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

[kasey197]

Originally Posted by Mark Johnson

Excellent! Please tell members here the voltage dropped (the reduction) from input to output of your cap multiplier, so they can decide whether it would be acceptable in their own application.

That's a good point - I tried a number of logic level mosfets. The one with the lowest drop was the IRL640. With this mosfet, at a load of 1A, the voltage drop was about 2.5V. That total drop includes some (0.3V?) dropped across the passive filter too....
The schematic i used was (post#51): Mean well vs generic power adapter vs audio oriented smps

Originally Posted by Mark Johnson

You might also consider uploading the Gerber files of your design, so that other builders can order PCBs and try it out for themselves.

Built mine on veroboard!

[longspeak]

Thanks for the book links Mark, I love the subtitles "A Handbook of Black Magic" and "Advanced Black Magic" .

Very good point about the ground being noisy in a poor setup preventing meaningful measurements. I used a differential configuration (pin 2 to PSU+ and 3 to PSU- on an XLR, using blocking caps in both) to feed the ADC it seemed to help reduce common mode noise. I just got the boards from konst so I'll get a couple of filters built for experimenting.

[music2myear]

Has anyone installed this circuit inside the Korg Nutube B1 pre- amp case or is this a no no? thanks

[elwood625]

I've installed it inline with my B1 Korg Balanced version, works very,very well! Mark Johnson even suggested using two in series, I just finished another to try that as well. The B1 Korg is exactly what this filter is for, I have seen external versions inline, and the filter installed inside the enclosure with the B1 Korg.

[music2myear]

Thanks, reading and seeing in in a small external box but no images of it actually in a Korg case got me thinking maybe there is a reason that I am not seeing . cheers

[safesphere]

I'd love to get a couple boards for my NuTube preamp. What is the best way of getting them? Is there some sort of a group buy or does anyone have extras? I'dbe glad to pay my share. Thanks!

[ClaudeG]

Quote: Has anyone installed this circuit inside the Korg Nutube B1 pre- amp case or is this a no no? thanks

It is a YES YES!

Absolutely recommended and no problem whatsoever to be in the same casing.
Tried daisy chaining 2 but (perhaps as...) my B1 Korg is already tweaked re PS (low ripple PS + 2200uF caps), it made no real difference - but of course always worth a try.

Next step is to try Mark's enhenced version with the better caps and daisy chaining aswell. Whatever is best will come in the casing permanently with my B1 Korg.

Mark's filters are really good and nonexpensive, it is IMHO always worth to build a few more: you will always find an application sooner or later and of course you can experiment a lot of combos that way.

Have fun

Claude

[SuppersReady]

Originally Posted by safesphere

I'd love to get a couple boards for my NuTube preamp. What is the best way of getting them? Is there some sort of a group buy or does anyone have extras? I'dbe glad to pay my share. Thanks!

Hi safesphere,

I have several boards left over from a recent order. Please pm me with your address and I'll let you know the shipping cost. The boards are free.

[SuppersReady]

Originally Posted by music2myear

Has anyone installed this circuit inside the Korg Nutube B1 pre- amp case or is this a no no? thanks

I'll be installing the filters inside the nutube case when the bench is clear of its current project. The plan is to use the slots in the sides of the case for mounting them without having to drill any holes.

[SuppersReady]

Which leads me to another thought. The plan is to permanently install these filters in all of my current preamps (AKSA Lender, B1K, ACP+, Starving Student x 2). At some point in the near future I aim to put together a linear power supply to compare with the SMPS.

Is there any issue with using a linear power supply with these filters in circuit? I can't see that there would be, but I'm no expert in these matters.