Meanwell Single, Bipolar and Triple Output Switching Power Supplies for Audio Projects

Construction information for DIY projects, including the MS Mid Side Matrix, Elliptic Equalizer, Mastering Console, Phono Transfer System, Insert Switcher and the Dual Class-A Amplifier. You can post your baby pictures here.
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JR.
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Re: Meanwell Single, Bipolar and Triple Output Switching Power Supplies for Audio Projects

Post by JR. » Thu Apr 26, 2018 12:08 pm

mediatechnology wrote:
Wed Apr 25, 2018 11:43 am
wereoflu used the TPA7AXX-series in his minimixer which is where I found it: viewtopic.php?f=6&t=882#p10291

There's another ripple eater I recall from a Design Idea.
I'll dig, scan and post.

My goal is to have something that plugs in and works without any additional filtering.
Most of the Meanwell and TDK models I tested are great.
The simple RC required for the 24V and 48V supplies aren't a deal-breaker.
In the case of the 24V for powering relays external filtering may not be needed at all.
I haven't tried the 24V yet.
When I designed the PS for my last (big) console I used double regulation, so 3-terminal regulators on each strip and a several amp master power supply that was a glorified ripple filter using a simple pass element to put out roughly +/-19V, but that voltage was a fraction of the unregulated voltage to scrap off ripple.

If the mains sagged, this pre-regulator would sag too, to stay comfortably below the ripple.

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"Feed-forward cancellation rejects supply noise by 26 dB"

Post by mediatechnology » Fri May 04, 2018 1:23 pm

"Feed-forward cancellation rejects supply noise by 26 dB," Ken Yang.

This is one of the ripple-rejection circuits I was thinking about: https://www.eetimes.com/document.asp?doc_id=1272276

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Re: "Feed-forward cancellation rejects supply noise by 26 dB"

Post by JR. » Thu May 10, 2018 9:04 am

mediatechnology wrote:
Fri May 04, 2018 1:23 pm
"Feed-forward cancellation rejects supply noise by 26 dB," Ken Yang.

This is one of the ripple-rejection circuits I was thinking about: https://www.eetimes.com/document.asp?doc_id=1272276

Image
This sucker has been bugging me for several days... when I first looked at it with my beer goggles on I thought hey that's NF not FF, but looking at it later through coffee goggles reveals the FF, but I still see NF.

If current draw from the output causes C2 to sag, NF will cause current drawn from that output node to be reduced presumably helping lift the output, but the availability of current through that vector is modest (limited by class A bias).

Designing a PS with intentional 100 mOhm source impedance is not great, but I appreciate this is a specialized circuit.

Next if we add a capacitor to the output the RC from Rs and this output cap will cause phase shift that could interfere with the FF cancellation current.

This is cute but I might be tempted to just use the mosfet as a pass element (in fact I did use one that way to make a pre regulator for my battery powered tuner to deal with fresh battery voltage hotter than my audio power chip could handle.)

Interesting way to showcase some components but I question the utility..

JR

PS: As usual let me apologize in advance, for being a negative nellie.
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Re: Meanwell Single, Bipolar and Triple Output Switching Power Supplies for Audio Projects

Post by mediatechnology » Thu May 10, 2018 9:29 am

I had wondered about this one too.

There is another circuit I'm looking for that the author specifically called a ripple eater.
IIRC it used a series pass element and had much deeper attenuation.
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Re: Meanwell Single, Bipolar and Triple Output Switching Power Supplies for Audio Projects

Post by Gold » Wed Aug 08, 2018 7:32 pm

Here is a power supply to test console units on the bench. I got tired of the rats nest that was the HP units and a million banana plugs.

This power supply has separate Modulation and Preview bipolar 15VDC and bipolar 24VDC. There is an On-Off-On selector switch for Modulation and Preview. There is also +12VDC for lamps and relays. There will be a +5VDC eventually that won’t get a current meter. The whole thing cost less than $100 to make not including the case which I had.
D57AC90F-772C-439A-947C-3BEDE09E0CAE.jpeg
0CB2C4FC-D044-477A-A0EE-FD52C7B11F77.jpeg

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Re: Meanwell Single, Bipolar and Triple Output Switching Power Supplies for Audio Projects

Post by mediatechnology » Fri Aug 10, 2018 9:40 pm

Nice!

It's been awhile since I made some metal shavings.
I'm itching to rack up my PTS EQ monitor switcher.
The flat preamp has been done for years now.

The Pico build seems almost a year ago now.
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Re: Meanwell Single, Bipolar and Triple Output Switching Power Supplies for Audio Projects

Post by Gold » Sat Aug 11, 2018 9:13 am

Thanks. Having to test the test setup every time I wanted to work on something was a psychic barrier to getting stuff done. Even though it only took a minute or so to check it.

I’ve always been curious to watch current draw when playing program material. With a current meter on each rail I can watch them bounce up and down. Now that the PSU is neat and tidy Its easier to modify the setup investigate things like the effects of PSU source impedance.

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Re: Meanwell Single, Bipolar and Triple Output Switching Power Supplies for Audio Projects

Post by mediatechnology » Wed Oct 31, 2018 1:29 pm

I found that a 3.9 mH common mode choke works wonders on the Meanwell RS-25-48 48V supply: https://www.proaudiodesignforum.com/for ... =16&t=1016
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Re: Meanwell Single, Bipolar and Triple Output Switching Power Supplies for Audio Projects

Post by emrr » Fri Feb 12, 2021 3:03 pm

I recently finished up two projects using Meanwell PD-2515, both with audio input and output transformers.

One was 990C based make-up amps for a pair of passive EQ's, no trace of noise heard, virtually nothing registering on a spectrogram. Gain roughly 16dB to get back to unity. No additional filtering before the onboard filtering around the op amp.
On this one I learned the lesson that some isolation is required on the op amp input when certain amounts of LC interaction is present, specifically old school 'K' filter high pass networks. Those would shut the amp down within a few seconds. I experimented with a couple of methods, and this being a 600 ohm passive EQ, a 2.3dB resistive 'T' pad was all it took to fix it.

The following is rambling discovery process, sorry. An edit and buildout of my initial post.

The other is a set of API type preamps. I don't hear anything, but the spectrogram at max gain of 60dB is interesting. There is a spike around 19.2kHz, a hump centered on 30kHz, and depending on how the unit powers up, a hump at 1.7kHz, which is not always present. I just discovered 1.7kHz will go away if the 3 channels not under test have their gain reduced from max....or power cycling the whole thing...or....any number of other actions. ....and there's a 13.5kHz hump popping up.... OK, I'm in the weeds here, the 19.2K is highest at -99dBFS, the 30K is similar. The 1K7 is no higher than -104dBFS. There is background of evenly spaced frequency bars throughout the audio spectrum, all below the primary hum elements and the couple of spikes. The hum elements are unchanged with power on or off, so I'm ignoring that as environmental, they're all well under -116dBFS with 60dB gain. If I disconnect the AC cable entirely, 60 is unchanged but the harmonics disappear. This isn't something I'm used to seeing, and I'm rarely looking at audio preamps at max gain with switching supplies, it may be entirely normal for the supply type, as it's all so much lower than what I'm used to. Again, I don't 'hear' any of it.

The preamps have 100mfd filters after diodes and 1000 micro-henry inductors. The audio input transformers are (supposedly) 60dB shielded, and are mounted on the other side of steel frames relative to the Meanwell, which is in itself mounted inside a Hammond cast aluminum box that's physically distanced from the inputs. The preamp furthest from the PSU with highest sequential shielding has no less noise floor than the one closest. The output transformers are open frame Jensen 600:600's, and I do see a bit more of the 60Hz in the one closest to AC input, it's probably 6 inches away. From the Meanwell there's 50Ω/100mfd in each power leg before the preamps.

This appears to be excellent noise performance with 60dB gain in a semi-antique product.
Best,

Doug Williams
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Re: Meanwell Single, Bipolar and Triple Output Switching Power Supplies for Audio Projects

Post by mediatechnology » Sat Feb 13, 2021 3:29 pm

I had an interesting experience with the Texar and the TDK switcher.

The TDK has been ultra-quiet on everything except for the Texar where there are peaks near 240 Hz.

viewtopic.php?f=12&t=763&p=15618#p15588
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