burnt amplifier

[stillwater]

More likely to be a ground loop problem if the noise was steady 60 cycle hum than motorboating, but still hard to see how it would work perfectly and then fail dramatically.  Also with only two devices connected to the powerline (amp and supply for the HDMI converter) most likely changing the way one or the other plug is plugged into the power (assuming at least one has an unpolarized plug) would likely change the amount of hum.  Also this is line level input, not small signal like a dynamic microphone or a phono cartridge, so the hum would have to be really large to be audible at the amplifier.  On the whole a classic ground loop problem seems hard to square with the situation and  history.   

[asbril]

Well....... now I know that it is not the converter. Today I tried with a new amplifier and an older Chromecast audio, and again the amplifier started to smoke and basically died  . It is either something wrong with the power or the speakers. I doubt that it is the power as I changed wall socket and also I have no issues with any other appliance. So now I will need to get professional help which is going to cost a bit. I could change the speakers but having now wasted 4 amplifiers (even if cheap Pyle amps, it adds up...), so probably better just to get help from a professional.

[apostolakisl]

43 minutes ago, asbril said:

Well....... now I know that it is not the converter. Today I tried with a new amplifier and an older Chromecast audio, and again the amplifier started to smoke and basically died  . It is either something wrong with the power or the speakers. I doubt that it is the power as I changed wall socket and also I have no issues with any other appliance. So now I will need to get professional help which is going to cost a bit. I could change the speakers but having now wasted 4 amplifiers (even if cheap Pyle amps, it adds up...), so probably better just to get help from a professional.

Takes me back to my original thought that your speaker impedance is too low.  Cheap amps don't do well with low impedance, too much current.

[larryllix]

15 hours ago, asbril said:

Well....... now I know that it is not the converter. Today I tried with a new amplifier and an older Chromecast audio, and again the amplifier started to smoke and basically died  . It is either something wrong with the power or the speakers. I doubt that it is the power as I changed wall socket and also I have no issues with any other appliance. So now I will need to get professional help which is going to cost a bit. I could change the speakers but having now wasted 4 amplifiers (even if cheap Pyle amps, it adds up...), so probably better just to get help from a professional.

How loud did you have it?

If just low volume, I doubt it would be your speakers.
If no crackling, I doubt it is your wiring.

I return to a DC bias injected from your source. Have you tried another source to test it?

Sent from my SM-G781W using Tapatalk
 

Edited February 18, 2022 by larryllix
spell check changed wording found->doubt

[asbril]

25 minutes ago, larryllix said:

How loud did you have it?

If just low volume, I doubt it would be your speakers.
If no crackling, I found it is your wiring.

I return to a DC bias injected from your source. Have you tried another source to test it?

Sent from my SM-G781W using Tapatalk
 

I really don't know and have reached the limit of my technical knowledge. I have already contacted a professional installer who maintains a C4 system for a friend of mine, and hopefully he will give me hand (for a reasonale cost).

[Brian H]

When you find the cause.

I would be interested in what they found.

[larryllix]

12 hours ago, asbril said:

I really don't know and have reached the limit of my technical knowledge. I have already contacted a professional installer who maintains a C4 system for a friend of mine, and hopefully he will give me hand (for a reasonale cost).

You don't know if you have tried another source?

Edited February 18, 2022 by larryllix

[asbril]

35 minutes ago, larryllix said:

You don't know if you have tried another source?

Yes, I did but same results

[larryllix]

9 hours ago, asbril said:

Yes, I did but same results

ewwwww... well so much for that theory! Just plain weird.
No EU 240v plugs in your home, I trust.

Flashing lights or brilliance dips you can see?

Edited February 18, 2022 by larryllix

[MrBill]

@asbril which specific pyle amp?  

@larryllix's post above just made me remember that the pyle amp that I drive the outdoor speakers with uses a wall wart.

If that's the case for you, then it pretty much eliminates a problem on the power side and indicates there is a speaker or speaker wiring problem.

[stillwater]

@asbril   I am very sorry that this has happened again.  Did it happen immediately on plugging in the new amp?   Did the speakers make noise?  If so what? At least if it fried the amp immediately you have an immediate problem rather than an intermittent one -- easier to diagnose if so. 

Please don't do anything else until someone can get a meter on those speaker wires.  Treat them as if they have house voltage on them until proven otherwise.  (I know this is unlikely but so is the whole scenario!)   Please check AC and DC volts to ground from each unconnected speaker wire, and AC and DC volts between each pair.   Check resistance of each pair and between pairs.  (It's possible that the two channels are bridged by the speaker wires which could cause certain types of amps to fail.  )   

Your expert may also be able to learn something by taking apart the failed amp and seeing whether damage is in the power supply section or elsewhere.  (it's possible that the amp has an internal fuse or fuses and if so can be brought back to life).  

Then before reconnecting any amp.  (assuming you haven't found the problem from the voltage and appropriate resistances), to protect the new amp. :

- have it at minimum volume if it has a voiume control

- short the inputs to signal ground using analog inputs. 

- As someone else suggested, put an 8 ohm resistor in series with each channel (or even better a 4 ohm resistor  in series with each side of each channel.  

Also if the voltage/resistance tests are good, consider replacing the speakers as the source of a weird intermittent problem.  (What kind of speakers are they? If they have a tweeter they may have a misbehaving cross-over network) .  

Good Luck!

Edited February 19, 2022 by stillwater

[asbril]

2 hours ago, stillwater said:

@asbril   I am very sorry that this has happened again.  Did it happen immediately on plugging in the new amp?   Did the speakers make noise?  If so what? At least if it fried the amp immediately you have an immediate problem rather than an intermittent one -- easier to diagnose if so. 

Please don't do anything else until someone can get a meter on those speaker wires.  Treat them as if they have house voltage on them until proven otherwise.  (I know this is unlikely but so is the whole scenario!)   Please check AC and DC volts to ground from each unconnected speaker wire, and AC and DC volts between each pair.   Check resistance of each pair and between pairs.  (It's possible that the two channels are bridged by the speaker wires which could cause certain types of amps to fail.  )   

Your expert may also be able to learn something by taking apart the failed amp and seeing whether damage is in the power supply section or elsewhere.  (it's possible that the amp has an internal fuse or fuses and if so can be brought back to life).  

Then before reconnecting any amp.  (assuming you haven't found the problem from the voltage and appropriate resistances), to protect the new amp. :

- have it at minimum volume if it has a voiume control

- short the inputs to signal ground using analog inputs. 

- As someone else suggested, put an 8 ohm resistor in series with each channel (or even better a 4 ohm resistor  in series with each side of each channel.  

Also if the voltage/resistance tests are good, consider replacing the speakers as the source of a weird intermittent problem.  (What kind of speakers are they? If they have a tweeter they may have a misbehaving cross-over network) .  

Good Luck!

Did it happen immediately on plugging in the new amp?   Did the speakers make noise? 

It did not happen immediately but afrer a few minutes, but the speakers were making a weird noise.

Your expert may also be able to learn something by taking apart the failed amp

He is (supposedly) coming on Thursday and I kept the "burnt" amp.  The suggestions of all of you are very useful but most go beyond my  knowledge and I hope that the technician can sort it all out. I have a spare Pyle amp, but to test we can also use a Denon amp that I use in another zone of the home (but I will try to make sure that we don't burn that one  )

 

[asbril]

Professional installer came today and he determined that the issue was in the wiring between the speakers and the amplifier. To access that wiring I would have needed to remove a wall unit and I came up with a better solution . I had bought this device for just in case and it actually gave me a better solution.

The speakers are in the bathroom and the wiring went all the way to the bedroom where the amplifier used to be. Below the speakers in the bathroom I had a volume control and the Wall Mount - 100W In-Wall Audio Control Receiver w/ Built-in Amplifier  fits right in the space of the volume control.  I connected the Chromecast  and the volume & quality of the audio is excellent.

It was for sure not the expected solution, but in fact a better one. Thanks to all for your guidance and ideas.

[apostolakisl]

@asbril I am curious as to what it was about the wiring.  The only possible reason I can think of is that wires were split off putting speakers in parallel resulting in too low of impedance.  Or perhaps there was a short through some material that had enough resistance to not dead short the system but rather again, cause low impedance.  

[upstatemike]

Old amplifiers were sometimes wired to share left and right speaker negative. Many newer amps do not share any common reference between speaker channels and will not survive if connected to that type of wiring. Old in-wall volume controls can sometimes be the point where speaker negatives are linked. I always use an impedance bridge across the two speaker negatives to make sure they are not linked someplace.

[asbril]

4 hours ago, apostolakisl said:

@asbril I am curious as to what it was about the wiring.  The only possible reason I can think of is that wires were split off putting speakers in parallel resulting in too low of impedance.  Or perhaps there was a short through some material that had enough resistance to not dead short the system but rather again, cause low impedance.  

My old setup included a Bose amplifier in the bedroom and  all the speaker wires were connected to the subwoofer. The bathroom speaker wires ran inside the wall to the bedroom because they were installed during the construction of the condo. When I replaced the Bose system, I "redirected" the bathroom speaker wires from the old subwoofer to a new Pyle amplifier. Those "redirected" wires ran from behind a wall unit and my suspicion is that something was moved inside the wall unit creating some kind of short circuit, or may even have touched an electric extension cord also inside or behind the wall unit, creating some kind of interference.

I guess that I will never know exactly what happened unless I unmount the wall unit, which I won't ?.

[palayman]

On 1/27/2022 at 10:33 PM, stillwater said:

As a replacement amp, consider the rather small  Class D Aiyima A07.  In the user manual it says it has overload protection, though it says this only indirectly in a FAQ.  It is marketed as a 300 W amp but of course this depends on power supply voltage and current capability and I don't think the box has enough cooling for anything like that on a sustained basis.  (You probably won't need more than 20 watts for a bathroom anyway)  The amp is rated down to 4 ohms (which some amps today aren't).   $80 on amazon (+ power brick) or cheaper on the Aiyima site if you can wait for delivery from China.  From China you can also choose LM4562 op amps which have better specs than the standard NE5532 though if the circuit is properly designed I  doubt anyone could  hear the difference.  

Been meaning to set up some ceiling speakers I had installed in a new house using chromecast, HDMI to audio convertor and a small amp.  On your suggestion I bought when of the these amps.  Works great!  And the 4 ohm operation saved me some money as I can now run my family room and living room in parallel off one amp.

Thanks!

Paul