nathanotis" data-source="post: 8758479" data-attributes="member: 683767">Hello, all. Brand new here. I apologize in advance for the long first post. I&#039;m trying not to leave out any details.Recently installed a new head unit, RCAs to a 75w 4ch amp powering 4 5.25&quot; speakers. And a compact 8&quot; powered sub.I also purchased an inexpensive oscilloscope to check output from the head unit and to set gains on the amp and sub. The O-scope shows a clear, clean square wave when connected to it&#039;s own ground terminal, but the attached image shows the sine wave I&#039;m getting from my head unit:[ATTACH]31681[/ATTACH]No matter what I do, (different connection points, car running, not running, etc), I can&#039;t get a clean sine wave. It&#039;s always jagged and spikey. Is it ground, or noise or something?I was playing a 1kHz test tone. The O-scope is not tracking the frequency correctly. Also, the amplitude of the sine wave didn&#039;t change while I was turning up (or down) the volume on the head unit.The V/Div in the photo is also way off (50mV, I&#039;m not sure why). I just pulled a very similar looking sine wave moments ago while V/Div was set to 2V. I went to &quot;Hold&quot; mode for a slightly clearer image.I know (from testing with a speaker attached) that the head unit (which has a volume range of 0-35) goes to 30 without any audible distortion. I bought the O-scope in order to see the waveform and confirm what my ears were telling me. The plan was to set gains at the 4ch amp and the powered sub using the O-scope as well.This is my first foray into car audio, and I&#039;ve never used an oscilloscope before. I admit that I might be connecting it wrong.It&#039;s been a frustrating couple of days trying to figure this out. That&#039;s why I&#039;m here. At this point, I know enough to know that I&#039;m flailing and nothing is getting accomplished. I hope someone here can give me some guidance.I guess my first question is: How should I be connecting the oscilloscope to the head unit?</blockquote>

[QUOTE="nathanotis, post: 8758479, member: 683767"] Hello, all. Brand new here. I apologize in advance for the long first post. I'm trying not to leave out any details. Recently installed a new head unit, RCAs to a 75w 4ch amp powering 4 5.25" speakers. And a compact 8" powered sub. I also purchased an inexpensive oscilloscope to check output from the head unit and to set gains on the amp and sub. The O-scope shows a clear, clean square wave when connected to it's own ground terminal, but the attached image shows the sine wave I'm getting from my head unit: [ATTACH]31681[/ATTACH] No matter what I do, (different connection points, car running, not running, etc), I can't get a clean sine wave. It's always jagged and spikey. Is it ground, or noise or something? I was playing a 1kHz test tone. The O-scope is not tracking the frequency correctly. Also, the amplitude of the sine wave didn't change while I was turning up (or down) the volume on the head unit.The V/Div in the photo is also way off (50mV, I'm not sure why). I just pulled a very similar looking sine wave moments ago while V/Div was set to 2V. I went to "Hold" mode for a slightly clearer image. I know (from testing with a speaker attached) that the head unit (which has a volume range of 0-35) goes to 30 without any audible distortion. I bought the O-scope in order to see the waveform and confirm what my ears were telling me. The plan was to set gains at the 4ch amp and the powered sub using the O-scope as well. This is my first foray into car audio, and I've never used an oscilloscope before. I admit that I might be connecting it wrong. It's been a frustrating couple of days trying to figure this out. That's why I'm here. At this point, I know enough to know that I'm flailing and nothing is getting accomplished. I hope someone here can give me some guidance. I guess my first question is: How should I be connecting the oscilloscope to the head unit? [/QUOTE]

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