Excess hum on all line level outputs?

Stage & Studio Power Station PS-100
1

Hi,

I get more hum into the line level outputs from PS-100 than I would expect. I’m wondering if this is normal or could it be an issue with tubes or something else? I have reseated the tubes which didn’t help. Hum and other frequency spikes are present in multiple frequencies:

  • Loudest at 50 Hz and 150 Hz
  • Power on makes things worse and also adds 100 Hz and its multiples
  • Operate seems to add ~175 Hz
  • Spike around 70 Hz is probably the fan (spike glides up on power on and glides down on power off)

To visualize my experience and the above description I tried to make a minimal setup to capture the issue in screenshots using VST frequency analyzer. Gear and connections:

  • PS-100 speaker out → PS-100 amp in AND
  • PS-100 line out / fx send / line out xlr → RME UFX → PC with vst frequency analyzer

Screenshots are shared in Google Drive folder: fryette-ps-100 - Google Drive

Variables for the screenshots

  • power on / off
  • bypass / operate
  • line out / fx send / line out xlr (balanced)
  • groudlift on / off

Used filename format: ps-100-poweron/off-(operate)-output-(groundlift).png

For comparison I used Bluguitar Amp1. Not an apples to apples but just made sure the connections and RME UFX are clean.

  • Bluguitar Amp1 rec out → RME UFX → PC with vst frequency analyser
  • filename format: comparison-bluguitar-poweron/off

Same power cable and audio cable (with TRS-XLR adapter as needed) was used for PS-100 and Bluguitar. Power cable was plugged into the same power outlet as RME UFX.

Another experiment I did to rule out PC, was to connect just the PS-100 line out → Neunaber Iconoclast → Headphones to listen if the issue was present. It was, I could hear the hum and overtones.

2

Hi @tubenoob

I have to say I am very impressed with your scientific approach. The Power Stations are not low noise devices. They contains large power transformers and a power inductor and cabling. All real electrical components are non-ideal and inductors are least ideal of the lot. The power station does an excellent job of keeping noise to the minimum for such a compact size. Certainly -60dB seems acceptable and usable to me.

These are exactly the type of measurements we do when designing a product so again hats off to you good sir.