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Today at Atelier Kaz - ex-Honda R&D, F1, Indy/CART engineer

Bose Speaker AMP Service 02

Rating: 7 votes, 5.00 average.
3 Comments
by
Kaz-kzukNA1
, 13-07-2011 at 11:11 PM (11341 Views)



All three AMPs showed lots of leakage from the capacitors.

One of the door AMP didn’t even make any noise/sound when it was powered up.

As the owner contacted me many months ago and he wanted to have them returned urgently, we agreed that instead of trying to investigate and refurbish this AMP, best to replace it with my spare unit refurbished a few years ago.



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Some of the leakage was dissolving the area around the Bose in-house IC.




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The AMP at the passenger foot well was really in bad condition.





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One of the two door speaker AMP and foot well bass one were refurbished.


For the Rear foot well AMP, the gain control was not correct when measured several voltage around the IC.

Therefore, pulled up the voltage by putting 1k ohm resister at one of the cap.





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As the owner sent me all three speaker boxes, I used them including the connectors and wires to bench test the system with MP3 player with moderate (quite loud) audio level for 2Hrs each.


Happy with the result and they are now going back to the owner abroad.

I’m using the International next day service so the delivery charge is ‘mega’ but hope it will arrive within the time limit…..

Kaz
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Categories
Audio

Comments

  1. avcrx's Avatar
    Hi Kaz,

    I just got a door amp bought online recently with the same code "137637-2205" as one shown in your pic, does the rear part 2205 means anything? the reason I ask this because the stock one from my 94 is 2305 instead.

    My concern is, as my driver side one is dead and this one is going to be a replacement for it, so wondering if they can work together to reproduce the original sound effect? or its has to be using as a pair with the same code? or they just the same but produced in different years? However, the layout of the caps seems like different to me...

    Thanks

    Alan
  2. Kaz-kzukNA1's Avatar
    Hi, Alan. Good to hear from you again.

    Bose modified the circuit board design as well as the capacitor and IC spec during the production of NSX.

    I don’t pay much attention to the sticker on the silver metal lid/case as it could be from another AMP or even from different models.
    They are using the same lid between the Front (door ones for our NSX) and the Rear (passenger footwell one for our NSX) AMP and also you can find the same lid but different AMP spec on other car models from different car manufactures.

    For our NSX, Bose changed the board design and possibly the EQ setup around 1995/1996 first and then another modification around 2002.

    What you need to look for is the IC model number at U1.
    It started as 121661 and then changed to 133524. It controls the EQ setup with the combination of different capacitors/resistors used.
    I thuink the changes were made without informing Honda and it is more likely to be oriented by sharing the board with other car models that had similar EQ setup than an improvement but not sure.

    So, strictly speaking, the frequency response would be different from the hardware point of view but will it be possible to notice it inside the cabin???


    Well, this is something you need to try by yourself.

    Please note that I’m not an audio guru and I don’t spend a lot for car audio system so other people will have different view.

    First of all, your ear sensitivity.
    With the age, your hearing will change and thus, the sensitivity against the sound frequency band will depend on each person. Therefore, even Bose tuned the AMP and speaker box for NSX, it may no longer be the same for your frequency sensitivity. Typically, you will loose around 4kHz.

    Secondary, any aftermarket parts that generate the noise and vibration.
    The sound can be heard not just through your ear but also through your body/bone/skull so changing the engine parts/exhaust/header/mount/air box/air filter/tyre/etc will change the listening environment and thus, it won’t be the same as the targeted original Bose spec.

    The source of the audio will also have the effect.
    Any compressed format such as MP3 will loose certain portion of the frequency bands so depending on how it was compressed, you are already loosing some of the sound quality at the source.
    If you use aftermarket audio head unit but kept Bose AMP and Speaker, then it will also have different effect at the source. OEM head unit is Alpine and not Bose.


    So, personally, as long as it’s from NSX, I don’t think you will notice much difference while you are driving or even stationally with engine speed at idle rpm when using different Bose AMP spec inside the cabin.

    Kaz
  3. avcrx's Avatar
    Hi Kaz,

    Thanks for your reply again and its as informative as always!

    And most important is after hearing your explanation, now I feel more comfortable about getting this used amp, will replace all the caps first and then try mounting it on my NSX to see how it sounds the weekend.

    Thanks

    Alan