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Modding Altec Lansing MX5021 speakers

I didn't increase main filter capacitors. They have identical capacitance, only voltage is higher (from 50V to 63V and from 25V to 50V) because I couldn't get any others with those exact capacitance. I'm aware that in general there is no problem using higher voltages and capacitance, but it may sometimes cause problems if you go way too high. Deviating values a bit doesn't harm anything, but going way higher may do so, like replacing original 4700uF with 10.000uF capacitors.

It went nuts because something was wrong on PCB, possibly a solder debris bridging some gap either on OP-AMP or the loose main stage capacitor (that was my mistake since I didn't make sure it' soldered perfectly). This is a DIY project with what I have at home. The solder tool is nowhere near professional, I don't even have OP AMP 8 point de-solder attachment or even basic weave to remove solder. It was all improvised.

As for the sounding "brighter", maybe I didn't use correct words, but describing sound is hard anyway. After replacing main stage capacitors with basically same values, just much better quality and replacing main satellites OP-AMP with way higher quality one, I can really hear more details and sound has changed for the better. I called it "brighter", one could call it "more detailed". I always thought these caps changes are bullshit and they don't change anything, it's just placebo effect because you expect it to change because you used expensive Japanese audio capacitors, you expect it to be better by default. So, my expectations were already zero, but I did it anyway because I was curious about it. But there is a difference and I was legit shocked how it actually changed the quality for the better whether that's good for circuitry life span or not. Plus, it was a nice lesson by working on tight circuitry. So far I've only been replacing components on large empty PCB's using big ass solder tool we used to have. You didn't even have to be precise, they were that empty. I've fixed few things so far with such DIY fixes. One was Creative's soundcard, another one was LCD monitor with swollen and leaking capacitors. This one was not out of necessity, it was out of curiosity. Gotta learn things somewhere. I've spent 50-60€ on more stupid things than this. Way more stupid, so it's fine :)
 
RejZoR said:
I've spent 50-60€ on more stupid things than this.
Click to expand...

Holy... not more than 15$...

You picked OPA2134? Those are one rather dull sounding old chips tbh... gdallsk was right suggesting LM4562/LME49720, they are not perfect, for an general purpose opamp I like them best sonic wise and put them everywhere from now on in my projects, I like them even more than OPA627(not 637 thou, that's not unity gain stable).

Buy a stash of LM4562 for the future... they will soon disappear.

There are few notes on caps... you do not need to put audio caps where shouldn't. Audio caps are a niche product(they kind of promise more linearity in audio spectrum range). Low ESR, general purpose etc you cannot mash them around, it will trigger some unwanted side effects as the capacity isn't the only parameter. Each place where the thing is used has it's use. Often with some good will you do harm ie... that place actually needs a crappy general purpose capacitor. Without measuring the THD curve it is kind of doing things on blind.

Try the coupling method. Put underneath some polypropylene caps underneath it will improve the sonic performance.

Gosh for 60€ you really could put some plain and proper AB class transistor based stage... :shadedshu:
 
OPA2134PA was like 2€. I did put audio caps only on the audio stages of the circuitry, the rest are stock because I assume those are just raw power delivery and have nothing to do with audio output.
 
RejZoR said:
OPA2134PA was like 2€. I did put audio caps only on the audio stages of the circuitry, the rest are stock because I assume those are just raw power delivery and have nothing to do with audio output.
Click to expand...

Yeah those are cheap. Also suggest putting caps(1-10uf) under the opamp supply pins to increase their stability. I don't see any of those near the amps, only the two further decoupling caps.

You could take simple nippon chemi or simple nichicons or panasonic... muses in the supply part man... my wallet organ hurts on the sight... and actually they perform a bit worse in the ripple suppression task than the plain supply caps. Well but what's done is done.
 
I may have inadvertently introduced slightly more hiss (noise) to the system as Ferrum Master described because of the capacitors replacement. It's essentially at levels I had before with Treble and Bass boosted to 50% on the speakers desktop controller. But the difference in sound makes up for it. I couldn't get rid of the hissing anyway, so why not make it better when it's playing and you can't hear hiss anyway :)

Still waiting for the bipolar Muse caps for satellites filtering stage :(
 
Hm, received caps for the satellites an they are freaking tiny compared to original ones. Voltages and capacitance is identical, but these are super small. All bipolar like the original ones. In fact the original 4.7uF one is larger than the new 22uF one. Since I'm a total noob, can anyone enlighten me what's the deal here?
 
satellite_caps.jpg


So, I just decided to replace them despite size differences. This is a filtering stage for high and mid drivers and I'm not exactly sure yet what to think. It certainly changed the sound. I'm just evaluating if it was in a desired way.

Highs don't seem to be as harsh anymore while detail is still there. If I crank the Creative Crystalizer to the max the audio becomes more "vivid" like before, but not harsh anymore which is interesting. The way how bass is delivered from mid drivers also changed a bit. Could observe it also when doing A vs B test with one stock and one modified satellite.

Need further testing with music and games. So far so god though :)
 
Are there any limitations when selecting OP-AMPs? Or can you just stick in any for as long as it's an audio OP-AMP? I've picked the one it was mentioned in the mod log from that guy (even though he fried his Altecs, mine still work :D).

For example, if I'd want to go absolutely mad for some reason and stick in Burson V5 Dual in it? I mean, what I'm asking is what factors are involved with OPAMP chips that need to be taken into account. For example, with capacitors, it's capacitance, voltage and polarity (or lack of it). Any such thing with OPAMPs?
 
Where could I buy a genuine MUSES 8920 Op-Amp in a DIP8 format? The stuff on eBay makes me question if any of the stuff is even genuine. Especially with the pricing gap from $10-12 for stuff from Japan and Europe to $5 from China/Hong Kong. And with such stuff, it's impossible to even know unless you tear the thing apart and destroy it.

Tried checking the official channels where MUSES 8920 isn't even listed, especially not in DIP8 format. So, now I'm extra confused...
 
I could found them on eBay as well. But are they genuine?
 
I've decided to go with eBay, picking the one for $12 and from Japan since the company which makes them is Japanese. It's probably more likely to be original than the one for half the price from China... Or I'll overpay a fake for 2x as much lol

It's a gamble either way, hoping it'll be genuine...
 
How do you know the direction of this one since it doesn't have that dip on one end?

s-l1600.jpg
 
it has a dimple, which is the same thing.
 
Ordered MUSES 8920 Op-Amp, but there was a mixup and I got the wrong stuff, so now I'm waiting for re-sent item :D At least the seller is totally cool so I'll just have to wait a bit longer...
 
This brings back good memories, when I modding my Klipsch Promedia back in 2007. Everyone calling me n00b back then (not on this forum though) so I done my own research. Some tips for you:

1) Don't swap ALL the opamps, you might make it worse, only change that on the signal path. Simple way is to trace where the input is and go from there.
2) LM4562 and LME49720 are pretty cranky opamps. Check your speaker opamp supply voltage, these opamp tend to sound good up to 15V if I'm not mistaken (max is 17V, too low like majority of soundcard supply 5V they don't sound good either). Also check their temps, if they get hot they might oscillate, a quick dirty way to stabilize them are to bypass their supply to ground via small 0.1uF capacitor, either + or - will do. Still, from my experience, a better design circuit that was build around opamp were miles better than blindly swapping opamps.
3) You better use film capacitor on crossover circuit instead of bipolar electrolytic. They are large but they sounds better.
 
I have working woofer and speakers, but busted volume controller (sometimes eq doesn't work). Mine is that version with round speaker

Can sell the whole set for spare parts if you want , 45€ sounds ok?
im from lj.
 
Finally received high end MUSES 8920 op-amp for the amplifier. It does sound slightly better than Burr Brown I had originally installed.
 
I'm not familiar with those speakers have you played with adding dampening either CLD or poly fill to the satellites or the woofer? If the woofer is ported you can also play with port lengths. --- You'd want to be careful with shortening (raising tuning frequency) port lengths, making them longer (lowering tuning frequency) is generally safer. Safe being relative to woofer excursion at low frequencies.

Just more ideas for tuning to your liking.
 
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