Posted on Thursday, 15th March 2007 by Auw Jimmy

If you haven’t read my previous article, please click here. I discussed the mod of MX5021’s satellites. Now, it’s time for the electronic parts ;)

I opened the Altec MX5021 subwoofer yesterday. Here’s the picture of the board inside. We can see two big rectifier, some big capacitors (removed from the board), and some op-amps (all are ST4558C).

We have two chip for amplifier here, one is TDA7265 and other is TDA7295. Both from ST. One for driving the both satellite (TDA7265, 2×25 Watt), and one for subwoofer (TDA7295, 80 Watt).

Photo above shows the removed main capacitor. Well, they come from “well known brand”, Samxon. You can see the value, 4700 uF, 2200 uF, and 1000 uF. I remove them all.

Photo above shows the new modded board. Giant capacitors there. I also change the coupling and supply capacitor for the TDA7265. This is quite important since that TDA provide amplification for the satellites (I expect smoother mid-range and treble). I don’t change the parts on TDA7295 since I believe the subwoofer should be fine with stock parts (to save the cost to).

Photo above shows the side of the main capacitor. The 10.000 uF is the lug type so can’t fit the small hole on the PCB. I have to create a wire extension to fit that. I think I will need to drill it someday ;) Two first pairs capacitors come from Elna, the last pair comes from Sanyo (Gold version). They are not the high price capacitors since I don’t have any intention to pay this upgrade cost more than the price of the MX5021 itself :)

You also can see two wires (orange and white). I remove the standard cable to the subwoofer and replace it with this cables.

Photo above shows the important circuit of TDA7265. I trace the circuit a little bit more by using TDA7265 datasheet. Then, I replace the two coupling capacitor and one supply capacitor. Both from Elna Cerafine (non-polar version – special order parts?). The op-amp also should be changed (later). The stock one is ST 4558C. Any op-amp from BurrBrown like 2134 or 2604 should fit this job perfectly. The sound at first impression: The high is more detail, but far from bright. The mid is warmer. The low extension has more punch, power, and control. Overall, the subwoofer and the satellites are blended perfectly (better than the standard one). I have no doubt that this mod increase the musicality of my MX5021 and it’s very significant. The final touch should be the op-amp. This should bring a lot of improvements. I have stock of BurrBrown 2134PA and will upgrade it soon. Will post my upgrade later.

Three hours later
Oh well, I can’t wait. I open the MX5021 again to replace the op-amp. I use BurrBrown OPA2134PA. Here’s the photo. Will update the sound impression later. I use a socket so I can change to op-amp easily next time. I have stock some op-amp (OPA2604/OPA627/AD825/etc).

Final impression (full upgrade with op-amp BurrBrown OPA2134PA):

I can’t wait any longer. I plug the fully modded Altec Lansing MX5021 to my EMU1820M sound card. Well, I’m shocked at first time. The vocal of Ingram Washington in “What a Wondeful World” locks tight on the center, while the other instruments have their own layers. The details of the baritone are there and you can feel it. Surely, the BurrBrown OPA2135PA increases the staging and separation of the music. I do enjoy this upgrade. The high is better in terms of extension, clear but not bright, quite airy. I think that is the most significant of upgrading that stock ST 4558 to the BurrBrown OPA2134PA.






Posted in CD/DVD Review, DIY Audio, Indonesia, Personal | Comments (587)


587 Responses to “Inside Altec Lansing MX5021: Amplifier Mod”


  1. Auw Jimmy says:

    Hi Pak Steaven,
    Mohon maaf saya kurang tahu tipe ICnya. Tapi saya pernah dengar kalo tipe IC nya ini khusus dan tidak umum.
    Terima kasih.

  2. Steaven says:

    Hi Pak Jimmy,

    Terima kasih atas reply-nya.
    Selamat Tahun Baru 2013.

  3. Auw Jimmy says:

    Sama2 Pak Steaven, Selamat Tahun Baru 2013 juga.
    Terima kasih.

  4. Darren says:

    Hey, any expert in here can teach me how to take out the power transformer for MX5021. Primary winding open circuit and need to replace or rewinding. But it was glued on the base of the panel.

    Terima kasih

  5. Auw Jimmy says:

    Hi Darren,
    You need to ‘cut’ the glue and ‘pull’ the transformer. I know it’s not gonna be easy, but there is no better way, I think.
    Thanks.

  6. lawrence says:

    Hi VC, nice meeting you. I’d mod my MX5021 few years ago and it works fine till recently i notice some static noise from left satellite. Turning the volume up and down didn’t help to minimize the static noise, I’ve tried to swap left and right speakers, cables and unplug the 3.5mm input jack but the static noise remain at left channel. So the problem goes down to the PCB board. Since there’s no static noise notice with headphone plug into the control pod, I assume that the problem goes AFTER the input signal been amplified along the way to speaker output instead of control pod headphone output. Problem is, I got no clue that which component seems more likely to cause the static noise and need to be replace. Any suggestion? Thanks a million!

  7. lawrence says:

    Opppss! sorry, hi Jimmy, hehe…

  8. Auw Jimmy says:

    Hi Lawrence,
    I believe most MX5021 has some static noise, although the level is quite vary. Some of them say the problem comes from the main transformer. Headphone out might not be impacted (probably) due to some signal attenuation circuit.
    Thanks.

  9. 国庆 says:

    Bro jim, where i can find OPA 2111 at Jakarta?

    Thanks.

  10. Auw Jimmy says:

    Hi Bro,
    Coba cari di Glodok atau LTC.
    Thanks.

  11. ray says:

    i believed i damaged my board for this mx5021… is there anybody else selling whole mainboard for mx5021? i badly need it.. i miss the sound of my mx5021… i thought the TDA’s are burnt and i replaced the 2 TDA but still no output.. if there’s anyone who is selling a working board then pls tell me including cost for shipping to philippines… thanks alot

  12. idho says:

    Pak Jimmy/Pak Steaven.
    Saya juga memiliki problem yang sama dengan Pak Steaven.
    Apakah sudah ada perkembangan terkait perbaikan atau problem ini?
    mohon dibantu pencerahannya.

  13. Auw Jimmy says:

    Hi Pak Idho,
    Maaf saya sendiri tidak tahu jawabannya, Pak. Sebaiknya dibawa ke toko reparasi untuk dicek.
    Terima kasih.

  14. Jason Damsing says:

    Hey Jimmy,

    Good read – thank you. I stumble upon you site googling around on the Altec Lansing MX5021.

    The question i have might not be your regular expertise. However, do you know if the sound output(mini-jack) on the subwoofer is replaceable?

    I ask cause the jack socket accidently splitted, since my dog stepped on the jack cable. :(

    Thank you in advance!

  15. Auw Jimmy says:

    Hi Jason,
    Which jack that you are talking about?
    Thanks.

  16. totof says:

    I succesfully modded my mx5021. Replaced all power supply caps with same value but high quality, higher voltage, low esr types. Replaced all audiopath caps with elna silmic II. Replace all green 0.1uF caps with ERO Polyprop types. Replaced crossover caps & inductors with Mundorf & bypassed each cap with a Vishay 1837 0.01uF. And lastly, replaced all 4558’s with opa2134. It went well for a week, i was overwhelmed by its new sound. I could hear voices & instruments never been heard before. Then problems started, i can hear a popping sound everytime i turn on the power & everytime i adjust the volume. Then all of a sudden i lost midrange & base. I think the opa2134’s are oscillating and it damaged the two surface mount ic’s on the back TDA7433 & TL074. So, i replaced both ic’s and put back the original 4558’s. Everything was back to normal. I then upgraded all 4558’s to TL072 and the sound is great, everything is stable. The midrange is better, it is as if the singer is singing right infront of me. My last plan is to upgrade the ic nearest to TDA7265 with opa2132. But i am still hesitant, that it might cause some oscillation and damage other components just like the 2134’s.

  17. Alex says:

    Hi, i just came across this article when i am reading up on some problems with my MX5021.

    My MX5021 will experience breaking and cracking in the sound when the volume is tune higher or a certain pitch of sound is played. This happens in both satalites so i suspect the problem is with the subwoofer itself. Just wondering if anyone has an idea what might be the possible causes for this problem? Thank you very much!

  18. totof says:

    Hey alex,
    Does the noise increase as you increase the volume? Or is it the same even if the volume is at zero? Does it sound like static noise? Is your unit intact or did you make any modifications?

  19. Alex says:

    Hi totof,

    The speakers are not modified. The sound breaking gets worse when the volume gets adjusted up. To the point where the vocals just becomes cracking sounds. The cracking happens only when the volume exceeds a certain “threshold”. If possible i can try to upload the sound clip of the breaking sound. Thanks!

  20. Alex says:

    Another observation that the sound breaking only happens to the satalites. When plug in my headphones to the control pod the sound does not break no matter how loud i adjust the volume. I tried swapping the audio cables but it does not help as well. Thanks!

  21. totof says:

    hi alex,

    try tuching the surround foam edges of your subwoofer driver. mine had a tear and it also produced a cracking sound when you raise the volume.

  22. ipanase says:

    wow,,.. rare genuine caps here :(

  23. Irhamna says:

    Halo mas Jimmy, Salam kenal. Saya mau cari IC no. NJU7313L JRC A5002C untuk MIxer Amplifier BMB model DA-X2 ada apa gak ya? Soalnya kawan saya sudah ubek2 kota medan tapi komponen tersebut tidak ada di jual. Klo mas tau dimana kira2 saya bisa dapat informasi jualnya IC_nya ya?

  24. Auw Jimmy says:

    Hi Mas Hamma,
    Maaf saya kurang tahu. Mungkin harus cari di Glodok.
    Terima kasih.

  25. Mardy Saragih says:

    Hi pak Jim, i have divoom speaker that use jrc4558 as opamp, recently i bought opa627au2 plan to put it as replacement to stock opamp, but when put it to the system only sattelite speaker sound better, the sub woofer no sound only hum, then i put the old stock and the system back to normal, what is the problem?

    Does jrc4558 incompatible with opa627au2?

  26. Auw Jimmy says:

    Hi Pak Mardy,
    I think 4558 is dual opamp while 627 is single one.
    Thanks.
    JA.

  27. Mardy Saragih says:

    I bought 2 opamps last week, opa2134 and lme49720na, try them both to replace jrc4558, then much prefer lme49720na, the detail impressive than opa2134, warm and open. I’m glad to say that my speaker improve a lot than using stock opamp, maybe you can consider to use it too.

  28. Ronny says:

    Bro Jimmy, mau nanya nih.
    Kl nge MOD Altec MX5021 nya persis sama kyk punya anda itu kira2x habis dana brp ya?
    Trs cocok ga MOD spt punya bro Jimmy buat nntn film?
    Apa karakternya lebih enak dari aslinya atau lebih bagus ini?

    Bgmn Middle nya? Trs suaranya msh pedes kayak bawaannya apa ga?

    Sory kl pertanyaanya rombongan ya, hehe
    Thx Bro Jimmy.

  29. Auw Jimmy says:

    Hi Mas Ronny,
    Dulu kayanya sekitar 300rb an saja habisnya.
    Cocok atau tidak rasanya relatif, tergantung selera juga. Tapi yang jelas lebih bagus dari aslinya.
    Terima kasih.

  30. blued says:

    Hi, just got to say that I was never pleased with the mx5021 system as a whole. But the satellites took on a whole new life when I used them as surrounds connected directly to a Yamaha AV receiver. Much clearer and sound much better than with the sub. To me the sub was the weak point, maybe its amp was the problem.

  31. Michael says:

    Hy Mardy Saragih. i saw your post and i want to ask you how is the sound with opamp LME49720NA. in my country, i found the LM4562NA and the LME49720NA too, but i don;t know which is the best choise. can you tell me please how sounds the satellites with opamp LME49720NA? Or Jimmy, if you can help me with choise between those opamps, i`m glad to listen your advice. thank you verrt much

  32. Auw Jimmy says:

    Hi Michael,
    Opamp is quite subjective. So to hear yourself is the best way to decide.
    But from technical stand point, I think 4562 and 49720 are more or less similar.
    LME49720 should be graded a bit higher with LME prefix, than LM on 4562.
    Thanks.

  33. Michael says:

    thank you Jimmy. i think i’ll try LME and after i’ll come back with a post. thanks again and have a nice day

  34. Michael says:

    hy everyone. i replaced the stock op-am 4558c with LME49720na. people, the sound is great now. i have no words to say it. is absolutely amazing. now, i can say that i have the amazing 2.1 audio system. thanks Jimmy for your help and thank everyone for suggestions. best regards to everyone

  35. Auw Jimmy says:

    Great to hear that, Michael!
    Thanks.

  36. Ahmed says:

    hi Jim,glad to meet,n very interesting mod,
    but here, plz i come with a question n need a help. i have a problem with my mx5021, when i unplugged this speaker n plug again, there is a sound like “boomm”, after that speaker does not power up anymore, no led lit, and totally dead. please show and teach which parts should i check and repair or replace, thanks a lot Jim

  37. Auw Jimmy says:

    Hi Ahmed,
    Before starting this discussion further, do you have electronic repair background?
    The process will require at least basic electronic repair skill, otherwise, it might be dangerous for you to follow.
    Thanks.


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