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Amazon Prime Video kills my amplifier

LarsS

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#1
Here's an odd problem I've encountered with Amazon Prime Video and The Expanse series season 1, episode 1 at about 09:20 - 09:25 min into the episode.

Audio through my Norma integrated amplifier with input either through the built in DAC or external Topping D50 DAC. Browser either Chrome or Firefox all with same result.

Every time this part of the episode is played my amp engages into DC Protection with flashing LED. Need to turn amp off and on to fix.

What coukd be the reason? Has Amazon screwed up audio in this series? Anyone else with Amazon Prime video encountered this behaviour or is my amp too sensitive?

1567758707760.png
 
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LarsS

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#2
Played episode on my second system. Amplifier is a Pioneer A6 integrated one. Everything works fine on this system which leads me to one of two possible conclusions.

Either my Norma Revo IPA-140 is too sensitive or the Pioneer A6 lacks DC protection.

1567758550583.png
 
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RayDunzl

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#3
Every time this part of the episode is played my amp engages into DC Protection with flashing LED.


Some wild swings around 9:20

(the time on the track here doesn't correspond to the video time)

1567760416936.png


About 350ms is marked above, corresponding to one cycle of a frequency of 2.85 Hz.

That's almost DC.




Apply 5Hz low pass 48dB/octave to all that I recorded, with a 20Hz tone for comparison at the bottom:

1567760909795.png
 
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solderdude

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#4
Either my Norma Revo IPA-140 is too sensitive or the Pioneer A6 lacks DC protection
Correct... The Norma may have a DC protection that is either too sensitive or is too high in frequency or the Pioneer lacks DC protection or it has DC protection but isn't as sensitive or the protection doesn't react to subsonic frequencies.

Maybe a high pass filter before the Norma would solve the issue.
Maybe playing the same part of the video at a lower volume could help as well.
 

Willem

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#5
It is one of the reasons amplifier designers like Peter Walker preferred some bandwidth limitation. Your speakers will not like such signals either.
 

RayDunzl

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#6
The entire segment I recorded, top, and the same source low passed at 5hz, bottom.

1567761714247.png
 

LarsS

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#9
Correct... The Norma may have a DC protection that is either too sensitive or is too high in frequency or the Pioneer lacks DC protection or it has DC protection but isn't as sensitive or the protection doesn't react to subsonic frequencies.

Maybe a high pass filter before the Norma would solve the issue.
Maybe playing the same part of the video at a lower volume could help as well.
Lowering volume does not help. Not sure where/how/with what I'd implement a high pass filter? Needs to be either before or after DAC.
 

Willem

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#10
I have been measuring the in-room response of my system, and it has some pretty nasty lingering peaks at 13 and 26 Hz or so, even though I am using a DSpeaker ANtimode 8033 to equalize the subwoofer. These peaks probably correspond to the length of the room, so I am now planning to use the subwoofer's low cut filter to reduce deep bass output. There is no real music at such ultra low frequencies, and I am not interesting in nuclear explosions and the like. The ANtimode has a 15 Hz low cut filter, and the power amplifier is somewhat bandwidth limited, but neither seesm, to be enough. I use a high pass filter in my RME ADI-2 DAC but that does not seem to be enough.
 

solderdude

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#11
Lowering volume does not help. Not sure where/how/with what I'd implement a high pass filter? Needs to be either before or after DAC.
When the volume control is turned down to really low levels, does it still happen ?
With the volume turned down a lot it should not happen.

a high pass needs to go between the DAC and amplifier but one can also highpass before the DAC if the sofware allows this.
Would set it as steep and 20Hz at first attempt
 
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Willem

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#12
I suppose you mean a high pass filter. A simple version would be a Harrison Labs FMOD, but that may not be enough.
 

LarsS

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#13
When the volume control is turned down to really low levels, does it still happen ?
With the volume turned down a lot it should not happen.

a low pass needs to go between the DAC and amplifier.
You're right, works until 9 o'clock (low volume), kicks in at 10 o'clock.
 

solderdude

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#14
When it is only this movie and you play it back using a player that has tone control you can probably use software filtering.
If it happens often with music and videos a high pass filter will be the best solution (cheaper than another amp)
 

RayDunzl

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#15
I wonder why modern DAC chips simply don't cut everything below 20Hz with brickwall filter.
Then you'd miss out on those 16Hz notes from the 32 foot pipes.

1567765242672.png
 

AudioSceptic

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#17
Lowering volume does not help. Not sure where/how/with what I'd implement a high pass filter? Needs to be either before or after DAC.
You are watching this on a computer? Does the same problem happen if you watch on a TV, with audio routed from the TV out to your DAC or amp?
 

RayDunzl

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#18
Here's the spectrum of the whole snippet:

1567807789852.png


The absolute level means nothing here, but a relative 20dB peak (to the typical content) at 2Hz is eye opening.
 

scott wurcer

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#19
Then you'd miss out on those 16Hz notes from the 32 foot pipes.

View attachment 32753
That's funny. Back in the early 70's we had the stupid idea to borrow 4 pairs of Bose 901's and Crown DC300's to drive them for our first showing of 2001 on campus. You can imagine the smoke after about 30sec., it turns out optical sound tracks can have lots of sub 10Hz content and it was back to the typical Altec system.
 

restorer-john

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#20
Played episode on my second system. Amplifier is a Pioneer A6 integrated one. Everything works fine on this system which leads me to one of two possible conclusions.

Either my Norma Revo IPA-140 is too sensitive or the Pioneer A6 lacks DC protection.
The Norma Revo IPA-140 has over sensitive or just badly designed DC protection.

We also know this specification is likely misleading....: Frequency Response: 0 Hz – 1.8 MHz (-3dB, non filtered)

Put a series 2.2uF capacitor in line (each RCA hot) with the external Topping D/A converter. Coupled with the input impedance of 10K, that would likely solve the problem for you without impacting the bottom octave too much. Without a subsonic filter, the internal D/A converter connection is harder to solve.
 
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