Schiit AC adapter broken again???

[DriedSponge]

Some of you may be familiar with my previous thread where I mentioned a broken Schiit AC adapter for my Magni heresey headphone amp. Anyways, they sent me a new one without even requesting the old one back, however a few days after I received the new one, I noticed it started to buzz again. This time it's a bit quieter, but it's still noticeable to me. I feel like if I leave it plugged in it's only going to get louder.

 

I'm wondering if this quite buzz is standard with this sort of plug, and I'm being paranoid, or if they've sent me another faulty unit. I'm honestly annoyed at this point and I wouldn't mind investing money into a third party AC adapter that doesn't break after a few days, so if anyone has any suggestions that would be great. I do plan on submitting another help request to schiit. Also as far as I'm aware, I have the same plugs as every other standard American household.

Here are some video links in case you care to listen.

• Buzz of original unit that shipped with my magni heresey
• Buzz of replacement unit

Thank you!

[Oshino Shinobu]

For what it's worth, the AC adaptor for my Magni buzes as well, though it doesn't seem to havbe caused any problems, but can be annoying if the room it's in is quiet.

[An0maly_76]

I would call an electrician and have them sound the wiring. This sounds suspiciously like a ground loop or ground fault, which can be very dangerous. It would appear that this might not be the piece of Schitt hardware you think it is... Sorry, couldn't help myself. Even the manufacturer makes light of this.

Edited August 7, 2022 by An0maly_76
Revised, more info

[Somerandomtechyboi]

52 minutes ago, An0maly_76 said:

It would appear that this might not be the piece of Schitt hardware you think it is... Sorry, couldn't help myself. Even the manufacturer makes light of this.

Well the front page and this makes fun of their own name

[H713]

Really hard to tell how loud it is from a video, but it doesn't sound like it's particularly loud to me. 

 

It's normal for 60 Hz transformers to make a buzzing sound. Some are quieter than others, but most of them can be heard if you put your ear up to it. Some cheaper transformers (and some industrial transformers where noise isn't an issue) are really annoyingly loud.

You may try an outlet in a different part of your house to see if this is still present. Some high-power devices have a rather nasty input current waveform, and parasistic impedance in the house wiring can thus result in a not-so-sinusoidal waveform, which has a tendency to make transformers buzz. Toroids in particular are NOTORIOUS for buzzing when there is even a few mV of DC offset on the mains.

 

Unless this is much louder than the video makes it out to be, I would not worry about it. If it gets hot (warm is fine - most of these run warm), as in uncomfortable to touch, then I'd be concerned. Again, I think your first AC adapter was probably electrically okay, but had a loose lamination in the core that was making a racket. I suspect this one is normal.

 

 

54 minutes ago, An0maly_76 said:

I would call an electrician and have them sound the wiring. This sounds suspiciously like a ground loop or ground fault, which can be very dangerous. It would appear that this might not be the piece of Schitt hardware you think it is... Sorry, couldn't help myself. Even the manufacturer makes light of this.

This really doesn't make any sense. Firstly, this type of AC adapter doesn't use the safety ground (it's double insulated). Even if it did, I am struggling to think of a way that a miswired outlet ground could possibly cause this kind of thing. I see zero reason to suspect the house wiring here. 

 

Also, ground loops are an unrelated issue that has nothing to do with what we are observing here. 

https://en.wikipedia.org/wiki/Ground_loop_(electricity)

[An0maly_76]

1 hour ago, H713 said:

This really doesn't make any sense. Firstly, this type of AC adapter doesn't use the safety ground (it's double insulated). Even if it did, I am struggling to think of a way that a miswired outlet ground could possibly cause this kind of thing. I see zero reason to suspect the house wiring here. 

 

Also, ground loops are an unrelated issue that has nothing to do with what we are observing here. 

https://en.wikipedia.org/wiki/Ground_loop_(electricity)

I have seen a number of things in my life that turned out to be caused by the last thing I would have suspected. Better to know than not to know.

[H713]

8 hours ago, An0maly_76 said:

I have seen a number of things in my life that turned out to be caused by the last thing I would have suspected. Better to know than not to know.

So have I. But by that logic, any time a piece of hardware fails I should call an electrician. 

 

When I say I am struggling to think of a a way that a miswired outlet could cause this, I mean it. From an engineering standpoint (and I know transformers fairly well), there really isn't much you could do to a normal outlet to cause this. Residential wiring is reasonably simple, and as such there are limited ways to screw it up. Can it cause a safety issue? Sure. Could it cause a wall wart to behave this way? Nope. 

 

If you had a normal outlet wired for 240, it would destroy the transformer in a matter of seconds (saturate core, L goes to zero, I is limited only by parasitic R, time until smoke is limited only by thermodynamics).

Since the safety ground DOES NOT CONNECT to this particular device, nothing that is done with the safety ground will affect it. 

[DriedSponge]

I think I might just wait to see if the buzzing gets worse/louder. I can only hear it when it's dead silent and I'm listening carefully (the sound of my pc idling covers it). Thanks everyone for your input!!!

[An0maly_76]

56 minutes ago, H713 said:

Since the safety ground DOES NOT CONNECT to this particular device, nothing that is done with the safety ground will affect it. 

 

Let me give you an example of what I am referring to. In my taxi days, I owned a car that out of the blue would spit, sputter, buck and jerk to beat the band if you tried to drive it. Idled fine, but the second you opened the throttle in gear, you'd better have your seatbelt on, because it could launch you into the steering wheel. No check engine light, no codes.

 

Long story short, after replacing the ECM, it went to a shop, who found a sensor voltage problem, but couldn't explain why. Since only the crankshaft position sensor could stop the engine if disconnected, I backprobed the sensor voltage, checking voltage while disconnecting the other sensors that fine-tuned for conditions.

 

When this did nothing, I found what I thought was a temperature sensor in the radiator. Disconnecting it turned on the coolant level light, but restored the voltage and corrected the problem. Only it wasn't a temperature sensor, it was a grounding switch for the coolant level warning light. I disabled the light by jumping the connector with a paper clip. The light had not been on, and the switch had no direct connection to the ECM. With the radiator full, there was no reason for its contacts to open. Yet it was still grounding the ECM's outputs somehow.

 

So when you can explain that, you can rule out a ground fault or ground loop causing OP's problem. I've asked many mechanics about this, who were stumped and said I was lucky to have even discovered it, because most people would have junked the car before they found the problem, when I found it in a couple hours once I knew it was a voltage problem.

 

@DriedSponge

 

As to OP's problem, I'm of the mind that the transformer in the wall wart actually needs a ground, but someone was too cheap and too lazy to manufacture it that way. It's certainly happened in a wide variety of situations. Maybe there's a remote chance it's trying to ground through the neutral in the wall wiring (though I should think that would be a dead short). The only other possibility I can think of would be that the equipment being powered is overloading the transformer.

Edited August 8, 2022 by An0maly_76
Revised, more info

[H713]

8 hours ago, An0maly_76 said:

 

Let me give you an example of what I am referring to. In my taxi days, I owned a car that out of the blue would spit, sputter, buck and jerk to beat the band if you tried to drive it. Idled fine, but the second you opened the throttle in gear, you'd better have your seatbelt on, because it could launch you into the steering wheel. No check engine light, no codes.

 

Long story short, after replacing the ECM, it went to a shop, who found a sensor voltage problem, but couldn't explain why. Since only the crankshaft position sensor could stop the engine if disconnected, I backprobed the sensor voltage, checking voltage while disconnecting the other sensors that fine-tuned for conditions.

 

When this did nothing, I found what I thought was a temperature sensor in the radiator. Disconnecting it turned on the coolant level light, but restored the voltage and corrected the problem. Only it wasn't a temperature sensor, it was a grounding switch for the coolant level warning light. I disabled the light by jumping the connector with a paper clip. The light had not been on, and the switch had no direct connection to the ECM. With the radiator full, there was no reason for its contacts to open. Yet it was still grounding the ECM's outputs somehow.

 

So when you can explain that, you can rule out a ground fault or ground loop causing OP's problem. I've asked many mechanics about this, who were stumped and said I was lucky to have even discovered it, because most people would have junked the car before they found the problem, when I found it in a couple hours once I knew it was a voltage problem.

 

@DriedSponge

 

As to OP's problem, I'm of the mind that the transformer in the wall wart actually needs a ground, but someone was too cheap and too lazy to manufacture it that way. It's certainly happened in a wide variety of situations. Maybe there's a remote chance it's trying to ground through the neutral in the wall wiring (though I should think that would be a dead short). The only other possibility I can think of would be that the equipment being powered is overloading the transformer.

Cars have tend to have a lot of rather messy wiring, and a tendency to use the chassis of the car as a current return. Without seeing a schematic I can't really comment on the issue you're describing. 

 

Let's be clear about what the purpose of the 3rd pin on a standard mains outlet. It's a safety ground. It serves one purpose and one purpose only - to ensure the conductive chassis of a device cannot under any circumstances become live in the event of an internal fault (chaffed wiring, shorted Y capacitor, etc). The safety ground is tied to the neutral in your breaker panel. If for some reason the hot line were to short to the chassis, it instead presents an overcurrent condition which trips the breaker (or the device fuse). The only time the safety ground should ever see any current is in a fault condition.

 

The Schiit AC adapter doesn't need a safety ground because it's a double-insulated device. In its case, this is accomplished through its non-conductive plastic enclosure. The current path for powering the device is between the hot and the neutral. This is a very standard configuration, and is not an issue.

 

If we were talking about an issue inside the Schiit device (after the power supply), then a grounding issue would be on the table. It is still possible that the device is overloading the transformer, but it's unlikely, and if it was then the transformer would be getting uncomfortably hot. 

 

Again, I don't think there's an issue here. Subtle buzzing is common in 60 Hz transformers, and while a bit annoying at times, it is benign.

[An0maly_76]

35 minutes ago, H713 said:

Cars have tend to have a lot of rather messy wiring, and a tendency to use the chassis of the car as a current return. Without seeing a schematic I can't really comment on the issue you're describing.

We're talking about a 1990 Lumina with a now-antiquated control system. The grounding switch itself had one ground wire, with no connection to its own power of any kind. I'm pretty sure its purpose was to ground a collapsible circuit, to turn on the coolant level warning light, nothing more. Hence, no mechanic I've ever asked about it could explain it, because by rights, it should never have affected battery or sensor voltage. But it did.

 

35 minutes ago, H713 said:

Again, I don't think there's an issue here. Subtle buzzing is common in 60 Hz transformers, and while a bit annoying at times, it is benign.

So are most of these 50hz as opposed to 60? Because I've never heard a noise of any kind from anything like that.

[H713]

Both 50 Hz and 60 Hz transformers have this characteristic. 

[An0maly_76]

25 minutes ago, H713 said:

Both 50 Hz and 60 Hz transformers have this characteristic. 

My hearing's not perfect, but I've never heard this noise before, must be quite faint. As OP said, they only hear it when the room is dead quiet, which tells me they have very sensitive hearing, or it's just that quiet otherwise. As you say, there may not be an issue. I just have never heard of this before.

[H713]

It varies from transformer to transformer. With really good transformers, it is inaudible, and this what you ideally want for audio equipment. On the other hand, I've seen some industrial transformers where you can hear them buzzing from another room. 

 

It's a combination of issues, but primarily it's an issue of how hard they're pushing the core in terms of maximum flux density. Higher magnetic flux densities mean greater forces on laminations and windings, and as such more movement. 

 

Designing transformers is tricky, but like any engineering problem, it's a balancing act. High flux densities tend to lead to high core losses, but it's very difficult to design for low flux densities without unacceptable size and/or copper losses. Usually silence isn't a huge concern, so engineers will try to minimize losses for a given cost and physical size.

 

 

The other reason you probably haven't heard this is that most people don't encounter all that many 50 or 60 Hz transformers anymore, as the vast majority of devices employ switching power supplies that operate at frequencies above 50 kHz. Usually this is described by PC hardware people as "coil whine". It's more or less the same thing, only coil whine usually comes from inductors rather than transformers, but the same thing is taking place. 

[DriedSponge]

2 hours ago, H713 said:

It varies from transformer to transformer. With really good transformers, it is inaudible, and this what you ideally want for audio equipment. On the other hand, I've seen some industrial transformers where you can hear them buzzing from another room. 

 

It's a combination of issues, but primarily it's an issue of how hard they're pushing the core in terms of maximum flux density. Higher magnetic flux densities mean greater forces on laminations and windings, and as such more movement. 

 

Designing transformers is tricky, but like any engineering problem, it's a balancing act. High flux densities tend to lead to high core losses, but it's very difficult to design for low flux densities without unacceptable size and/or copper losses. Usually silence isn't a huge concern, so engineers will try to minimize losses for a given cost and physical size.

 

 

The other reason you probably haven't heard this is that most people don't encounter all that many 50 or 60 Hz transformers anymore, as the vast majority of devices employ switching power supplies that operate at frequencies above 50 kHz. Usually this is described by PC hardware people as "coil whine". It's more or less the same thing, only coil whine usually comes from inductors rather than transformers, but the same thing is taking place. 

I came home today to discover the transformer buzzing even louder than before, this time and a very audible level. I'm going to see if schiit will send me another one that will maybe work better, but if you know of any third party ones/brands that you could recommended that would be great. I've looked up other cases of this happening to people who use schiit products, for other people it seems like the issue was resolved after a replacement.

Thanks!