Scosche TA-03 Harness Noise Mod

PacificBlueGTS

Scosche TA-03 Harness Noise Mod

What is VVTL-i ? password: sashimi

(update 1/05: fits 2000 & up GT's & GTS's w/optional Premium 3-in-1 AM/FM ETR/Cassette/CD w/8 spkrs & separate amp)

(update 7/07: Latest notes on the new TA-03B Harness, BestKits.com BHA8113 harness, Metra TYTO01 harness)

1) Some time ago the original Scosche TA-03 was superceded by a newer TA-03B harness which uses a different connector that has an extended shell covering the pins, making it more difficult to mod.

2) When selecting resistor values from the Termination Resistor Table for the newer TA-03B, add +16% to the value from the table, or use the following calculator to find the exact value, substituting 2200 ohms for R1 (the TA-03A uses 1900 phms for R1):

3) There are many wiring harnesses out there which claim to be compatible with the 00-02 / 03-05 Celica's but members have discovered are not compatible. We know the original TA-03 was the easiest to modify and absolutely works, as well as the newer TA-03B, even though it's a bit more difficult to mod. We also know the BestKits.com BHA8113 Harness http://bestkits.com/i/BHA8113-new.jpg also works, and may still have the original Scosche TA-03 style connector that's easier to work with.

4) Recently members have been asking me about a new harness called the Metra TYTO01 http://www.circuitcity.com/ssm/Metra-Toyot...roductDetail.do At this time all I can say is that it looks like it might work with later JBL-equipped vehicles which use the Toyota databus to control Turn-On. Other than that, I don't know yet whether it needs the mod or not. Note: Metra does not list any Celica's in their TYTO01 compatibility table.

(update 8/07: BestKits BHA8113 identical to TA-003 Original)

1) Confirming: the BestKits.com BHA8113 Harness is identical to the discontinued original TA-03 harness, including long pins making it easy to modify compared with the newer Scosche, so I'd recommend you use the BHA8113 instead of the Scosche TA-03B.

2) 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. For example if the table says use 600 ohms, use 1000-1200 ohms instead.

PacificBlue

Remove heatshrink from audio pins (notice hidden resistors in black shrink, also 4 new resistors in front

Back of TA-03 showing 4 audio pins - (Red Wire is Right Channel & Top Row is Front)

Unsolder the 4 RCA wires from the connector pins and twist termination resistors onto them before soldering

Add heatshrink tubing (yel) to prevent shorts & add structural support, then tin the ends and solder em back to the pins

Add more heatshrink (blu) then twist the ends of the resistors together and tin with solder

Add larger heatshrink to Analog GND wire (blk/wht making U-turn) & solder it to the twisted end of the resistors

After applying heatgun to shrink tubing - (Top Row is FRONT Left & Right)

Another closeup showing the new resistors bulging out from the blue shrink tubing

Completed Mod - tie-wrap all power leads together, then separately tie-wrap all audio & gnd's together

#16 guage heavy-duty flexible copper wire (GRN) from the Celica's dash frame to the back of my HU.

Scosche TA-03 FactoryAmp Noise Fix Mod - Basic Pictorial Diagram & Notes

The output impedance of my head unit is 60ohms at 5vrms, so the 1.9k (1900 ohm) series resistors don't hardly reduce any level and it's easier to leave em in. Basically what you're doing is adding a terminating resistor from each signal wire to ground, closest to the FactoryAmp's inputs. (Ideally you would do this right inside the amp, but this won't be necessary unless you plan on listening to your stereo while driving thru an MRI Scanner or past some military radar dish)

SCOSCHE SLC-4 "BLUEBOX":

( comes w/TA-03 Kit - see notes below )

* 4-channel HV LINE LEVEL to 4-channel LINE-LEVEL converter

( don't need SLC-4 for HU's w/Preamp Outs - Only use TA-03 Conn w/Mod )

* 4-channel SPEAKER LEVEL to 4-channel LINE LEVEL converter

( up to 80 watts max per channel )

( use SLC-4 together with TA-03 Conn w/Mod - adjust trimpots on SLC-4 to match levels )

* Transformer circuit for noise cancellation.

* Common ground adapter.

So what's with the blue box Scosche provides? Well in an ideal noise-free world you would set the switch to "Line" and plug your RCA's into it and wire the other end into your amp, but if you don't have a HU with high-level preamp outs you can connect your HU's speaker outputs into it (thru the screw terminals) and it will drop speaker-level down to line-level to feed the FactoryAmp. Will you still need to do this mod? Uhm, yeah probably... it's because inside the TA-03 are 4 level-dropping circuits and impedance matching/isolation transformers. What's great about transformers is that they can match the impedance of one circuit to another almost perfectly, plus they can isolate DC path between two devices and only pass the audio signal, but what's not so great is that they can also act like guitar pickups when designed to be connected to high input-impedance amps like ours.

Ever hookup a Scosche TA-03 and wave it around the inside of the dash with the ignition on? Acts like a Theremin doesn't it? That's cuz its transformers are picking up the noise from the data bus running all thru the Celica wiring harness. Ever play with a telephone pickup coil? Almost the same thing.

Notice the TA-03 has 3-ground wires coming out of it. Make sure you connect the ends of the 4 resistors (tied together) to the wire labeled Analog GND in the photos & diagram. The other two GND wires can be tied together and connected to your HU's GND wire. Believe it or not, once you terminate with resistors, your grounding problems will pretty much disappear.

I forgot to mention that when you terminate audio lines with the matching impedance of your HU, your frequency response will probably be restored more closely to what it's supposed to be too. In otherwords if it sounded too bright & tinny before, your bottom end (bass & lows) should come back to life again and you won't have to subtract your treble & max your bass eq settings anymore.

thanks for the help on the board & enjoy your FactoryAmp, I hope it helps...

ps ~ i want to give some credit to EvilED who posted a msg way back in 10-12-2002 about a mod for the factory amp. I found it while searching to make sure the TA-03 Noise wasn't a topic already covered. It just goes to show that doing thorough research pays off if you bother to do it (and no, I didn't find it until it was too late cuz I was lazy too... crap!)

Curious what the Scosche TA-03 Harness sounds like -without- the mod?


				*PacificBlueGTS* *Scosche TA-03 Harness Noise Mod*



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		PacificBlue What is VVTL-i ? password: sashimi



		(update 1/05: fits 2000 & up GT's & GTS's w/optional Premium 3-in-1 AM/FM ETR/Cassette/CD w/8 spkrs & separate amp) = click to jump to post about which GT's this will fit & about TA-02 harness vrs. TA-03 = (update 7/07: Latest notes on the new TA-03B Harness, BestKits.com BHA8113 harness, Metra TYTO01 harness) 1) Some time ago the original Scosche TA-03 was superceded by a newer TA-03B harness which uses a different connector that has an extended shell covering the pins, making it more difficult to mod. 2) When selecting resistor values from the Termination Resistor Table for the newer TA-03B, add +16% to the value from the table, or use the following calculator to find the exact value, substituting 2200 ohms for R1 (the TA-03A uses 1900 phms for R1): Voltage Divider Calculator 3) There are many wiring harnesses out there which claim to be compatible with the 00-02 / 03-05 Celica's but members have discovered are not compatible. We know the original TA-03 was the easiest to modify and absolutely works, as well as the newer TA-03B, even though it's a bit more difficult to mod. We also know the BestKits.com BHA8113 Harness http://bestkits.com/i/BHA8113-new.jpg also works, and may still have the original Scosche TA-03 style connector that's easier to work with. 4) Recently members have been asking me about a new harness called the Metra TYTO01 http://www.circuitcity.com/ssm/Metra-Toyot...roductDetail.do At this time all I can say is that it looks like it might work with later JBL-equipped vehicles which use the Toyota databus to control Turn-On. Other than that, I don't know yet whether it needs the mod or not. Note: Metra does not list any Celica's in their TYTO01 compatibility table. (update 8/07: BestKits BHA8113 identical to TA-003 Original) 1) Confirming: the BestKits.com BHA8113 Harness is identical to the discontinued original TA-03 harness, including long pins making it easy to modify compared with the newer Scosche, so I'd recommend you use the BHA8113 instead of the Scosche TA-03B. 2) 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. For example if the table says use 600 ohms, use 1000-1200 ohms instead. PacificBlue



		Remove heatshrink from audio pins (notice hidden resistors in black shrink, also 4 new resistors in front Back of TA-03 showing 4 audio pins - (Red Wire is Right Channel & Top Row is Front) Unsolder the 4 RCA wires from the connector pins and twist termination resistors onto them before soldering Add heatshrink tubing (yel) to prevent shorts & add structural support, then tin the ends and solder em back to the pins Add more heatshrink (blu) then twist the ends of the resistors together and tin with solder Add larger heatshrink to Analog GND wire (blk/wht making U-turn) & solder it to the twisted end of the resistors After applying heatgun to shrink tubing - (Top Row is FRONT Left & Right) Another closeup showing the new resistors bulging out from the blue shrink tubing Completed Mod - tie-wrap all power leads together, then separately tie-wrap all audio & gnd's together #16 guage heavy-duty flexible copper wire (GRN) from the Celica's dash frame to the back of my HU. [ Click to view an SWF following the GRN ground wire added in the Pic] Scosche TA-03 FactoryAmp Noise Fix Mod - Basic Pictorial Diagram & Notes The output impedance of my head unit is 60ohms at 5vrms, so the 1.9k (1900 ohm) series resistors don't hardly reduce any level and it's easier to leave em in. Basically what you're doing is adding a terminating resistor from each signal wire to ground, closest to the FactoryAmp's inputs. (Ideally you would do this right inside the amp, but this won't be necessary unless you plan on listening to your stereo while driving thru an MRI Scanner or past some military radar dish) SCOSCHE SLC-4 "BLUEBOX": ( comes w/TA-03 Kit - see notes below ) * 4-channel HV LINE LEVEL to 4-channel LINE-LEVEL converter ( don't need SLC-4 for HU's w/Preamp Outs - Only use TA-03 Conn w/Mod ) * 4-channel SPEAKER LEVEL to 4-channel LINE LEVEL converter ( up to 80 watts max per channel ) ( use SLC-4 together with TA-03 Conn w/Mod - adjust trimpots on SLC-4 to match levels ) * Transformer circuit for noise cancellation. * Common ground adapter. So what's with the blue box Scosche provides? Well in an ideal noise-free world you would set the switch to "Line" and plug your RCA's into it and wire the other end into your amp, but if you don't have a HU with high-level preamp outs you can connect your HU's speaker outputs into it (thru the screw terminals) and it will drop speaker-level down to line-level to feed the FactoryAmp. Will you still need to do this mod? Uhm, yeah probably... it's because inside the TA-03 are 4 level-dropping circuits and impedance matching/isolation transformers. What's great about transformers is that they can match the impedance of one circuit to another almost perfectly, plus they can isolate DC path between two devices and only pass the audio signal, but what's not so great is that they can also act like guitar pickups when designed to be connected to high input-impedance amps like ours. Ever hookup a Scosche TA-03 and wave it around the inside of the dash with the ignition on? Acts like a Theremin doesn't it? That's cuz its transformers are picking up the noise from the data bus running all thru the Celica wiring harness. Ever play with a telephone pickup coil? Almost the same thing. Notice the TA-03 has 3-ground wires coming out of it. Make sure you connect the ends of the 4 resistors (tied together) to the wire labeled Analog GND in the photos & diagram. The other two GND wires can be tied together and connected to your HU's GND wire. Believe it or not, once you terminate with resistors, your grounding problems will pretty much disappear. I forgot to mention that when you terminate audio lines with the matching impedance of your HU, your frequency response will probably be restored more closely to what it's supposed to be too. In otherwords if it sounded too bright & tinny before, your bottom end (bass & lows) should come back to life again and you won't have to subtract your treble & max your bass eq settings anymore. thanks for the help on the board & enjoy your FactoryAmp, I hope it helps... ps ~ i want to give some credit to EvilED who posted a msg way back in 10-12-2002 about a mod for the factory amp. I found it while searching to make sure the TA-03 Noise wasn't a topic already covered. It just goes to show that doing thorough research pays off if you bother to do it (and no, I didn't find it until it was too late cuz I was lazy too... crap!) Click Here: EvilED's factory amp mod Click Here: to go back to the original nc.org thread Curious what the Scosche TA-03 Harness sounds like -without- the mod? ** CLICK HERE "Bill? What is it Ted?"**