4Ch Amp Help

[SHO_POWER]

Recently I bought an Infinity Reference Series 7540a 4Channel Amp.. I did all the wiring myself and have a couple questions. I am getting a high pitched wine from the speakers when I accelerate hard. I feel that this is due to a bad ground?? I grounded the amp and the Head Unit to one of 3 nuts in the rear strut tower on the passenger side.

The next question I have is concerning Xover mode. My amp has 3 modes HP/FLAT/LP right now I have it powering my front 6 1/2" JBL components and in the rear I have JBL 6X8" 's. I am currently running the amp in FLAT mode, should I be running it in HP (High Pass) mode ??

Last question... I just have my JVC head unit sitting in the dash with no mounting bracket. I have done a bit of research on how to mount the deck on the forum and found that the best way is to use the metal mounting sleeve..does anybody have any pictures of this ??? I just can't picture how this will work.

Greg

 

[Brandontw]

engine noise is a big problem with aftermarket systems, especially In SHO's it seems, becasue i have the same issue, after lots of advise the olny answer i got is "reground amp and HU", so that is what i suggest to you. use big wire,keep it as short as possible and have a SOLID place to ground it. i got rid of mine for the most part, but it is still there and faint, im not sure what to do either..and i know quite abit about car audio.

also, wether to run you speakers in high pass or no filter (flat) is up to you mostly, if you dont have a sub and want your speakers to produce as much of the low frequencies as possible, leave it on flat, but if the soeakers are distorting at higher volumes or too much bass is being reproduced for the speakers capabilities, try it on high pass, also usually the amp will have an adjustment for where it "cuts off" the frequencies, adsust that to you liking if you use the HP filter.

 

[tominos]

i just installed an alarm in my 95 sho, and i can hear a similar whine. the grounds on my speaker amp aren't that great, so i think i'm going to rewire it, and also reground the head unit. i have an eclipse 70x4rms speaker amp, weird because it didn't whine before i installed the alarm. must have knocked a ground loose or something.

 

[30footSHO]

Use a point somewhere on the chassis; I usually use part of the metal between the side of the trunk and the carpet covering that side. If you still get whine, try using a ground loop isolator on your RCAs. My guess is that your problem is simply a bad ground. Make sure to scrape off the paint and always ground to bare metal.

As for the mounting sleeve, here is a thread with pics to illustrate how to use it. It's extremely simple.

 

[SuperHO]

Agreed....your whine is caused by a bad ground on the amp. make sure the grounding point has been sanded down to bare metal and the connection's tight. If your deck is grounded in the trunk, that's very WRONG!!! Pull your head unit back out and ground it to one of the lil bolts over the top of the ashtray....you'll see what I'm talking about.

Your amp setting depends on what you like your mids and highs to sound like. If you want them attemptin to reproduce sub-bass frequencies, then by all means, leave it on flat....I'd personally run it on HP and get a sub....but that's just me.

As far as mounting...I have no idea....I know nothing about stereo installations....:hdance:

 

[tominos]

so would it be ok to run a 4ch amp on high pass powering the 4 speakers? wouldn't that cut out all midrange?

 

[SuperHO]

yep....most high pass filters that I've seen cut em out around 250hz....sometimes lower, sometimes higher...depends on the amp manufacturer..but that's usually where the HP filter is.

 

[SHO_POWER]

Agreed....your whine is caused by a bad ground on the amp. make sure the grounding point has been sanded down to bare metal and the connection's tight. If your deck is grounded in the trunk, that's very WRONG!!! Pull your head unit back out and ground it to one of the lil bolts over the top of the ashtray....you'll see what I'm talking about.

Your amp setting depends on what you like your mids and highs to sound like. If you want them attemptin to reproduce sub-bass frequencies, then by all means, leave it on flat....I'd personally run it on HP and get a sub....but that's just me.

As far as mounting...I have no idea....I know nothing about stereo installations....:hdance:

Why is grounding the amp and the headunit in the same spot WRONG????? I did some further reading on different sites and learned that the high pitched whine could be caused by a difference in potential grounds...by grounding the amp and the headunit in the same location, that will ellimate any differences in the 2 grounds...

 

[SuperHO]

A ground should be no longer than 3 feet....amp or head unit. Stock head units usually have longer grounds, but they sure as heck don't put out the power. For a high power head unit like todays aftermarket as well as ANY amplifier, the ground should be no longer than 3 ft....preferably under 18 inches....and the guage of wiring should match that of your power lead. If you have .4 guage as a power wire on the amp, your ground needs to be .4 guage.

 

[30footSHO]

FYI, my deck has a HPF feature. I have it set at around 100 Hz. You can usually pick between 80, 100, 120 and 160 Hz. If you have a Q function (read: dial) then just set it like you would set your gains. Turn up the music to the loudest level you would listen to it and set that sucker 'til it sounds right.

 

[dcadogan]

I just installed the same amp and have the same problem. I regrounded all my amps and HU and still get a slight whine when my lights are on. I leave the interior speakers on flat at about 1/2 gain and keep the low freq setting on the head unit at about +3dB (+9dB being the max setting) and I do not get any distortion (I do have a sub and pass everything under 300hz through a separate amp and the sub). I have also found routing your interconnects as far away from your power cable as possible can reduce a bad alternator whine.

 

[SHO_POWER]

that's cool how we both have the same car and the same amp. Do you have any pics of your install ?? I guess there is no way to get rid of this slight whine. I always run with my headlights on becuase I want the FOG's to be on.

Greg

 

[SuperHO]

I have no idea what y'all are doing wrong...I've installed oodles of amps and subs and what have you in SHOs and other cars, and I've never once come across alernator whine....

are you running with an aftermarket head unit? If so, then go ahead and try to chassis ground that....I've found the lil bolts that hold the ashtray on the underside of the dash work REALLY good for chassis grounds on the deck....

 

[pimp]

for your inside speakers leave it on high pass, only low pass for subs.it seems all older shos get that whine, got it in 2 cars before and they were 89s.adjust ground to a different point as stated in other replys and the 3ft ground wire rule is also a wise move.most likely the wine is comming from the deck connection but maybe both.

 

[93rev2sev]

I tried all of these tricks years ago. But still got whine...Turning my amp down was all that helped. Anything above 50% or so and the ignition system was audible.

Then I bought a high powered head unit and ran the in-cabin speakers off of that. I then used a 2-channel amp in low pass mode to run a pair of 10" subs. Low pass mode for the subs filtered out the RFI.

You will have to run new sheilded speaker wire throughout the car from the head unit directly to the speakers. This is the only way I have ever gotten rid of RFI in a SHO and I have put several systems in SHOs. I have chased this problem with ground loop jobbies and capacitor thingies and pulled my seats out to run power lines at least 18" away from RCAs...the whine was still there. Trust me...save yourself a lot of time and perhaps some money and forget about a separate amp for the cabin speakers...

I just bought a kenwood 4032 off of ebay brand new for about $125 shipped. It has plenty of power to run door and deck speakers. It also has subwoofer controls, high pass filters for the front and the back speakers, low pass for the sub output and zero engine noise. It's plenty powerful for door and deck speakers (high pass enabled) unless you have invested significant money in them...like $300/pr. In which case, you are probably at a competetition level and have capacitors and x-overs and dynomat and don't run the engine when competing.

If you want to chase this problem, start by disconnecting the alternator completely so that the engine is running off of the battery. If the sound goes away, your alternator is making the noise. If not, then your ignition is making the noise. Either way, the RFI will find its way into your amp...grounded 10' away.

 

[Titanium89sho]

I have an '89 SHO with a pretty powerful system (3 12" Fosgate, JBL powervalve Amp, Fosgate 601 S high amp, and infinity components) and I have no engine noise.
The quality of your RCA's and power/ground wires have a lot to do with engine noise as well as location. your power wire should be run on the opposite side of the car than your rca's and speaker wires. Also, you need to make sure that the power wire stays separate even when getting close to the amp for as long as possible. If your rca's or spekaer wires are run with your power wire, you will definitley get engine noise. Your rca's should be twisted and shielded and you should definitley move the HU ground to the front of the car. Make sure all of your connections are solid everywhere, one loose connection anywhere in the system, and you will get noise as well.

Also make sure to stay away from running any wires up under the dash as this will bring engine noise as well. When you run your rca's and speaker wire, keep it under the carpet until it is in the middle of the car, then run it up to the head unit. There are a lot of electriconics in the dash that will give off interference to the stereo.
Hope this helps.

 

[SuperHO]

don't run the engine when competing.

Erm...not running you car during a competition is a very bad idea. The amp(s) wouldn't be getting the neccessary voltage and something would wind up blowing...with one or two car audio competitions (including one 2nd place trophy), I've never once seen ANYone compete with the car turned off.

Titanium89 just hit up my next suggestion. If you're running your power wire next to your RCAs, then chances are you're going to get some noise filtered through. Unplugging the alternator won't solve anything....we already know that's where the noise is coming from. Pretty much a given, since the noise rises and falls with engine RPM. seperate your power, ground and RCAs and see what happens, and we'll go from there.