Has anyone been able to verify with an RTA if the factory HU output, pre factory amp, is clean all the way to 40? If not, what level yields the maximum clean signal? I saw another post on here where a user said he thinks its relatively clean all the way through 40 but was hoping someone had a definite answer as to what the most optimal level is.

 

yes

 

https://acurazine.com/forums/3g-tl-audio-bluetooth-electronics-navigation-94/signal-processor-no-signal-processor-888547/

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It's quite possible I screwed this up, but I tested my head unit with an oscilloscope and it started clipping at 33 with a 1khz 0dB tone.

 

hmm... and you definitely bypassed the factory amp when you did this? I ask because I recall the factory amp clipping at that same level.

 

Yes, that's one thing I am fairly sure of, since it's sitting in a box in my garage

 

Did you have all the PL2, SCV, bass/treb settings off/flat?

 

Yep. When I get a chance I'll try it again since I'm going to be settings my gains again anyway. I'll list the equipment that I'm using and try to document the process as much as possible so people can point out any mistakes I make or variables I didn't consider.

 

DiamondJoeQuimby, have you done an o'scope measurement?

 

I finally got my car back from service and could now hook it up to the trueRTA oscope to verify for myself. All those who say the HU is clean all the way to 40 are correct. I tested 0db tones at 50Hz, 200Hz 1KHz and 8KHz via cd and they were all clean. I inputted the tones to a behringer UCA202 hooked up to the PC. Rich if you also used trueRTA, I think I may know what gave you a false reading. If you leave your line input volume on your PC at 100, the tones will show clipping around 33/34 however if you back that volume off you will see the wave go back to being clean, so it would have been your PC causing the clipping and not the actual output of the HU. Hope this helps.

 

Sorry to not respond earlier, but I did do one forever ago. However I was an idiot and didn't write anything down, and then when I decided to go aftermarket h/u I forgot what I had done. LOL.

 

This is awesome information!! I wonder if the Dolby PLII has anything to do with it. I notice that when I turn it off, the audio gets way louder. Wondering if it has any filtering that senses clipping and backs off the preamp outputs.

 

It doesn't "sense" anything. The PL2 is simply a DSP program that simulates multi-channel output from a 2 channel input. It does it like all other DSPs by adjusting things like summing, crossovers, equalization, and delay. It is a preset program.

 

I never really researched how that works. I guess it's simpler than I thought. It seems trivial to me to install some harmonic filtering that detects clipping. Thanks for the note!