 
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
|
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
85.147.82.48
In Reply to: RE: cMP - the open source high-end Memory Player posted by cics on December 30, 2007 at 05:42:01
Hi All,
Since some inmates have reported that they discovered (with there scopes) all kinds of (high) frequency distortions on the 12V, 5V and 3,3V DC ATX power supply lines, I was wondering if there are any immates who try to filter these distortions.
The circuits of these filters all have a common lay-out. Mostly these filter circuits are first order filters which use an inductor to block (high) frequencies and use a capacitor to shunt these (high) frequencies too:
- the 0 Volt line (differential-mode) or
- shunt the Line and the O volt too the ground (common-mode).
The image shows a common-mode layout
Google-ing on AC filter and/or DC filter will show manufactures of AC filters and (some) DC filter manufactures and also the circuits designs they apply in there AC- or DC-filters.
I was wondering if there are any inmates using filters on the dc 12V, 5V and 3,3V lines? And if ‘yes’,
- what are there experiences with these filters,
- what circuit design are used?
- and what values are used for C and L and ohm resistance for the inductor ?
Mark
N.b. Smoothing caps on the P4 line is not only a way of buffering energy to lower ripple (buffer current to prevent Voltage drops), but it’s also a way of shunting frequencies. So the effect of smoothing caps might be a combined effect of these 2.
fully AOB optimized cMP2 PC -> Lynx AES16 -> XLR AES/EBU -> Lavry Black DA10 -> XLR Mogami Gold -> Klein & Hummel O300
Follow Ups:
Hi! What about Audiotrak Prodigy HD2 card?
Smoothing caps on the P4 line [is] a way of shunting frequencies.Yes, it was me who cited Ivor Catt's book - I'm very glad you found it interesting. As you know, the circuit you show is taken from his chapter on mains filters. I'd hesitate before using it willy-nilly in other applications as it's designed for AC mains with a safety earth, not low-voltage DC supplies.
Any power supply, be it SM, linear or battery, has an internal resistance. (In the case of lead-acid batteries, this is quite high and, obviously, increases as temperatures fall. That explains in part why cars are harder to start in cold weather - V is fixed, R goes up so I goes down and the starter motor struggles.)
If you place capacitors across e.g. a PC-PSU's 12-volt P4 line, you are in effect creating an RC low-pass filter (i.e. one that passes DC but tends to filter out HF) where the internal resistance of the PS and its cables provide the "R" bit.
As the values of R (and L) are, to put it mildly, imprecise, the effect is unpredictable but that doesn't matter as the aim is simply to filter out as much HF crud as possible at minimal cost. For a variety of reasons, I'd keep the safety earth well away from the motherboard and rely on the SMPS to provide competent earthing.
Several others here have forgotten more about all this than I'm ever likely to know and, if I've got it wrong, will hopefully explain why but that was the thinking behind my advocating the tweak way back when (though I was by no means the first to do so).
Dave
Edits: 12/15/09
Hi Dave,
Thank you for your reply.
So I remembered correctly. :-)
I think you made a very good move too point inmates too an online (!) quality knowledge source. Since it is an online source, it can serve as a common reference point in discussions on the forum. I often read so much ‘Vodoo’, Black magic’ and other blabla that such an online reference point can be extremely helpful.
So you also think the main effect of the smoothing caps is the effect of shunting ‘HF crud’ to the 0 volt. I think the same. But I asked myself if shunting to the ground would be a better way.
That’s why I pointed at both methods. The differential-mode (shunting ‘HF crud’ too 0 Volt) and the common-mode (shunting ‘HF crud’ too the ground) and showed a picture of the basic circuit of the common-mode method.
When using the common-mode, the ‘HF crud’ doesn’t travel back through 0 Volt which keeps the 0 Volt ‘cleaner’.
So I thought: well let’s ask if the more knowledgable and smarter inmates on the forum already do this. And most important: do they hear an improvement in sound quality.
Mark
Since it’s 12, 5, 3,3 volt DC I see no real safety issues. But If there are life safety issues please correct (!!!)
fully AOB optimized cMP2 PC -> Lynx AES16 -> XLR AES/EBU -> Lavry Black DA10 -> XLR Mogami Gold -> Klein & Hummel O300
hey hfavandepas,
well, it´s not much I can contribute to this, but I got a series of smoothing caps on my P4 line, and can report it definitely smoothed my audio right away.
my next project is to move onto pure battery on the P4 and further onto a Pico driven by the same battery. there are still a couple of hurdles that I need to figure out, but I have a friend who is gonna give me some help over the next few weeks.
I´ll keep you informed.....
Hey Playmate,
Yes I agree. Smoothing caps on the P4 power supply line, is an easy and very effective improvement. This ‘tweak’ started my ‘quest’ of improving the power supply. :-)
From what I read on the forum, moving to batteries is good move, but I think battery’s are too much of a hassle. The recharging, ect, ect.
So that’s why I chose not to move beyond linear supplies to batteries but instead to see how I can get the best out of Linear supply’s.
As for powering a picoPSU with a battery, keep in mind that a picoPSU only passes the 12 volt straight through the MoBo(when choosing the right picoPSU model). The 5 Volt and the 3,3 Volt are still processed by the picoPSU. Therefore using a picoPSU only gives some sound quality improvement when picoPSU models are used that leave the 12 Volt line untouched.
In spring 2010 I will try too assemble a setup with 3 linear PSU’s that power the 12, 5 and 3,3 volt lines directly and using a picoPSU too only power the PCC (Power control Circuit) on the MoBo too start the PC. See comments and suggestions from ForgotPassword, Gene_, and Bertel on this.
Thankx for keeping the forum informed on your progress.
New ways and new idea’s are always much appreciated and will bring everybody further and the road of optimizing the power supply.
fully AOB optimized cMP2 PC -> Lynx AES16 -> XLR AES/EBU -> Lavry Black DA10 -> XLR Mogami Gold -> Klein & Hummel O300
Post a Followup:
| FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
||||||||||||||
This post is made possible by the generous support of people like you and our sponsors:
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2024, Audio Asylum, all rights reserved ]
