How to improve an existing SMPS to use it with class D amplifiers

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#7
Mods are certainly possible but they're not necessarily easy. They have been fun for me though. Meanwell are a Taiwanese outfit, their quality is better than the normal China mainland sourced supplies I tend to use, but even the mainland-built supplies can deliver the goods if ultimate reliability isn't a major concern.
 
#13
Ah thanks I had totally forgotten about that 🙂

The AL value for those cores is 42. In my design I went for a target inductance about 13uH. This translates to 18 turns on these cores. According to my sims, we want about 30mohms DCR for optimum damping.

Looking at the mechanical data the core cross-section is 3.8mm X 6.35mm so a single turn would be about 20mm in length assuming zero wire diameter. Thus 18 turns is going to be 0.4m, roughly. We therefore need wire that's 75mohm/m and that works out to be 23AWG, allowing for terminations.
 
#15
Thanks abraxalito!

And yes, I would like to see the noise measurements before and after adding noise suppression. I have a scope but its needs some serious repair work. For now, can I be certain of some real measured improvements before I go ahead and purchase the the parts?
 
#16
I don't have those particular supplies nor anything likely to be able make reliable measurements at ultrasonic frequencies. But in simulation the filter does give substantial HF reduction. If the switching noise you're hearing is common-mode induced then this filter won't have any impact on that - for CM noise reduction you'll need a CM choke.
 
#17
Okay, I think I'll wait until I can take measurements.
And, sometimes its hard to audibly determine the origin, of the effect that I'm hearing.

The meanwell spec sheet states that noise+ripple measures 120mvP-P(max)

The Sima 11 linear supply states that the ripple on the DC output is 35uv RMS. I'm using 2 of these in Class D mono blocks.
 
#18
abraxalito said:
Ah thanks I had totally forgotten about that 🙂

The AL value for those cores is 42. In my design I went for a target inductance about 13uH. This translates to 18 turns on these cores. According to my sims, we want about 30mohms DCR for optimum damping.

Looking at the mechanical data the core cross-section is 3.8mm X 6.35mm so a single turn would be about 20mm in length assuming zero wire diameter. Thus 18 turns is going to be 0.4m, roughly. We therefore need wire that's 75mohm/m and that works out to be 23AWG, allowing for terminations.
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Sounds well. How do you connect them?

(But as you mentioned, CM noise is a different story, and usually this is the more critical coupling mode.)
 
#20
voltwide said:
I wonder what kind of noise you are hearing. Do you hear it through the speaker of the powered class-d-amp or does it emanate out of the power supplies directly?
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From the speakers - treble characteristics, strident, etch, course etc.

I do listen any music that I like, regardless of the recording quality so problem could be starting from here.
The Class D amps that I have are very revealing of the recording detail and ambient type and I love this regardless.

I have no absolute conclusion yet, subjective or objective but planning on lots of experimenting, next is listening to CD vs LP through Class D with SMPS and Linear supplies.
 
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