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.