mononoaware
Addicted to Fun and Learning
- Joined
- Apr 6, 2021
- Messages
- 816
- Likes
- 669
Hi everyone,
Just thought I should clear some things up.
Noise directly from device (switched on in isolation):
- SMSL SU-8 V2: with ear to DAC constant quiet whine, silent from listening position.
- Apple TV 3 streamer: with ear to ATV, silence.
Noise from ATV -> Optical -> DAC (SU-8 V2) + Monoblocks connected to speakers - all switched on
- XLR outputs: silence from speakers.
- RCA outputs: “coil whine” like sound from speakers, audible from listening position (when nothing is playing, during quiet passages in audio).
Temporary fix: With everything else on, Turn off the ATV. The noise stops.
-
At first since the SU-8 switched on in isolation makes a coil-whine noise (quiet auxiliary sound from device itself), I first assumed this is the same noise coming from the speakers when using the RCA outputs from DAC.
But after further troubleshooting and understanding of the components, it is most likely a ground loop due to the ATV acting like a switch for the noise.
The “coil whine” noise coming from the speakers sounded that way because the speakers used single Fostex FE103NV drivers which when given a pure/un-colored signal produce little to no low-frequencies. This is what must have taken away the typical low-frequency “hum & buzz” associated with ground loop noise, making it sound more like a high pitched whine through the speakers.
Plugged all other components into the same power board into a single wall socket and there is still noise.
Then tried plugging only the ATV to every single other Wall power socket in the room and there is still noise.
So current conclusion is still:
Only use the SMSL SU-8 V2 for its XLR outputs.
A better description of the noise coming through the speakers is like the “ringing” you hear after an extremely loud noise.
It is audible from listening position as soon as the ATV is switched on (playing AirPlay wakes it up from standby) and depending on the dynamic range of the audio content. A way I found to check this is by listening to music that fades away slowly at the end.
Currently it seems like the only option to connect to Monoblock RCA inputs is to get a decently built Streamer/DAC/Pre-amp like the Yamaha WXC-50, and connect the RCA pre-outputs to the Monoblock Power Amplifiers.
Update.
After changing the source to the M1 Mac Mini (via USB) and having the Apple TV 3 unplugged, the coil whine noise from speakers in gone.
Then the auxiliary noise (also coil whine like noise) directly from the SU-8 V2 DAC became more obvious and could be audible from listening position.
I only noticed it occasionally before when close to DAC (sometimes it is just silent) but now it is more noticeable.
I remember reading somewhere that the noise is related to the display, so I tried changing the brightness level of SU-8 display.
When noise is present, I go into menu then change brightness 1-4 (+auto display off = 0), after changing display and then time-out (returning to previous display) the noise changes in pitch and volume.
Oddly Brightness level 3 noise is the loudest, level 4 is slightly quieter, level 2 is then quieter than 4, and level 1 is quietest and inaudible from listening position.
I am currently using level 1 since I need to have a power indicator.