Left mono amp clip?/shutdown on at least 1 song

Audio Gear Talk Lumin
1

I am not sure I have this problem with my Lumin U1 Mini, the amp, ROON, speaker, power, or any thing in the chain.
My system:

  • Digital front end streaming: fiber connection to EtherGen->Lumin U1 mini (latest firmware) ->USB->Matrix->IS2 to PSAudio DSD, plugged into PSAudio Stellar power regen.
  • Preamp- CJ ACT2.2- plugged into PSAudio Stellar.
  • Amp- 220 watt tubed Monos plugged into PoweWedge.
  • Speakers: SoundLab
  • Digital Playback: software Roon/Mimiserver, Dell desktop PC, music files on HDD.

The problem: When I play one DSF file of an album at volume level 67/100 or higher, the song started playing then at around 1:17 minute the left mono amp shut down and restarted. Other files/songs in the same album do not have this issue.
I have done the following to isolate the problem:

  • swap output L and R from preamp, the problem did not follow to the R channel.
  • both ROON and Mini server had same issue.
  • swap input tubes of mono amps, left amp still had problem.
  • lower volume to 60/100, no issue.
  • played same song but on WAV format, no issue.

I suspected it could be the L amp, I had it checked, but could not find any issue with it. It could be that the signal spiked along the digital chain and clip the amp.
I may try the following to further isolate:

  • swap speaker cables to see if amp/speaker interaction problem.
  • swap output tubes of amps.
  • copy the song onto disc and play from DVDA player.
  • swap out mono amps to using stereo solid state amp.

Any suggestions what I should do to troubleshoot? One solution is to delete that song or any songs that caused the amp shut down. Thanks for reading and any comments.

2
  1. Check for clipping.

  1. Bypass the Matrix I2S, use Lumin USB output to PS Audio.

  2. Also try applying -3dB headroom, see if it fixes the problem.

3

Thanks, I can try #1 and 2, but on #3, if i reduce headroom by -3db, would my sound level be lower overall from my speakers? then if i need to crank louder I would be back with same issue?

4

Yes

This may be affect by which item is the culprit.

5

My findings:
#1 show clipping (red) through out the song.
#2 USB input clipped amp and shut it down.
#3 Reduced headroom by -3db could play whole song but still show clipping. I tried reduce by -2db but increase vol to 69/100 then shut amp.
This song (Hotel California) has high headroom. Other songs in this album have no clipping signal.
Conclusion: reduce volume when playing this song? Any other alternative?

6

I did another test, I swapped speaker cables but the L amp did shut down so for some reason it could not handle clipping as good as the right mono.

7

This is probably the reason. The PS Audio DS is meant to be used at volume 92, according to its designer:

Hopefully it does not clip at volume 92, even without adjusting headroom in Roon DSP.

8

If you still see clipping at -3dB you’ve got to go even lower, so try -4 and so on…

EDIT:
Are you using DSP upsampling when experiencing the problem?
That could cause intersample overs, necessitating headroom adjustment.

If not, then your source file may contain the clipping and all measures won’t change that.
You may want to analyze your file with XiVeros’s MusicScope or Audacity to find out…

9

I do not use DSP upsampling.
Since my speakers are highly insensitive and demand current and power from amps, for few songs in my music DB have clippings, I may have to play those at lower SPL to overcome the issue. Thanks for suggestions about analysis software. XiVero business was closed. I am not sure Audacity can handle DSF file. I can rely on Roon’s headroom to help with detect clipping files.

10

You can still download and use MusicScope for free…

11

Yes, I will try to set PS Audio DSD volume at 92 and see, but how about volume leveling in Roon for Lumin, it is off now, should I set it to Auto or track or album?

12

Turn off volume leveling.