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Old 09-10-2016, 09:40 PM   #1
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M50W repair thread

Today's patient: A Swans M50W that starts to distort and crack at high volumes.

Sounds perfectly normal at low volumes though. But when I increase the volume and switch to quieter and more classical-y music, it starts to produce the sound of clipping.

So, measured it and listened to it using sine tones. Sine tones are very effective when it comes to detecting distortions, as even a minor distortion can cause it to sound all square-wavey. But of course, measurements are still the most precise as they can detect things that can't be heard.

Here is what it looks like with a 1kHz sine wave (M50W's amplifier's output, with speaker connected):


Notice the lower voltage once every ten cycles. Or, 100Hz. This points to a DC-side power supply issue. Or in other words, the capacitor for the positive supply is a goner.

Here is how the failing amplifier sounds like, starting from low volume where it works to higher volume where it clips:

1kHz
http://www.mediafire.com/file/hy2un1...z_recorded.wav

250Hz
http://www.mediafire.com/file/dn6k8h...z_recorded.wav
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Old 09-10-2016, 10:47 PM   #2
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Inside the M50W

Well, there's your problem:



Two failing capacitors, 6800uF 25V that power the satellite speakers' amplifier. The one that is failing more is on the positive supply.



Another view. The arrow points to the legs of the power supply indicator LED, which is soldered directly onto the power supply PCB, and also glued to the back panel. I definitely can't desolder it, so to remove the power supply PCB I will have to snip it off. Maybe connect it back using solder later.

6800uF 25V capacitors... and I would prefer to also replace the 4700uF 50V capacitors just in case... this would cost quite a bit. And by quite a bit I mean $10 for 2 or $20 for 4. Which is quite a bit in electronics.

Maybe I'll go for Rubycon PK just so both types of capacitors are from the same series. But in reality lead spacing and outer diameter and height will restrict my choice after I measure them.
http://sg.element14.com/rubycon/25pk...rad/dp/2346512
http://sg.element14.com/rubycon/50pk...rad/dp/2346530

I would really prefer something with higher lifetime @ temperature rating tho. Time to see what RS Online has. And if really want to be safe, up the 25V to 35V.
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Old 12-10-2016, 12:04 AM   #3
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Capacitors that need to be replaced:



*Although the original caps are 16mm OD, the PCB has space for 18mm.

Yup, the 4700uF 50V is slimmer than normal. This limits the capacitor choice - had to get Nichicon VZ
6800uF 25V will receive Panasonic M
220uF 25V will be my favourite Panasonic FM



With the capacitors removed, the rest of the circuit becomes clear.

The remaining part of the power supply board are 7812 and 7912 regulators, providing power for the preamp board. The 7812 is bigger because it also has to power the digital volume control. The 220uF feeds the input of the regulators. People who are afraid of resonance from paralleling caps need not worry - the 220uF is in an RC arrangement. This also means the capacitors are less likely to have been damaged through extra stress when the 6800uF failed.

Preamp board. Those 4 tiny op-amps are TL072.


Main amp. Quite well-constructed. Metal bar to clamp the amp chips instead of using screws directly on the amp chips. An irregular-shaped cutout on the back panel so that the amp chips are directly in contact with the heatsink, and they even used thermal pads. I have seen studio monitors that do worse.


Overheating and eventual failure will not be a problem with this speaker.

And then they go and use KSC capacitors.
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Old 12-10-2016, 12:06 AM   #4
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Transformer. 14.5VAC @ 220V mains (China voltage) will give around 21.5VDC after rectifier @ 245V mains (Singapore actual voltage), so 25V capacitors are still safe. If they're not of horrible quality.
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Old 13-10-2016, 02:57 PM   #5
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O.o you do repairs for M50W?
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Old 14-10-2016, 12:56 AM   #6
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The capacitors being replaced and their replacement.



The poor quality of the printing on the Chinese capacitors is an indication of the poor quality of the inside. If you buy branded capacitors like Elna and Nichicon and etc from China and they have shyt printing like that they are most likely fake.



Recapped. Looks much nicer now.
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Old 14-10-2016, 05:50 AM   #7
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If everyone can repair their kit, we won't need to throw so much away. Thumbs up.
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Old 14-10-2016, 10:55 PM   #8
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Listening review part 1: Against Usher S-520

I decided to compare it against more than one speaker, because I know my Usher's sound signature makes all other speakers sound thinny/screechy/brighty. So if the M50W sounds light compared to the S-520 that I am used to, and I call M50W light because of that, I may draw the wrong conclusion.

And to make sure it isn't the onboard sound that's giving me slight symptoms of headache and ear bleed, I feed the M50W with LJM CS4398 DAC this time.

Using multiple audio devices so I can switch between things quickly.



Part 1 conclusion: Worth no less, and worth no more

The M50W satellites, surprisingly, were not as dark a tone as I expected, from a 3-inch driver in a cabinet that is relatively large for a 3-inch. When I tested them as 2.0 bookshelves, they started rolling off higher than expected. Still pretty useable for desktop 2.0, but there are smaller 2.0 speakers that have more bass. Bose Companion 2 definitely has more base, but that product is an anomaly. Audioengine A2 should have more bass. And if I remember correctly even products like Creative T20/T40 are comparable.

Time to add the subwoofer.

First impression - That sub is powerful. And goes quite low. And this is not entirely a compliment.

The satellites don't go low enough, so I need to get the sub to do some of their job. But no matter how I adjust, I can only get either "flat sound down to a certain point and then my ears get slaughtered by bass drum" or "sensible amount of bass drum but there is some middle frequency missing". Eventually I settled for just a little above 9-o'clock for the sub setting. At this setting, I can still hear most of the bass notes, and boy they do hit low and controlled, but the response isn't entirely flat.

To be fair, this is a problem seen by most 2.1 speaker products.

But to be fair, this speaker costs $340 and has 3-inch satellites so I expected better results from them. This is first time I describe a speaker as "sounds smaller than it actually is" in a review. Not in real life though - I have seen too many useless 6.5-inch bookshelves out there. Yes, useless 6.5-inch bookshelves, I said it.

And, because the satellites don't go low enough, the subwoofer is still noticeably directional, so don't put it too far from the middle.

The tiny lack of middle-low frequencies would have been better received if the satellites have a laid-back treble. But nope, the treble is rather aggressive. Probably because it uses a 20mm tweeter - which is on the small side - and made of aluminium - which is on the bright side. The sound is very clean and clear, but often I can't tell whether that is distortion or not.

And because of a lack of middle-low frequencies, sounds that are supposed to be epic (e.g. orchestra) are not epic, and there's a lack of space, and vocals are not that great either.

Certain songs end up being all bass drums and cymbals.

Well, that's all the bad parts about it.

And the good part? Despite all the negatives listed about it, it for the most part produces an acceptable sound. The constipated treble is quite noticeable tho, to the extent that I wonder if other products like Klipsch Promedia 2.1 and Aego M can fight it in this department. But as mentioned at the start, this may be due to me getting used to Usher's sound signature.

Yea, it falls into the category of "does not have any major glaring error to people who entered this price range for the first time and hence feels like a total upgrade and nobody is complaining". Like Audioengine, and Bose for those who don't know better. Basically, if you ask people, what is an alternative product at those price ranges, and people will fail to answer. By being the only product at a particular price range, you essentially become the best product at that price range.

For SGD$340, there are actually alternatives tho. Klipsch Promedia is $349. (Currently $314 @ Tat Chuan) Aego M is also $349. Maybe Aego M would win in terms of SQ vs speaker size. Satellite sound quality and musicality... I can't really tell who would win, I've never had a fully-working Aego M in my room, and that was a long time ago.

The real competition comes in the form of 2.0 speakers. PreSonus Eris E4.5 and Fluid Audio F4 are just around $270, and they should clean the floor in treble quality. But when you buy M50W, you're choosing to have a subwoofer at the cost of treble. Only half or less of what you're paying for goes into the satellites, so around $170 if inclusive of amp or around $128 without, assuming amp costs ~25% of the whole speaker which is the case for studio monitors.

$170, which is somewhat questionable. It's close to the price of D1010-IV for example. I'm assuming the M50W satellites cost less, but still for maybe $30-50 more you can get stuff with importantly better sound that doesn't bottleneck the subwoofer.

Wharfedale WH-S8E is $199 and it has crossover adjustment for your personal tweaking. Leaving us with $140 for the satellites... which, to be honest, you won't find much active satellites at that price, but spending a bit more to get the D1010-IV mentioned above becomes a tempting proposition. Or spend more, or less, on 2.0 speakers and amps now and upgrade later, the choice is yours.

But of course, if you have only $340, and want an easier time controlling the volume, then the M50W becomes a legit choice.

As you can see, with direct and indirect alternatives available and without scoring a clear win against either, the M50W is worth its price, but nothing more.

Stay tuned for comparison with other speaker next. Will the comparative performance against a more-typical-sound speaker coupled with bad audio memory of speakers auditioned in the past give the M50W a turnaround?

Addendum:
I run S-520 with the bass boost below:


Measured output from speaker-out of PM6005, with load (S-520) connected.
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Old 15-10-2016, 01:23 AM   #9
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Old 15-10-2016, 10:37 AM   #10
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Listening review part 2: Against Paradigm Atom v.1 with modded crossover

Addendum to part 1: That bass setting still too strong for normal usage, I was watching video and the male voice was booming at certain frequencies. Now I've adjusted it to 9-o'clock and just a teeny-weeny-bit more; that knob is sensitive.

I don't think this is what people mean when they say totem speaker



This arrangement boosted M50W's sound slightly. Could be different reflection paths, could be due to being more off-axis. Now the mid frequencies have more warmth and is a pretty balanced speaker, although peaky / horny at some treble frequencies. Standing up reverts the sound back to Review Part 1, so I'm sure this sound change is due to room acoustics. This also reinforces the notion that these satellites lack middle-bass frequencies.

Note that most people would probably put the satellites on a table, which will boost low-frequency output, and further help the lack of mid-bass.

Also note that I may want more mid-bass than normal. Because I like bass guitar and piano to be audible, voices to sound like voices, and rock music to have impact. Or maybe that is how things are supposed to be? I have no idea of the current meta.

Time to move on with the second comparison.

Part 2 conclusion: It is exactly what you think it is

Now, comparing it to the Atom v.1's treble which I already had to mod the crossover to tone it down, M50W tweeter starts to sound normal. (Note that this opinion was formed when I was standing up, so both speakers are near ear-level, so no midrange boosting effect and the M50W sounds like in Part 1.) The overall treble sound is warmer than the Atom v.1, more forward, overall less harsh, but the Atom v.1 has more air. Yea, the Atom v.1 sounds thinner but has more air, quite laid-back and bright sound, but seems to have a wider treble frequency response. That's all I can manage to describe with English words.

In this arrangement, due to the warmer sound, I could reduce the subwoofer volume. I settled for something that sacrifices bass volume for a subjectively flat frequency response in the bass region. With this setting, the bass guitar and stuff are still not as strong as the other two bookshelves, the bass drums are comparable in volume to S-520, not as punchy, but hits lower.

Mind you, my S-520 is bass-boosted, and hits very low and very flatly for a 5-inch bookshelf. Meanwhile the Atom v.1 bass drums are just "piak piak piak", although still reproducing a good amount of bass notes.

So, overall verdict of the M50W -

-Well, the satellites aren't as bright as I initially thought, and can be further made warmer with room acoustics. But forward-sounding and still not as "big" / spacious-sounding as I hoped for, but at least they don't sound thin. Satellite bass extension is still limited though, but this can be somewhat covered up by a warmer treble.
-Also I just tried different positioning, including on the table and very close to me. It reduces the treble but without generating more bass, so just made the sound more muffled. So I conclude there really is not much bass to work with.

-Yea, so the sound signature is like a having a satellite with warm treble, but roll off in the mid bass, and then the subwoofer roll on again. Which is what is expected from this speaker I guess.

-The sub can be adjusted until the system gets relatively balanced bass, a bit on the soft side compared to other 2.1 systems, but already commendable that this can be achieved at this price point. (Balanced as in what you would get from a pair of 7-inch studio monitors.)

-Overall, this speaker is what you would expect. Mainly better sound than other 2.1 due to the bigger satellite, and performs at that price range. Probably sounds better than the other $350 2.1 alternatives, probably lose to other 2.0 in treble-to-midbass but win in bass due to having a sub. At this point, it is up to personal preference which route you want to take.

-It is almost "there", just held back by the satellite bass extension. And by "there", I mean that in the speaker market there comes a point where despite throwing lots of money like $1k plus, you still get different speakers that sound different, which may go against the idea of accurate reproduction. But none of these companies are wrong - they will sound similar, when put in different room acoustics. This is why there are so many brands and sizes of studio monitors. Basically, past the $400-$500 mark, differences between speakers are small enough that room acoustics play a significant role, and you can play around with room acoustics to get the sound you want. Same goes for M50W, but you are more restricted in the positions you can use and the size of sweet spot.

-The other $350 speakers get removed from the list of possible alternatives, but the Wharfedale sub and 2.0 speaker combination stays. Swan could possibly make their own 2.1 system with bigger satellites, but that would be called M200 with sub and cost $700. Actually not a bad idea when you think about it... (M200MKIII costs 1785 RMB in China, M200MKII costs 1096 RMB - around the same as M50W)
-If you consider their price in China, their value is hard to beat. Or so you thought. But there surely exists another local brand that has somehow excellent price-performance locally. For example Usher S-520 costs NT$4800 in Taiwan.
For Singapore, we have... Sound Blaster. Also, that is the sound of me trying to suppress my laughter in the background.
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Old 15-10-2016, 03:35 PM   #11
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RMAA



Distortion % better than the typical entry-level amps (T-amps and others). I can't tell whether the noise is real or fake (setup-related) or high or normal at my settings. But the spectrum is white-noise, so no more power-supply related issues.



Frequency response of the signal out from the amplifier, with the satellites connected


Pretty clean distortion, dominated by the second harmonic


Crosstalk is close enough to datasheet spec. Distortion is also close enough. THD+Noise... dunno. For all we know could be due to the TL072.
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Old 17-11-2017, 05:20 PM   #12
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@wwenze

I am unable to PM due to the forum's requirements of 10 posts before sending PMs so I apologize if I bumped an old thread.

I am facing a no power problem with my M50W subwoofer. The satellites still work when I switch on (red to blue light) using the volume control knob. There is no red light at the back of the subwoofer.

I contacted Tech-Dynamic and they said it costs approx S$80 (or more) to change the entire subwoofer circuit as my 2 year warranty ended around June 2017. Their repair guide on VRZone is also missing pictures and I am not confident of doing it myself.

I was wondering if you could provide repair services for my Swan M50W?

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Old 18-11-2017, 12:00 AM   #13
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I am facing a no power problem with my M50W subwoofer. The satellites still work when I switch on (red to blue light) using the volume control knob.
Replace the fuse in the bottom of this picture circled in yellow. Also check and may need to replace the two big caps circled in yellow-white.


There is no red light at the back of the subwoofer.
The LED is powered by the same rail as the remote control... I'm going to assume the LED spoilt by itself.

I contacted Tech-Dynamic and they said it costs approx S$80 (or more) to change the entire subwoofer circuit as my 2 year warranty ended around June 2017. Their repair guide on VRZone is also missing pictures and I am not confident of doing it myself.

I was wondering if you could provide repair services for my Swan M50W?
Just repair with them? I won't be working for free either.
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Old 22-03-2018, 11:05 PM   #14
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Hi, did u encounter any issues regarding the volume auto decreasing by itself and after a few days increasing back again?
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Old 22-03-2018, 11:21 PM   #15
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That would be either volume knob issue or something loose somewhere, didn't encounter that.
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