PO89ZB , an inline DC filter for SMPS wall warts . Preamps, HPA, Korg NuTube, etc

[Mark Johnson]

This week I'm shipping the prototype of a 48 volt, 6 amp version which DOES have PCB mounting holes that fall on 1.00 centimeter gridlines. DC series resistance is less than 40 milliohms so it ought to be suitable for Raspberry Pi applications and sub-40-watts-per-channel Class A amplifier applications like the First Watt amps. If the early adopters like what they hear, I'll publish the Gerbers. If not then it never happened.

[rabbitz]

Originally Posted by konst

These sure are turning out to be quite the hit.

Certainly is and big thanks for Mark for this design.

[ClaudeG]

GLOL Mark, I am sure it will exist at least in one parallel universe

Thanks for all this again, very interseting not only for Class A IMHO

Claude

[ClaudeG]

Tried this fab little filter again yesterday and I wish to reiterate my great thanks to Mark for this valuable contribution. What I did might be of some interest to others, hence my post.

Making it short, a friend of mine ordered the latest offer re supposedly VFM super SINAD chinese DACs in the 400$ range, including Topping D90 and SMSL M200. He burned them in for 2 weeks and wanted to keep the best one while returning the others. He is very happy with the functionalities, but when I popped by to tweak his power amps I wasn't impressed by the sound to say the least. Took them home and my 20y old DIY played them to the wall.

Back to his, I expressed my heavy concerns re fine dynamic, grob dynamic, bass drive, flesh, treble definition and total lack of stage depth. Very flat sound by all means on all of these, a lot of missing details vs my 20y DAC though instruments are probably a tad better nailed in terms of 2D spacialisation. I was expecting far more given 6 generation DAC chip gap.

We could't understand why so we opened 2 units and indeed they aren't top notch re PS regulations, no contest vs mine. So we tried several 5V PS but I couldn't bring my 50x bigger lab supply with me. Little differences though, but OK, we ended up with a low ripple 20W SMPS of acceptable quality being quite better than the rest and being a 6x times current overkill. Still not there. I had Mark's filter with me just in my case, as ever, in fact with Papa's H2 music box, as I wanted my friend to give this H2 box a try.

And then the bright idea: why not postponing the H2 test and using Mark's SMPS filter betwen the DAC's oversized SMPS and the DACs? And whaoo, what a result! I would say that for less than10$ we easily doubled the DAC's value. It moved their sonic quality from flat and to me unacceptable midfi to quite acceptable HIFI.

We tried it on all DACs with similar findings. It addressed all the points I was missing. OK, they are still not on a par with my old DAC (but once you open the box and look at PS you understand why), but say that if the initial gap was 100 points, then the little external filter has covered 40 points on its account alone.

Bottom line: try this filter on the B1 Korg, it works great. Try it on average SMPS, regardless the audio device, it works even better. Last but not least, you HAVE TO try it on any cheap DAC using a wallwart... it does miracles!

In my view it makes low ripple quality SMPS very viable and competitive to some quite advanced linear PS, saving a lot of money and complications.

We might do another test at some stage, trying the SMSL M200 vs the big M400 brother, as that one is supposed to have proper power supplies inside, but who knows... still ground to be covered vs my old DAC but all points moving in the right direction.

Thanks Mark... the application field of this filter is even wider than intented, I hope people give it a try

Claude

[Mark Johnson]

What a wonderful story! Thank you for sharing the experiences of your friend (who is rather an arms-length, disinterested third party; he isn't a Proud Parent who lovingly assembled a PCB on his own kitchen table) and yourself. It's delightful to hear that this inexpensive, puny little board can make a big difference sonically.

Claude, I recommend that you build four more of these, equipped with male & female barrel jacks so they can be very quickly installed, in-line with existing wall warts. In fact I will split the cost with you, I'll pay 55% and you pay 45%. When spending my money instead of your own, you can afford to buy those top-of-the-line patch cords and use their very robust plugs and large diameter wire. the first link.

Why four boards? So you can keep two of them in your briefcase / backpack / man-bag at all times; and two more of them in the glove box / boot / trunk of your car at all times.

Now, wherever you go and however you get there (walking, bicycling, motor-bike, train, bus, subway, automobile, skateboard), you'll have two of these SMPS filters with you. So you are always equipped to perform exactly the experiments you just described ... without any advance planning. You've got the gear, with you, at-the-ready.

Why two filters? So you can try the follow-on experiment to see whether or not, "If some is good then more is better." Two filters in series cascade.

Send me a PM with your PayPal address and we'll figure out the proper cost figures.

Mark

[ClaudeG]

Dear Mark,

you are, as ever, right on all accounts... well, that is except one ;-)

Indeed I am going around to Hifi enthousiasts / friends / family with your filter. Indeed, I am now short of filters as I have only one left (for my own B1 Korg!) and I understood yesterday that there would be no way for me to make it back with my forelast filter, so good it is performing.

Indeed (LOL - and I haven't posted pictures because of that) I still using my cheap plugs and the filter I carry is in a small plastic bag. Shame on me, and you told me twice your view on jacks - I got your points, will build properly the next ones with yours.

Daisy chain! Bloody hell, how could I forget about that? It was more in the diminishing returns category on my own various builts, or they didn't deserve more than one... plus here the results are so good you can't dream it could be more. But YES, of course we should try with this DAC and on other occasions!

My friend, who is reading these lines (we are still at his, enjoying families and tweaking his 2 Class D amps), says now "because of you": I WANT 2 FILTERS. The addition of your filter on his DAC is by far one of the most significant tweaks we did (out of 10 mods on his amps only), far more effective than replacing costly output coil...Argh, need at least another filter and some for me, indeed!

I don't know if 4 is enough, they tend to be so good people want them and I feel most of the time I won't make it back home with them, regardless if they build their own later!

Thanks to Konst and SupersReady I have just received a total of 6 boards, need to hurry to build them. My friend wants to try daisy chain and we he just agreed - you did and you read this - that in return he would assemble suitable enclosures for all of them. He is good at these things, I shall be less ashame posting pix :-)

Mark, where you are wrong is that there is NO WAY for me to accept your very generous offer. YOU invented this filter and shared with us for free, YOU did so many projects and are so helpfull to others on the other threads I follow. Other members here try to support best they can, say providing the boards. We all owe YOU! No way for you to contribute kindly to my part's purchase. And I will always carry 3 filters with me, so I have always 1 to give away. Thanks Mark, but it is my Bday this WE, so I decide ;-)

Mark, if you want to make me happy, just keep sharing your very well thought and fool proof work. I am interested in your next filter 6A: you inspired me on the two 5A SMPS filters I built for that same friend, and we are listening to them since, but I can't wait to listen to YOURS, as these will be proper ones.

Thanks for all your kindness Mark

Enjoy music

Claude

[Mark Johnson]

Gerber files for the rev-A PCB are attached to post #1 of this thread; anyone can send these files off to a PCB fab, and get as many boards built as they like, with my blessings and good wishes.

Here are today's price quotes, for quantity=30 PCBs, made on the super thin 0.6mm boards as shown in the photo. Shipping to France, price quoted in Euros. I got the quotes from the very handy website, pcbshopper dot com . Click on the image to remove distortion, and then click again on the white "X" at bottom left, to see it full size.

Total cost is about 1 Euro per board, including shipping. Use as many as you need, and then give away (or sell) the extras to other diyAudio members!

_

[ClaudeG]

Thanks Mark :-)

Claude

[strongbow60]

I find more and more usage for this filter.
I have a 1 kHz very low noise oscillator from member Vicnic for use with Rew. This is using a 35 volt regulated power supply (besides having it's own regulator to +- 15V). The current power supply is kind of clunky when considering the oscillator is a very small device and beside I have use for it somewhere else.
Now I'm able to us a 36V led driver and an approximation of this filter (that I had before) in its own small plastic box and the oscillator and PO89ZB in another even smaller metal box.
First very crude test gives that the noise floor is the same but I have to do another round of measurements.

Another thought that popped in to my head, would there be any benefit in using a filter on a USB cable that powers external sound card such as a Focusrite? Computers are noisy bastards even on battery. The data cables would be kept as is and only the power leads would be broken up and passed through a filter.
I don't have the time right now but if anyone else want to have a go, feel free to do it.

[Tfive]

Originally Posted by Mark Johnson

Here are today's price quotes, for quantity=30 PCBs, made on the super thin 0.6mm boards as shown in the photo. Shipping to France, price quoted in Euros. I got the quotes from the very handy website, pcbshopper dot com . Click on the image to remove distortion, and then click again on the white "X" at bottom left, to see it full size.

May I ask what service you use to get that quotation from multiple fabs?