TOPIC: SHD Studio - Hum Noise

Hi all!

I recently added the SHD Studio to my system and while it is working properly (wow BTW!), it is introducing hum noise that is transferred over the digital coaxial cable to the DAC, and from there to the Amp.
The case of the SHD Studio is at 150V at very high impedance (Mains are 230V), so I suppose it is coming from the switched mode power supply.
While the hum noise is only noticeable at very low level, it is something I want to have fixed. Any suggestions?

Processor: MiniDSP SHD Studio
DAC: Schiit Modi 3

Thanks!
Sebastian

Hi all!

Additional information: I tried with another switched mode power supply with the same polarity and same voltage. The SHD-case voltage is then only 40 V to GND (with very high impedance) and the Hum-Noise is gone!
BUT: The sound is not as good as with the power supply that comes with the Minidsp SHD.

Are there any tricks I could try to reduce the high case-potential due to the power supply which is causing the hum noise? Any thoughts?

Thanks and kind regards
Sebastian

Hi Sebastian

Something isn't right here... what do you mean 150V? The case is right now earthed as per safety standards. i.e. the earth pin goes straight to the earth. If you see any voltage, something is definitely not right. Are you sure that your outlet or equipment downstream correctly earth correctly? Maybe worth a trial... We've never seen/heard of issues with grounding on the SHD so far...

Feel free to start a tech support tix with our team to help. (support.minidsp.com)

Devteam

Hello!

Thanks for the reply! I'm sure that my Earth connector is working correctly, since I'm one of the crazy guys that also watch for the polarity of the mains supply connector and need to disconnect ground to do the measurement of AC-Voltage between the case and the ground to get the polarity right.
The high (but high impedance) Voltage present on cases is typical for switched power supplies without case-grounding and does not represent a hazard to humans due to its high impedance. The Power supply of the SHD Studio is making use of the ground connector, but I have not checked if the ground is fed through to its output. Since the case seems not to be grounded my guess is that it is not fed through.

Remember that I'm talking about the Studio-Version of SHD with an external Power Supply. Are you sure the case of the should be grounded in that version? If yes, I will start a support ticket.

Thanks and kind regards
Sebastian

Just measured the resistance between the 12V output and the Ground Connection: it is 50 kOhm.