Hissing from Aiyima A70

[NovaWasp]

Hi, I'm new here. I've read a lot of reviews and enjoy the YouTube vids.

Here's the issue. I have the following:
Aiyima A70
48 volt 10 amp power supply
Fosi SK02 connected with 4.4 to xlr
USBC to my PC for source.
Polk ES20s

If the volume is maxed on the A70 there's no hissing using the XLR. If I use a headphone to RCA there is hissing at all volumes, but noticeable at high volumes. If I switch to something like my cell phone off of a dongle style DAC, no hissing. If I connect the SK02 to just a USB power supply and optical in, no hissing. In the optical in scenario the signal is coming from my PC via a ART USB Phono plus.

This is driving me insane. Why does it not hiss at full volume using the XLR? It's useable, I have volume control on the SK02. Would something like the Fosi ZD3 with a separate power supply not have the issue?

 

[amirm]

Your headphone is way too sensitive for a speaker amp setup. It is natural to hear noise that would not otherwise be audible on a speaker. Good headphone amplifiers have far lower noise for this reason. As to XLR, it has higher output so better signal to noise ratio.

 

[Guddu]

Your headphone is way too sensitive for a speaker amp setup. It is natural to hear noise that would not otherwise be audible on a speaker. Good headphone amplifiers have far lower noise for this reason. As to XLR, it has higher output so better signal to noise ratio.

super quick and easily done

 

[NovaWasp]

Thanks, I appreciate it.

 

[AnalogSteph]

If the volume is maxed on the A70 there's no hissing using the XLR. If I use a headphone to RCA there is hissing at all volumes, but noticeable at high volumes. If I switch to something like my cell phone off of a dongle style DAC, no hissing. If I connect the SK02 to just a USB power supply and optical in, no hissing. In the optical in scenario the signal is coming from my PC via a ART USB Phono plus.

This is driving me insane. Why does it not hiss at full volume using the XLR?

Because the balanced connection works as intended and is suppressing common-mode signal components. The unbalanced connection over the 3.5 mm to RCA cable has no way of fending those off, and so you get to experience the ground loop between the PC and Aiyama PSU in its full glory. The hiss you are hearing is actually switch-mode power supply noise. (JBL 305 owners who ever dared to used the unbalanced input may be familiar with this phenomenon.)

Once you are switching to an optical connection and a floating USB charger, there's only a minimal amount of leakage currents going around, but the main ground loop that was bothering you is severed. The phone with a dongle DAC is a floating source, so no ground loop there either.

 

[NovaWasp]

Nice to put a name to the issue. Sounds like ribbons blowing in a hurricane. It's interesting that it stops at max volume on the A70. I appreciate the info. All of my electronics knowledge is electric guitar based.