[PROBLEM] HiFiBerry DAC+Pro and Amplifiersettings

[lissid514]

Hello Forum, I run moOde via a Raspberry Pi 3b+ with the sound card HiFiBerry DAC+ Pro.

The amplifier of the connected active speaker (Nubert nuPro A300) develops a high temperature in standby. In addition, the speaker emits a "noise" in standby. Have I selected settings (see screenshot) that are the cause of this?

Thank you very much for your support! Best regards! Peter

   

[Tim Curtis]

Why do you think that moOde settings are causing high temp and noise in your nuPro device?

The electrical signals sent by the Hifiberry device are line level voltage and amperage which are super low.

[Nutul]

The amplifier of the connected active speaker (Nubert nuPro A300) develops a high temperature in standby (...)

This is the typical (and hence expected) behavior of class-A / AB amplifiers... roughly 75% for class-A, and 50% for class-AB of the stand-by (no signal) power goes into heat... My PreSonus active studio monitors are the same... they do not burn, but I believe their (amplifier) temperature goes beyond 60 degrees when in "stand-by". Actually, I believe that running them full-throttle could indeed lower their temperature... ;-)

Cheers, Al.

[lissid514]

Why do you think that moOde settings are causing high temp and noise in your nuPro device?

The electrical signals sent by the Hifiberry device are line level voltage and amperage which are super low.

Basically, I did not locate the cause at moOde, but merely formulated the question for a possible explanation as a layman.

In another context, I was told that the ALSA options should be set at about 95% - to prevent damage to the amplifier. Unfortunately, I asked only when the amplifier of the speaker has already been damaged.

[lissid514]

The amplifier of the connected active speaker (Nubert nuPro A300) develops a high temperature in standby (...)

This is the typical (and hence expected) behavior of class-A / AB amplifiers... roughly 75% for class-A, and 50% for class-AB of the stand-by (no signal) power goes into heat... My PreSonus active studio monitors are the same... they do not burn, but I believe their (amplifier) temperature goes beyond 60 degrees when in "stand-by". Actually, I believe that running them full-throttle could indeed lower their temperature... ;-)

Cheers, Al.

Hi Al, if the heat generation is normal, I'm reassured. I just wanted to get to the bottom of the cause to thereby prevent an error. Thank you for your comments! Greetings, Peter!

[Nutul]

The amplifier of the connected active speaker (Nubert nuPro A300) develops a high temperature in standby (...)

This is the typical (and hence expected) behavior of class-A / AB amplifiers... roughly 75% for class-A, and 50% for class-AB of the stand-by (no signal) power goes into heat... My PreSonus active studio monitors are the same... they do not burn, but I believe their (amplifier) temperature goes beyond 60 degrees when in "stand-by". Actually, I believe that running them full-throttle could indeed lower their temperature... ;-)

Cheers, Al.

Hi Al, if the heat generation is normal, I'm reassured. I just wanted to get to the bottom of the cause to thereby prevent an error. Thank you for your comments! Greetings, Peter!

Hi Peter,

careful with "my assumptions", as I do assume the amplifiers of your speakers are indeed class-AB as mine. If, OTOH, they are class-D, then you must investigate, as class-D's usually dissipate little to no heat...

P.S.
The ALSA thing is, IMHO, a hoax... you cannot damage an amp which accepts line-level at its inputs, with a device that also provides line-levels at its outputs. The only way you can get higher levels in the signal path is by having -another- amplifier in the signal chain.
Just my 2c on it, anyway.

Cheers, Al.

[TheOldPresbyope]

Hi, Peter.

I'd think the first people to ask about heating issues are Nubert staff themselves, via their forum.

Of the amplification process, i cite this quote from a 8moons.com review (because the review was published in English, not German).

With that in mind I asked Markus Pedal, key developer in the nuPro range, what distinguishes their so-called digital amps.

[Markus said] "As you know, class D generates a PWM signal by comparing the analog signal to a triangle wave. The result is a signal with two amplitude states at variable pulse width. It's neither fully digital nor analog but a type of hybrid which shouldn't be called a digital amplifier. In our nuPro models there's no D/A conversion after the DSP stage which mathematically converts incoming PCM data to PWM which now switches the output transistors directly. Unlike conventional class D this is purely digital [hence NAD and NuForce refer to their equivalents as direct-digital amplification – Ed]. The elimination of a D/A stage creates astonishing S/N ratio particularly when the digital inputs are used to avoid conversion losses."

[the reviewer added] To reiterate, the most direct input path is via digital since the analog input relies on conversion to digital by Cirrus Logic CS5364.

Bottom line for me is the speakers should not get hot with zero audio input. The German-language spec sheet says the standby power consumption is

Standby-Leistungsaufnahme 0,4 Watt

I'm intrigued by this sentence in your original post

In addition, the speaker emits a "noise" in standby.

There should not be any noise. What is the nature of it? A broad-frequency hiss-like sound or a low-frequency hum-like sound? 

The latter in particular could be hinting that a ground loop exists in the wiring interconnecting your Pi/DAC, your Nupro speakers, and their respective power sources. An unwanted AC signal generated in the group loop could be driving the Nupros continuously even with zero audio signal from the DAC. This, in turn, could cause both "noise" and heating.

Or not. I'm just conjecturing here in the face of almost no information.

Quick tests: 

• Do the speakers get hot when they're disconnected from the Pi/DAC (or when the Pi/DAC is disconnected from its power source)? 
  
• Do they get hot when they're connected to some other AC-powered line-level music source, a CD player perhaps, via the same aux-input RCA connectors?
  
• In either case, does the noise go away or does it remain?
  

Regards,
Kent

[lissid514]

Hello, I realize after your feedback that I am rather naive to the matter and, if I had thought logically, could have fathomed one or the other circumstance myself.

I will now try to use the process of elimination to narrow down the problem - if it is one at all (as far as I understand...)

@Al: I am grateful for every hint and will not derive any claims from it. I take responsibility for my own actions!

@Kent: Thank you also for your efforts. I realize that things are much more complex than I imagine them in my world

Greetings, Peter!

[lissid514]

Hello, I had contacted nubert in parallel in this question. The support has recommended me a mass separation filter. In response to my question, the support team also told me that the optical connection of the speaker is to be favored. Now I have replaced the existing sound card with a HifiBerry Digi2 Pro sound card. And lo and behold: the noise has disappeared!