Kenwood Excelon HU clipping

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Unfortunately while my car was in storage my Nakamichi CD45z died. Since funds are tight and my Sony Mobile ES HU (CDX-C780) ended up in the wife's car I could only afford a Kenwood eXcelon KDC-X494. It was at a decent price and had all the features I needed, and not too many useless bells and whistles.

With the CD45z I could go all the way up to full volume without clipping. I also used to have a Crossfire CFQ20.2 that had a line driver and clipping lights. So setting the amp gains was relatively easy. A long time has passed since my days as an installer and my ears are not as well tuned as they used to be.

I have heard a couple of times that the current generation of Kenwood eXcelon deck will give a 4v unclipped output at full volume (I have the internal amp turned off). I no longer have access to an oscilloscope only a couple of DMM's. Can anyone confirm that they will go full volume unclipped on the preouts?
 
There are very few head units that won't go into clipping at full volume unless the bass, treble, loudness are set to flat or off. With the bass/treble set to flat and the loudness off, you can generally go to one step under full volume without clipping. When you set the tone controls above flat or the loudness on, it will clip well before full volume. The loudness is supposed to roll off at ~60% of the volume control's range but if it's on and the bass is set to the maximum level, the head unit will often clip before 50% of the volume control's range.
 
I totally understand the loudness and tone controls effect on the signal strength. So let's say a given HU can go full volume unclipped set to "flat". at these settings things don't sound quite right but the HU puts out say 4.05 VAC. Would it be safe to assume that the tone controls could be adjusted to sound better as long as the outputs do not produce 4.05 VAC. Like say once using the tone controls you have to back the dial down 3-4 notches to get the same 4.05 VAC. Would this be a reliable way to determine the max unclipped signal from said HU?

I generally try to not ever use the loudness or bass boost settings, but I do adjust the parametric settings for mid and treble. With the excelon units it does appear that the sub level control is also not an attenuation like on many other units. The voltage output stays the same as the fr and r set with it set to o, even though it has a range of +/-15. Obviously a way to get a distorted signal very quickly. So I may just have to leave all sub and bass controls flat and simply adjust the sub level via amp gain and match to the output of the other amp in the system, hence my question regarding when the HU clips.
 
When you measure the voltage and are trying to determine the effects of the tone controls, you have to use a test tone that's at the same frequency as the tone control.

Why not simply increase the gain settings on the amps so that the amps clip before the head unit? If they're set to clip at 3.5v, the head unit will no longer be an issue. Then you'll simply listen for clipping when driving the system hard.
 
Currently I'm trying to level match the two amps (4ch and 2 ch), but I don't know where the HU clips. So I'm trying to determine the max clean output, and them max the sub amp there, then walk down the 4ch amp to match the subs output. When maxing both amps outputs with a DMM and the HU at 75% the mids get louder much faster and louder than the subs. In total I am trying to set 4 gains between the two amps, but don't know teh HU's max clena output yet. So I'm just trying to simplify it as much as possible. I am using the appropriate 0db test tones for each respective amp/output.
 
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