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In Reply to: RE: cMP - the open source high-end Memory Player posted by cics on December 30, 2007 at 05:42:01
I haven't seen this modification posted so I thought I would share something back after being a long time lurker and benefiting from the huge amount of time and effort that some folks have invested in this project.A CLC type filter can be set up on the voltage output of the Juli@ 3.3V regulator for the digital supply that gives additional filtering compared to using only smoothing capacitors. YMMV of course.
To implement, the VR 3.3v output connections (there are two) have to be lifted from the board. Then a small toroidal inductor installed between the VR and the board. Add smoothing capacitors on each lead of the inductor to ground. The inductor can be attached to the end of the board in a convenient place with a little hot glue. I found these inductors (Bourns part no. 2112-RS, 100uH, 2.4 IDC, 0.13 DCR) at Digikey for less than $3 each. I used a Nichicon Muse 100uF cap on the VR side of the inductor and a Blackgate 220 uF cap on the board side, although I don't think the size is as significant as the quality of cap, especially the second cap.
I have had this mod on my board for some time, but I did some AB testing by shorting across the inductor to really get a feel for the upgrade before making this post. In my system the sound has a quieter noise floor with more midrange detail apparent using the inductor. Care should be taken not to make the inductor too large or it can have some detrimental effects to SQ.
My Audiophile 2496 soundcard also has a similar filter arrangement on both the analog and digital voltage regs. as well as my DAC's on all the voltage regs. I also have put toroidal inductors on the supply out of a CCS (without using caps) to block the solid state sounding crud. Works well, a lot of bang for the buck.
Edits: 03/02/12Follow Ups:
Would like to see a picture if you would so oblige.
Hi Orediger,I can confirm your statement: “Works well, a lot bang for the buck”.
Smoothing, decoupling and filtering the power supply works has major impact on Sound Quality.You (and other inmates) might find this Linear Technology application note 101: ‘Minimizing Switching Regulator Residue in Linear Regulator Outputs’ an interesting read.
The application note shows that only adding caps, has only some little positive effect. VERY MUCH (!!) more effect can be had, when caps are combined with ferrite beads or inductors too create a filter. Adding ferrite beads or inductors (combined with caps) has a spectacular effect on the effectiveness, as can be seen on the scope pictures in the application note.
For some time I tried too give filtering some more attention on the PC audioasylum.
(clamping ferrite beads onto the power supplies (as much as possibly fit) and/or insert (ferrite based) inductors in the power lines.
But there was not much response from inmates.
That’s a pitty because as the Linear Technology Application Note 101 (again) shows, it is very effective too filter psu lines with caps and ferrite beads or inductors.
Your results show again how effective filtering can be.
The application Note is a very interesting read because it describes a case situation which is similar too the situation in a cMP + ESI juli@ digital part setup.Situation application Note:
* switching PSU -> (filtering) input -> linear regulator -> (filtering) outputSituation cMP + Juli@ digital part:
* Switching PSU -> transport through MoBo too Juli@ input at PCI slot-> Julia linear voltage regulator -> output to the logic on the Juli@ digital part PCB.Similar as described in the application note, you also apply filtering too the regulator- input and too the regulator-output in a very elegant way. The removal of the Juli@ stock voltage regulator is not needed that way. Although one must master ‘micro-soldering’ skills
Another very interesting thing too read in the application note is that the application note takes into account that capacitors and regulators in a real world situation, have an imperfect response too very high frequencies. The application note describes ways on how too compensate for this in a real world situation.
Here the application note differs very much from the ‘standard audiophile DIY approach’. The ‘standard audiophile DIY approach’ always propagates the use of boutique and ‘near perfect’ electronic parts (like Blackgates caps ect.). That way hoping too avoid the need for compensating measures because of the imperfectness of the used parts.For convenience I put the Linear Technology application note 101 here for download:
http://www.mediafire.com/?7ur9k0puyrz9t3iThe application note is also interesting for inmates who consider too build an all linear PSU based on a standard linear bench PSU. Starting with a standard linear bench PSU one only has to concentrate on creating 3,3 volt DC , 5 Volt DC and 12V Volt DC from the standard linear bench PSU low voltage DC output through use of linear regulators with input and output filters.
Hope your results encourage other inmates too start experimenting with caps + ferrite beads or caps inductors or all three.
Mark
cMP2 PC > ESI Juli@ > Van den Hul Optocoupler MkII > Lavry Black DA10 > XLR Mogami Gold > Klein & Hummel O300
Edits: 02/24/12
Interesting post Orediger,
Inmate hfavandepas did a lot of research and reports on PI-filtering, i think it was around june 2011.
He did the same on juli@ and other power lines.
If you're gonna try these Pi-filters, please report.
tia
Douwe
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