burnt amplifier

[asbril]

5 hours ago, stillwater said:

you think the amp has died

I just checked..... The amp is dead  

[larryllix]

5 hours ago, stillwater said:

Very possibly the problem is the power supply (wall wart) for the HDMI to RCA converter, or less likely with the HDMI converter or chromecast.     Unless -- I assume you didn't reuse the same power brick for the 3 amplifiers...  

Maybe the power supply leaking high voltage  into the HDMI converter.  Otherwise  I'd be surprised the amps are permanently damaged due to an input condition from a 5 volt powered source. (assuming the HDMI converter is powered from a USB wall wart -- if not maybe it's 12 volts...  but still ...).  Or maybe it's leaking a lot high frequency from the switching power supply and that is overheating the amps.  

How do you know the amps  are toast?    (Just re-read your original post.  One or more of the amps could have turned themselves off with overheat protection.)  If you haven't tested them separately from that input configuration it's possible they aren't actually destroyed.  Even if they aren't destroyed the most likely culprit is still the wall wart for the HDMI converter (failed capacitor).  

(If the amps are not destroyed what could be happening is the following -- something in the HDMI wall wart or HDMI converter (less likely in chromecast) is failing.   You unplug everything or turn off the power strip and these components cool down.  You replace the amp.  It works again until something warms up and fails and you think the amp has died... repeat.,   

 

 

 

I have to concurr with that idea! I was just thinking the same scenario myself. The power supply capacitors stop working and create buzz in the input. Then when you shut it down the caps get a rest of a few days and partially heal again, working for a day or two until the next surge or heat.

[larryllix]

Just now, asbril said:

I just checked..... The amp is dead  

The buzz indicates the power amp is still working so part of it is still good.

How do you know / test this?

 

[asbril]

5 hours ago, stillwater said:

most likely culprit is still the wall wart for the HDMI converter (failed capacitor)

I have a spare one but it is unlikely the wall wart, because I replaced that before installing the last amp.

If I go by elimanation , it is not the power strip (replaced and no problems with TV, Comcast box, sound box), not the wall wart (replaced), unlikely the speakers as they worked fine after replacing the first 2 amps. It could be the HDMI to RCA converter, but would it not be unlikely that a low power device (powered by usb cable) damages an amp ?

[asbril]

3 minutes ago, larryllix said:

How do you know / test this?

No red light on the amp when powering on and not getting warm.

[stillwater]

It would seem that if the amplifiers have been replaced and the power supplies for the amplifiers have been replaced and the wall wart for the HDMI converter has been replaced with a known good one then the only remaining potential culprits are the HDMI converter and the chromecast dongle.  (As a pure digital device I don't think the Chromecast could be responsible unless it were somehow modulating the 5 volt supply by shorting out or drawing too much current-- though this is is all so strange I can't rule that out completely.)  I don't know enough about the internals of these amplifiers but the failure mode would be somehow the HDMI converter is injecting some sort (non audible) oscillation  (or DC if the amps are DC coupled) that is causing the amps to draw too much power and blow either an internal fuse or some other power supply component.  (Otherwise the red light would be on).   It's a stretch. None of these things should kill an amp... let alone three.   You would think an op amp would die rather than the power supply.   

In any case it's odd that it works for a while and then dies.  This would seem to rule out some sort of wiring fault resulting for example from non-polarized plugs. 

The idea that you replaced a failed wall wart with another failed one is also  a stretch. You might check that the Wall Wart is rated for enough current to power both the HDMI converter and the Chromecast.  The HDMI converter on its own may draw as much power as its wall wart gives and then the additional draw from the Chromecast is too much.  You can find power supplies (for example for raspberry pis or for Ipads that proved an amp instead of the 500ma that is nominal for a USB port) .  But an underpowered USB supply on its own shouldn't be causing this problem, especially assuming the first one worked for a long time before the recent troubles.  And I'm guessing you have the same configuration for other rooms...  

One more thing -- I don't understand the sequence -- the speakers play normally for some time (days?) and then without any change they buzz loudly (for how long?) and then the amp dies and the buzz stops at the same time?   Is that right?   

I suppose there is another possibility which is that somehow power from a doorbell transformer or thermostat  (24 vac) is being transferred to the speaker wires causing the loud buzz,  and killing the amp -- but then how does the loud buzz stop (maybe ground path for the power is through the amp, and when the amp dies the buzz stops ? )   But then how does it work for days before the buzz appears?  Any chance that it dies when someone rings a doorbell or when your heat does something?   Was there any wiring change in the period before these failures started? 

(I certainly hope 120 volts isn't straying onto the speaker wires from lighting or exhaust fan wiring! This would be an electrocution and fire  risk.  )   Anyway I'd be very careful around any of this wiring until the mystery is solved.  

Sorry I don't have any better ideas.... 

 

[asbril]

21 minutes ago, stillwater said:

One more thing -- I don't understand the sequence -- the speakers play normally for some time (days?) and then without any change they buzz loudly (for how long?) and then the amp dies and the buzz stops at the same time?   Is that right?   

Yes.  I disposed of the first 2 amplifiers, but before disposing, they gave a bass buzz.  I still have the last amp and this actually first gave a buzz as well, then became very hot and then just died.

[apostolakisl]

I'm with @stillwater on this.  Very hard to know wtf is going on with this.  You hate to keep blowing up amps trying stuff.  Might be time to take this whole thing apart and start over.  If you care to take a chance, try moving your chromecast etc over to a completely knew location with a different amp and see how things go there, just to rule out a problem within them.  Or conversely, take a completely different audio source and run that into your current location (with of course another new amp).  

[asbril]

29 minutes ago, stillwater said:

And I'm guessing you have the same configuration for other rooms...  

I had 3 chromecast zones in my home. One still works with same setup, but with a more expensive 5.1 Denon amplifier.  In my study I also had the same setup but then used the amplifier in the master bathroom, which then blew up. I replaced the  Chromecast in the study with 2 paired Nest Minis, giving me an excellent stereo sound in this smaller space.

Temporarily I did the same in the bathroom (2  Nest Minis), but ideally I would use the Chromecast casting to the built-in speakers. When I come back from my trip, Im will use the Chromecast/HDMI-RCA converter from the study in the master suite and get a new amp, but first I want to check the cabling.

Edited January 28, 2022 by asbril

[asbril]

4 minutes ago, apostolakisl said:

I'm with @stillwater on this.  Very hard to know wtf is going on with this.  You hate to keep blowing up amps trying stuff.  Might be time to take this whole thing apart and start over.  If you care to take a chance, try moving your chromecast etc over to a completely knew location with a different amp and see how things go there, just to rule out a problem within them.  Or conversely, take a completely different audio source and run that into your current location (with of course another new amp).  

I rule out the Chromecast itself (though I can try your suggestion) because it still shows up in the Google Home App and shows it is actually playing music in the App. I am more inclined to try with another converter and the Denon amp.

[apostolakisl]

2 minutes ago, asbril said:

I had 3 chromecast zones in my home. One still works with same setup, but with a more expensive 5.1 Denon amplifier.  In my study I also had the same setup but then used the amplifier in the master bathroom, which then blew up. I replaced the  Chromecast in the study with 2 paired Nest Minis, giving me an excellent stereo sound in this smaller space.

Temporarily I did the same in the bathroom (2  Nest Minis), but ideally I would use the Chromecast casting to the built-in speakers. When I come back from my trip, Im will use the Chromecast/HDMI-RCA converter from the study in the master suite and get a new amp, but first I want to check the cabling.

The Denon blew up too?  In my whole life I have only blown up one amp, a Carver from about 35 years ago.  But I rode that one hard and put it down wet.  Back in the day.

[stillwater]

Too bad you don't have the amps that buzzed.   For example It would have been good to know if they still buzzed with no input connected, or with their inputs shorted.   Or if they worked ok connected to other speakers.  

In the meantime I assume the HDMI converter is cheaper than an amp.  I'd treat the HDMI converter as guilty until  proven innocent (and I certainly wouldn't risk the Denon amp to prove the HDMI converter innocent, which it wouldn't really do anyway) 

[asbril]

1 minute ago, apostolakisl said:

The Denon blew up too?  In my whole life I have only blown up one amp, a Carver from about 35 years ago.  But I rode that one hard and put it down wet.  Back in the day.

No the Denon is fine.  "Only" 2 Pyle and 1 Fozi blew up. The weird thing is that the first Pyle worked fine for some two years before blowing up.

[asbril]

1 minute ago, stillwater said:

Too bad you don't have the amps that buzzed.   For example It would have been good to know if they still buzzed with no input connected, or with their inputs shorted.   Or if they worked ok connected to other speakers.  

In the meantime I assume the HDMI converter is cheaper than an amp.  I'd treat the HDMI converter as guilty until  proven innocent (and I certainly wouldn't risk the Denon amp to prove the HDMI converter innocent, which it wouldn't really do anyway) 

Yes I will get another Pyle and try with different converter and , just to be sure, different electric outlet.

[apostolakisl]

6 minutes ago, asbril said:

No the Denon is fine.  "Only" 2 Pyle and 1 Fozi blew up. The weird thing is that the first Pyle worked fine for some two years before blowing up.

My gut tells me you have some voltage (and thus current) spikes being fed into these amps.  Somehow.

[stillwater]

Good luck!   I feel better in knowing that the first two amps just buzzed rather than having their power supplies fried also.  Was the buzz a constant hum (likely to be 60 cycle noise) or what audio engineers called "motorboating" (more a succession of impulse noises -- see https://en.wikipedia.org/wiki/Motorboating_(electronics) )

Motorboating could  be caused by the wall wart for the HDMI converter providing insufficient current.   Unless you the amps buzzed  without being connected to the HDMI device  it is plausible that you threw out 2 perfectly good Pyle amps.  

[asbril]

13 minutes ago, stillwater said:

it is plausible that you threw out 2 perfectly good Pyle amps.  

That would be a shame. But as I said, when I come back from my trip, I try a new amp with different chromecast and different converter, plugged in different outlet, but with same speaker wires, after checking that wiring as much as I can, because the larger part of the wiring is inside the wall and celing.

[stillwater]

Sure.   Do you remember whether the buzz was more like a constant hum or more like a staccato bup-bup-bup?  At about a minute into this video you can hear what 60 cycle hum sounds like (plus some distortion from the speaker)

 https://www.youtube.com/watch?v=Vf6Bq-vStLA

 

Also worth looking at the various usb wall warts you are using and ensure that you have a relatively beefy one powering the replacement HDMI converter (and through it the chromecast).  

[stillwater]

Also, just to be sure, when you get back from your trip, before you do anything else, consider measuring the voltage between ground and each of the four speaker wires.   If you have one you could first use a proximity probe to see if there is 120 vac present, and then use a multimeter on both AC and DC ranges.  For ground you can use the 3rd ground terminal on an ac outlet or possibly the case of your power strip (if metal).   

It should be zero (up to a few 10s of millivolts might be noise).  

 

But of course this wouldn't tell you much if the problem only appears intermittently...  

But I am guessing it is indeed the HDMI converter or a combination of the HDMI converter and the wall wart that is the source of an input problem, rather than anything on the speaker side -- but if it were me I'd put safety first.  (Again I am relieved that only the last amp died completely...) 

 

Edited January 28, 2022 by stillwater

[larryllix]

4 hours ago, stillwater said:

Also, just to be sure, when you get back from your trip, before you do anything else, consider measuring the voltage between ground and each of the four speaker wires.   If you have one you could first use a proximity probe to see if there is 120 vac present, and then use a multimeter on both AC and DC ranges.  For ground you can use the 3rd ground terminal on an ac outlet or possibly the case of your power strip (if metal).   

It should be zero (up to a few 10s of millivolts might be noise).  

 

But of course this wouldn't tell you much if the problem only appears intermittently...  

But I am guessing it is indeed the HDMI converter or a combination of the HDMI converter and the wall wart that is the source of an input problem, rather than anything on the speaker side -- but if it were me I'd put safety first.  (Again I am relieved that only the last amp died completely...) 

 

I think you may have something with the DC bias on the output of the HDMI converter. DC amps available now may not take this continuously and blow an internal fuse or the power supply. Many equipment manufacturers will put a internal fuse in series with another user serviceable fuse. If the user abuses it by replacing it with a higher rating he internal fuse blowing will get the amp to a repair shop.

[stillwater]

If  @asbrill has a multimeter he can measure DC volts on the outputs of the HDMI converter --and if not zero he could put a film capacitor in series with the center pin of the rca connector  -- preferably in a shielded housing to prevent hum.  (value of the capacitor determined by the input impedance of the amplifier which is probably 15k to 25k ohms..   

  I suppose he could put 1.5 volts from an AAA cell on the input of the amp and see if there is DC on the output but that would only tell you if the the whole amp is DC coupled and not if the input is DC coupled, so probably not worth doing.  

But it's equally likely the HDMI converter is actually sending out a lot more power than the amplifier is expecting above the audio band (at least for us old people) and this is taking more power than expected  and creating the buzzing by subharmonics or by overloading the supply.  I actually think this is more likely than DC bias... because I very much doubt these relatively inexpensive amps are DC coupled. 

 

[stillwater]

Also -- if the Pyle amplifiers were buzzing in the absence of a chromecast signal, then that might indicate that the HDMI converter is outputting something when it is not supposed to output anything.    Using a multimeter to measure its output (with both AC and DC ranges) in the absence of a music being cast to the chromecast would tell you a lot without risking another amp.   You could compare the output of the known good one and the possibly bad one.  Of course it might take days for the problem to reoccur...     Full volume is probably around 1 or 1.5 volts AC.   Without any input it should be close to zero AC.   (DC was discussed previously). 

 

But this is not dispositive because it might require some "exciting" for the unwanted oscillation to occur...    Which could explain why it took a few days for the right input to appear.   (It's possible some new program material or music type was played that hadn't occurred in the past 2 years and then again with the new amp... I'm clutching at straws here... 

Edited January 29, 2022 by stillwater
additiona though re "exciting"

[gzahar]

Do your neighbors ever complain about the volume?

[DaveStLou]

@asbril If it comes to getting considering replacing one or more of your Chromecasts and you're using it only for audio, you may want to consider a Chromecast Audio device. Google quit selling them years ago but they are still available on eBay for about $50. Since it has a mini-jack out, you can eliminate the hdmi converter if you're going to RCA. I bought 3 of them years ago and have had no issue. Just a thought.

They also support digital out if that's an option.

Edited January 29, 2022 by DaveStLou

[DDavidson]

Pick Up a inexpensive Ground Loop Isolator it eliminates ground loop noise between the audio source and Amp. For use with portable devices that have RCA audio outputs, including pre-amp outputs