Help me understand the issue: crackle at low volumes with RPi + DAC HAT on my Genelec 8010A

[sheeple]

Hello educated electronics people,

I have an issue that I want to shortly describe.

I run a pair of Genelec 8010As and a Raspberry Pi 4 + Hifiberry DAC+ (Hardware) with piCorePlayer + Lyrion + CamillaDSP (Software) as their source. In the evenings I like to listen to low level music, and sometimes at fade-outs and fade-ins, or on very silent parts of a song, I hear an audible crackle from the speaker when it seemingly clips into silence and again into activity. I first thought it was the speaker hardware, as the issue only appears on one of the two speakers. But when I use my workstation computer for playback and its 3.5 audio jack output instead of the Raspberry Pi, I can play at even lower almost inaudible levels without any of the crackles that to my understanding appear when the speaker cannot detect an input signal anymore.

For the Raspberry Pi + DAC+ an RCA to XLR cable is used, for the workstation an 3.5 jack to XLR cable.

The laymen I am I was guessing maybe the output voltage is relevant and my workstation has something like a constant voltage on the audio jack, whereas the Raspberry HAT does reduce voltage with volume until it reaches too low levels to be registered by the speaker?

I hope you have a better understanding than I do and can point me to a solution. The attached zip-file contains an MP3 with a recording of the issue from my hand recorder.

 

[wwenze]

Maybe it isn't the speaker cutting out the signal, but the source is.

 

[Nicoff]

I once had a RPi 3 with similar HAT running RoPiee. No problems for a long time, but then similar issues started happening. I think that it was software related because RoPieee was having issues connecting with Spotify at the time.
I decided to let go the RPi and got a WiiM Pro. No issues since. No more wasting time with software upgrades either.

 

[sheeple]

Maybe it isn't the speaker cutting out the signal, but the source is.

I probably should have provided more information: I would set the volume either from the interface of Lyrion Music Server (formerly Logitech Music Server or LMS), and also tried instead to use the volume control from Camilla DSP. I know from discussions about DSP speakers that receive an analogue IN that higher input levels are preferred so to saturate all available bits. Thus I figured that lowering the volume on the Lyrion Music Server interface would reduce the voltage and thus the bandwidth of the signal (layman terms again). I tried to use LMS on full output levels and use the volume controls of CamillaDSP to set volume to low levels, but the consequences are the same.

When I hear the crackles and look at the CamillaDSP interface, the volume bars of each channel still indicate an uninterrupted audio stream.

Audio Chain: Raspberry Pi 3+ (Hardware) -> piCorePlayer (Software OS) -> Squeezelite (Software) -> Hifiberry DAC+ HAT (Hardware) -> CamillaDSP (Software) -> Lyrion Music Server (Software)-> RCA Output (Hifiberry DAC+, Hardware) -> RCA to XLR cable -> 8010A

 

[terryforsythe]

DAC+ an RCA to XLR cable is used

The first thing I would try is swapping the left and right channel cables and determine whether the crackles stay with the same speaker or move with the cable. If the crackles move with the cable to the other speaker, then it is a bad cable.

If the crackle stays with the same speaker, then it is the DAC or the speaker. But, as you noted, the speaker does not do it when you run it from your computer's audio card, so that should eliminate the speaker and narrow it down to the DAC.

If you know anyone from whom you can borrow a DAC with USB input and XLR output, I would test with that, using XLR cables, to determine whether it cures the issue. Alternatively, you can buy one from a vendor with a liberal return policy (e.g., Amazon Prime). If it solves the issue, great, use that DAC. If it doesn't, return it.

EDIT: Also, double check to make sure that the DAC hat is seated well on the Raspberry Pi GPIO header. It is a long shot, but you may try removing it and pushing it back into place. Like I said, it is a long shot, but is free to try.

 

[phofman]

What is your CDSP configuration? Perhaps the silence_threshold/silence_timeout kicking in?

 

[sheeple]

It appears to be an electronics incompatability between the Raspberry DAC HAT and the Genelec 8010A's. Instead of the HAT I checked with an USB DAC (Focusrite 2i2) and the Genelec still reproduces input with the volume control on LMS set to 1% and CamillaDSP to -10 dB. CamillaDSP defines the peaks during playback as ca. -87 dB, while with all volume controls set to maximum, which is not a proper setting as it causes overload distortion, 90% on LMS would be correct to allow headroom for EQ, it reaches -4 dB. At this low levels while sometimes only peaks are reproduced and the lower volume sections remain silent, there is no crackle.

I am not educated in electronics, but I assume the DAC HAT cuts the current when certain low levels aren't surpassed and this causes the tweeter diaphragm to move in an uncontrolled way, crackle, sort of the occasional pop when the speaker is connected to mains. I don't know if this can be solved, would need to ask the developer of the HAT Hifiberry but they are seemingly a too small team to micromanage very specific customer issues.

 

[sheeple]

Nope, as usual the problem was sitting in front of the screen. Everything is solved.

 

[Nicoff]

Nope, as usual the problem was sitting in front of the screen. Everything is solved.

Wow, that must have been a quick conversation with the developer. Sounds like user error.

 

[sheeple]

I still don't know what caused the problem, but it disappeared when I disabled CamillaDSP. So the routing goes from the Raspberry Pi -> Squeezelite and then either via ALSA mixer to the HAT Hifiberry DAC+ Pro or as an intermediary from Squeezelite ->CamillaDSP and from there -> the HAZ -> RCA-out -> Speakers.

Now there is room for wrong settings, such as sample rate differences between the elements. I guess this was the issue. I switched through a number of settings after reenabling CamillaDSP and at some point the crackle stopped. I am yet not convinced it is all stable, will see.

 

[wwenze]

Spare CPU power is a concern too, when dealing with weak CPU

 

[phofman]

Still we have not seen if the silencer was enabled in CamillaDSP and if so, whether it was kicking in. Trial/error is a tedious way of troubleshooting, it's typically better to proceed systematically.