Mini Audio Amp Teardown and Mod!
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- Опубліковано 6 сер 2018
- I picked up a mini audio amp for a project that cost only $45 -- let's take a look inside, and the modification I had to perform to get it to function properly.
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Music: "Summereyes" and "Noreste" by Birocratic (birocratic.lnk.to/allYL).
Additional music by Lakey Inspired ( / lakeyinspired , Anitek freemusicarchive.org/music/Anitek) and Epidemic Sound (www.epidemicsound.com).
Intro music by BoxCat Games (www.box-cat.com). - Наука та технологія
The Nobsound / Douk products are always fun to reverse engineer, they are very nice people however and are happy to send you schematics, the fun part of that is they are hand drawn, with hand written notes on them.
First thing I noticed - Main DC rail cap silkscreen 2200uF, guy desolders a 1000uF cap. Cost cutting at its finest ;)
It seems like it's a common practice in China that maybe a handful of big oem will make such amps (n other electronics) and they are being bought and badged by different resellers brands.
Therefore, the components will vary according to the price the resellers are paying. You will see brands like nobsound, douk, fx... Etc selling similar things but slightly different in prices.
They may also be using the same box and pcb but fitted differently to accept 24Vdc (vs 12Vdc) giving better specs
The switch only switches a "mute" signal on the chip. It is just for removing hiss and hum on the speakers when the amp is "off".
Might also be the SD(shutdown) signal
so u don't get a pop noise thu it and speakers
Just wanted to give a bit of my opinion as a professional electrical engineer who routinely designs and tests pcbs. The gist I got from looking at the board is of a company having used an application note's suggest circuit to design an amp, and later asking another amateur electronics hobbyist to bodge on additional features.
The redundant meandering traces, random copper keepouts, odd component layout, and tacked on antenna coax on the end of a trace antenna looks like a board a beginner would throw together because they haven't learned fundamentals yet. Not saying it is utterly worthless and wont work, but the inconsistencies in the design all point to rushing a product out for minimum cost without any thought or understanding as to why things are generally designed the way they are.
Oh and to put your mind at rest Colin, your mod will work just fine and will not cause any damage or magic smoke to be released. Of course it is preferable to generally switch the positive rail, but doing the opposite is technically fine as well.
If you switch the negative instead and leave the positive always connected then depending on input and output devices connected then there could be leakage current even when off ie the device could draw current through external devices it is connected to since there is a possibility of an unintended current path to ground.
An analogy is a hose (circuit) and water (current). If you have a cutoff valve at the end of a hose (the "ground" side) and there are tiny holes all along the hose then even when the valve is off there will be water leaking all over the place, but if you attach the valve at the top of the hose right after the spigot (positive supply rail), then when it is off even if the hose has holes in it no water can flow.
soldering the lead of external antenna connector to a random point of trace antenna matches (in rf sense) probably just horribly leaving bluetooth performance poor even with good external antenna
Yeah, this board is a hot mess. I'm not sure if it's so much that a beginner designed it, but rather that it's probably been iterated upon a ton of times. I definitely would have preferred to switch on the positive side, but without major surgery to the PCB it wasn't feasible. It only looks like a double-sided board, so it might be interesting to buy another one, depopulate it, and reverse-engineer it into a better design. (I just wish I had the time for a project like that.)
This Does Not Compute Isn't that always the truth, with more time we could do so much. Anyway I don't think it's really worth any more of your time for something you will use as background music while working with low expectations as to its quality. At least you got an interesting video from it and a few good laughs.
In DC applications, especially automotive or marine, positive is treated like the hot lead in your house wiring vs. neutral. As a lot of things are at the ground/neutral/negative potential, the whole chassis of the car for example, you want to switch off the positive which is less exposed. If you shut off negative and this were mounted in a car (and if the case was grounded), you would defeat the function of the switch as there would be another path for current to flow.
For home use, it makes no difference. I'm guessing that the negative from the power brick is not tied to ground since it didn't appear to have a grounded or polarized plug.
I suspect there is more power wasted in the power brick than in the amplifier at idle.
Very likely, especially since the 'off' position probably shuts the amplifier part of the chip down. See the data sheet, pin 2, SDZ, Shutdown logic input for audio amp.
Damn straight...
Only one issue is that now that the tiny switch contacts are now handling to the full current of the amp, that will cause power losses in the switch. This switches are not designed for actual current carrying uses normally. That amp really is a fairly powerful IC, you are correct, it is a TPA3116 IC. That little switch was as you mentioned was actually turning on/off the enable and mute function of the ic, in other words it uses a "signal with no current really at all" to enable the high current output of the ic.
I used to love building my own Cmoy pocket amps. I have a Nobsound MSD10 Mkii integrated tube amp and it's surprisingly great. After rolling the stock Chinese tubes for Russian tubes, it sounds incredible
A benefit of having Bluetooth on constantly would be easier pairing, instead of a delay (or possible connection issues) after power on before any chance of playback.
no pops as well.
Well with that bodge on the internal antena there will be really lot of problems with signal strength.
You know you are a nerd if you have an opinion about center negative barrel connectors
adventureoflinkmk2 This was not supposed to be negative at all
Ich bin ein Nerd!
@@ozzelot3349 Ich auch!
Like you want to stab the designer? (unless there's a legit reason to do it)
@adventureoflinkmk2 Most connectors are centre positive. Centre negative is done by jerks, or for very specific reasons (positive ground environments would be one)
You may want to check the spec sheet for that amp. I got one of these, same chip, slightly different layout. Anyway, there is a table of resistor values to change the gain of the chip. They had it at the maximum gain so the amp was noisy and a bit distorted. I changed it to a lower gain and the sound was much improved. Also, the inductors tend to run hot. Not dangerous hot but very warm. I went with a 20v power supply.
Unless you get another Amp, you could always try installing a switch on the AC or DC side of the power adapter cables, or just make sure you have your audio setup in a place you can eaisly unplug the amp.
Though in the end the only downside I can see to having the amp on all the time is that if it does get warm while in operation that might shorten its life being on all the time.
You did a great job! Just if you do a sound test try variable power supply 0-30v just to see the difference on the fly between 12v and 24v.
Maybe the switch is under-rated for the rather high current demand of that hi power IC...?
30 minutes for ending like this?
holy cow.
Yeah, he could've cut more content out. I kept hitting the Right Arrow button to skip ahead to see what he got to do.
for long videos, go to settings (lower right Gear symbol) and set PLAY speed to "1.5" = all the info @ less time.
@@rz1246 LOL... I do the 50% speed for those east-indian speed yakers.
It's also a good idea to add some non conductive or small enough washers in between the heatsink on the screws and the board just enough to make a good connection so when you tighten down on the two screws, the board doesn't bend on the edges of the chip and crack it when it gets hot.
Used components - gotta love it :)
Neat little hack job, Collin. Nothing wrong with choosing the simplest possible solution to the problem. As for the switch, I think sometimes manufacturers just use whatever components they have handy or get a good deal on irrespective of whether or not that switch is the intended type of switch for the product.
It didn't line up right because you're supposed to apply the thermal paste to the chip, not the heatsink. Interesting video, thanks!
Hahaha
Very interesting,can't wait for next video, thanks
Maybe you're going to have to pair the amp every time now since the chip loses power?
Most likely ...great name BTW
I have a more "mature" miniamp based on the D-amp chip from TI who drives the most of todays similar audiogadgets. Its an SMSL AD 18 and It´s pairing 24/7 via bluetooth. By the way, I don`t shut down, it doesn´t get warm at all if I dont crank up the volume during listening. So I figure there´s no need to think about how much power it draws. A good design take care of problems instead of creating them. A TAS5508C from Texas Instrument is used, both for DSP processing and pre-amp.TAS5342A is used as a power amplifier. I´ve tried a lot of D-class Mini Amps and this has all the bells and whistles needed, still affordable and very reliable.
I recommend TDNC to do a complete teardown and test the functionality of this amp instead. The cheaper stuff from the chinese market is just disappointing from what I´ve seen.
Not an issue. You pair 'em again every time you leave & revisit Bluetooth range anyway. The TPA3116 IC doesn't remember your device. It's vice versa. That's why you can rename the amp in your phone - Android can anyway.
It called instant on blue tooth connection. So you don t have to manually connect each time. Also there is a bad pop noise when powered on for many mini amp chip because the power supply creates a large surge. . The soft power on eliminates that. .
Maybe for soft turn on, or thump reduction.. due to the type of switch used to turn things on/off?
Very interesting that this episode turned into a mystery case. I would be curious to know how well it works for sound on speakers too.
Chances are, by messing with the original power switching arrangement, you'll make your speakers emit an unpleasant (and possibly damaging in the long run) popping noises during the power on and/or off. The integrated amplifier chip's datasheet even states the anti-pop feature specifically in its title (noticed the big yellow relay?). Most probably, for it to work properly, you need the chip itself to already/still be under stable power supply, not during the power off/on transient state. Also, the puny switch integrated into the potentiometer really isn't designed to handle the current in the range of 5A, contrary to what your gut seems to be telling you. The input filtering cap presents a dead short causing a high current spike briefly during power-up. Having said that, both the amp chip in its sleep state and the Bluetooth module take next to no power in the grand scheme of things so the whole mod is rather pointless. The very first thing you should have done instead was to measure the actual power consumption in the standby state only to find out it's negligible and hardly worth the effort.
What he said. ^^
KernArc yes, I also wondered why he didn't test standby power.
The input filtering cap will also cause this amp to bang spectacularly if you accidentally plug it into an AC power supply.
Have to agree here. Chances are, that pot was controlling the 7805 regulator (5v) -- not the full dc rail. That 'not hooked up' part of the pot switch you checked likely ran to the regulator, or near it. I did not see you check that (maybe didn't film that part?)
Also, that cap you cut the traces on was likely working as a reservoir cap rather than a filtering cap, hence the second ground tracks (moving it further in to the power path than the beginning, which is where a filtering cap would be -- Also, the film caps are likely doing any filtering that is needed, not the big electrolytic.) Unfortunately, from the looks of the picture, it looks like you pulled the vias out when you unsoldered that cap, as they seem to be still attached to the legs of the cap. Be careful there -- You'll probably get away with it here, but some multi layered boards won't be too happy to have their vias removed mid-circuit!
My 'thought' on the all-time power? They did, or had planned for at one time, designed it so that the blue tooth would 'soft power on' the amp (regulator) when sound was received and soft power down the amp via the regulator when no sound was being received. The sleep state of that module and the amp chip itself use very, very little power in sleep mode.
(And yes, before you all mention it, I know the 5v regulator is not the power for the amp chip, as it can have up to 24v. However, that amp chip, and many like it, take a 3.3-5v signal voltage to turn it on and off for soft power. Without that 5v reference, the chip stays in a power down state, so even with 24v applied, it consumes zero power. Therefor, the idea of the regulator being controlled by the blue tooth when it receives a signal for soft on/off makes much more sense, and as does the constant need for power. Especially considering that MOST bluetooth modules (especially all the ones I have here in my bin) have their own internal voltage regulators, so it wouldn't depend on that 7805 for its own primary power!)
Well, a reservoir cap does function as a 'filtering cap' from a DC power source. It is the voltage droop that is the source of a lot of noise from a DC supply, and a reservoir cap corrects that, as long as it has plenty of capacity. It literally smooths out any momentary droops.
what does it sound like?
Good video, lots of AvE references. Luv it.
TPA, TDA, 3116, 3118, etc. they're all Mosfet amp chips. They're all over the Parts Express board section.
The chip was not "etched away to get better heat transfer". The TPA3116 is made that way from factory. The part number is besides the metal part, you could even see the TPA text in the video. 13:52 look in the left top corner..
Did you check if the switch was not wired to a standby input on the amp chip through a pull-up resistor?
Real neat concept for a video series. Simple but engaging. Love your vids, Collin! (Collin? Colin? Kahlenn?)
And, taking it apart was worth it to find the loose heat sink on the chip. As well as what you stated about the grease. Interesting. You gave me an education on the ground plane being on both sides. Thanks
Would have been faster and better QC if they just shipped you the parts and let you assemble it LOL!
Looks like to me that a student built this thing in an electricity and magnetism lab at some university.
A potentiometer is adjustable by the knob and can change the resistance on a variable resistor. The resistor is actually a coil of wire that you can change to which part of the coil you connect the electricity to vary the resistance.
love it when you get pissed xD
Looking at the way this guy's hands shake, I think he's almost always pissed (drunk).
Did you try powering on the amp while connected to speakers before modifying it? Pin 12 of the TPA3116D2 is mute. It is possible that the purpose of the switch was to mute the amplifier chip so that power on thump was avoided. I had a TPA3118D2 amplifier board which had an annoying power on thump and I added a circuit to mute the amp for a few seconds after power up which avoided this. Personally I wouldn't have had a problem leaving this Nobsound amp powered constantly allowing me to connect via bluetooth quickly. Standby power usage would be minimal.
Yeah, this is good how-to video for people who go bumbling in before actually understanding the circuit. It seems unlikely that switch on the volume control will handle the current that amp needs. He will quite probably burn out the switch which is NOT rated for that application.
I'm more worried about under-powering the capacitor. It could start pulsing and fry something, especially the Bluetooth module.
There looks to be a relay on the board (yellow thing near the volume control) which would probably serve as a de-thump relay - my big amp makes a satisfying click after a few seconds when the relays click on. It was difficult to tell though as he had music playing in the background, and it was difficult to hear the switch click, let alone that baby relay.
Here's the spec sheet for the relay in question: bit.ly/2nPRBBx
Looks to be controlling either power or signal to/from the Bluetooth receiver module. Not sure if that relay is still functional with the modification.
More likely it is pin 2, SDZ, Shutdown logic input for audio amp, so that the BT module can stay powered, but the chip shuts down the amp and goes quiescent.
I got another "OR": maybe it's simply thought to be a mute switch, not power :D
Also, there is actually an issue with your fix.
When the switch is open, you have a theoretical current path through the chip. Depending on the architecture this could damage the chip badly.
Imagine some sort of output gate on the pin wich is off (connected to GND) by default. Now you provided a clear current path from plus through the BT module, the LED and stuff, into a GND pin of that chip and out of the IO-Pin to the outer sleeve of the jack.
And I might have spotted a pull-up resistor on that pin. If so, you have it permanently connected across your power supply.
Obviously the thing didn't blow up. But the chip could still fail prematurely (and if so then when its off). Or you got a winner here and nothing happens ever at all ;) I'd check the resistor think, though
My TDA3116 amp goes into standby when the power turns off. I assumed it was because of it's anti-pop anti-distortion circuitry, but it would be nice if there was a standby and a switch to totally cut the power. However, pretty sure the power drain when in standby is lower than 100ma.
The chip under heath the red heat sink I saw what looked like a solder bridge,on one side ,it looks hand solder ,doesn't set straight?
The amplifier in the picture is upside down because it is a ceiling amplifier.
Because of its Bluetooth input and its bridged D amplifier configuration it doesn't matter, but usually one should never put a power switch into the ground rail. The input and output grounds are still connected to the circuit and the entire circuit is floating as long as it is switched of. This may lead to unexpected functions in the moment when the power is switched on.
I have a similar amp same brand and model number and it does in fact do 100w (see Wilson audio labs's video) but for it to do it's full rated power it does need a capable power supply thoi bought a 24v 5a one for mine and it works well and my power switch works just fine
Probably 30watts x2 = 60watts total 12v x 5amp = 60watts. If any of that Artic Silver which is electrically conductive touches the legs on that chip, it's a short. For this I use this heat conductive white silicone. When you screw the heatsink down tight to the chip, the least amount of any silicone or paste or grease will spread out.
Looking at the datasheet, pin2 is a start-up/shutdown signal and the switch was there to just shut down the amp IC for minimal current draw. The BT module probably should have been wired up to the switch as well to further save on standby power, but as other suggest it does make pairing easier if always on, and may already be a low power component.
I would guess the "unused" is actually hooked to the "mute" input of the chip. This would normally be used for "de-thump" which keeps the amp from blowing the speakers until the system is power stable. Using the switch for power and not putting a delay on the mute input of the chip can eventually do serious damage to the speakers.
At 22 mins in, I'm thinking the switch on the volume turns off the relay to stop thumps. It's got enough pins for a dual pole. The amp and the blutooth look like they stay powered up, minimal loss there at class d compared to the brick losses. Is this the type of amp you'd buy to put into a small bookshelf speaker to convert from passive to powered?
Hi, Did you test the amp switch before open up the little case? some of TPA3116 design using a switch on pin 12 to actually mute the amp. The manufacturer didn't use the power switch on the volume pot for main power because the switch can't withstand the peak current draw.
The picture shows the feet on top to give you an option to hang the unit the little black tips are glue pads...
Great video, thanks for sharing. I think have the reason why the Bluetooth are always on. I purchase a mini amp for listen music on the kitchen and the speakers and amplifier are in top of the cabinets. Have no access to turn on or off. I will like to keep permanently on.
Thanks
Alternatively, you could have added a small toggle switch on the front panel and intercept the +ve terminal of the d.c. jack,but if no problems are experienced,your method is the simplest.
My AV components are all plugged into a remote switched Power strip anyways, so this power switch issue is no issue to me.
Onkyo TX-SR303 on Craigslist just now - $30, fully working. It's larger than that, but internal power supply, it's an Onkyo, has a remote, and putting a shelf up on the wall with a pair of bookshelf speakers on top of it isn't difficult. That's the route I probably would have gone. Wouldn't have made as interesting a video though. haha
Am I the only one that noticed they used a 25 volt cap and Max voltage is 24. I thought you were supposed to allow more headroom on capaco voltages.
You're lucky that your modification worked.
The switch is actualy more likely to be connected to the mute pin on the chip: remember, the PCB is double sided...
What you just did was connecting the mute pin to the ground whenever this thing is now powered on. In fact, I could bet all I have on it since you cn actually see the trace coming from the switch and going under the chip (to pin 12 exactly) on the top PCB side.
Looking at the datasheet, the output is enabled whenthe mute pin is logic low. So it made sense to connect the other side of the switch to the ground.
Anyway, not the cleanest way to do it in my opinion, but it's working with no strange side effect, congratulations!
Yeah, I would have preferred to switch on the positive side, but there's no space to mount an additional switch in the casing and it would have taken dramatic rework of the board to isolate the existing switch contacts. I've tested the amp since the video was shot and it works just fine (well, as fine as an inexpensive amp should). Time will tell if there are any long-term ill effects, but even with that switch originally just controlling the mute function, the modification I made really just "piggybacks" on it.
you should have cut the connection after the cap you partially bypassed the 60 hz filter so now you will have line in destortion (aka humm) in your speaker output
No, he won't have distortion, because the chip is now dead, and there'll be nothing to distort!
Next time try one of those hybrid mini amps that come with a vacuum tube on top.
I am no electronics expert, but wouldn't the potentiometer need to be in the 'on' position to register continuity?
Even the heat sink on this inside is red. Interesting touch.
got it working at 24 volt in my car with a step up module best sound at 24v
Maybe I'm wrong here, but now that both sides of the trace are cut, won't this defeat the capacitor completely?
Beitie Beitie The capacitor will be connected across the power rail when the switch is on.
No, but it does make for a rather long return path to the main filter capacitor, making local bypass capacities all the more important...not that it was ideal to begin with since there is a rather long and narrow path between that input capacitor and the main ground plane even as it was to begin with...so probably comes out to be six of one, half dozen of another on this project (which is to say, it won’t make much difference in this case as neither of the two are ideal to begin with).
Noice. I kinda started on something along those lines. I usually listen to podcasts around the house while i do chores. Normally i just leave my phone somewhere close and that's it but i found a speaker with line in at goodwill for a buck (there's tons of them) so i am making it into a raspberry pi powered internet radio. XD so far its been fun. I got everything working how i want it but the pi is outside and powered by its own psu. And its a pi3 so its overkill. Gonna change it to a pi 0w and im gonna power it off the same psu as the speaker and then mount everything inside
Someone can correct me but if you have a spare heatsink around I'd throw one on that 7805 voltage regulator. Those things get really hot especially if you start supplying them with 20 or more Volts.
Hi there,
Could you tell me what the small screw driver set you use please, great video 👍
Your switch will not last long if you do not add some active input current limiting. Your power supply has a large charged capacitor at the output and you connect a large empty one every time you switch your amp on. I personally would switch on and off the mains so that the power supply gets disconnected too.
It will probably be connected to the mute on the chip, your bodge wire is fine
I also bought a nobsound amp on eBay. Different model with sub out. Same exact behavior. Power light always on. Seems the company has done this by design.
The trace op the top that goes underneath the 100k resistor is what connects the other side of the switch to the enable pin op the amp chip to put it in sleep mode.
With the mod you have now the power supply is is connected to the logic level enable pin, and when it is switched off only the internal protection diode of the amp chip is holding back your entire 12V 5A power supply.
I would have designed the switch part the same because those switches usually cant switch more than 0.5A, switching more current will burn the switch contacts rather quickly.
Username checks out.
Some of these micro amps are not bad, all things considered. Nowadays if you're not looking for "audiophile" quality (or in a few cases, even if you...are), all you really need for quality music playback is a pair of good speakers, one of these micro amps, and a smartphone. Or a Bluetooth receiver, if bluetooth isn't already built in like it is here. As recently as a couple years ago, the hot ticket in micro amps was the Texas Instruments TPA3116 single-chip Class D amplifier, which could supply 50WPC into 4 ohms on a 24V supply and sounded quite nice doing it. It could also support operation down to 12V, so I recently ran mine on a portable battery pack and it worked for longer than it needed to, and it was good for a few watts (but not full power). It's remarkable what you can now buy in a cost-effective power amp IC that is smaller than a postage stamp.
for the supply with 12 volts the not so perfect heatsink is ok :-)
but of course with this supply it is not possible to crank out 2+50 watts on 4 ohm.
an important question: how did it sound?
You are absolutely right.
That's most probably the reason they add a 12V power supply.
At 12V and with 4 ohm speakers the thing won't be able to do more than 2x 10 Watts and most probably the heat protection of the amplifier chip kicks in even before that. With those tiny Chinese class-D amplifiers it's best to use 8 ohm speakers and a notebook powersupply of 19V. It still won't give you more than 2x 10-15 Watts.
It makes me smile when i saw its manual i guess..😄😄😄
perhaps ill make just one like that it looks nice.
So is it just me or is the input power for the whole board now controlled by the volume knob? Ie everything is on a dimmer switch? Or am I just missing how that is being handled?
The dial actually performs two separate functions. The first is that it's a stereo potentiometer for the audio, and the second is that it's an on-off switch. The two are electrically separate, though. There's a little "bump" in the rotation of the dial where it clicks to turn the switch on. Any further rotation simply changes the audio volume.
Maybe those arent feets. Thise are plastic antennas
It's upside down to show that the measurements don't include the feet. Have to think like a Pure geek to figure it out. :-)
It's so it makes less noise when you throw it in the bin..
Didn't you basically just take the capacitor out of circut by cutting the trace where you did
I can't decide if the weirdness/cheapness of the amp is worse than I expected or par for the course. That power switch is definitely a new strange level of cost cutting. Even $45 seems kinda expensive for this thing.
Soft power on, so most off just standby power basically the LED draws two thirds of the power draw until switch moved to on.
Maybe the rotair click is the on/off for bluetooth
29:39 - Maybe it's meant to be operated upside-down? :)
Did you ever do the follow up on this video?
I didn't understand any of this, but I enjoyed the video. :)
Just wondering...if you were planning on showing us an amp, why not have speakers and such to test things?
You did a mistake on cutting the trace because TPA3116 have a pin when is connected to ground will mute the amp! so before cutting you should check the tiny trace that goes to the switch on the other side of the board!
Haven’t you now permanently powered the amp chip? The switch disconnected the ground, but now it is permanently grounded.
This
Have you ever tried to push the volume knob? You may not have read the manual carefully.
Nice video - made for a lot of interesting comments.
I think using Arctic Silver, which i believe is electrically conductive, is not a good idea, as some of that stuff could easily squeeze out under pressure and touch some of the pins. I would use ordinary non conductive silicone grease instead if i were you.
Arctic silver is NOT conductive, as it was, for many many years, the go to paste for PC builders and I still use it to this day for regulator / mosfet heatsinks.
I have the same one. I can drive a professional audio daul 18inch sub and a single 15inch woofer top box
The chip Mark is normally scratched off at the chip maker factory when the chip fails to meet the specified parameters. Or at the chip recycling company who can not leagaly resale with the manufacturer mark in place. Likely the case here.
Colin. The switch on the back of the pot will probably not be rated for the current requirement at full load. I bet the other side of the pot switch goes to an mute pin on the amp chip with a pull up resistor. Pin high = mute. Pin low with switch on = unmute.
Nobsound generally makes affordable products with a little touch up.
I love your channel.. this is what and exactly what I want..
Thats conductive (silver), you should use it VERY sparingly so it doesn't bleed off and short those connections.
Fun stuff!
I think the error come from the CAD layout designer he didn't see that he can open that trace and have on/off functionality "enable to work"
Cause you wanna switch strip and then your power brick don’t run all the time
i think that amp IC has an ENABLE pin on it and it was keeping the bluetooth module powered all the time and switching the leg on the amp IC to power it up. *just my opinion from what i could see pausing and looking at both sides of the board. the topside of the board has a trace running from the power/vol pot to the IC. the datasheet for that IC says PIN2 (SDZ) = Shutdown logic input for audio amp (LOW = outputs Hi-Z, HIGH = outputs enabled). Hi-Z means high impedance or no output.
It's always a good thing to hack your stufs so congratulation on that.
That being said the reson they dont use that switch on the buton to turn the power on and of is that i seriously doupt that this kind of small swiches can handle switching 24V 5A with complex reactive load. That might work but that will probably blow at some point. But hey it's cheep chinese electronic, that shitty cap would probably go bad befor the switch anywhay so ...
Just my 2cts...
Considering he de-soldered the ground lead on the filtering cap, the power supply will likely dump the maximum instantaneous power output through the switch terminal upon closing, creating a dead short and a spark in the range of 20-100 amps. Definitely going to wear down the contacts!
Car distributor modules, and amplifiers get white silicone compound. CPUs and GPUS get artic silver.
Let me guess, Chinese import from ebay?
If you wanted the whole thing to turn off then why dont you just off the socket????
It would also stop the power brick from converting the voltage constantly.
12 x 5 = 60 watt power supply, so amp is from 20 to 25 watts per channel at max.