Sharing HU 4ch RCA output between 2 amps... want to retain fader function if poss...
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by John_Smith
Start New Question Here -- Back to Tree
Year Make Model: 1994 Audi 80 Quattro

First off, what a FANTASTIC resource this forum is!!! I've only just stumbled across it doing loads of research for my upcoming build. Very reassuring back-up

Now, I'm not overly experienced with car audio install, but I'm getting up to speed pretty fast . Though despite having many of the more complex concepts in hand, I do have a couple of "noob" questions...

Firstly, the ingredients -

Car - '94 Audi 80 Quattro
HU - Alpine CDE9845 (4ch RCA outputs)
Front door speakers - Eclipse SC8365 6.5" 3 way splits
Rear door speakers - Eclipse SC8355 5.25" 3 way splits
Subwoofers - 2x Eclipse SW6210 12" 4ohm DVC with 2cu/ft ported box
Amp for Splits (front & rear) - Eclipse XA4200.4ch
Amp for Subs - Eclipse ZA1200.1ch
+ some nice heavy AWG wiring on hand for power/GND.

Basically, I'm looking to run the 4x RCA LF+RF/LR+RR outputs from the HU back to the XA4200.4 amp to drive the 2 pairs of splits in the doors and would love to retain the native fading function from the HU, but am wondering how to tap an unaffected (by fader/stereo function) signal to simultaneously feed to the ZA1200.1 amp for the subs...

That could be kind of a silly question, I'm not sure…

... do I just grab the (pre XA4200.4) output from (say…) RCA lines "Left Front" + "Right Rear" (via RCA double adapters) and send this to the ZA1200.1 RCA input jacks at the same time it's sent along with the other two signal lines to the XA4200.4? This is the only way my feeble brain can see that the fader/balance function of the HU would be retained for the splits and also leave the sub amp consistently fed a signal ... I think... (this is my main concern)

Hold on.... but what if I “faded” to say the front entirely and “balanced” completely to the Right channel which would isolate the splits in the RH Front door. Then I guess my ZA1200.1 would be receiving no signal to throw to the subs.... ARGH!!!

What would typically be the way to go here fellas?

The Alpine HU's RCA outputs are also soft switchable for front+rear (full stereo) or front (stereo) +sub (mono) functionality. I'm assuming it just bridges the "typically" stereo rear output to mono for subwoofer connection. I’m not sure if this disables the fader function, or allows fader control between front/sub signals.

Hrmmm.... starting to think out loud now

If I went this way (above paragraph), could I simply use the Gain controls on the XA4200.4 to balance the amped output sent to the two pairs of splits and just ignore the "actual" fader function on the HU as it would normally work?... And perhaps instead use it to proportion the Splits vs. Sub volume levels?...

Ah guys… I’m so sorry if the above comes across as confusing waffle. Any input would be really appreciated

Thanks so much in advance
Toby

Page Views: 264
Reply Posted: 11/5/2009 19:41:49 by: Sponsor of ClubKnowledge! swez Old Man Audio

Finally have some time to read your great post and some very fine gear in this system. Nice job packaging a outstanding kit!

From what I can tell, the Alpine HU has 4 channels of RCA outs to your 4 channel amp. The 4 channel amp (XA4200) seems to has 2 output channel RCA's to feed audio to your sub amp as well? (Please clarify that)

http://akamaipix.crutchfield.com/Manuals/099/099EA4200.PDF

If there are no extra RCA outs in the XA4200, you can easily run "Y Splitter" cables from the rear channel to the sub amp to insure fade control and audio signals to the sub amp. If you have a 1/2 Din space in the dash pocket, we can even entertain adding a multiband EQ unit that requires 1 pair of RCA inputs and offers 6 channels of output. (F/R & S outs with EQ, Master volume, and Sub control at the dash + EQ and Aux inputs too)

There seems to be plenty of power in the XA4200 to run both 3-way splits off the passive crossovers with no additional hardware. The crossovers do all the work for you as expected in a package like Eclipse.

There are several ways to do all this, but let's get some dialog going before you begin the install process. One thing I do see here is having adequate electrical power for both amps. It looks like the XA4200 will draw close to 80 amperes of current at full power. The ZA1200.1 seems to be fused at 40A's x 4 or 160A's at full power. That's a major electrical upgrade for most vehicles. (H.O. ALT, the Big 3 wiring upgrade and 1/0 wire from the BAT to a Power Distribution Block and maybe a 2nd BAT for the sub amp)

Chew on this a bit for now and respond as needed,
Swez

Reply Posted: 11/8/2009 21:09:50 by: John_Smith

Hey Swez!! Thanks so much for the reply, very helpful :) Also, cheers for the added reassurance on my hardware selection. I looked over a bunch of different gear before settling on these Eclipse parts and it can be a little anxiety inducing dropping the cash on pricey parts when there's no guarantee of the end result being everything you'd hope for. :)

Anyway, back to business!! The XA4200.4 amp doesn't have line level outputs to feed to the sub amp, but I think it's a great suggestion on the addition of an EQ!! I reckon I'll head down that route, tis the perfect solution and will give me a nice pinch of extra sound tweakability too!!! :D And yes I'll absolutely be performing the “Big 3” upgrade under the hood! It'd be unrealistic not to in this instance by the looks. I'll have to check into a HO Alternator and aftermarket battery too ASAP.
Oh one thing… on the HO Alternator side, will I need to upgrade other parts of the cars electrical such as current rating on a fuse or two?
Thanks again for your input on my query, I'm sure I'll have further questions as I start to put this kit together.

Toby

Reply Posted: 11/8/2009 22:14:37 by: John_Smith

Okay, I've gone ahead and ordered a cute lil 1/2 DIN Eclipse EQ1000 to compliment this system of mine and I have one quick question... In people's opinion, am I better off using the HPF and LPF etc on the EQ or leave it to the Amps to handle this end of things??... could be much of a muchness I'm guessing... though best to use one rather than the other....??

URL for specs on EQ -

http://www.eclipse-web.com/us/equalizer/eq1000.html

Thanks again
T

Reply Posted: 11/9/2009 09:21:35 by: Sponsor of ClubKnowledge! swez Old Man Audio

Hi T,

Glad you came back and took the idea of adding that Eclipse EQ to your front end control panel. It will make a big difference in the overall mix and fun to learn too. (A big upgrade for a nominal price)

As for the crossover and filtering tools, your amps, EQ and HU have redundant features. In most cases, the amps will have the tools needed to get you where you want to be. (Feel free to experiment if you like having these features in the dash)

Powering your amps will likely require a H.O. ALT or other tools to feed these monster amps. Fortunately, the power/amperage issues will not affect other parts of your car. They only draw what is needed and the regulator and vehicle computer(s) will manage the rest.

The output voltage/current (Wattage) will be in range and not damage other components of this vehicle. (Fuses will insure that too) The bulk of the extra power will be fed to your amplifiers as needed when you dial up the audio volume.

Proceed with your install and if you have questions, bring it on and we'll address them as needed.

Swez

PS You're gonna love the on the fly adjustments that this EQ 1000 will provide. Did an install a while back with another CK reader and we were very pleased with the aeddition of the 1/2 Din EQ. Wow, it took things to a whole new level and the client was one happy puppy too. He used a Nak HU, JL amps and top line Components and a 10" ported sub. In short, the results were phenominal.

As you move to the install phase, consider using sound dampening products in the front/rear doors and perhaps the trunk to reduce vibration and panel rattles as you go. It's a tedious task initially, but the results were definitely worth the time and effort. (Yep...yep)

Reply Posted: 12/22/2009 07:45:45 by: John_Smith

Thanks so much for the spot on feedback thus far Swez!!! Really helpful stuff.

Okay I've opted for a big wattage dual Amp wiring kit to string together my components ( this one by Scosche - http://www.sonicelectronix.com/item_7280_e2+E3200+by+Scosche.html ) The included dist block has a pair of ANL fuses rated at 60Amps a piece that feed through to the two 4awg outputs for each amp... it just occurred to me that my amps both comfortably exceed this with the XA4200.4 wearing a cute lil matching pair of 40amp fuses and the nasty ZA1200.1 with a bank of FOUR 40amp parts!!!! I'm confused with this, do I work on a total of all fuses on each amp and fit an ANL fuse equivalent to this to each outlet on the dist block?? ie. a 160amp ANL for the ZA1200 and an 80amp one for the XA4200.... Oh and what about the inline ANL holder up front by the battery (currently [no pun intended!!] wearing a 125amp ANL)? 240amp maybe???!!!!!! GOOD GOD!!! :O

I'd be really grateful for some clarity on this one.... REALLY don't wanna cook anything here ;)

Thanks again!
Toby

Reply Posted: 12/22/2009 13:20:09 by: Swez1

Hum, there's a lot of power issues and such to consider as you go on to the install phase.

1. Use the proper wire gage for the entire system as required by current draw. (160 +60 = 220 A's @ max draw) Here, the main power feed off the BAT should be a 1/0 gage line, fused with an ANL fuse, (200 - 250A's) about 12-18 inches from the BAT. (1/0 cable can handle 300A's)

2. The Disty Block is OK for the 4 channel and a 80A ANL fuse to #4 gage line. That's easy as replacing a fuse.

3. As for the sub amp, a #2 gage line and a 150A ANL fuse would be good off the D-block's #2 fusing circuit. You may have to modify the D-Block to accept a larger gage wire, but with some careful attention, it looks doable. (drill out one of the #4's to accept a #2 wire seems like an option?)

In a nutshell, we choose the wire gage to match the current consumption of a given circuit and then fuse it to the current rating of the wire(s) used.

Got all that?
Swez

Reply Posted: 12/22/2009 17:31:43 by: John_Smith

Wow!! Cheers for the super fast reply Swez ;)

And yep, tis all clear now on the fusing as it relates to the current capacity of cabling. Looking at the D-Block, there is quite a bit of extra metal thickness I can drill away from a 4 gage outlet to allow for a 2 gage line to feed the sub amp. Keep ya posted on that little mod ;)

One other query while I'm here... on the subject of soldering rather than crimping connectors to power/gnd wires where needed, I'm assuming it's more thorough to solder ring terminals to exposed copper wire than to crimp the connector on? (I have a 380watt solder station that shouldn't have too much trouble with heavy gage copper)

Oh and how about tinning the exposed copper that is then attached to Fuse holders/Dist Blocks etc....? Could this be a good measure to optimize current conductivity? Or does it have drawbacks too?

Thanks again!
Toby

Reply Posted: 12/22/2009 20:11:36 by: Swez1

Hi Toby,

Yep, we're fast on replies now as I'm off for the Holiday and maybe looking for a new job come January.

Soldering heavy gage wires if fine when splicing is needed. Here, copper rings work nice and then sleeve it with shrink tube. When doing heavy gage ring terminals, if it does not have a good set screws, soldher them too if you like. But a solid crimp will often do the trick and then sleeved with shrink tubing will keep it clean for a long time.

In the D-block, the anchor screws look adequate. When we solder/tin wires there, they get hard and swell sometimes. This makes a clean fit very challenging and not advised. The more surface contact the copper can get to the hold down lugs, the better the condictivity.

Sound about right to you?
Swez

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