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Hello Everyone,

It's been awhile since I've been on the forum, but I'm in the midst of my new audio build and I've run into some issues.  I'd really like help to problem solve these issues.  I'm running an active 2 way front stage and a 12" sub in the rear.

First things first, here is a short run down of the parts related to my issues:

H/U= Pioneer 80prs. network mode. internal amp off. running directly to my 4 channel amp and sub signal to my monoblock.

4-chan amp: Jensen Power 400.4  rated at 75w rms @ 4 ohms per channel

monoblock:  Hifonics brutus brx1600.1 

First issue.   I was beginning to set the gains on my amps, but when setting them I can only seem to turn the gains about 5 to 10 degrees above minimal gain before distortion on both amps.  I'm using a DSO oscilloscope to see distortion in the signal. On the 4 channel amp, I measured 4.9v from the deck and nearly 17v out of the amp. Does that sound right? The math seems to check out.  17v on a 4 ohm load gives 4.25 amps equalling 72ish watts. Is it normal to only turn the gain knob a few degrees?

 

Issue two.  Stick with me for this one.  Since the 80prs' high frequency outputs lowest setting is about 1.25kHz, I used the midrange rca's to set the gains for the tweeters and mids.  I used a 100hz and 1k Hz test tones at 0db , -2.5db, and -5db. During this test is when I noticed an issue. I had the drivers side speaker wires unplugged from the amp and all rca's unplugged except the driver side mid rca.  I had that plugged into channel 4 which is set up to be the driver mid. (note: channels 3/4 share a gain and 1/2 have a gain, so 3/4 are mids and 1/2 are tweets.)  When I played a 1k Hz tone into channel 4 (driver side mid) I heard an audible, but low volume tone out of the passenger mid. I played pink noise to test and I heard an even more noticeable static sound out of the passenger mid.  Now I might be wrong, but if the rca for that channel is unplugged, shouldn't that speaker be completely silent? 

 

Just another thing,  I left all the gains where the scope showed clean signal, where I left it was set using a 100Hz -2.5db tone at max headunit volume, and playing music at max volume the sound is what I would call regular driving volume.  It is not loud.  You can definitely talk to the passenger with the volume at max.  There should be more volume.  In the previous build, I had the same amps and a pioneer avh double din and the gains were set by ear. That system got so much louder it's laughable. The last build the gains were set at around 75% with no audible distortion.  Now they are at around 10%. 

So I'm curious, bad amp? bad scope?   Help, Please.

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