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Old 3rd January 2013, 11:27 AM   #31
marce is offline marce  United Kingdom
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In order to help, I would be grateful if someone would give me an insightinto what benefits some believe adding a linear PSU to a PC will provide, as I am struggling to see any benefits.
Thanks
Marc
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Old 3rd January 2013, 11:33 AM   #32
qusp is offline qusp  Australia
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there-in lies the rub...
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Old 3rd January 2013, 11:59 PM   #33
kp93300 is offline kp93300  Malaysia
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Hi
I wish to state that i start this project because i have most of the parts in my bin and is aware of the debate about smps and linear dc for pc audio.

My smps is is cheap product and not what you called audiophile standard.

This is not an exercise to convince anybody else but myself of the sound benefits or not.
My opinion is only my opinion which is very subjective. After all, this is a diy forum and anyone can share the opinions.
If you think that i am on a futile exercise, i can accept that.

One of the aims of my posts is to gain knowledge about regulated dc power supply as i am hoping to use one of this supply for an amp i am planning to build in the near future.

I apologies if i have irritated anybody by my posts

cheers

regards

kp93300
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Old 4th January 2013, 06:40 AM   #34
marce is offline marce  United Kingdom
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kp93300, you have not irritated anyone (I may have ).
I think this is a very valid discussion, and I have asked my question above in all seriousness as I want to determine what some see the benefits of linear over SMPS for PC's used for playing audio.
SMPS's have had a bad press over the years and still do, this is unfounded to an extent as the technology and techniques have improved and changed greatly over the last 20+ yeards. Also our understanding and methods of EMC prevention have grown and improved over the same period.
What has also changed over the same period in the world of digital is higher density of switching nodes on a single device (Moores law) and more improtantly Tr (the rise time, and fall time) of digital signals, this has increased the noise produced by the switching itself, simultaneous switching noise.
More later goto go to work.
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Old 6th January 2013, 07:41 AM   #35
kp93300 is offline kp93300  Malaysia
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Default Sound comparison-linear power vs smps power for pc audio

I did a sound comaprison between linear power and smps power for my atom based audio pc running on linux.
I organize 2 sessions with 2 guests per session. This was done just now and yesterday .
My guest for 4 middle age man between 40 to 60 yr and have been playing hi fi for more than 20yrs and own expensive equipments .
I am the only one to know the type of power supply in use.

The 4 listerners are unanimous in concluding that there is a difference and all 4 are in favour of linear power !

The description of the sound difference is also remarkedly similiar.
I will try to describe.
Linear ps gives a darker background , better silence between noted with more natural decay of piano and guitar . Harmonics are more realistic.
Bass seems more with smps but it is more homogenous and separation between the different types of drum is blurred.
Vocal is more natural in linear with better depiction of microdynamic .
The high notes are cleaner with linear ps.
Sound stage is better and hold up better when the music rise in tension with linear ps.
BTW,
I have a very modest set up with Buffalo 2,
RJM buffer circuit which is from one of our member here,
amp is here
TI TPA3100D2, Amazing Class D Amp

speaker is V2 from GR research V-2

cheers

kp93300

PS I do not expect expect everyone to agree with my observations and I accept dissenting views .
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Old 6th January 2013, 07:45 AM   #36
kp93300 is offline kp93300  Malaysia
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BTW, I also did a sound comparison between solid state and spinning hard disk.
The best sound in my set up as decided by all the 4 guests is solid state hard disk with linear regulated power supply using LM 317
kp93300
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Old 6th January 2013, 07:57 AM   #37
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Hi kp93300

Nothing particularly surprising in your findings. I know nothing about Atom boards but quite possibly you can take this a step further by disabling on-board switching regulators one by one and supplying your own regulated voltages. Are you able to identify the regulators and the corresponding circuits they supply?
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Old 6th January 2013, 08:01 AM   #38
qusp is offline qusp  Australia
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sounds like the dac system has terrible PSRR

LM317 does not come close to the bandwidth or slew rate needed for supplying an SSD drive directly and it will be packed with SMPS internally.
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Old 6th January 2013, 08:23 AM   #39
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Qusp, things are not so obvious or straightforward. I am sure you are aware of sata filters, bespoke CAT5 and USB cables and other illogical entities.

At the time of the first asynchronous USB device most listeners expected the end of "audiophile" digital cabling, dependence on PC OSs, software and hardware. It wasn't to be. Next step was the ram buffer, optical isolation and subsequent recklocking. Did it eliminate the PC from the list of variables in the sound chain? Hardly.

For me it's far from clear what the linear supply achieves. The improvement in sound may be entirely coincidental and have nothing to do with the dac but rather with the level of RF pollution in the room. I recently used a class D amp to amplify a sine wave for my turntable motor. It achieved that admirably but made the sound of my phono setup extremely unpleasant just by spraying the room with RF.

No one in their right mind expects a 317 to have any bandwidth beyond a few kHz. So, what?
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Old 6th January 2013, 09:06 AM   #40
marce is offline marce  United Kingdom
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I give up, a linear PSU will have only a little difference to the noise spectrum you will find in your PC...layout, decoupling etc are the main contributers as a lot of the noise is generated by the circuitry switching. Get a de3cent scope and do some measurements you may get a shock.
What this does confirm to me is that the high frequency noise superimposed on the analogue signal is not audible.
As to sptraying the room with RF, get somthing thgat has been designed properly and dosn't spray the room with rf, thats common sense.
It is only after the DAC that we get analogue, up to that point the digital streem dose not care whaqt the PSU is and linerar or SMPS will not make any difference to the digital data flow.
Anyway its been an interesting discussion, I was hoping others would have some empirical data (measurements) that I could compare to measurements I have (I can not post them as they are covered by NDA's and other restricions), from these findings and subsequent tests developemnt, linear supplies lost out, due to bulk heat and noise already in the audio spectrum.
I must ask what is the difference between audiophile digital cabling and normal digital cabling, digital cabling is digitalk cabling, it very nicely follows the transmission line theorys first developed by Heaviside, so can and is engineered adequatly without any audiophile esoteric features.
A lot of the stuff being sold regarding digital audio is pure snake oil, it is a whole new market to pray and influence people fear of this new (!!!) digital age. Myths like solid state disks sounding better!!! Digital requires proper engineering practices and measurements to detect and solve problems...
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