multi amp remote turn on question

Hello, I am new to this board and am about to install a new system into my 1999 Honda civic.     I am installing an Alpine cda-7998 headunit and 3 profile br400 2 channel amps in the trunk.    I have a few questions.   

First, I am installing three amps for the first time and I need to know if i can connect all 3 to my remote turn on lead of my headunit without risk of hurting my remote turn-on circuit of my alpine.    I visited the crutchfield advisor website and they said that multi amp systems may require a relay, but it did not show you how to determine if it is needed.     If a relay is needed, please tell me which one is good and where can i get one?    Also, how and where do i install one.    Believe it or not, ive never heard of a relay before tonight. 

My second question is this.    After reading many of the forum posts tonight, it appears that there are quite a few mixed opinions about capacitors.    I already bought one from a friend for a good deal and I intend on installing it unless i know it will damage my system.    A general rule of thumb, taken from the crutchfield advisor website, is that you only need a 1/2 farad for systems up to 500 watts and a 1 farad for systems up to 1000 watts.    Well, my capacitor is a 1 farad and my 3 amps are only rated at 100 wpc RMS each.     Do I run the cap inline BEFORE my power distribution block so that all 3 of my amps pull from it.    OR should i run the cap only to my 1 of the 3 amps that is powering my subs?    Does the fact that im using a 1 farad for such a low wattage system hurt me, help me, Or is it just overkill?   Also, can i ground my cap to the same distribution block that im grounding my 3 amps to?

My last question.     When im finally ready to start tweaking my system, setting my gains, and so forth, where do i set my headunits tone controls and parametric equilizer?   I want to set the variable crossovers and the low pass/high pass filters an my amps properly so that i can get good volume without too much distortion from low bass notes.    I am assuming i should set my equilizer to flat or about midway so that i have room to increase or decrease the settings depending on the music without it adding any distortion to the overal system.   

thanks so much, steve

You might just want to use a relay.....just because, no other reason.  Better safe and secure, than sorry!

Your cap IS OVERKILL....but thats OK. Install it as close to the sub amp as possible, after the dist block.

Do you have instructions for charging the cap??? Don't just "hook it up"  Bad things can happen

 Charge it slowly.....

Set your tone controls FLAT....no plus, no minus. As far as XO's go..just don't have any LARGE gaps where your subs stop...and your mids start...get it?

Have fun, and make it sound good to YOU....  your the one driving....

I looked for the model # of those amps and couldn't find 'BR' on the Profile site, so I'll assume the numbering is similar to their other products with each amp rated at 2 X 100 watts at 4 ohms.  You can post a link to these amps.  Use a relay when sharing the remote turn-on with more than two amps.  Use a SPDT relay... here is a source and additional information.  Also refer to the relay applications on this site ("connecting additional devices" , #30 will go out to all three amps).  Refer to the links provided in this paragraph for complete how-to.  You'll find a spot near the amps to install it.

Opinions about stiffening capacitors is generally one-sided (not what I would call 'mixed') on this forum, as this site is frequented by install professionals more so than other forums.  If you want to put a cap in the system because you were sold one, you will want it as close to the amp that will "benefit" from its use as possible.  If the cap works as you wish it to, it will store some power from the battery and release it (in milliseconds) to the amp when the music source signal demands a larger than normal peak.  The cap will then recharge from the battery and store energy, releasing spikes of power as needed.  Too much distance between the drawing amp and cap will defeat the purpose.  You have not posted the use of the three amps, but a cap, if used, would be used only with an amp that provides sub-bass power.

That said, there are several more important things to do before a cap is installed.  Make sure the overall system wiring and grounding is more than adequate for anticipated current transfer.....provide a new high current battery....provide a high output alternator (the power source)....replace the car's power and ground wiring under the hood with larger gauge....use ample gauge power and ground wiring to the audio system...clean and remove paint from chassis grounding points.....and some etc. etc.

Keep the cap ground separate from the amps (which should share the same ground point).  (There may be other opinions on that).  If all three amps are used for sub bass, (and you intend to use caps), each would have a cap installed just prior to the amp, after the distro block.  Professionals will leave this useless clutter out of the install, as power is produced and transferred starting at the alternator.

Profile brand amps will not tolerate high current applications.  Keep it simple and keep the amps at the highest ohm load possible.  Keep bass boost controls set to 'OFF', keep deck controls at flat and below.  Your loudest bass response should be with deck bass control at '0', and then adjust down if needed.  Use the low pass filter on the amp for bass use, and set the amps up identically if all three are used for bass purposes.  About 80 Hz is standard cutoff for sub bass.  If one of the amps is used for highs, it will use the HPF also set to 80 Hz (or the same freq. as the LPF).

Two things you have that might be negative to your sound/install quality:  the cap and the equalizer.  The cap has been covered here, the equalizer should only be installed in the signal path if it is needed.  Don't put it in if you can adjust sound to your liking without it.  Pay more attention to speaker quality, enclosure specs/quality, placement of subs, damping of sheet metal (Dynamat, etc.)....  Once you have all the things I mentioned here accomplished you'll likely find that an EQ or a cap would only detract or cause problems.

Search for threads on setting gain for more info.

thanks for the quick responses guys.    The BR400 is last years model of the profile baja amps.   pretty much same specs and features as this years BA400.   I chose them because i used profile Clarus line amps before and felt that they had so much bang for the buck.  

As for the equilizer, the Alpine cda-7998 has a built in 5 band parametric.   I can even utilize their online i-personalize website and store my preferred eq curves in the event i need to re-enter them.  

I have a pair of MB-quart discuss 6.5 components in my doors and a pair of MB quart discuss 6x9s in my rear deck.    My subs are a pair of fosgates 8 ohm 10" woofers.   

Im going to bridge one of the 3 amps and wire my 2 subs in parallel so my amp only sees a 4 ohm load.    the other 2 amps will of course run the front and rear speakers.

thanks for the advice about the relay.    i will look into this further.    Last thing i want to do is damage my headunit.   

thanks for the advice about the cap.    i have installed these before and understand fully the need to charge them.    every manual you ever get makes sure you know to do that.     

My system is nothing big or extravagent.    I am more of a hobyist than a luthier when it comes to car audio.     I am into value and bang for the buck.    but i tell you nothing is more satisfying than to install a system like this or others that i have done and to turn it on and have it all work and with minimal or no troubleshooting required.   

i will be sure to let you know how it comes out.

steve

Sorry I got a bit elementary in my answer.  I didn't know what level of experience you had with installing systems.  (...and I was up an hour too early for work, anyway...)

I use a Clarus amp, too, with my bangforthebuck system and it's been a solid performer, although I don't ask too much of it.  Good luck putting it all together.

thanks for helping me out with a few answers guys.    I have researched and decided that I will add a relay to my system.    I just purchased an Alpine cda-7998 and am patiently awaiting its arrival.    since i have never heard of a relay  till yesturday let me ask a few questions so that I install it correctly.    First, I visited www.alpinetechcenter.com, entered the free consumer site, and scrolled down to the bottom of the first page to a pdf document titled "auto-open/close tech tip for cda-7998 & cda-7897".     Would somebody kindly review that with me?    Upon examination, it clearly shows how to install a relay, and in doing so, you must add a 2 amp diode to prevent malfunctions in the auto open/close function.   

Well, my first question is to see if i understand the wiring diagram correctly.     The relay is installed at the end of my radio's remote turn on lead and a wire continues on to my 3 amps.    In addition, a lead is run from the relay to the battery, and also to a ground.    If i understand the concept correctly, it appears the relay takes a "turn on" signal from my radio and boosts it by taking power from my battery?    Cant I simply splice the yellow battery lead of my radio's wiring harness instead of running a dedicated wire back to the battery?    In addition, can i simply ground it by again splicing into my radio's wiring harness' ground lead?   Either way, if i installed it correctly, then i should be able to then run my remote turn on lead back to my trunk, and then splice it 3 ways to each of my amps and turn them on without worry or trouble right?  

My second question is this.    I bought the spdt 30A bosch relay today and sure enough, its exactly like the diagram in this pdf file i mentioned above.   Each numbered post (85, 86 etc..) looks to me just like the positive posts of most car speakers.    Can i simply crimp on the proper sized female quick slide to each post in order to attach each of the leads or should i solder them securely?    More importantly,  How do I attach the 2 amp diode to the 86 and 85 posts properly?     Do all diodes have a cathode and an anode?    If so, how can I tell which end is which and which direction to install it? 

My last question is this.    If its true that i run a lead to my battery, it says that i must fuse it with a 1amp fuse.    For this application, is the 1 amp fuse and  the 2 amp diode the critical ratings or can I use other sizes and still have the same protection and resulting functionality?    I only ask because i went to radio shack tonight and sure enough they only have 1 amp and 2.5 amp diodes but no 2 amp diodes.

for an unrelated question.    I am installing XM radio in my car also and I received the little terk magnetic antenna that looks like a miniature computer  mouse.    It would be easy to install it on my roof like the manual says but I cant peel away my window moldings safely enough to hide my wire as i run it cleanly down the back and into my trunk.    Instead, I have my antenna mounted on my trunk lid about 4 inches away from my rear window.     The manual says this is the next best thing but I am very unhappy with how this looks asthetically.    Can I simply mount this antenna on my front dash or my rear deck and accomplish the same reception?    If not, what is the next best thing--a window mount antenna?

Please somebody help me because Im expecting my head unit to arrive in the next 2 days and I want to start enjoying it as soon as possible. 

regards, steve