[rdsu]

Hi,

I want to build a Felix to put between AC Adapter and AudioPC.

The output of AC Adapter is 12VDC/5A, and I would like to know what choke can I use without voltage drop, or to much DC resistance...

I thought about Coilcraft CMT4-26-6L 26mH 6A 0.115Ohm, or Coilcraft CMT4-17-9L 17mH 9A 0.062Ohm is better?

What is the max DC Resistance value to avoid voltage drop?

AC Adapter
cap 1uF
cap 0,1uF
cap 0,01uF
electrolytic cap 100uF
choke
electrolytic cap 10000uF
AudioPC

Thanks

[Folsom]

Look at the ratings on the Felix capacitors. They are rated at something that won't even affect 60hz, like in the link you sent. Also you're using a switching power supply. They have very small ripple. They are not like a linear that has constant voltage drop corrected by the capacitors.

I'd skip the small film capacitors and just make sure your electrolytics have very low ESR, and use several. They affect a larger frequency range, at a greater level. Perhaps you should look at Panasonic FM's. You could use many on each side of a choke. Skip the films.

Ideally you could upgrade the switchers output inductor but...

Here's something interesting for switching noise.

[rdsu]

This is if you intend to use it on the AC side, otherwise it's different. I say this because I can't figure out why you'd try to put it between on the DC, as the capacitors in a Felix won't do anything on the DC side. They'll just charge and stay charged, so it isn't even possible for them to filter. Your diagram is only showing capacitors to prevent voltage drop. SO assuming you want to re-think the design and put the Felix AC side...

I don't know how the capacitors works on DC, to function as a low pass filter, but they remove noise, and even the caps of Felix works on it...
http://www.seattlerobotics.org/encoder/jun97/basics.html

Here you have one, and what Paul (Occam) replied...

To prevent voltage drop? Can you be more specific?

I already have a Felix on AC side...
http://www.audiocircle.com/index.php?topic=25757.msg1221696#msg1221696

From what I gather your adapter probably uses around tops, 1A. That'd be 50% efficient. Given that it's probably a switcher, it'd be more efficient. Let me know if that isn't the case. But for example it's 5A 12VDC, or 60W. 60W/120V = .5A usage at 100% efficient (which it isn't) .

This is my AC Adapter:
http://www.fspgroupusa.com/fsp060dbab1/p/696.html

So with no shortage of concern, a 3A rated CMC would be fine, but I'd recommend a CMC/DMC. It does more filtration because it not only does common mode, but also differential. The P3717-AL would be a great choice. Overall it will reduce more noise.

The Coilcraft CMT is more appropriated for this application...

I don't like to used almost the max current of the choke, and it seems that is always better to use a choke with higher current than AC Adapter, to prevent some problem:
http://www.audiocircle.com/index.php?topic=25757.msg1037400#msg1037400

[rdsu]

More info...

What is a Bypass Capacitor?

[Folsom]

I updated my response, since you have a Felix on the AC side.

Capacitors don't work the same on the DC side. The concerns are different, and I'd recommend filtering more than just the high frequencies (with low uf rated capacitors). But ultimately depending on ripple, they may or may not do a lot of filtration. More ripple = more filtration, funny enough.

As far as which choke, I'd go with the lower resistance one. But I still wouldn't go with the CMT, just because I'd rather filter differential mode noise on this side of a power supply. Common mode noise (AC side) tends to make differential mode noise in switching power supplies. But yes, do not exceed the current ratings, and prefer a margin of error. I can tell you that you can make a choke melt, no doubt. I've replaced one that was improperly used with too much current demand. I was recommending one for the AC side, originally (before I knew you already had one).

[rdsu]

Thanks for your suggestions...

I already thought about buiyng a good AC Adapter 19V/5A, use a voltage regulator (Fidelity Audio SPower ‘HC’), and make something like this:

AC Adapter 19V/5A
cap 0,1uF
cap 1000pF
electrolytic cap 100uF (low ESR)
choke
electrolytic cap 10000uF or 20000uF (low ESR)
electrolytic cap 470uF (low ESR)
voltage regulator 12V/5A
electrolytic cap 470uF (low ESR)
AudioPC

And this may worth the little investment...

For this, Kemet F461-F464/PHE450 and Wima MKP4/MKP10 seems more appropriate...

Something like John Swenson PSU, but with SMPS, and latter try to add a very good toroidal transformer and bridge rectifier...

[Folsom]

If you use say four caps instead of one, with low ESR, you'll lower the ESR how the circuit sees it. You are already doing that partially. But you have a mix of caps.

Also if you use a voltage regulator look into ones that attenuate a lot of noise. There have been a few threads mentioning them recently. Otherwise a Bybee Music Rail might be a nice option. Personally I'd like to compare Bybees and regulators; not for noise levels on instruments, but sound. Bybee's are not as effective for removing noise as some of the better regulators out there. The Music Rail may be, but not the original Bybee black things. However which one sounds better is still another debate.

[rdsu]

Thanks for your tips...