Factory amp bypass necessary?

Discussion in '80-Series Tech' started by flintknapper, Dec 26, 2007.

  1. flintknapper

    flintknapper

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    Getting ready to install my new stereo....I have harness from Crutchfield that allows the use of the factory amp.

    I thought it was desirable to bypass the factory amp. when doing a four door speaker system?

    Is the HU amp superior to the factory (maybe a dumb question).

    Looks like I need a couple of Metra 70-1761 wiring harness'.

    I'm not sure Crutchfield will be much help on this install.
     
  2. davnic6

    davnic6

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    I used the factory amp with my Z-1 Pioneer and it sounds mushy not clear at all. When I turn it down you cannot even tell what song your listening too. Will be bypassing the amp ASAP.
     
  3. zcruiser

    zcruiser Needs monitoring

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    If your HU has pre-amp outputs and you feed that into your factory amps you should be OK.

    Is there something unique about the LC factory amps? Assume there also has to be an 'ON' signal from the aftermarket HU...
     
  4. hadji_85

    hadji_85

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    you dont need to remove the factory amp or do something complicated. just unplug the amp to bypass it.
     
  5. Rookie2

    Rookie2

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    Contrary to the other opinions, I followed Crutchfield's advise and left the factory amp in play. The stereo I bought had pre-amp outputs and the pre-amp voltage was 4 volts instead of 2 volt which some of the others I was looking at had. The Crutchfield guy said this wouldn't normally make much difference, but in this particular instance due to the stock setup and leaving the amp in play, it would make a significant difference in sound output over what the stock system was currently producing. And he was right. Night and day difference.

    My $0.02, use the harness Crutchfield sent, and leave the amp in place.

    BTW, the directions Crutchfield sent me, included the amp removal procedure which kind of confused me. Called them, and found out that was a mistake. So I tossed that part.

    :beer:
    Rookie2
     
  6. roncruiser

    roncruiser

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    How do you disengage the stock amp? Where's the power located for the amp? Matter of fact, where's the amp located?

    I installed an aftermarket HU some time ago. Never got around to bypassing the stock amp. Is it a matter of just removing power to the stock amp to bypass?
     
  7. Rookie2

    Rookie2

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    The amp is located behind the dash by the glove compartment. Based on Crutchfields write-up, didn't look that hard to get to and unhook, but there was some wiring to be done to bypass it, and that part wasn't exactly straight forward to me.
     
    Last edited: Dec 26, 2007
  8. flintknapper

    flintknapper

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    So.....which is better, the factory amp. or the Kenwood HU amp.

    I don't mind doing some wiring...I just want the better of the two amps. powering the system.

    Somehow I doubt the OEM unit with its 10 year old (or older) technology would be the equal of the Kenwood amp.

    Anyone got specs. on the OEM, or opinions on both?
     
  9. flintknapper

    flintknapper

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    Bump,

    Apparently... this is a topic without well defined answers.
     
  10. trevdawg

    trevdawg

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    well, if I remember correctly the factory amp pushes ~20 v. When most new HU's push around 50 v. So in most cases its better to bypass the amp
     
  11. flintknapper

    flintknapper

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    So, if I bypass the amp. what is the recommended procedure?

    Can I just splice into the wires below the factory amp. outputs...or is there a harness available that will let me connect to the old output harness and then run my wires back to the HU?

    Somehow...I'm thinking a pair of Metra 70-1761 harness' might do that. I can't remember if I read that while doing a search or not.
     
  12. flintknapper

    flintknapper

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    BTT


    I must be on a lot of ignore lists.:)

    I know someone knows the answer to this.
     
  13. Rookie2

    Rookie2

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    I found Crutchfield tech support to be pretty helpful and they should be able to help answer you questions as to which way would be better for the particular head unit you purchased. You should be able to also to request the directions for bypassing the amp if that's what you choose to do. As I mentioned, my install directions included the amp bypass procedure by accident. I don't know how well the harness they sent with the unit I bought, was gear towards bypassing the amp. Seem like there was a lot of extra shiz nit to go through.

    :beer:
    Rookie2
     
  14. Cruisin'Carolina

    Cruisin'Carolina

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    I would by-pass it Flint. I do not recall extra harnesses or anything, I just made sure what color speaker wires went to each door and wired them to the headunit i put in.

    I can't imagine there being a real long term benefit to leaving anything Toyota installed in the 90s being a long term sound solution, but that is just me.
     
  15. flintknapper

    flintknapper

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    Thats what I am thinking too.
     
  16. flintknapper

    flintknapper

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    Already talked to "AJ" there twice. He wants me to use the harness they supplied and go back with the factory amp.

    I think the factory amp. probably sucks compared with the new one in the HU.

    He didn't have any suggestions except to tap into the wires below the connectors on the factory amp bypass.

    I'm sure they know what they are doing on other vehicles, but he didn't sound too confident about this one.
     
  17. flintknapper

    flintknapper

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    Did use the "search" feature for several days before posting my questions.

    I am not a newbie here and wouldn't impose upon my friends unless I couldn't find what I need.

    There are indeed posts concerning radio installs....but some are conflicting. Some folks keep the amp, others bypass.

    Couple that with what I just found on the Crutchfield site (no thanks to their tech dept) and you can understand why I have questions.

    The only harness I got from Crutchfield is one designed to keep the factory amp. in the system..and it damn sure DOES involve splicing.



    From Crutchfield:

    '93-'94
    SYSTEM INFORMATION:
    If the vehicle has a four-speaker system (front and rear doors), all speakers run off of the stereo unit directly. The five-speaker system adds an amplifier (located just to the right side of the glove compartment) for the four main speakers and an amplified woofer (located behind the right/rear quarter trim panel). The seven-speaker system adds front tweeters to the front door speakers, wired in parallel. The nine-speaker system adds rear tweeters in the headliner just forward of the back door, wired in parallel with the rear door speakers.

    AMPLIFIER BYPASS, ALTERNATE METHOD (1993-94 Only):
    If the vehicle has an amp and you are installing a new stereo, the amp must be bypassed. The 70-1761 harness will fit the two output plugs at the amp, which is just to the right of the glove compartment. There is also another set of plugs in the vehicle that fit our 70-1761 harness behind the radio, but make sure to see the warning that follows.

    Vehicle is wired for standard radio (70-1761 harness) and high end radio (15-pin plug that feeds to amp). Follow the head unit wires just a few inches to where they merge into a larger wire bundle. You will find the unused standard plugs from this same bundle. WARNING! When you connect the 70-1761 at the radio it is crucial that you MUST unplug and do not use the output harnesses on the amp! This is because all the wiring, speakers, power, etc., in the vehicle are parallel wired to both locations. If the amp output remains connected, even though it isn't used, it will short the radio speaker output.



    ‘96
    SYSTEM INFORMATION:
    If the vehicle has a Four-speaker system (front and rear doors), all speakers run off of the stereo unit directly. The Five-speaker system adds an amplifier (located just to the right side of the glove compartment) for the four main speakers and an amplified woofer (located behind the right/rear quarter trim panel). The Seven-speaker system adds front tweeters to the front door speakers, wired in parallel. The Nine-speaker system adds rear tweeters in the headliner just forward of the back door, wired in parallel with the rear door speakers.



    ‘97
    SYSTEM INFORMATION:
    The 1997 Landcruiser was a 40th Anniversary Limited Edition and had a standard 9-Speaker system. The only option was the addition of a CD player. The vehicle has front door midranges and dash tweeters (wired together in parallel) and rear door midranges and rear roof tweeters (wired together in parallel). All speakers are wired to a four channel amp, located just to the right of the glove compartment, above the right dash tweeter. Also, there is a woofer with a separate amplifier located behind the right/rear quarter trim panel.



    Answer
     
  18. flintknapper

    flintknapper

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    Here is the Radio harness and Adapter harness that came with the unit.

    Also a pic of the back of the unit.

    Clearly this is not plug and play (no splicing) as alluded to by one person.

    I don’t mind splicing or doing anything else necessary to achieve a four speaker system (doors only). I just want to do it the most efficient way.

    If there is “another” harness that just plugs in (and someone can tell me which one it is) then I’d love to do it that way.

    If not, I’ll splice….no big deal.

    [​IMG]

    [​IMG]
     
  19. flintknapper

    flintknapper

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    Bump

    Sorry.:eek:
     
  20. Rookie2

    Rookie2

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    Here's one thought, why not hook it up leaving the amp in play and see how you like it. It doesn't take much time and won't cost you anything. If you aren't impressed with the sound (like I was), then you can work more on the bypass version. I've got the bypass instructions for the LX 450. If you want them, I can scan and send them to you. They're at home, so probably can't get them to you until tomorrow.

    :beer:
    Rookie2

    Edit: Those harnesses look alot like the ones I got. FYI, all the wires don't get hooked up.
     
    Last edited: Dec 28, 2007
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