New SGCD loud pop/thump when changing to/from HT input?

Your PS Audio device has been like this since brand new, and now it’s over one year old. Whilst I admire your patience, I think it’s time to look somewhere else for peace and happiness.

Why would you guys ever change inputs or connect or disconnect cables without turning the volume level down to zero or muting the output? You have a remote so how hard can it be if you know a problem exists to just avoid it instead of continuing on.

Are you serious? You have got to be kidding.

I can change sources with my Yamaha all day long and plug in my head phone anytime without even a glimpse.

Even the Sony IPod docking station ten years old of my son takes any switching of sources and sudden docking / undocking without a glimpse.

Everything without muting.

A pre Amp is a switching device that is supposed to make this work without manually muting.


Not sure if you are aware, but the source switching and switching the speakers of when inserting the headphone jack-plug, is performed digitally controlled.

The source select dial is a multi purpose input device for the digital control unit.

So all issues reported could potentially be resolved by a firmware update, the unit could even be programmed to mute before switching.

Best regards, Rudolf

Mute does not resolve the issue. I have the latest firmware at the moment (mute -> HT input -> unmute) and still there is a loud thump when it unmutes. Large amount of DC voltage builds up on the output and when the relay connects the output you can hear the thump from the right speaker. Left channel is dead silent at the same time. So this is definitely SGCDs fault or design flaw. :frowning:

Are you using XLR or RCA for input 1?

Sorry Brodric, I should have addressed the question to @spezwend,

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The reason I ask is that XLR is shared with input 1 RCA.

I have posted my review of the Dac / Pre. I am bringing an elaboration of what i consider a major problem. This may also serve as a warning to any others that use the HT setting.

Switching from the Coax (music server) to the HT (analog 1) causes a horrendous thump. This shows up particularly with the HSU 15" sub i use via RCA outputs. I am sure that the woofers and amps in our ML Expression are not happy either.

The original input/volume setting of 76 has been changed, as has my whole HT system, to allow a lower setting to be used at 61. When switching from listening to music to the HT, the thump is so bad i think i may blow out a window. I am on a slab, and it resonates and scared the crap out of our dog, and my wife. She literally jumped out of her seat (Calif…thought it was the start of an earthquake). At 76 it was really awful, at 61 it still pounds our walls and is bad.

I am using the mute button prior to making the switch, but it is a bad design “feature”.

It does not make the same thump switching back to the coax.

Thank you


I’ve only used analog 1 xlr with external dac and usb input… didn’t notice any thump switching between them but I’m not using HT bypass.

I did notice a thump when muting/unmuting. It’s the only annoying thing I noticed about the gain cell dac. It’s otherwise very polished and free of little annoyances I’ve noticed on some other dacs like clicking when switching from pcm to dsd etc

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FWIW here are a couple of files that have audio. Please ignore the video. THere was NO signal playing prior to the switching. Please dont play this on your big system. I had trouble recording the size and impact on my phone, so please only turn up the volume to hear the thumping gradually. There is resonance after the thumps, that is my house shaking.

Switching from Coax 6 at 0 volume to analog 1 at vol 61 again, no signal. Sub is connected via RCA, main speakers via XLR.

Note that the clicking is my mains speakers coming up as they were at zero signal before the recordings. the continuous thump is (me pressing the analog button), and it sends that sound through my system.

Again, sorry about the poor quality, it may take a couple tries to here this. it is more obvious when displaying waveforms with a video editor. This was made with Microsoft Movie Maker via Win 10…sorry…

You may notice that in the second recording, the thump gets quieter with each press of the analog 1 input button…dunno…

Sorry to hear about that!

Can you let me know what firmware you have? Feel free to reach out to me at

(This got bumped to me from another customer - Just realized this is 2 years ago. I hope you got helped by then actually!)

@Elk Maybe you want to merge this one also with the " New SGCD loud pop/thump when changing to/from HT input?" thread.

Best regards, Rudolf

Thanks, Rudolf!

You are correct in keeping it all in the same place.

You’re right and that’s how the SGCD works to. You can switch between inputs all day long without any glitches or noises.

The confusion happens when, for some reason, when they are switching in and out the HT bypass feature. When this happens the inputs are switched and the volume fixed. Otherwise, it’s no different than simply switching inputs.

Perhaps their source has some DC on it (a possibility). On your Yamaha it probably wouldn’t matter because they use coupling caps to block DC. On ours we don’t in an effort to keep signal purity.

It’s just a guess and I am working with the customer now.

One easy was to check is to disconnect the inputs and try switching between sources. If the SGCD was at fault, then without any sources connected you’d still get a thump. I suspect if they try this they’ll note there’s no thump.

Testing that right now as we speak, report in 30 min.

Report: HT mode thump test.

Test item: Stellar Gain Cell DAC
FPGA: 1.04
230 Vac European Unit


  • XLR (Analog 1): nothing
  • RCA 1 (Analog 1): AudioQuest RCA Jack Noise-Stoppers, see top picture
  • RCA 2 (Analog 2): AudioQuest RCA Jack Noise-Stoppers, see top picture
  • RCA 3 (Analog 3): AudioQuest RCA Jack Noise-Stoppers, see top picture
  • I2S (Digital 4): empty
  • Coax 1 (Digital 5): AudioQuest RCA Jack Noise-Stoppers, see top picture
  • Coax 2 (Digital 6): AudioQuest RCA Jack Noise-Stoppers, see top picture
  • Optical (Digital 7): Technics SL-P477A, renamed to “Technics CD”, interconnect: 2 m Atlas Element Optical
  • USB (Digital 8): iMac, renamed to “iMac”, interconnect: 5 m Atlas Element SC USB


  • RCA: AudioQuest RCA Jack Noise-Stoppers, see top picture
  • Power amp, speakers: Yamaha MSP5 (Active)
    Amp sections: LF 40 W + HF 27 W
    Rated frequency range: 50 Hz to 40 kHz
    Interconnects: Pair of 1.5 m Atlas Element XLR cables
    Set to full volume.


  1. Enabled HT bypass mode with volume set to 76
  2. Let USB, digital 8 input, “iMac” play for 15…30 minutes at volume 10-15
  3. Switch to HT bypass enabled input
  4. Switch back to USB, digital 8 input, “iMac”
  5. Repeat steps 3 and 4 multiple times
  6. Let Optical, digital 7 input, “Technics CD” play for 15…30 minutes at volume 10-15
  7. Switch to HT bypass enabled input
  8. Switch back to Optical, digital 7 input, “Technics CD”
  9. Repeat steps 3 and 4 multiple times
  10. Switch to other Analog Channel
  11. Switch to HT bypass enabled input
  12. Repeat steps 10 and 11 multiple times
  13. Removed the USB cable to my iMac to check if problem persists with no galvanically connected source
  14. Changed polarity of the Yamaha active speaker power plug to check if problem persists with NO galvanically connected source

Repeated above sequence for Analog 1, Analog 2 and Analog 3 (each set into HT bass mode, volume 76).


For HT mode on any analog channel the same observations were made. There is no difference.

  • When switching from either Optical, USB or Analog channel:
    1st time into the HT mode channel:
    Lower frequency medium audible volume, less then in @spezwend video, thumb.
    (note: my speakers are specified only till 50 Hz bottom frequency, which is probably at -6 dB)
  • When switching back to the original channel, out of HT mode channel:
    Little higher frequency medium (same) volume thumb.
  • Switching repeatedly (2 to 5 sec intervals) in and out of HT mode channel, the thump volume becomes less and less, till it settles in at low but audible noise
  • All thumps consistently on the right channel
  • The thumps were at quite lower volume in my system then in @spezwend system, but they were definitely there
  • It was very well possible to reproduce the phenomena
  • The phenomena remained even with NO external source galvanically connected (USB cable unplugged)
  • The phenomena remained after changing polarity of the active monitor

With no external source, even with noise stoppers covering the HT mode input channels audible thumps are observed, when switching back and forth the volume of those thumbs decreases, but the thumps remain audible.

Based on my observations and the voltage level videos of @spezwend.
Something seems to be charging and discharging in a 15 min frequency, causing the DC voltage the right channel output to rise and fall in a e-curve (natural logarithmic) manner. The Thump volume seems in direct relation with the DC voltage level.

With HT volumes at the default “25” value I could hear absolutely no thumps.

There are absolutely no thumps when switching between non-HT mode inputs.

The thump I heard initially when connecting my headphones disappeared. Or the thump was covered by the noise the relay isolating the outputs made. That relay switches the moment the headphone jack is inserted.

The volume of the thumps may be louder or lower depending on the amplifiers / speakers that are connected to the output.

Technical speculations, nothing more:
I don’t know the electronics diagrams, but the absence of any analog sources and additional noise protection strongly indicates that the thumps are generated by the Stellar Gain Cell DAC when switching to and from HT mode analog channel.

Maybe it’s only on 230 V units, and some components in the power supply or other auxiliary circuits might not be up to the task.


Maybe. 230V Export units fleet wide seem to be more problematic than US spec units.

My only inputs are an NPC and a PWT - hopefully they are not having DC issues.

I get a right speaker thump at volume 14 (very audible but not window shaking) when

  1. switching from digital to HT and
  2. when unplugging my headphones.

I only performed the HT test described above for this thread - normally do not use it. I had written off the headphone thump as a product anomaly that I have to live with. If you do come out with a firmware fix I’d like to try it.

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