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Amazon Prime Video kills my amplifier


Addicted to Fun and Learning
Mar 23, 2016
Sweden, Stockholm
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.
So I soldered a couple of Wima 2.2uF caps on a new pair of cheap RCA-cables as you advised. Good news is that the amp no longer goes into protection mode when viewing The Expanse.

Bad news is that I have to turn the volume up to 80% and sound is truly anemic with no bass at all. Tested also with music thru Roon, unlistenable I'd say.

Oh well, I can live without The Expanse. Maybe time to look for another amplifier even though I'm really fond of the Norma.


Active Member
Sep 14, 2019
I just wanted to add this has nothing to do with Amazon. First of all, the expanse was produced by Syfy channel and later purchased by amazon. And it's also not Syfy's fault, or any company as such, but probably a mistake made by whomever mixed that series. I never heard of a streaming service that applies any form of band limiting on their content, so this mistake probably originated in the sound effects editor's room, and wasn't noticed by the guy doing the final mix.


Major Contributor
Patreon Donor
Apr 13, 2017
True. Btw, I wonder why modern DAC chips simply don't cut everything below 20Hz with brickwall filter.
Because AV surround tracks deliberately go below 20hz, as might be the case here, and big subs can reproduce it. The correct place to filter is in DSP before the DAC, which is what I do.
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