SQ issues. Alternator whining noise in speakers.........

[Slammer 10+ year member]

Okay, I decided that I hand't had too much to drink to be jacking with the stereo, so I went ahead and hooked up the ground isolator. NO difference. It is only for two channels, so I disconnected the rear RCAs, and ran the isolator in the front channels. Turned the gain all the way up with HU volume down, and still had the whine. Then I backed the gain down to 3/4, and finally down to 1/2, and still had the alternator whine. Only with the gain at 1/4 or less, is the whine inaudible (which is the same as without the isolator). I have no idea now, unless it is in the output of the amp. The isolator should be cleaning up anything coming from the HU, the factory amp, as well as from the RE-Q5 processor. Seriously puzzled on this one. If it weren't for the fact that it requires extensive mods and great fabrication skill, I would just run an aftermarket HU. Going to swap amps next. We will see.........

 

[helotaxi 5,000+ posts]

Where are the output levels on the RE-Q5 set?

 

[Slammer 10+ year member]

It has a gain knob for each channel, and ranges from 0v to 2.5v. I currently have all four set in the middle (1.2v). I tried a ton of combinations the other day. Went with more gain at the RE-Q5 and less on the amp, and the other way around. What I know for sure, is that with the gain on the RE-Q5 turned down, it barely plays at all. I left it at 1/2 and then made all of my other adjustments at the amp.

With gain on the RE-Q5 at 1/2, I can not go higher than 1/4 on the amp or I get the whining noise. If I run the gain higher on the RE-Q5, it whines with the amp gained at 1/4. No combination that I tried would let me get adequate power to or volume out of the speakers without the whine. Don't get me wrong, it plays loud, but gets much, much louder (and is still clear) with more gain. The only reason I have the gain down, is that the whining noise will drive you crazy anytime the HU volume is lowered.

 

[Slammer 10+ year member]

I could try using a cheap hi-lo converter, and tapping the front speaker wires, then running that to the front channel of the amp, just to bypass the RE-Q5..........? Just a thought.

 

[helotaxi 5,000+ posts]

Just curious why you're summing all the channels. I really can't help but believe that is a big part of the problem.

 

[Slammer 10+ year member]

I just assumed that it would be the wiser choice, so that I would have full range going into the amp. Coming out of the factory amp, there are channels for each rear door, two channels for the factory sub, channels for each front door (mid and tweet), and channels for each front door's woofer. When I installed the components, I used the only channels for the rear doors, but used the "woofer" channel for the front doors to run the front components. I did this before the install of the amp and the RE-Q5 and had no whining noise. SQ was horrific, as the factory amp is probably putting out 15-20w rms per channel, if that, and there was no way to get it loud without maxing out the HU and sending clipping signal. With the processor and amp, the SQ is much better and the volume has doubled, but now have the issue with the whining noise.

When I started studying the schematics on this car, I was looking at using the JL CleanSweep. While I decided not to use the CS, both processors have enough high level inputs to get all channels out of the factory amp, so that the processor can convert them into the fullest range possible. Just thought it would be the right way to do it.

 

[helotaxi 5,000+ posts]

I would at most use the one set of door outputs (front or rear) and the sub outputs, assuming that there is no way to tap the signal ahead of the factory amp (which would be my first choice by a long shot.

 

[Slammer 10+ year member]

No way to tap the input of the factory amp. Mentioned earlier that there is only one audio input (+ and -), and then one pair of digital ATX inputs. Not to mention that all of the balance, fade, mute and steering wheel controls would be lost without the factory amp. I may try the hi-lo converter tomorrow, or possibly even pulling the inputs for the rear speakers and front mid/tweet stage out of the RE-Q5 to see if that helps. I wish I had a way to tell what the crossover points are in the factory amp for each channel, but that info is not to be found anywhere.

 

[helotaxi 5,000+ posts]

That +/- cannot be an audio input then if there's only one. I find it very odd that Lexus would spend the time, money and effort to put an amp with a DA converter in it in a factory stereo.

 

[Slammer 10+ year member]

My bad. Just double checked the schematic. Ther are two channels of audio input, which are then sent out of the amp as 8 channels to the 13 speakers (dual voice coil sub has two channels). I could try splicing these inputs into the RE-Q5, and taking the other channels out. Would be a ton of work, but worth it if it works. I currently have 14 lines spiced into the RE-Q5 now. If I do this, I think that I will disconnect the 14 lines (7 channels) one at a time, just to see if the whining stops when one of them is disconnected.