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Okay, so as long as I don't use the SLC-4, & just use the TA03 I won't have any problems with noise from the alternator coming through my speakers?

GREAT!

Amer Q.
 

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Discussion Starter #22 (Edited)
Troubleshooting Grounds

Checklist:

1) Plug the 4 Male RCA's directly from the TA-03's harness into the HU's 4 Female RCA's. (Unless your HU only has SPKR Out's, in which case you'll have to use the BlueBox and mount it carefully behind the dash so it doesn't pickup noise, but also do #6 below).

2) Connect your HU's GND (-) wire to the 2 BLK (Digital & Chassis) GND wires in the TA-03 harness. Don't connect anything else to them.

3) Connect your HU's +12v wire to to the TA-03's own +12v wire. Don't connect anything else to this wire.

4) Make sure your HU's GND wire is not conected to something else's GND, sharing it. Only connect it only to the 2 BLK wires in the TA-03.

5) Check any crimp or butt connectors you may have added to any of the wires. Check for loose crimps making poor connections.

6) Run a separate GND wire from the HU's chassis (case) to a GND bolt on the Celica's frame. On many HU's you'll find a GND lug sticking out the back of the chassis for this. Don't rely on the tin mounting brackets to do your grounding for you, use real copper.

I ran a length of #16 guage heavy-duty flexible copper wire (GRN) bolted to the frame behind the Celica's dash to the back of my HU (hard to see in the pic, but follow alongside the green line drawn-in, or click on the link below the pic to view the ShockWave animatic). On one end I crimped a heavy-duty spade lug which slips under the Celica's top-left bracket bolt (see left arrow). On the other end I crimped a smaller eye lug and screwed it to the back of my HU. (You can see the HU's GND lug sticking out of the back in the pic (right arrow), but I didn't use it cuz i wanted it bolted-down instead)


Added: #16 guage heavy-duty flexible copper wire (GRN) from Celica's dash to back of HU.
[ Click here to view an SWF animatic following the GRN ground wire added in the pic ] [ Don't use the BlueBox! ]


Note: I didn't want use this pic in the original post cuz it shows the Scosche BlueBox (which wasn't used in the final mod). Yes I hooked it up, yes I made-up 4 nice extra RCA cables to go between the HU and the box, and no it doesnt work very well in the Celica, so don't use it.

The only time the SLC-4 BlueBox should be used is if your HU only has SPKR LVL Out's (no PreOuts) and then you'll have to do the mod anyways because the transformers inside it will pickup noise inside the dash. You'll have to be careful about where you stick it and try to find a quiet place for it to live.

Anyway sorry, me bad for not mentioning this in the original post... without this chassis-to-frame ground wire you're almost sure to get some residual noise. I know cuz during testing I could hear the ECU buzz leaking thru until I cinched the bolt down tight.

I hope this solves any remaining noise problems for you.

(edited 12.30.05: add Red HL's)
 

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pacificblue,
I haven't tried the ground yet, but everything is finally hooked up, subs, changer, etc.. i still need to remove the deck again to ground the body of the deck to the chasis.

another question for you is after your install, did you experienced any engine noise or turn on/power up "pop"? i have this turn on pop right not and i think it only on the stock speakers.
please let me know.
thanks,
dchan8
 

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Discussion Starter #24 (Edited)
No noise, but I get a "pop" if the ignition's already ON and I turn the HU OFF manually, but I never hear it cuz I always leave the HU on and turn everything on/off with the ignition key: When I put the key in and start the car, everything turns on and comes up smoothly. When I turn the key OFF, same thing... everything shuts down smoothly, no pop - ever.

I forgot all about the HU PowerOFF pop until your post and had to run out to the Celi to check it out. Right after I did the mod I remember trying to figure out what was causing the pop whenever I turned the HU off but not the key. I never took the time to look into it, then forgot all about it cuz I always leave it ON.

The two common causes of PowerON/PowerOFF "pops" are:

1) HU's preamp outputs have DC transients on them during power-up or shutdown.

2) Power amp's outputs have DC transients on them during power-up.

Most head units have an AMP CONTROL wire which connects to the Remote Input on the external amp to turn it on/off by the power button on the HU (including the stock radio). But how elegantly they control the remote PowerON/PowerOFF timing of the external amp may be different from manufacturer to manufacturer (like from nil to maybe a one-second delay). Interesting thing is, the stock radio never popped no matter what.

Some external power amps have built-in muting relays to keep the speakers from getting connected to the output stage until the amps have stabilized (ever hear that delayed "click" coming from the inside of a high-end high-power amp, EQ, or crossover?)

Head unit PowerOFF pops are harder to fix than PowerON pops. If you turn your HU OFF and its preamp outputs have transients on them during the shutdown and the external amp is still ON, there'll be a pop in the speakers. But how do you turn OFF the external amp before the HU if the OFF button you're pushing is on the HU? Ideally the remote AMP CONTROL wire should turn OFF first, then the HU should turn itself OFF a second later.

PowerON pops are easier to fix because you can connect a delay relay between the AMP CONTROL wire and the Amp to turn it on a second later after the HU's preamps have stabilized. If you've got a PowerON pop you can try a STINGER "SGN21" which supersedes their older "SPSON" module to see if it fixes the problem:


"SGN21: Stinger PopStopper"
 

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This thread is exactly what I have been looking for, but I was hoping someone might be able to answer a few questions.

I just ordered a Sony CDX-MP80, it should be here soon and I wan't to install it asap. After reading this post I also ordered the Scosche TA-03 adapter kit from sound domain. From what I understand, I DO NOT need the SLC-4 blue box because I have rca pre-amp outputs. All I need to do is the noise reduction mod to the TA-03, right? Now I am not sure on what kind of resistors I need to purchase for my head unit. I was hoping someone here could help me figure this out.

Here is detailed info on the Head Unit http://www.crutchfield.com/cgi-bin/S-cA07i69X0uC/ProdView.asp?a=1&s=0&cc=01&g=62700&id=features_and_specs&i=158CDXMP80
I am having a hard time finding out the ohms on the deck, all I can find is 2 4volt preamp outs with high pass and 1 4volt sub out with low pass. So what kind of resistors do I need? Do I need to modify the resistors already inside the TA-03 or can I leave them? Any help would be greatly appreciated. thanks in advance.
 

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Discussion Starter #26 (Edited)
TA-03 Mod Termination Resistor Values for HV HU's

This post goes out to dchan8 & Tryan77 who've been brave enough to try this mod and to keep me on toes searching for the math to resolve the termination value question. Reverse-engineering is like hacking, you don't give up until you've got it all figured out and then you're a little smarter and grin a whole lot:

I knew the series resistors that Scosche put in the RCA cables of the TA-03 were part of an "L"-pad attenuator network, used to drop higher-level audio to lower-level audio. But what was their intended design spec? My best guess was that it was originally meant to be a 50% voltage divider into a 2k input load for some Toyota factory amp (500mv in = 250mv out, etc), but not ours.

Our factory amp has practically no input termination, so it puts no load on the TA-03 & HU and the series resistors basically don't do anything except pass pretty much the full voltage from the HU to the amp (which in turn makes it sound too loud & the volume dial way too sensitive).

I searched the internet looking for some old audio equations I knew were out there and yep, it's true - the Truth is out there somewhere... I'll give you a range of resistor values first, then leave you with a couple of links if you want to learn more about this sort of stuff:

8v : 36 ohms = 150mv / 48 ohms = 200mv

5v : 60 ohms = 150mv / 79 ohms = 200mv

4v : 74 ohms = 150mv / 100 ohms = 200mv

2v : 154 ohms = 150mv / 211 ohms = 200mv

(this table is updated in a later post: Final test Results)

Assuming the factory amp wants to see 150-200mv of signal at its inputs w/termination, and using the existing series resistors in the TA-03 harness, these values should work.

In my setup I used 60ohms so the factory amp is theoretically getting 150mv. It sounds & works great, but I'd probably try using a higher value resistor next time to get me closer to 200mv so I'd have more volume range to crank up the quieter tunes.

Don't forget, these numbers are based on using the existing series resistors Scosche put in the harness. If you want to build a "by-the-book" perfect "L"-pad, you may have to replace them with other values. Here's a couple links explaining attenutation and voltage-dividers:

"Line level signal to microphone input adapter"

"The Voltage Divider Rule" - Resistive Dividers

"Voltage Divider Calculator"

If you want to follow dchan8 & Tryan77's troubleshooting thread click here:
"Termination Resistor" - dchan8 & Tryan77 (for Alpine 10k 4volt PreOuts)
 

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Discussion Starter #28
Yes.

In audio, 10k impedance is still considered a "high-impedance" and prone to picking up some noise unless well-shielded.

I'd try the 100 ohm, it should kill any remaining stray noises you've been tackling, give you plenty volume, and leave your volume control set so you don't have to max it out to hear the softer tunes.
 

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Discussion Starter #30
lowendfrequency - Yep it looks that way so far, least on paper. We're waiting for dchan8 & Tryan77 to finish tuning their Alpine 4volt HU installs to find out if the math works.

It's kinda difficult trying to figure this out by "remote" cuz I'm not there in front of your rides where I can help you test & tune them. That's why in the TA-03 Noise Mod post I said the 60 ohm terminators's worked for my HU, but the values might be different for yours (if it's got different output voltages & impedances than mine).

According to the math there are many ways to accomplish the same goal (match levels, impedance, signal transfer, minimize or eliminate noise). But which one to use depends on the gear's specs, type of power source, grounds, electrical envoironment (noise), shielding, etc.

For us, with our super high-tech, muchly-electronic, almost fly-by-wire 7th Gen Celica's, there are computers communicating with & controlling everything everywhere, talking over wire harnesses that rival ones used in 747's, we share power to everything off of one poor little 12 volt battery, we share the same ground which floats on rubber insulators (tires) that keep us from using a "real" ground (mother earth), we generate high-voltage sparks to startup our HID's, more sparks to fire-off the sparkplugs that make us go & give us Lift, we generate mega-pulses of power to recharge our battery (alternator), and we generate more noise everytime we switch-on or roll a window, sunroof, or cabin air blower, and we expect our super-sensitive high-end audio gear to be noise-free in all this soup?

Yep. So, based on collecting the 411 from mod'ing mine & others trying to mod their's, then applying the formulas used for calculating the resistors for building an "L"-pad attenuator (with a little rule-bending), it looks like the resistor values in the last post (above) will probably work ok in this hostile environment. Just find your HU's PreampOut voltage in the left column and pick a resistor value between the two values listed in the chart.

You're right about the Sony CDX-MP80 output impedance specs being difficult to find. But that's okay, the math has already been done for you and the termination resistor values in the last post should work fine for the PreampOut voltages shown. So if your CDX-MP80 has 4volt PreampOuts, you'd use a 100 ohm termination resistor on each audio pin on the TA-03 harness connector just like the 4volt Alpines.

But, you might wanna hang out for the results from dchan8 & Tryan77 first, or go ahead and be real brave and join their "Alpha test" team. The more 411 we get the better and the sooner we'll know what works best.
 

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Thanks for getting back to me man,

I should be getting my HU on monday, and the TA-03 sometime soon after, so I'll hold off till then. After that I think I will become an alpha tester as well.... gonna pick up some 100ohm resistors today and go over everything to make sure I know what I'm doing.

So, just to make me feel better, humor me real quick. Worst case scenario....The noise mod doesn't work, I get loads of alternator whine and electrical buzz, and am forced to bypass the factory amp to get rid of it, right?
 

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Discussion Starter #32
Don't worry there's no question the mod works, you just have to pick the right value termination resistors for your particular HU and you're done.

Personally, I tried the TA-03 just to see if I'd be happy with a new HU powering the existing amp & speakers. Answer? I'm very pleased. Plus, I always knew I could install an aftermarket setup later if I wanted to. In fact I went ahead and added a sub because the Celica's sound system really lacks bass (it doesn't have a trunk or airtight enclosed compartment that can support a decent low-end bass setup). Now, it kicks ass.

How much sub, bass, midrange, highs and SPL (sound pressure level) you want is a personal choice. Take a look at the "Pics of trunk setups here!" thread and you'll see what I mean.

You can always bypass the factory amp if you want to, but it's a little bit more work than mod'ing the harness. You'll have to locate a place to mount your new amp, disconnect the old one, patch into the wiring harness for power, IGN, and GND, and splice into existing speaker wires. You'll find instructions on this board and others complete with color codes.

Try your new HU with the TA-03 & Noise Mod for now. You can always add aftermarket gear later if you want to.
 

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pacificblue,
i just tried the 100ohm resistor, and there is pretty much no ecu or engine noise, but i have to max my volume to get it to be pretty loud(kind of normal for me) but it's not loud enough, what size should i try next?
dchan8
 

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dchan8 said:
pacificblue,
i just tried the 100ohm resistor, and there is pretty much no ecu or engine noise, but i have to max my volume to get it to be pretty loud(kind of normal for me) but it's not loud enough, what size should i try next?
dchan8
Are you running 4volt preamps? I just purchased some 100 ohm resistors to do this mod but it sounds like I might have to take them back. How loud is it compared to what it was stock? I usually listen at a medium level but I like to crank it now and then and I don't want to lose any power.

Also, what should the wattage be on these resistors. I bought the ones that looked most similar to the ones in the pictures that pacific blue posted, they are QW110 100ohm 1/4Watt Flameproof resistors w/ metal film. Does that sounds right?
 

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according to pacificblue,
1/4 to 1/2 watt is fine for the resistors.
i have 4v preouts too. i suggest to use 470ohm resistors. i think this is the boundary for engine nose and not. keep in mind that you probably won't be able to hear any engine noise when the car is running and you have some volume with the stereo.
dchan8
 

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Discussion Starter #37 (Edited)
TA-03 Mod Termination Resistor Values for HV HU's - Final Test Results

Wow!, looks like everyone finished tuning their mods... Excellent! This is my first chance to catch-up with the board since returning to work after vacation. You guys just made my day.

So it looks like feeding the factory amp about 500mv signal is the magic number. Here's a list of the termination resistor values each of us ended up using w/comments about the results:

150mv / 5v 60 ohms "It's plenty loud but the dial is spread out, so I may try it with 211 ohms later so I don't have to max it just to hear the softer tunes." - PacificBlue

432mv / 4v 230 ohms "If I changed anything I would try a "slightly" lower resistor. I think something between my 230 and the next lower size of 150 might eliminate virtually all the noise and still give people similar to me, enough volume." - Tryan77

546mv / 4v 300 ohms "The 300ohm resistor was the perfect match for me, I can't even detect a hint of ecu/alternator noise but I can still crank it as loud as I dare and have room left to go." - lowendfrequency

793mv / 4v 470 ohms "i settled on 470... this has a little/faint ecu noise when the car was off, but on start. no ecu noise when the key was in the on/acc position" - dchan8

So 333.3 ohms was the average of the three Alpine 4v setups.


Here's the updated termination resistor selection table. Don't forget, these numbers are based on using the existing series resistors Scosche put in the harness:

(update 7/07: Instructions for Calculating Values for newer TA-03B harness)
Note: The TA-03A harness uses 1900 ohm series resistors while the newer TA-03B uses 2200 ohm resistors, so if you're using the newer TA-03B and want to be precise, add +16% to the value found in the table below for your termination resistors, or follow the instructions on how to use the Voltage Divider Calculator linked further below. Resistors are usually rated with a +/-10% tolerance, so it's really no big deal if you want to stick with the table.


(update 8/07: Termination Resistor Values for HU's with only 2-RCA Outs)
Note: If your HU only has two RCA outs (L&R) you can use an RCA Y-Cable to connect to the StockAmp's Rear RCA's, but you'll need to roughly double the value of the termination resistors to avoid double-terminating the signals and losing level. For example if the table says use 600 ohms, use 1000-1200 ohms instead.



Just find your Preamp-Out Voltage on the left, then use the resistor value shown in BOLD for your mod.

8v: 36 ohms =150mv / 48 ohms =200mv / 61 ohms =250mv / 126 ohms =500mv / 271 ohms =1volt

5v: 60 ohms =150mv / 79 ohms =200mv / 100 ohms =250mv / 211 ohms =500mv / 475 ohms =1volt

4v: 74 ohms =150mv / 100 ohms =200mv / 127 ohms =250mv / 271 ohms =500mv / 634ohm =1volt

2v: 154 ohms =150mv / 211 ohms =200mv / 271 ohms =250mv / 633 ohms =500mv / 1.9k =1volt

1.8v: 173 ohms =150mv / 237 ohms =200mv / 306 ohms =250mv / 731 ohms =500mv / 2.4k =1volt

The resistor values in BOLD to produce 500mv are highly-recommended, the values for producing 1volt out are for reference only and definitely not recommended. If you want to put more spread on the volume dial use a lower value resistor, if you want more guts on the dial use a higher one.

If you want to build a "by-the-book" perfect "L"-pad, you can do the math and replace the series-attenuator resistors Scosche built into the TA-03 harness and the mod's termination resistors with custom values. Here's a couple links explaining attenuation and voltage-dividers:

"Line level signal to microphone input adapter"

"The Voltage Divider Rule" - Resistive Dividers

"Voltage Divider Calculator" {updated 2/10/18 to replace another dead link}
(update 7/07: Instructions for Calculating Values for newer TA-03B harness)
Note: For TA-03 enter 1900 for Input R1, or 2200 for the TA-03B. Enter .5 for the Output Voltage (500mv) to get the correct termination resistor value.


If you want to follow dchan8 & Tryan77's troubleshooting thread click here:
"Termination Resistor" - dchan8 & Tryan77 (for Alpine 10k 4volt PreOuts)


And here's a review & summary of all the 411 we gathered from reverse-engineering, mod'ing, testing, and tuning:

High-end aftermarket head-units equipped with high-voltage (2v, 4v, 5v, 8v) preamp outputs place the audio signals way above the noise found in our cars, but are too hot to directly drive the factory amp used in the 2000-2002 GT-S w/Premium 8-Speaker Stereo system without sounding too loud in the midrange and picking up all sorts of electrical noises from the car.

Because the stock amp has a very high input sensitivity, the aftermarket HU's PreOuts need to be attenuated from 2v, 4v, 5v, or 8v to approx. 500mv (.500v) in order to drive it to full output without distortion. Also, because the amp has a very high input impedance of 1-meg or higher, it needs to be properly terminated in order to drain the electrical noise picked up by the audio lines to ground before they reach the amp. Among the potential sources of noise in the Celica are its multiple ECU's, cabin light dimmer, power windows, power sunroof, power doorlocks, front & rear windshield wipers, HID's, ignition system, alternator, and any aftermarket gear like neons, inverters, guages, etc.

Using the inexpensive Scosche TA-03 wiring harness you can connect an aftermarket HU with the Celica GT-S' wiring harness without cutting the connector off or splicing wires, but it must first be modified with the addition of 4 termination resistors to accomplish two things: 1) to attenuate the HU's signal level down to 500mv's and 2) to terminate the audio lines between the HU and factory amp so that any noise they pick up will be drained to ground thru the resistors before entering the amp. By adding the 4 termination resistors in a bridging configuration and using the existing series attenuating resistors already built into the TA-03 harness, we form an "L"-pad attenuator which reduces the level and drains the noise at the same time. The factory amp can then be driven to full output without loss of low-end (over-bearing midrange), distortion at high levels, or picking up surrounding electrical noise.


btw: If you don't feel comfortable doing an audio install by yourself after studying these boards, I highly recommend you find a professional installer in your area by posting a question in the Audio & Electrical Forum and asking for one; some are better & more familiar with the Celica than others and this is probably one of the best ways to find one. You could also ask if any nc.org member in your area would be interested in helping you or doing it for you, can't hurt.


Thanks again to everyone who posted their questions, comments, suggestions, & results. Like I said, I'm real pleased with how the Celica sounds now with the stock amp & speakers w/new head-unit & sub, and even more pleased to be rid of that god-awful noise.

Now the rest of you Celi lovers out there that have been dyin' to stick a better head-unit in the dash and were worried about how to do it, can do it.


"Bill?" "What is it Ted?

"...the next sound you hear will be 1.21 gigawatts of most excellent silence!"
 

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Discussion Starter #39
Because the stock amp has a very high input sensitivity, the aftermarket HU's PreOuts need to be attenuated from 2v, 4v, 5v, or 8v to approx. 500mv (.500v) in order to drive it to full output without distortion.

...according to the chart 633 ohms is what you'd use, but since that's not a standard off-the-shelf value buy the next closest value: 620 ohms.
 
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