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My Topping L30 II just "explode" being off, but connected to power (still works)

artdeco

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While trialing an L30 II the unit stopped amplifying. The LED began flashing even when the switch was in the off position!

After reboot the LED came on solid while a loud mains hum came through the headphones. This lasted about 15 seconds until the LED began flashing again with a loss of sound through the headphones.

The wallwart appeared OK but the shortness of the cable in this situation could have stressed the plug inside the amp's power input socket and caused a short.

Suggestion: lengthen the wallwart-to-amp lead with an extension to keep the plug free from sideways tension.
 

Cars-N-Cans

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While trialing an L30 II the unit stopped amplifying. The LED began flashing even when the switch was in the off position!

After reboot the LED came on solid while a loud mains hum came through the headphones. This lasted about 15 seconds until the LED began flashing again with a loss of sound through the headphones.

The wallwart appeared OK but the shortness of the cable in this situation could have stressed the plug inside the amp's power input socket and caused a short.

Suggestion: lengthen the wallwart-to-amp lead with an extension to keep the plug free from sideways tension
I doubt that was the connector on the PCB. That will just cause intermittent power. What you describe sounds like an internal short or maybe a failed rectifier if it had lots of hum in the headphones. That indicates either raw 50/60 Hz AC or excessive ripple on one or both of the power rails. At least the internal protection circuitry activated in that situation, probably from the output no longer being at 0V when nothing was playing, or a total loss of one of the rails.
 

Cars-N-Cans

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Yet nearly every time a new peep comes to ASR looking for a DAC/DAC-Amp or a amp somebody starts recommending Topping. These peeps completely ignore that Topping has had the most abysmal service for the past year or so. I think it's time to let somebody else have a chance at being the DAC-DAC-Amp solution. Topping has had more than enough encouragement, enough chances and enough failures.
I've deliberately avoided them from the start. Not because the designs are bad, but because products that wholly originate in China are such a mixed bag. Even if the company makes a solid attempt at the use of quality components, when the entire supply chain is there the components could literally come from anywhere, and change at any time without notice to anyone but the guys on the shipping dock swapping containers in the middle of the night. Never quite know what "surprises" might lie inside waiting to be discovered later on when you buy it. Its a shame as otherwise they seem to really put a solid effort into the designs with respect to performance.
 
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Merkurio

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A little update.

Since I'm not going to cover the return costs and honestly I don't have much time for this, I've decided to keep it, open it up and take some photos of the board to see what could have happened.

To my surprise, everything seems to be fine and the components appear to be of good quality as one would expect from Topping, but of course, I'm not an expert by any means, so I post them here in case someone can diagnose this type of stuff (sorry for the quality of the photos, I took them with an iPhone XS in less than ideal conditions yesterday, when time allowed):

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I'm still intrigued with what happened, I don't know if it was an ESD incident (since I had it next to my PC when all this happened, near the area where the PSU is) or what else it could be, but the truth is I'm not going to buy anything else that doesn't have proper DC and ESD protection after this.
 
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restorer-john

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OK, if there was an 'explosion' and smoke coming out of the RCAs as you describe, there will be evidence. I see no evidence. There is a faint possibility there was a short below the barrel connector to the chassis or pin to PCB- check that. Smoke generally means vaporised solder/copper and that usually leaves a 'film' on the PCB/component or adjacent casework.

Perhaps the power adaptor connector itself shorted in the lead/plug and the 'explosion' and 'smoke' was actually outside the unit.

Based on your excellent photos, I wouldn't be overly concerned about using the unit, power supply connector check notwithstanding.
 
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Merkurio

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OK, if there was an 'explosion' and smoke coming out of the RCAs as you describe, there will be evidence. I see no evidence. There is a faint possibility there was a short below the barrel connector to the chassis or pin to PCB- check that. Smoke generally means vaporised solder/copper and that usually leaves a 'film' on the PCB/component or adjacent casework.

Perhaps the power adaptor connector itself shorted in the lead/plug and the 'explosion' and 'smoke' was actually outside the unit.

Based on your excellent photos, I wouldn't be overly concerned about using the unit, power supply connector check notwithstanding.

First of all, thanks for your valuable observations and shedding some light on the subject based on my images, I appreciate it a lot. :)

About what you say regarding to the explosion and the smoke, it was indeed visible (and strongly audible like a bang) on the outside of the case as a small sparkling beam of light just near the RCA inputs, followed by odorless smoke in that zone that vanished in a matter of seconds.

I had the courage to use it shortly after the incident as I described in the first post (with a cheap Koss KPH30i that I have lying around) and certainly everything worked without any problem despite the scare I got.

Anyway, can this show some flaw in the design or can it have a possible explanation, in order to avoid it in the future (or to take certain usage considerations)? I've only had a Schiit Magni 3 a few years ago (connected directly to the RCA outputs on the motherboard of the PC I had at the time) and a DX3 Pro after that connected by USB, neither gave me any similar issues or scares.

The only things that have changed with this Topping L30 were:

-It was very close to the case of my new PC rig, right next to the PC's PSU (however, that area does not generate any heat, on the contrary, I have a radiator that expels air towards the front). This close.
-I had the RCA cable connected to the L30, but the 3.5mm termination (it's an RCA to 3.5 cable) was disconnected and lying on the desk mat, since I only use it to connect the Qudelix-5K as a "desktop" DAC/DSP. Like this.

The only thing I want is to avoid that something like this happens again, be it with this amplifier or with another one that I end up buying, since it was audible throughout the house and scared the hell out of us, especially me who was nearby.
 
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Cars-N-Cans

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My concern would lie with the units upstream as well. This sounds a lot like a loss of mains isolation in one of the supplies. The amp will be fine since it’s still locally getting the correct voltage, but with a loss of isolation the whole enclosure will go up to the same voltage as the wall plug, causing a loud bang when the AC voltage flashes over. The smoke will indeed be odorless because it’s vaporized metal. There may be little or no evidence, either, since its not like two wires shorting out, but an actual arc which may only leave a small pit behind. If a switch mode supply feeding a DAC or some other source is no longer isolated, this is what can happen. I think the amp and it’s supply are OK as well since it’s just a plain vanilla 50/60Hz transformer. Those rarely go bad. It’s also possible it was a brief surge, but that would mean arcing in the power brick as well.

As a CYA, you could get a new AC wall pack and power brick for the amp and DAC. This would at least ensure it’s safe and can be used again without a lot of risk. Given its a headphone amp, I would strongly encourage it, just to be safe.
 

Cars-N-Cans

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About what you say regarding to the explosion and the smoke, it was indeed visible (and strongly audible like a bang) on the outside of the case as a small sparkling beam of light just near the RCA inputs, followed by odorless smoke in that zone that vanished in a matter of seconds.
Can you provide a complete list of the equipment that was connected to the amplifier at the time? I can say with a fair degree of certainty that the amplifier itself is likely fine. But, at this point I would not use it until you figure out what allowed AC voltage from the actual wall outlet to make its way onto the RCA cables. Given this is a device you physically place on your body, having live components could be deadly, so its worth the time to take a step back and see if any potential causes can be located. But, before that is done I would not consider the setup to be electrically safe.

Edit: I don't think this was the wall pack's output shorting since it was so energetic.
 

Cars-N-Cans

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Looking at the photos I do see one area of concern, and that's on the molded supports for the RCA connectors. There looks to be some discoloration on the inside of the plastic. I suspect its probably just some dust, but it would be good to try and see if it really is just a dust bunny and not a skid mark inside with a corresponding crater in the metal contact for the RCA. Edit: This is on the RCA input side of the amp, which makes it all that much more suspicious.

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Sokel

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Looking at the photos I do see one area of concern, and that's on the molded supports for the RCA connectors. There looks to be some discoloration on the inside of the plastic. I suspect its probably just some dust, but it would be good to try and see if it really is just a dust bunny and not a skid mark inside with a corresponding crater in the metal contact for the RCA. Edit: This is on the RCA input side of the amp, which makes it all that much more suspicious.

View attachment 244544
You mean the spot on the red mark?

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Eagle's eye!
 

Roland68

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A little update.

Since I'm not going to cover the return costs and honestly I don't have much time for this, I've decided to keep it, open it up and take some photos of the board to see what could have happened.
Since the owner chose not to send the device in, I can now point out something without jeopardizing his warranty.

How should the L30 II with its transformer brick (2 poles without connection to the protective earth) have triggered the described scenario?
It should be noted that I have its power brick connected in a surge protector and everything that was plugged into it turned off after the explosion (including my pc and monitor)

@Merkurio Was the L30 II off or on when this happened?
 

Cars-N-Cans

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Since the owner chose not to send the device in, I can now point out something without jeopardizing his warranty.

How should the L30 II with its transformer brick (2 poles without connection to the protective earth) have triggered the described scenario?
It should be noted that I have its power brick connected in a surge protector and everything that was plugged into it turned off after the explosion (including my pc and monitor)

@Merkurio Was the L30 II off or on when this happened?
If it was a short or flashover on the mains side I would think it could. There are other scenarios as well. As I said earlier on in this thread, I had this issue with arcing contacts in my HP amp's power switch causing RFI and making my monitor misbehave (shut off just like the OP's did). Turn it on, monitor goes off. Conversely, the monitors refresh rate could be heard in the audio as buzzing. Solved by adding some decoupling inside the amp, but this was a Schiit Heresy, which is absurdly minimalist in comparison to the Topping. Power side after the barrel jack is a bridge rectifier, two electrolytics, and two tiny little MLCs on each rail before the op-amps, and that's it for the power filtering.

I would assume the breaker on the power strip (if it had one) did not trip since everything powered up again once cycled off, but that detail would be helpful if the OP knows.
 
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Merkurio

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Can you provide a complete list of the equipment that was connected to the amplifier at the time? I can say with a fair degree of certainty that the amplifier itself is likely fine. But, at this point I would not use it until you figure out what allowed AC voltage from the actual wall outlet to make its way onto the RCA cables. Given this is a device you physically place on your body, having live components could be deadly, so its worth the time to take a step back and see if any potential causes can be located. But, before that is done I would not consider the setup to be electrically safe.

Edit: I don't think this was the wall pack's output shorting since it was so energetic.

The amplifier was connected only to the surge protector at the time, the RCA cable wasn't even connected to the Qudelix (which I use as a DAC).

Since the owner chose not to send the device in, I can now point out something without jeopardizing his warranty.

How should the L30 II with its transformer brick (2 poles without connection to the protective earth) have triggered the described scenario?
It should be noted that I have its power brick connected in a surge protector and everything that was plugged into it turned off after the explosion (including my pc and monitor)

@Merkurio Was the L30 II off or on when this happened?

It was off (with the front switch in the "off" position, but as I said, connected to the power using a surge protector).

All this leads me to suspect that the possible culprit could be the PSU of my new PC build, since I have investigated a bit about it and it seems that this loud bang sound is common when one of the capacitors of the power supply is blown, and it also match the description of the odorless smoke and the shut off of all the devices nearby connected to the surge protector.

As I said before, my PC was turned on and right next to the Topping when the incident happen, possibly that light that I saw was a kind of electrical arc that "jumped" to the L30 (right in the area of the RCA inputs, the closest to the PC) when the power supply capacitor blew, hence that mark could be produced on the molded supports of the RCA connectors.

Does this make sense to you, guys?

In any case, I will process a return for the PSU as it was a refurbished unit (Corsair SF750), but I'm not sure if this could have been prevented with proper ESD protection or it's just an unavoidable electrical phenomenon when one device is so close to another.
 

Cars-N-Cans

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The amplifier was connected only to the surge protector at the time, the RCA cable wasn't even connected to the Qudelix (which I use as a DAC).
What was being used as the source? The PC? In other words, what were the RCAs hooked to on the other side?
 
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Merkurio

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What was being used as the source? The PC? In other words, what were the RCAs hooked to on the other side?

The source is whatever I connect the Qudelix-5K to (usually the PC when I'm on the desktop), but this time was just the RCA cable connected to the Topping without the Qudelix connected on the other side, just the 3.5 mm termination laying around on the desk mat as I described in previous posts.

The usual workflow is:

PC/Mac > Qudelix-5K via USB > Topping L30 using a RCA to 3.5 mm cable.
 

Cars-N-Cans

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The source is whatever I connect the Qudelix-5K to (usually the PC when I'm on the desktop), but this time was just the RCA cable connected to the Topping without the Qudelix connected on the other side, just the 3.5 mm termination laying around on the desk mat as I described in previous posts.

The usual workflow is:

PC/Mac > Qudelix-5K via USB > Topping L30 using a RCA to 3.5 mm cable.
Hmmm. My thought then would be the arc may have completed the path to ground thru the other end of the cable. As to whether it was due to a PSU issue, or some severe transient on the mains, hard to say. The only time I have seen that sort of thing was as a kid when my grandparents house got struck by lightning. The line voltage from the grid came into the house, and arced over pretty much everything before finally melting the feeders coming from the pole transformer. Spectacular sight to see while it happened, but also kind of a rare occurrence.
 
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Merkurio

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Hmmm. My thought then would be the arc may have completed the path to ground thru the other end of the cable. As to whether it was due to a PSU issue, or some severe transient on the mains, hard to say. The only time I have seen that sort of thing was as a kid when my grandparents house got struck by lightning. The line voltage from the grid came into the house, and arced over pretty much everything before finally melting the feeders coming from the pole transformer. Spectacular sight to see while it happened, but also kind of a rare occurrence.

At this point I've gone back to the Mac mini (the nerdiness of having two computers on the same desk has paid off!) until the new PSU arrives and I can open the PC to diagnose what happened.

It has been an unfortunate event, for sure, but at this point I cannot draw a conclusion that leads one to think that the Topping was to blame, in fact I was surprised by how well made this thing it's inside and the components of apparently good quality it contains.

Hell, I had a DX3 Pro (first generation) for over two years and it never gave me a single problem, nor did to the friend I sold it to.
 

Roland68

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If it was a short or flashover on the mains side I would think it could. There are other scenarios as well. As I said earlier on in this thread, I had this issue with arcing contacts in my HP amp's power switch causing RFI and making my monitor misbehave (shut off just like the OP's did). Turn it on, monitor goes off. Conversely, the monitors refresh rate could be heard in the audio as buzzing. Solved by adding some decoupling inside the amp, but this was a Schiit Heresy, which is absurdly minimalist in comparison to the Topping. Power side after the barrel jack is a bridge rectifier, two electrolytics, and two tiny little MLCs on each rail before the op-amps, and that's it for the power filtering.

I would assume the breaker on the power strip (if it had one) did not trip since everything powered up again once cycled off, but that detail would be helpful if the OP knows.
I don't want to destroy any illusions, but the Schiit Heresy, Magni 3+ and Topping L30 (and many others in the price range) are very similar on the power supply side.
Brick AC transformer with 1 x 15 - 16 volts, in the device then half-wave rectification with 2 diodes, no bridge rectifier (how else should you generate the +/- 23v from a voltage?). Then 2 electrolytic capacitors and LM317/337 and again 2 electrolytic capacitors. In the L30 II, the LM317/337 have been replaced by a discrete circuit, but the bottom line is no different.
 
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