Swapped PSU - Gained 9dB SNR

[Theriverlethe]

So, I was bored yesterday and swapped my Corsair CX750M for an AX1200i I had lying around from crypto mining. CX750M is a "bronze" PSU and AX1200i is "platinum" efficiency. Looping a Xonar STX through an external headphone amp with three-prong plug, it looks like I lowered noise floor by about 9dB in RMAA and the card is noticeably quieter with no audio playing. It doesn't look like ripple or voltage regulation through the AX1200i is THAT much better. Any idea what's going on?

https://www.techpowerup.com/review/corsair-tx750m/8.html

https://www.techpowerup.com/review/corsair-ax1200i/8.html

 

[DonH56]

The larger supply has about 1/4 the ripple, a reduction of 12 dB in voltage. Seems like the audio circuit is sensitive to power ripple, someplace. Poor audio design IMO, but at least a new power supply improved it.

 

[Theriverlethe]

The larger supply has about 1/4 the ripple, a reduction of 12 dB in voltage. Seems like the audio circuit is sensitive to power ripple, someplace. Poor audio design IMO, but at least a new power supply improved it.

Would you characterize the first gen Xonar STX or ODAC rev.B as poor circuit design? Noise occurs even without the headphone amp in the loop, unless I use an ADUM4160 with the ODAC.

 

[DonH56]

I don't know anything about them, sorry.

 

[Theriverlethe]

I don't know a nything about them, sorry.

I mean, they're using RCA connection, which was never designed to interface multiple devices in the first place. So I'll concede the point.

 

[pozz]

Interesting example.

 

[DonH56]

Poor ground isolation is not (just) because of RCAs... Differential (balanced) connections make it much easier to isolate the signal from noise, including ground noise, but there are plenty of devices that do OK single-ended. And some that have problems despite being "balanced".