LM4780 + TDA7293 Power Amplifier

National Semiconductor LM4780(Stereo Treble) 120watts

ST Microelectronics TDA7293(Mono Bass) 100watts

Specification:

- 60Wx2(stereo) + 100W(bass)
- this amp is well designed and built with great quality and accuracy components for its best frequency reponses.
- 1% tolerance resistors, film capacitors signal path/powerail decoupling, semi-gold plated 8-DIP sockets,
- WIMA MKP4 input coupling capacitors, Nippon-chemicon powerail capacitor(well known for DIY power supply cap, Nichicon LQ power filter capacitor(seen a lot in Tube amp) and etc..

- preamp stage two NE5532 opamp, (woofer loudness control, crossover control(50~150Hz), and volume control)

- when there is no woofer connected, cutoff to fully stereo channels automatically which no need to tune the crossover point again to the lowest.

Trying on smaller heatsink because not going to maximize the volume.


Dynamic quite good.
This is an GREAT amplifier, I don't even know it is already on after I powering on it in the 1st time.
It is dead silent, can't hear any hum or hiss 1 inch away from tweeter.

Changed RCA interconnects, cut off the internal preamp and removed TDA7293.

Sounds faster, airy and cleaner without NE5532 preamp.
and lesser harsh with the changed from standard RCA to coaxial RCA.

This is my another new PCB board, planning to redo it.

Altec Lansing MX5021 Modification

I'm new to this. Please do at your own risk and I won't give any responsibility.
For how to solder, please Google it.

Altec Lansing MX5021 is the best PC speaker that Altec Lansing ever made yet it is one of the best 2.1 PC Audio Systems in the world. You guys thought MX5021 might sound fantastic, but the truth is that its sound is far from being Hi-Fi. To all modifications I made had brought the sound quality to a whole new level, I must tell you that not everyone can hear the differences in Audio Quality. Audio is very Subjective for personal so modify it in your own way to suit your taste.

Most critical modifications are done to the main PCB inside the MX5021 subwoofer. I had changed poor quality China made electrolytic capacitors (Samxon) with better quality ones. Only changing the capacitors will not be enough, changing op-amps to high quality audio grade ones is neccesary, the Stock ST4558 op-amps are very old, has narrow sound stage and high noise level.
Make sure you change the capacitors with a same value ones, unless you know what you are doing. For op-amps, make sure it is a dual op-amp and please get those are compatible with supplied voltage and current of your MX5021 PCB.

In audiophile field, cheap electrolytic capacitors and cheap carbon resistors are extremely bad choice in a audio signal path cause of the poor tolerances ~10-30% and ~5-10% respectively. Metalized polypropylene, polyester, tinfoil capacitors and metal film resistors are highly recommended for signal path.

I also changed the thin subwoofer cable to a thicker ones.

For details, please navigate to the links below.
Altec Lansing MX5021 Modification (Part 1) Satelites and Amplifier Re-cap

Altec Lansing MX5021 Modification (Part 2) Swap Op-amp and Second Stage Re-cap

Altec Lansing MX5021 Modification (Part 3) Upgrade Coupling Capacitor
Huge Improvement





Altec Lansing MX5021 Modification (Part 4) Mundorf ZN & MKP
Audiophiler Coupling and Crossover, not really worth it.



Altec Lansing MX5021 Dead and precautions.

Altec Lansing MX5021 Dead

My MX5021 is dead.
Don't know which part is dead without the diagnosis tools.
Guess it must be the signal path because there is no hum when it is switch on until I play the music.
Plus, my test pen short circuit and pop the TDA7295 while checking each of the components so it is totally dead now. I also lazy to fix it already, going for bookshelf.

My advise, handle it with care to prevent any impact onto components during modification and plan which component and brand to use before start your work. Keep soldering and de-soldering will damage the PCB trace and try your best not to touch the SMD components with naked hand because they are sensitive to electrostatic.

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Altec Lansing MX5021 Modification (Part 4)

Mundorf Audiophile grade capacitor.
Mundorf MKP and Mundorf ZN.

Mundorf ZN 1uF to replace coupling capacitor.

Mundorf MKP 4.7uF and 15uF to use in satelite speaker's crossover.


Result:
Mundorf MKP in crossover, soundstage wider and sound also more detail than electrolytic capacitor.
Tweeter and mid-range sound a LOT sweeter after few days of playing it.
Mundorf ZN, unfortunately the leg is too big to go through the hole of PCB so can't test it.

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Altec Lansing MX5021 Modification (Part 3)

Bought this Metalized Polypropylene Film capacitor from RS-Components.

Vishay MKP1848 1uF 900V to replace both 1uF coupling capacitor in the circuit.

C61 and C54 stereo satelite speakers input coupling capacitors.
(recommended Metallized Polypropylene > Metallized Polyester over here)

Pin too short, so extended it with wire.

Saw the C118?
This is subwoofer input coupling capacitor.
Replace with a good capacitor eg. Nichicon Fine Gold. 22uF will do.

Conclusion: IMPRESSIVE!!
You can feel the high and warmth sound is surrounding and fill the whole room.
Not like other electrolytic capacitor sound dull.

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