Good thought. I recommend an analysis along these lines
- The maximum rated current of the PO89ZB filter card, is 3.0 amperes
- The series resistance introduced by a single filter card, is low enough that (3A x Rseries) is acceptably small
- DOGMA: when connecting "N" filter cards in series, do not draw more than (3 / N) amperes from the supply
- Now the total voltage drop across "N" filter cards in series, is less than or equal to the drop across one filter card as it supplies 3A
Since very, VERY few pieces of DIY audio gear draw more than 1.5 amperes from a DC wall wart, and the majority draw far less than 1 ampere, there appears to be plenty of room for experimentation with N>1 .
That is logical but of course I mean with the same load so same device. Also logical as users won’t change devices to lower power ones to be able to use 3 filters.
Plenty devices here that use 1 to 2A at 5V. I just mean it is better to recommend just 1 filter as you Will likely receive many questions otherwise
Specifically from the RPI/SBC crowd.
Coincidentally I am experimenting with an SBC powered by an LPS and that one already has issues with 4.7V. Again logical
Plenty devices here that use 1 to 2A at 5V. I just mean it is better to recommend just 1 filter as you Will likely receive many questions otherwise
Specifically from the RPI/SBC crowd.Coincidentally I am experimenting with an SBC powered by an LPS and that one already has issues with 4.7V. Again logical
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Since these boards already exist, it's comparatively easy to try them out in various configurations and find out what does and doesn't work in your application(s).
If a string of N filters in series doesn't happen to work for you, and if you really do need steeper filtering AND lower DC resistance, your next option is to create a new circuit design and new PCB. If you give yourself permission to use physically larger components, you can get the same or greater inductance using much larger diameter wire on the coil, thus much lower copper resistance. You can also intentionally select different ratios of L to C and of L to R. The new ratios could provide plenty of damping (ringing prevention) while at the same time reducing the value of the series resistors (2 x 0.04 ohms in PO89ZB). I have a feeling that not only will the L need to be physically larger; so will the C. But that's just a guess and could be completely wrong.
ProTip: brush up on your Laplace Transforms before undertaking a redesign -- see post #9.
If a string of N filters in series doesn't happen to work for you, and if you really do need steeper filtering AND lower DC resistance, your next option is to create a new circuit design and new PCB. If you give yourself permission to use physically larger components, you can get the same or greater inductance using much larger diameter wire on the coil, thus much lower copper resistance. You can also intentionally select different ratios of L to C and of L to R. The new ratios could provide plenty of damping (ringing prevention) while at the same time reducing the value of the series resistors (2 x 0.04 ohms in PO89ZB). I have a feeling that not only will the L need to be physically larger; so will the C. But that's just a guess and could be completely wrong.
ProTip: brush up on your Laplace Transforms before undertaking a redesign -- see post #9.
I know what I have to do or not but I guess you underestimate the number of people with 5V RPI/SBC applications. It is just to prevent you from having to reply to many arising issues/questions etc. I once did a GB with another member here and I can tell it took a lot of time as people may find the most peculiar applications for a device.
As you have read I use an SBC with a Linear Power Supply (that did don't work as I wanted/it also does not need an extra filter) and there I found out these can be pretty sensitive to PSU voltage. You can of course point to this thread being in the analog section but you know how things can develop as many SBC have a standard cheap 5V 2A SMPS and now there is a board that can clean up stuff...that even works better when you put 3 x PO89ZB in series.....
With a 5V 1A load and 2 x PO89ZB (around 200 mOhm) we already have a loss of at least 0.2V. I would not do this.
As you have read I use an SBC with a Linear Power Supply (that did don't work as I wanted/it also does not need an extra filter) and there I found out these can be pretty sensitive to PSU voltage. You can of course point to this thread being in the analog section but you know how things can develop as many SBC have a standard cheap 5V 2A SMPS and now there is a board that can clean up stuff...that even works better when you put 3 x PO89ZB in series.....
With a 5V 1A load and 2 x PO89ZB (around 200 mOhm) we already have a loss of at least 0.2V. I would not do this.
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Some posts split to here - 
I have 2 because I do trust the excellent quality of all of Mark's projects, and that applies in that case in advance. It is not that a risk in terms of finance or time, isn't it ;-)
More seriously, one is for testing with various combos (transportable), the other one to fit, as I am trustfull at least 1 module will find its home, be it with my test rig with low cost SMPS or with my B1 Korg.
If both... then I will have to build a third
Enjoy music
Claude
More seriously, one is for testing with various combos (transportable), the other one to fit, as I am trustfull at least 1 module will find its home, be it with my test rig with low cost SMPS or with my B1 Korg.
If both... then I will have to build a third
Enjoy music
Claude
I ran out and suddenly realized there are at least 3 more applications around the house. Looks like I am getting some more made if anyone needs one more (no eta at the moment as I am super busy, but they are coming).
I am soldering directly in line with devices I am using (to cheap to buy plugs )
I am soldering directly in line with devices I am using (to cheap to buy plugs
)
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Ok that was a little weird, the max I could reorder without incurring a pretty steep engineering fee was 30, they are being made and should be here (slowly). I am working on an election project so won't be able to forward them until after Nov3 due to time constraints, so I got them shipped non-express.
I'll let y'all know when they get here. I am happy shipping to everyone who wants one, if you want to contribute, $2 shipped anywhere in the world, if not, you can have them for free (25 will be available).
@Mark, not to worry I got this, let me know if you need a couple. Please keep contributing, it is much appreciated!
I'll let y'all know when they get here. I am happy shipping to everyone who wants one, if you want to contribute, $2 shipped anywhere in the world, if not, you can have them for free (25 will be available).
@Mark, not to worry I got this, let me know if you need a couple. Please keep contributing, it is much appreciated!