Yes! It is exactly what you described. White noisish hiss in mid-high frequency region.If it is the same as I observed, it;s not anything close to a 50/60Hz. It's more like a broadband white noise centered around the 2.5k region. Only shows up on sensitive drivers (in my case, 12" waveguides).
Infineon calls it out in their design whitepapers and I mentioned it in the 2nd paragraph here.
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Topping PA3s Review (Desktop Amplifier)
Does anyone have a channel misbalance under 1/4 volume. It seems that right channel is very slow to come up to the match volume of the left channel. I worked around it by lowering the volume of the DAC but i was wondering if there is a way to fix this permanently? Another thing i noticed with...www.audiosciencereview.com
Signal needs an analog ground ref near the chip or else stray capacitance causes injected noise. Topping uses the mode without compensation in SE, so the chip does not sample AGND. Just acts as a transistor amp like proper old school design instead of using basic on-die filtering and signal conditioning.
ETA: IIRC I want to say that there was also an op-amp in an inverting output mode in SE operation which took signal after input. So the poor pot can strike twice there? I admit, been a hot minute since i was really inside the amps. Been sitting next to my speakers just... doing amp things.
Long story short, the board deviates a pretty havily from the infineon whitepapers and infineon;s own eval options so there were def cuts to hit a price point and keep a heavy chunk of profit for intl sales.
That said, the infineon eval kits are not worth the price diff because (atr least back when i was researching) I want to say they were 25%+ more and no PSU and no case?
I don't think it's anything external because it comes even without any interconnect cables connected. A little bit of noise like that is common among most AB class I've experienced, but not really so for decent D class amps.
I thought it was weird that it only comes when unbalanced input is selected. On the contrary my recently bought Topping B100 monoblocks are very silent from both inputs.
Thanks guys for your valuable opinions.