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PO89ZB , an inline DC filter for SMPS wall warts . Preamps, HPA, Korg NuTube, etc
PO89ZB , an inline DC filter for SMPS wall warts . Preamps, HPA, Korg NuTube, etc
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Old 15th May 2021, 07:18 PM   #671
avdesignguru is offline avdesignguru  United States
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Default Question for Mark

Do you think I could/should add a TVS diode across the power jack input to the DC-DC converter to prevent someone plugging in a reverse wired wall wart supply and accidentally damaging the converter? Does the attached look correct? Am I correct in assuming the TVS does not load the supply in any way unless the input to it is reverse wired or exceeds 68V?

Oh, and the input should probably be labeled something like 18-48VDC, not 18-72VDC, correct? In the USA at least, you probably won't find a wall wart above 48VDC.
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File Type: jpg TVS Protection.jpg (110.3 KB, 370 views)
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Old 15th May 2021, 08:03 PM   #672
Mark Johnson is offline Mark Johnson  United States
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PO89ZB , an inline DC filter for SMPS wall warts . Preamps, HPA, Korg NuTube, etc
Yes, 48V seems to be about the highest. I'd definitely include a unidirectional TVS, a big ole bohunker 5000 watt device in a R-6 or P600 package with mongo hefty leadwires. Here's an example for just under two dollars: Digikey link
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Old 15th May 2021, 09:38 PM   #673
ranshdow is offline ranshdow  United States
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Originally Posted by ranshdow View Post
I have 5 of these boards left if anyone else is interested.

Now down to two.
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Old 16th May 2021, 08:42 AM   #674
ClaudeG is offline ClaudeG
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Hi Mark,

Thanks for the TVS link, always interesting...

I am not familiar with the big Mean Well SMPS and don't know if they include some kind of protection should they fail. In short, I want to make sure my VFET will be protected if the SMPS fails and nothing like 230V or whatever bad may happen / could destroy the nonobtanium output transistors.

In your experience, could it make sense to add such a TVS at the power input in case the SMPS (or else) fails? Or are in fact these devices already protected / include similar inside?

What would be your recommandation?

Many thanks for your help

Claude
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Old 16th May 2021, 10:40 AM   #675
Kartapus is offline Kartapus  France
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On most modern AC/DC SMPS, there is a lot of protection. The input can whistand the "normal" transient on an AC line (input is 85-265Vac) + abnormal transient such those defined in IEC 61000-4-5 (a TVS is used to pass the IEC 61000-4-5 test)
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File Type: jpg Meanwell AC-DC 1.jpg (67.7 KB, 310 views)
File Type: jpg Meanwell AC-DC 2.jpg (328.2 KB, 289 views)
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Old 16th May 2021, 12:27 PM   #676
Mark Johnson is offline Mark Johnson  United States
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PO89ZB , an inline DC filter for SMPS wall warts . Preamps, HPA, Korg NuTube, etc
Sorry, you'll need to find someone else to engineer a total protection solution for you. That's an area in which I have zero experience and zero knowledge. Maybe Nelson Pass can recommend a consultant whose hourly fees are not astronomical.



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Old 16th May 2021, 01:11 PM   #677
ClaudeG is offline ClaudeG
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Fair enough, thanks Mark...

Kartapus, yes, they all have that, question is how do they do that. Failsafe mode is my worry. SMPS die quite abruptly on my computers, only place where they are regulary used. When on laptops, no problem, but then perhaps because of protections and battery. On stationary units, let's say the protections were OK when all was working, not when the SMPS itself failed woith age, with sometimes disastrous consequences beyond the SMPS. Not sure it is representative, I lack experience...

Anyway, it is perhaps time I get my hands and mind dirty and dig into all that

Thanks for the replies


Claude
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Old 23rd May 2021, 09:45 PM   #678
ranshdow is offline ranshdow  United States
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Originally Posted by Mark Johnson View Post
Please let us know how well it works when playing music.

So, after extensive listening with two different Pi/DAC HAT combinations, I don't hear any obvious improvement when the DC filters are in use. If anything, there may be a slight reduction in dynamic range when they are, but I could be hallucinating. Setups are:


Raspberry Pi 2 Model B Rev 1.1, AD1868 based R-2R DAC HAT (audiophilediyer.com)

Raspberry Pi 3 Model B REv 1.2, HiFiBerry DAC2 HD


There's a rhythmic pop-hiss from the AD1868 card that isn't helped by the DC filter HAT. That said I personally prefer the sound of this card over the DAC2 HD, at least for the rock/pop/"girl and guitar" type music I typically listen to.
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File Type: jpg DAC_HATs_under_test.jpg (675.4 KB, 215 views)
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Old 23rd May 2021, 10:32 PM   #679
turion64 is offline turion64  United States
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PO89ZB , an inline DC filter for SMPS wall warts . Preamps, HPA, Korg NuTube, etc
Default My two enclosure designs

Both cases were ordered from Amazon.

The black plastic case is: DGZZI Electrical Junction Box 4PCS Electric Plastic Black Waterproof Project Junction Case 3.15x1.97x1.38 inches(80x50x35mm; $8.60 for 4 boxes) while the silver aluminum box is: Eightwood Aluminum Box Electronic Amplifier Project Enclosure PCB Circuit Board DIY Case, 4.32 x 2.82 x 1.13 inch (LWH); $11.00. Little soft plastic feet stuck on underneath.

Thanks for the board design & kit sales!
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Old 23rd May 2021, 11:00 PM   #680
rikiheck is offline rikiheck
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Originally Posted by ranshdow View Post
There's a rhythmic pop-hiss from the AD1868 card that isn't helped by the DC filter HAT.
Bummer. I've heard that same sound and was hoping this might help. Maybe I'll get lucky, though.
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