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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
(Note that I also posted this in the fully-linear supply sub-thread below).
I was putting my original Linear-Hybrid supply back together this weekend so I can make some comparisons to my fully linear supply and also try running the P4 from a supply that's plugged into my 'dirty' AC line.
When I was testing it, I saw that the -12v was not working... it only registered about -3v.
Then I remembered that early in my PSU experimentation, I'd damaged the -12v output on a PicoPSU when poking around to find the voltages in a Juli@. At the time I'd replaced that PicoPSU, but later put it back into the system when I went to separate power for my Juli@ & DAC.
Although I didn't remember this, my system has been starting up with a very low -voltage since about this time last year!
So I tried starting up the system with the fully linuear supply with the -12v (9v battery) not on... and it worked ok.
Gene, not sure why this didn't work for you, but it works very consistently for me.
Gene, Mihaylov, and Mark, can you retest this with the GA-G31M-ES2L boards?
JackWong, can you check with the GA-H55M-UD2H board?
If it works with these newer boards, it will simplify the setup of fully linear supplies by eliminating the need for one voltage!
I've unplugged my -9v battery!
Greg in Mississippi
Everything matters!
Follow Ups:
-12v is not needed for motherboard startup, but the Power OK is. -12V is required if you have a card which needs it, such as Julia.
And what about +12v (for motherboard startup)?
Interesting.
JackWong, your response reminded me that I forgot to check the GA-EG45M-UD2H board with no -12v... and of course, it worked ok.
So now we have the following data points:
Boards that can boot without -12v:
- GA-G31M-S2L
- GA-EG45M-UD2H
- GA-H55M-UD2H (JackWong, I assume that's the main board you've been using... let us know what your experience with other boards has been)
Boards that require -12v to boot:
- GA-G31M-ES2L
This just gets better & better!
And of course, the Juli@ only needs -12v if you are using the analog portion of the card. The digital only uses the 5v rail (and regulates that down to 3.3v internally for some chips).
Mihaylov, I haven't tried starting a Mobo without the +12v. I assumed it was needed, but looking at the power usage table JackWong published in this thread: http://www.audioasylum.com/cgi/t.mpl?f=pcaudio&m=75904 , it may not be. Next time I have a chance to try it, I'll see if I can boot a board without it.
Greg in Mississippi
Everything matters!
Great! I can confirm that GA-G31M-ES2L require -12v and +12v to boot :(
Oh well... thanks for trying!
Greg in Mississippi
P.S. I think the next direction for fun experimentation is in the extreme motherboard power supply bypassing & power feeds ala JackWong... That's why I'm sticking with the S2L boards for awhile, I have several spares and want to learn to do this on these older, less-valuable boards! I've let the magic smoke out a few times doing mods and even doing this cMP stuff... no need to do that with a bright, shiney new board!
Everything matters!
EDIT: Updated comments on sound of fully-linear supply below...Linear-Hybrid Supply:
I went through a series of experiments with my fully-linear and linear-hybrid supplies last night... Found out some very interesting stuff & made one breakthrough!1st, I did a quick swap of the supplies after the computer and system warmed up (I normally leave it on all the time, but we had a chance of thunderstorms during the day yesterday). Interesting to compare the two supplies. The linear-hybrid was closer than I remembered. It had a warmer balance than the fully-linear supply (With VERY similar parts!), but the fully-linear won on detailing and definition all across the spectrum AND I would judge it to be more neutrally-balanced... The linear-hybrid reminded me of a good, but not SOTA tube stage while the fully-linear was a SOTA tube stage.
A large portion of that more neutral balance on the fully-linear supply is a more-level treble. The linear-hybrid is a bit recessed in the treble... it's as if it slopes down slightly from the bass to the treble. The fully-linear does not sound as tho the treble is emphasized or too high in balance... if anything, it may still be a tiny bit lower in level than neutral (I'm very sensitive to treble anomolies, within the range of hearing of an audiophile in their mid-50's!).
I'd suggested originally that the fully-linear supply was not nearly as large of an upgrade over the linear-hybrid as that was over a modified Antec-430. Later I reported that that it was nearly so. This comparison last night confirmed my first impression. Again, based on what I heard, I'd suggest the linear-hybrid using very high-quality parts as a very good upgrade to a computer audio setup with less cost, bulk, and operational hassle than the simple fully-linear supply I implemented. But the fully-linear supply really is better... And worthwhile if you want the ultimate! And I expect it to be even better with better regulators... And also with battery power.
An aside, the two supplies are built with very similar parts... But there are a few differences that would favor the fully-linear. Most notably is that I used the very nice IXYS DSEP30-06A rectifiers in the fully-linear, but the still very good, but not as detailed-sounding Motorola MSR860 in the linear-hybrid supply. I know the sonic difference between these two diodes in this application as I'd swapped out the DSEP30-06A's for MSR860's while debugging the fully-linear supply, then changed back when I realized the diodes were not the problem AND that the DSEP30-06A's were more detailed (and less warm... Hmmmm?).
The other differences which I think will be less significant are that the fully-linear supply uses 47,000uf Jensen 4-pole caps while the linear-hybrid uses 15,000uf caps of the same type. Then the fully-linear uses adjustable LT1083 regulators all around while the linear-hybrid currently has a fixed LT1083 on the P4 supply. Back when I first built the linear-hybrid, it had 2 fixed LT1083's, but I upgraded them to the adjustable and that was a minor, but noticably upgrade. But that position's adjustable LT1083 got stolen while I was debugging the fully-linear and it was easier to put a fixed LT1083 back in this likely less-sonically important position when I put the linear-hybrid back together.
2nd, I tried to start up a GA-G31M-ES2L board with both the linear-hybrid supply with the damaged -12v and the fully-linear supplies with the -12v(-9v) deactivated. Yes I got the same results a Gene reported, in that the board required the -12v (-9v) to start, again different than the S2L board that will start with that voltage off.
3rd, I have been running the fully-linear supply with a small, separate 5v supply to provide the 5v control voltages for 5vSB and PWR_OK. I had previously upgraded the capacitors on that supply from Elna Silmec to Black Gate Standards and heard an difference (I'd rate it as an improvement as I prefer the BG sound to the Silmec sound, but not everyone would). Last night I cut that supply out and powered those lines from the main high-current 5v supply. It was not as good in that configuration as with the separate supply (which was clearly more detailed, more real), so I put that back in.
4th, the breakthrough. While I had the fully linear supply out of the cMP case, I re-tried to make it work with a GA-EG45M-UD2H board which has the newer Dual-BIOS setup. I expect that the startup sequence of this board, where it starts up the power supply, then turns it off for a moment, then turns it back on, will also be needed for newer GA-H55M-UD2H board. I tried several combinations of manually switching the PWR_ON off and back on during the startup... And found this sequence to work:
- Turn on main power supply (activates the ATX 3.3v, 5v, 12v, 5vSB, and -12v(-9v battery) and the P4 12v)
- Press the power button
- Switch on the PWR_OK
- Wait 8-12 seconds, then switch off the PWR_OK for 1-2 seconds, then switch it back on
Although I have not tested it with the GA-H55M-UD2H board, this gives me a lot of confidence that the simple 2-switch setup I'm using will work with that board too!
That's all for last night!
Greg in Mississippi
P.S. Next experiments are to try the system using the linear-hybrid's P4 supply plugged into my 'dirty' AC line... And to try the LT3080 regulators on the fully-linear supply.
Everything matters!
Edits: 07/27/10 07/28/10
Hi Greg,
Several time battery was dead ( 5-6 volt, I forget switchet off)
and computer refuse to start. I find solution ,using wall plug PSU
for -12volt, and happy with this. I am going to buy second, Auto Lead acid battery to be completely dicconected from AC.
Gene.
This would be very interesting, I will follow this thread to see what results you get. I am planning to go with the Pico in my audiopc and this info whill be very usefull.
I figure, at least, half of discoveries are due to this excellent mechanism.
I know I was glad to a 9 volts battery could be used and now this: better still!
I have made my first foray into linear supplies with a choke input supply for the JULI@. Followed by another LC section to get my five volts. I like the idea of the chokes blocking all of the high frequency noise going in either direction (or at least I think so!).
I love traditional supplied with tube amps and pre-amps so I thought WHY NOT?
One needs an eight volts, around 50 VA transformer to get it. Using low resistance chokes (8 ohms).
Another thing I would like to add is within the Mihaylov supply I would like to suggest a refinement. I think I will stick with the three terminal regulators here but instead of cascading voltage regulators I would think it better to have the first one wired as a constant current device and let the second unit do the voltage setting. I have seen this done so many times in the past I figure there must be something to it. I first came across this idea from Allen Wright's preamp cookbook.
Thanks for your report,
Rick McInnis
LOL!I'd never call any of my mistakes brilliant, but this one was at least fortuitous!
But then of course, JackWong already knew this for everything but the ES2L board! Oh well, so much for 'new' discoveries!
I'm curious how your choke-filtered supply will work. I've been looking at John Swenson's computer supply... I can find a link to it if you haven't seen it. I get the feeling he does a very good job of designing a power supply that has accounted for all the important factors PLUS I get the impression he listens carefully too... a great (and all too rare) combo.
I'm fully intending to move to choke-filtered supplies. But that will have to wait until I re-case my setup... I just can't fit them into my current setup.
I am also curious about a comment you made a few weeks back. I got the impression you'd be doing this supply without regulators. I saw in another thread that Thorsten is doing that in some places, so there must be merit to it.. but it sounds a bit dangerous given any significant AC line voltage variation. Let us know how that works out.
On the alternative regulator scheme you mentioned, I'm planning to try something similar to that too, but not using three-terminal regulators. I'm hearing some very good things about shunt regulators and one of the more favored ones for DIY use is the Salas Simple Shunt from this thread:
http://www.diyaudio.com/forums/power-supplies/143693-simplistic-salas-low-voltage-shunt-regulator.html
But even better, in this thread, Salas shows his shunt circuit that'll provide sufficient current to handle the 5v ATX line:
http://www.diyaudio.com/forums/power-supplies/168631-5v-high-current-low-noise-regulator.html
While I doubt these will beat PH's offerings, they should be pretty good, better than most, and pretty inexpensive.
Later!
Greg in Mississippi
Everything matters!
Edits: 07/28/10
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