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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
What is the purpose of Granite digital PSUs (mentioned as secured under the CD/DVD drive)?
I see a standard PC PSU and a power cable going into the case through one of slot covers at the back, is this 2nd power cord for those Granite PSUs?
Is the purpose to power hard drives and minimize ripple on main PSU powering motherboard?
Would not the same be achieved if externally mounted SATA hard drives with their own PSU are used?
Follow Ups:
Good questions.
I see a standard PC PSU and a power cable going into the case through one of slot covers at the back, is this 2nd power cord for those Granite PSUs?
Yes.
What is the purpose of Granite digital PSUs (mentioned as secured under the CD/DVD drive)?
Is the purpose to power hard drives and minimize ripple on main PSU powering motherboard?
See this for background information. HDDs generate a great deal of power supply noise pollution. See this for noise measurements on both 5V and 12V lines using an oscilloscope. When this load is taken off the main PSU, we get cleaner voltage lines and the 5V line is measured here . Edward did a great post here on his experience.
Granite Digital's PSs allows for other components to be externalised . It offers a standard SATA connector and a Molex connector. These Molex connectors are used to power other computer items:
- CD/DVD-ROM Drive
- wireless mouse USB receiver
- ROM drive's USB port
- Touch screen LCD monitor (which uses 12V line)
- Touch screen USB connection
This is a lot of stuff and they're bound to pollute the critical mobo and CPU power lines (12V1 & 12V2).
Would not the same be achieved if externally mounted SATA hard drives with their own PSU are used?
Yes this would work for HDDs but doesn't help with other stuff mentioned above. I also wanted a single box solution.
Thanks.
PS - sorry for all those links.
Thank you for great information.
I built my PC around Zalman TNN 300, but did not do separate PSU for hard drives, this will be my next step.
What are your thoughts about taking hard drives physically out of the case for reasons other then power pollution (I do not care about looks), would it be beneficial to have them outside for heating and RFI/EMI reasons?
This was actually something I was thinking about, having SATA hard drives in external enclosures, but so far I have not found well reviewed enclosures that provide passive cooling.
BTW I did not keep CD-ROM in Zalman, I rip on another PC, then transfer files over network (NIC is enabled on Zalman during file transfer only).
I am not following the idea of powering externally wireless mouse USB receiver?
In my PC I have mouse and keyboard connected to PS/2 ports, all USB ports are disabled, so I assume I am as clean as possible, hard drives aside?
I built my PC around Zalman TNN 300...
Mine is still operational (and am very reluctant to move it). The retailer where I get this was very proud that a recording studio is using it. Anyway, I'm getting brilliant results with the HD160XT as well - and that's using ESI's Juli@ card which is 4 times cheaper than my RME HDSP 9652.
What are your thoughts about taking hard drives physically out of the case for reasons other then power pollution (I do not care about looks), would it be beneficial to have them outside for heating and RFI/EMI reasons?
It would be an improvement as vibrations and HDDs radiation is taken away. Vibrations do impact jitter but this is not as significant as power supply noise (both ripple and ground). My preference is for a good case that dampens these HDD vibrations. The heat is not an issue: its more important that temperature remains constant as varying temperatures cause clock jitter (that's why they have temperature compensated crystal oscillators - TXCO/OCXO/VCTCXO ). This is also the reason why source equipment is on 7x24. Varying temperature has more jitter impact than vibrations.
If you plan to install this separately, let us know of the results.
I am not following the idea of powering externally wireless mouse USB receiver?
In my PC I have mouse and keyboard connected to PS/2 ports, all USB ports are disabled, so I assume I am as clean as possible, hard drives aside?
When playing music I have no keyboard. Mouse is a Logitech wireless one which operates via a USB receiver device. This USB receiver provides a wireless connection to mouse and in turn the mobo sees a normal mouse. This functionality requires power which it takes from the USB 5V line. Hence, I source this power from GD.
In your case, you have a standard mouse connection which would consume a very small amount of power from the PS/2 mouse port. My need was to be able to change CDs from my listening chair... problem comes when using wireless mouse receivers which operate at 2.4GHz and I would hear its interference.
C
problem comes when using wireless mouse receivers which operate at 2.4GHz and I would hear its interference
So are you saying that by having a separate power supply for USB, the rf from your mouse will not be heard??
Before separate power supply I had to use a ferrite core.
After separate power supply I don't need that ferrite core. I didn't detect a difference with or without it.
You can hear a difference between a mouse with a ferrite core around the cord and one that does not have one???
Hmmmmmmmm 0.^
Yes! This happens when I use mobo USB port. It also helps with the kit I have - maybe I should do a 'Equipment Used' post.
Here's an example: I've been planning to install shelves etc. and after doing that, I reinstalled my cMP. Played music and simply couldn't understand why sound was poorer - low level details being fudged! So, was my new shelves causing this... anyway went to bed disappointed.
Only then I realized I plugged the wireless receiver (now without ferrite core) into mobo USB port (!!!) and not the alternate one. Next morning I corrected this and alls well.
Cics, you put in a lot of work with this, I appreciate your effort and willingness to share...
However in the intrest of science I would like to see this repeated.
First we need a system with the resolving power to make such a change audible, then someone willing to participate.
I volunteer Dawnrazer
Hey Dr.
THanks for thinking of me. I don't have a wireless mouse that I could test with, and quite frankly, I didn't do much of what CICs is proposing....so I don't think it would be definitative if I did it.
NOw if someone sent me a cMP player I would be happy to test. :)
Also, my system is using dacs INSIDE the PC, and CICS is advocating getting the D to A out of the PC.
BUT, I think that if I get around to it, I might have some info that could explain why different players sound very different. I just need to buy a piece of gear that will help me measure different players.
One day....
Also, my system is using dacs INSIDE the PC, and CICS is advocating getting the D to A out of the PC.
cMP is totally flexible here. Mine based on Zalman HD160XT is currently set for analogue output via Juli@'s analogue PCB. This was also part of my
testing. I have headphones connected to its RCA outputs and volume control via Foobar. SRC upsampler set to 192k (of course, no SPDIF interface ☺ ). Juli@'s internal DACs then do the rest...
Some questions on your setup:
- Soundcard being used
- RAM type, size and settings
- Player and upsampler being used
- Mobo type (mATX, ATX?) and make
- Are you applying any BIOS optimizations
Make sure you apply the critical Windows settings that's required to run cMP's software. You'll see this in the Installation Guide. Output 24/192 to your soundcard and try the optimizations - just a recommendation.
In my setup, I get stable 24/192 analogue playback. SRC at 'Best Sinc interpolator' does put significant load on E2140 CPU and causes CPU voltage to transition to higher levels. Juli@ latency at 48 samples (0.25ms) gives dropouts but not so at 64 samples (0.33ms). cMP Optimize set to Critical. Sound is good.
I want to connect powered speakers directly to Juli@'s analogue outs (preferably balanced via its TRS connectors). Can someone recommend something at reasonable cost? I'm looking at:
- JMLab's Solo 6Be - expensive (& JMLab strictly sells to studios)
- Meyer Sound's HD-1 - even more expensive but comes highly recommended
- M&K MPS-1611P - a cheaper alternative?
I want an elegant, high sound quality low budget system (total cost ~$3500).
at 48 samples (0.25ms) gives dropouts but not so at 64 samples (0.33ms).To be a RAM player wouldnt you want more samples [in] RAM as supposed to less?
I know in the recording industry they want very low or no latency on music coming in....but for music going out we would want to use RAM to buffer the music by increasing the samples...yes/no? maybeso???
48 samples would require less time than 64 samples, but .25ms is more time than .33ms.........as my Japanese friends would say [doshite? Are wa totemo hendayo!]
Why are we very strange? (my Japanese is non-existant)
To be a RAM player wouldnt you want more samples [in] RAM as supposed to less?
All samples are in RAM as per wav (or flac or other) content file. For a CD wav that would be ~600MB loaded in RAM.
Foobar does playback via sound buffers (or chunks) which are prepared in RAM. This allows for DSP processing like SRC upsampling. The buffer size is determined in foobar's settings ( preferences > output > buffer length ). Buffer size can be specified in time, samples or bytes (foobar uses time).
Samples are streamed to the soundcard from this sound buffer - for audio, 2 or more are used. While one buffer is being played, another is being readied. Sound buffers are prepared (during playback) from wav (or other content) file samples and processed by SRC upsampler to the new sample rate (in my case 24/192). This processing is not time critical and with enough CPU capability, sound buffers are prepared ahead of time .
For example, a 100ms foobar buffer setting at 24/192 will require 19200 samples (each sample contains both L & R signal amplitudes). Alternatively, that would be 300KB (19200 x 2 x 8) - foobar processes in double precision (thats 8+8 bytes per sample). It's very important when using SRC and no other DSP, that you set foobar's buffer to the minimum of 100ms as more would cause heavier CPU demand and potentially prevent buffers from being prepared ahead of time. Wav file at 16/44.1 would provide 4410 samples for each 100ms buffer.
I know in the recording industry they want very low or no latency on music coming in....but for music going out we would want to use RAM to buffer the music by increasing the samples...yes/no? maybeso???
48 samples would require less time than 64 samples, but .25ms is more time than .33ms...
This is very important: both Recording and Playback are realtime events .
All playback occurs from RAM. Consider a 100ms foobar sound buffer being played. Samples converted to 24 bits (or 32 bits depending on soundcard driver) from this buffer is streamed in real-time to the soundcard. This is where latencies come in. At 24/192, 48 samples give 0.25ms (48/192000) latency and 64 gives 0.33ms (64/192000) which is longer. You must see latencies as the amount of sound data being transfered. So why is less better? For me, its two-fold:
- PCI: See P18 of AOB Computer Transports v0.3. PCI prefers high volumes of much smaller payloads (data transfers). (Note, newer mobos run USB and Ethernet outside of PCI bus but still share traffic with North/South chipset so traffic sharing here must be avoided).
- ASIO: Also prefers lots of small payloads.
Hence, there's excellent synergy between soundcards and ASIO. Most optimal setting is with smallest stable latency as this utilizes both PCI and ASIO to its respective strengths, ie. lots of small data transfers. This lays the foundation for real-time bit-perfect delivery and reduces jitter. See Bit Perfect Measurement & Analysis for cMP at 24/96 output using SPDIF coax. How many transports have you seen capable of 24 bits resolution (technically 23.5+ bits due to rounding error in measuring)?
In the measurement performed, source is set to 32 samples latency (RME 9652) and target to 48 samples (Juli@). Both machines configured to full cMP specifications with target running Steinberg's Cubase LE recording sw.
Thanks for the detailed explanation!!!!
BTW, Are wa totemo hendayo = That is very strange...not we....
Powered Speakers.
You may want to look at Dynaudio, I am loving my BM 6A MkII's. However I did find they sound a lot better when I changed the wire inside.
.
Not sure about the cost, but if you look at the line you may not want to settle on the 12's. The AIR line has features that you may or may not want.ADAM loudspeakers are another brand you may be interested in...Very very good. My next speakers [floorstanders] will be ADAM's.
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