Installing new head unit. Need help!

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Gottagetone said:
Splain how you ran the RCAs off the amp, I am considering one of the double din units off of ebay and that sounds like the best way to install it.
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This part is simple, just get a set of RCA cables, or buy a set of RCA plugs, and solder your amp wires to the center wire of the RCA cable, or the center post of the RCA plug.



RobRed said:
2x

Simply adding RCA's to the amp shouldn't make an electrical difference unless Toyota is doing something pre-amp between the oem head unit and oem amp.
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It makes an enormous difference. The factory radios have no built in internal amplification. They are essential just producing a source sound. Like a pre amp for guitars or home audio systems. What most on here try to do is take the easy route and just solder the amplified leads from an aftermarket unit directly to the factory amp. You don't amplify and amp. Those damn things are fairly noisy, even high quality ones. Those little mosfets, capacitors, and torrodial transformers make a pretty nice buzz. When you amplify a source that is designed to power a speaker there is going to be a ton of interference. Every time you amplify something you introduce noise.

Just look at the amperage draw difference alone. A pre out is only sending 6 volts at the high end, with very limited amperage. That amplified section is sending a couple of hundred watts and drawing 15 amps or so. If you ever walk by a large transformer you can hear the sound electricity makes, albeit is it less so with DC.




To save yourself from having to run 15 feet of cable, you can disconnect the wires to the factory amp, splice into the cables running to the factory amp, disconnect the wires from the factory amp output, and hook connect them to the spliced wires from the input side. You will get the same answer either way. Would still be much quicker just to solder RCA's onto the factory amp wires that are already behind the head unit.
 
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So would you use something like this 24-Ft. 18-Gauge Speaker Cable with RCA Plug - RadioShack.com to go from the aftermarket H/U speaker outs to the amp in? or from the H/U RCA out to the amps speaker in? Would you only do this to keep your sub working? Seems like a better option is to bypass the amp....
 
Why would you want to bypass a decently functioning amp that will sound better than what they put in the headunit. Truthfully I would just buy a bare rca plug from somewhere and solder them to the amp wires that are already behind the dash. No noise, quick job, keeps the amp, and saves from having to run a ton of wires through the vehicle. You want something like this Phono (RCA-Type) Plug (2-Pack) - RadioShack.com

If you are really looking to upgrade sound quality you will need to rewire it all anyway.

This site give a pretty good idea of how to wire it from step 6 on. Only difference is you are not running a ground wire.
Belden 89259 DIY RCA Interconnect Cables
 
snapaxle said:
This part is simple, just get a set of RCA cables, or buy a set of RCA plugs, and solder your amp wires to the center wire of the RCA cable, or the center post of the RCA plug.





It makes an enormous difference. The factory radios have no built in internal amplification. They are essential just producing a source sound. Like a pre amp for guitars or home audio systems. What most on here try to do is take the easy route and just solder the amplified leads from an aftermarket unit directly to the factory amp. You don't amplify and amp. Those damn things are fairly noisy, even high quality ones. Those little mosfets, capacitors, and torrodial transformers make a pretty nice buzz. When you amplify a source that is designed to power a speaker there is going to be a ton of interference. Every time you amplify something you introduce noise.

Just look at the amperage draw difference alone. A pre out is only sending 6 volts at the high end, with very limited amperage. That amplified section is sending a couple of hundred watts and drawing 15 amps or so. If you ever walk by a large transformer you can hear the sound electricity makes, albeit is it less so with DC.




To save yourself from having to run 15 feet of cable, you can disconnect the wires to the factory amp, splice into the cables running to the factory amp, disconnect the wires from the factory amp output, and hook connect them to the spliced wires from the input side. You will get the same answer either way. Would still be much quicker just to solder RCA's onto the factory amp wires that are already behind the head unit.
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As an audio technician in a former life I'm definitely aware of all of these concepts. Wire harness adapters from various manufacturers like Metra have the RCA ends on the radio side, my AVIC is currently using one. These RCA's make the connection you talk about soldering. The HISS is caused by the OEM amps mismatch of input impedance from a 75ohm (2-4 volt) line level out of an aftermarket head unit.
 
If you have a Levinson based system, here is the way to go. Retains all factory amp's / speakers.

Beat-Sonic SLA-100/82AAD

My CD player is going out in my Levinson in dash changer, I am going to get this kit, plus a new Double DIN w/ NAV as a first step. Later I will upgrade the amps and speakers.
 
Here's what I think everyone is missing.

The hiss happens even when NO speaker outputs are connected from the head unit to the amp. Even if the ONLY wires connected at the back of the head unit are unswitched power, switched power, ground and the lead to power up the amp. In other words, as soon as this head unit sends the voltage to the amp that tells it to wake up, I get a hiss. In the accessory position, it lasts just a couple of seconds and then goes away. In the On position and when the engine is running, it's hissing. From on to accessory, no hiss.

It has nothing to do with the RCA leads as the hissing happens whether they're connected or not. Also, if the RCA's were the issue, why does it sound great in accessory mode?

To speak to the RCA's for a second, my head unit (a JVC from Best Buy) has two sets of speaker outputs on the back. 5 female RCA jacks (front and rear, left and right and a sub) OR 8 wires coming out of a harness. I've tried all of the above with no change. But, like I said above, speaker connections aren't the issue. Powering up the amp in the on or while the engine is running is the issue.
 
Still sounds like a possible ground loop. Do you have the head unit constant hot running directly to the battery? Or is it spliced into the factory harness?
 
alfredhyrid; As I said earlier your issue is different but not by much. The HISS is the amp's input gain looking for a signal. The response, Accessory versus On is interesting but the root cause is the same.

Do you find if you have the HISS in On mode that it lowers when the music is louder?
 
CappyKD said:
Still sounds like a possible ground loop. Do you have the head unit constant hot running directly to the battery? Or is it spliced into the factory harness?
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x2

If you can connect the amps wake wire back to your factory head unit, without speaker connections, that would rule out anything to do with the amp increasing gain due to lack of input signal. More than likely it is a grounding problem within the head unit. The acc mode might rectify the problem as the head unit is then using an outside source and possibly different wire paths and grounding. That is the only thing I can think of why ACC would change it. Acc have to be plugged in through the HU chassis and could be more solidly grounded?
 
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CappyKD said:
Do you have the head unit constant hot running directly to the battery? Or is it spliced into the factory harness?
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Non switched hot is coming through the OEM harness, connected via the Metra harness that I bought, then spliced into the Head Unit's harness into the HU.

RobRed said:
Do you find if you have the HISS in On mode that it lowers when the music is louder?
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With music, it's hard to tell. You can't hear the hiss any longer when the volume is higer, but I'm not sure if it's still there. With a DVD or talk radio, you can hear the hiss during conversations, at any volume.




The worst part about this situation is when you're on the road and decide to turn the radio off, the hiss is still there. So the only way to get rid of the hiss while driving is to mask it behind music or wind noise with the windows down.

I'm confident that the amp bypass will eliminate the hiss, but I'm not sure I'll get the volume needed out of the speakers, that I'll be able to connect to all of the speakers in the truck, etc. It would be so much better to find the cause and fix that.:bang:
 
I'd run the constant straight to the battery and the HU ground to a new ground under the dash. Then find out which wire is gound on the factory amp and run that ground from the amp to the location where you grounded the HU.


HTH
 
To that point, anyone have a wiring diagram of the harnesses going into the amp?
 
Interesting the hiss doesn't go away when the radio is off...

I'm on my mobile so I don't want to go back and reread the thread.... You are using RCA out of the JVC correct?

If so I suspect the JVC RCA outputs have a blown chassis ground. With the truck on and getting the hiss take a piece of speaker wire stripped at each end and touch one end to the chassis of the radio and the other to the ground of the RCA output on the JVC. Reply with result.
 
Done that in a way. I've taken a wire, tied one end to the chassis of the truck and have touched it to everything. The ground component of the RCA, the chassis of the head unit, the amp, everything I could find, etc.

Also, yes, using the JVC's RCA outputs. But the hiss happens w/o anything connected to them. Radio is off, but it must still have the amp turned on. With amp on and truck on, I get a hiss.

Things I haven't tried yet....

-- 12V in line filter on the blue/white amp wake cable from head unit.
-- disconnect new HU and jumper hot wire to amp wake cable to see if I get a hiss with a 12V signal and no HU in place.
-- jumper the switched power to the amp wake cable so the amp powers on when the ignition is turned on, but so the wake signal isn't coming from the HU.
 
I would try the other two before you try the filter. A filter is only a patch, not a fix, it could still creep back up later on. Jumpering it to anything but the hu will certainly eliminate anything other than the HU being the problem. Might even use a 9 volt battery as the wake source for the amp.
 
alfredhybrid said:
To that point, anyone have a wiring diagram of the harnesses going into the amp?
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From the 2000 EWD... Pwr and grnd go through the amp to the HU. Note the two different pwr sources to the amp from the cigar fuse and the radio fuse.
 

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alfredhybrid said:
Things I haven't tried yet....

-- 12V in line filter on the blue/white amp wake cable from head unit.
-- disconnect new HU and jumper hot wire to amp wake cable to see if I get a hiss with a 12V signal and no HU in place.
-- jumper the switched power to the amp wake cable so the amp powers on when the ignition is turned on, but so the wake signal isn't coming from the HU.
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OK, done these now.

-- no change. Still hisses with noise filter in line with amp wake cable.
-- with the head unit completely disconnected, I jumpered switched power to the amp wake cable. No hiss. I could tell the amp woke by the small thumps I got from the speakers when I connected and disconnected the jumper.
-- still hisses when I put switched power to the amp wake, even when the switched power isn't running through the head unit.

Sounds like it's an incompatability between the head unit and the amp. I'm bypassing the amp now.
 
Astralplane said:
Did you turn off the JVC built in amplifier?
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Yeah. There is a setting for off, medium or high. I tried all of them.

Stupid harness I got in tonight to bypass the amp. When it's connected, you have to disconnect one of the two harnesses that go to the amp. With them disconnected, the head unit has no power. I know I saw on here somewhere that someone did this and had to run a jumper from one amp connector to another. Off to find that thread.
 
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