" Having an ultra-low noise PSU is fairly irrelevant when the circuits being powered (CPU, logic, memory) generate such huge self-noise - this is not generally the case in pure analog circuitry."
Hi Richard
Then you had better go back to the drawing board with your new design.
Try telling that to the very many constructors of the Twisted Pear Buffalo DACs that have gone to lot of additional trouble by fitting numerous power transformers and shunt regulators such as the Salas and Paul Hynes regulators.
Power supply is every bit as important with digital, as it is with analogue.
I suggest you check out the original very B11 long thread if you haven't already done so. They aren't suffering from mass "Expectation bias" either .
Regards
Alex
P.S.
"Originally Posted by abraxalito
What I think happens with the 4A supply is its generating more RF (higher output currents mean bigger switching currents). This translates to more noise in your analog circuits and I think this results in greater sibilance. My guess is the result of this sibilance is emphasized transients (leading edges). That sibilance also brings grain and is more fatiguing to listen to over the longer term."
That seems a quite plausible explanation.
Hi Richard
Then you had better go back to the drawing board with your new design.
Try telling that to the very many constructors of the Twisted Pear Buffalo DACs that have gone to lot of additional trouble by fitting numerous power transformers and shunt regulators such as the Salas and Paul Hynes regulators.
Power supply is every bit as important with digital, as it is with analogue.
I suggest you check out the original very B11 long thread if you haven't already done so. They aren't suffering from mass "Expectation bias" either .
Regards
Alex
P.S.
"Originally Posted by abraxalito
What I think happens with the 4A supply is its generating more RF (higher output currents mean bigger switching currents). This translates to more noise in your analog circuits and I think this results in greater sibilance. My guess is the result of this sibilance is emphasized transients (leading edges). That sibilance also brings grain and is more fatiguing to listen to over the longer term."
That seems a quite plausible explanation.
Last edited:
Quite possibly faster slew rates of current inside the PSU yes. But the voltage slew rates will be about the same. Why do slew rates internal to a PSU interest you particularly? The 4A supply will have a bigger transformer - bigger normally means higher capacitance and hence more noise flowing around the loop.
Y caps are there to filter noise to ground. But unless you have a great quality ground connection, all that results is a more noisy ground. Better not to invite the noise in at all by presenting high impedance to it across a wide band. Have a look at my blog for ideas for DIYing better mains filters
To my ears, this filter does greatly improve the sound, but I may try the system without it, just to double check
Try with just CM chokes and no Y caps. Try more CM chokes in series and see how that affects the sound.
Actually, it is the slew rate of the digital chips in the router that interests me.
I could be way off the mark, but, faster rise time (even if only a tiny bit faster) giving squarer edges, may improve the sound??? I might be on my own with this one
but, I'm just trying to wrap my head around the stuff that shouldnt make sense, but does make a sonic difference. You see, I suspect that it was not only the extra noise that caused better dynamics, and I'm trying to figure out what that was.Y caps are there to filter noise to ground. But unless you have a great quality ground connection, all that results is a more noisy ground. Better not to invite the noise in at all by presenting high impedance to it across a wide band. Have a look at my blog for ideas for DIYing better mains filters
Try with just CM chokes and no Y caps. Try more CM chokes in series and see how that affects the sound.
OK, that makes sense. I will try this. Thank you for the suggestion
Then you had better go back to the drawing board with your new design.
Well if I hear a difference, I'll change various aspects, including the PSU and then I'll let you know what works OK?
Well then I'll just set the cat among the pigeons a bit more by saying that anyone using the Buffalo in my personal estimation has cloth ears and they're welcome to their investment in whatever turns them on
Try telling that to the engineers whose digital designs sell in the 100k and up volume market.
They aren't suffering from mass "Expectation bias" either .
My individual expectation bias says they most definitely are. How have you come to the conclusion they're not?
"Try telling that to the engineers whose digital designs sell in the 100k and up volume market."
They are one of the main reasons for the existence of DIYAudio !
Most commercial products are capable of improvement.
Part of this is undoubtedly due to the "bean counters" though.
P.S.
I don't have a TP Buffalo 11
But I trust the ears of several people who do, and can hear things that most EEs maintain are impossible !
They are one of the main reasons for the existence of DIYAudio !
Most commercial products are capable of improvement.
Part of this is undoubtedly due to the "bean counters" though.
P.S.
I don't have a TP Buffalo 11
But I trust the ears of several people who do, and can hear things that most EEs maintain are impossible !
Last edited:
The best way to control the slew rate of modern CMOS chips is via their power supply voltage. Lower voltage gives rise to slower slewing. This is not that difficult to try if all the circuits are fed from a single regulator - put an adjustable one in and see how low you can set the voltage before it gives up. If its running out of flash memory, probably that'll fall over first. But I see you want faster slewing - that might have an advantage in the few cases where its a clock signal, but otherwise I reckon slower is better.
My thinking tends to go the opposite way - slower slew rates mean lower noise levels. But I haven't tested it much - just when I play with HC logic I tend to prefer to run it cooler rather than hotter. CMOS takes a gulp of current from the power supply when it switches - an instantaneous crowbar if you will - the datasheets show this gulp of current is much lower at lower supply voltage. Running HC logic at 2.5V gives slower propagation delays (about double compared to 5V) but much lower noise and much lower power as a consequence. What's not to love?
Audio products, very definitely - check out my blog as I'm an avid modder. But what improvement would you suggest to the digital aspects of a mobile phone? Or to the embedded controller of a microwave oven ? Or of a digital camera? Those are the digital products I was more thinking about. Assuming there's enough space available to fit low noise supplies in these products, do you think you'd notice any improvement in their operation?
Perhaps we've been talking at cross-purposes here.
Faster rise times add more harmonics, increase the knee frequency and casue more signal integrity and EMC problems, goto go with Abraxalito on this one.
Using PC's and low cost consumer products as a generalisation regarding digital design is not going to give a true picture, cheep imports are not always up to the relevant CE or FCC specification, cos there is no stand alone testing, you sign the certificate, and cost cutting is necessary to survive in that market. If you want a good PC build your own from the best bits and get the biggest, best PSU you can afford, these are the main casue of failure for PC's and other consumer kit, as to build a good supply often costs more than the rest of the product.
Digital design does involve an awful lot of work on shielding, EMC compatability is a small part of the problem, the biggest problem is signal integrity (think of it as internal EMC to the circuit).
Regarding some of the differences heard, I would like to see info and waveforms of the digital data at the start of the convertion to analogue and the analogue output (we do this at work) only then can you start to understand where the issues are...
Using PC's and low cost consumer products as a generalisation regarding digital design is not going to give a true picture, cheep imports are not always up to the relevant CE or FCC specification, cos there is no stand alone testing, you sign the certificate, and cost cutting is necessary to survive in that market. If you want a good PC build your own from the best bits and get the biggest, best PSU you can afford, these are the main casue of failure for PC's and other consumer kit, as to build a good supply often costs more than the rest of the product.
Digital design does involve an awful lot of work on shielding, EMC compatability is a small part of the problem, the biggest problem is signal integrity (think of it as internal EMC to the circuit).
Regarding some of the differences heard, I would like to see info and waveforms of the digital data at the start of the convertion to analogue and the analogue output (we do this at work) only then can you start to understand where the issues are...
Bravo!....Same playback systems all the way to analog. Measure THAT output and see what really becomes of the digital distresses of PC audio. Given the prevelance and convenience of PC sound these days, it seems like analyzing one is about the most responsible thing we could be doing in this hobby right now. Whether or not some of these artifacts are actually audible could/should be determined by the end user. Proof of existence in measurements certainly helps to make informed decisions.
You would need some high resolution digital scope with memory and subsequent analysis of the stored series of samples. I do not know if precision of the ADCs in decent PC-based scopes would suffice. IMO it would require at least 16bits of resolution, possibly more.
Signal Integrity... EMC...
Two sides of the same coin, signal integrity is EMC problems at board level, i.e. the circuits self generated noise, crosstalk, reflections etc affecting itself, and EMC is noise from and to the environment surrounding the circuit. These days all digital design can and should be considered high speed, not only is the ultimate clock frequency important but rise time is also a determinating factor as the faster the rise time the higher the knee frequency and thus the higher the harmonics a circuit and its layout have to handle. And anything that relates to a PC will have very high speed digital interfaces, the two main culprits being the DDR memory interface and Ethernet.
Be it either a PC or and "audiophile DAC" for them to work correctly you have to follow high speed digital layout guidelines, and solve the signal integrity problems. PC's are built to a cost, as is most commercial equipment, and this will have an effect on the end product, this will affect the final result, and while it will work as a PC, audio is not generally on top of the design requirements. Thus there will be a certain level of noise present (SMPS are not the only culprit, one of the main causes is "simultaneous switching noise" generated by the device during its normal functioning), this noise can be tolerated by the digital system, but may/will have an effect on audio output quality. To make things worse for determinating you own factors this will vary greatly from PC to PC, sound card to sound card and between PSU's. This applies to ALL commercial products sold, cost is quite often king... but this does not mean corners are cut, they can be and generally the cheaper (bargain!) the product more corners have been cut.
But there are many products and equipment built and designed that are Audio (also instrumentation, control and visual) based with digital that are designed and PCB laid out to the highest possible standards, where signal integrity and function is king, and not cost. A lot of these designs make your average PC look like a calculator with numerous BGA based FPGA's DSP's etc for the digital signal processing of the audio (or other analogue) signal. These designs and good quality motherboards for PC's are laid out using not only the ECAD system , but also a powerful set of simulation tools for signal integrity, power delivery system verification, EMC and thermal verification. So not only are the boards laid out but all the critical aspects are investigated and hopefully solved before the first prototype boards are made. This is an iterative process that involves the virtual simulation, checking the functionality and verifying the simulation results with physical prototypes, rectifying any problems etc.
PCB Electronic Circuit Simulation Software, Solutions & Tools | HyperLynx® - Mentor Graphics
CADSTAR: Price / Performance PCB design software: SI Verify | Zuken
To do this requires both a lot of expensive equipment and some very expensive CAD software, plus a team of engineers and layout guys. The software I use (Cadstar, full blown with all the add-ons) runs into the 50K (£) region, the hardware guys have lots of funky and expensive equipment, and quite a substantial amount of time, plus having the money to pay for multi-layer boards (mandatory with digital these days). Even then a suspected problem may be hard to find and isolate, as there are so many influencing factors.
But if I was laying out an "Audiophile DAC, or any ultimate performance digital or analogue digital design (which I do quite often) what would I do:
Clocks, the heart of any digital system. On any digital design once you place a FPGA, microprocessor or any device that requires a clock, you place the clock generating circuitry next, with the clock signal being as close to the clock input pin as possible (nor through wires, that are uncontrolled impedance), and make this track as short as possible and shield it on both sides with ground tracks or pours, with a contiguous ground plane underneath (or better still route it as a stripline with ground on all 4 sides). Also use a good quality OCXO based oscillator, with either a pi filtered power supply (COG caps, ferrite bead) or even its own linear LDO regulator.
Use controlled impedance PCB stack up.
Use HDI (high density interconnect) PCB layout techniques, with outer layers ground for shielding, for the ultimate design.
Follow high speed layout and EMC reducing layout techniques and verify results using simulation.
Use closely coupled ground and power planes for planar capacitance for increased noise reduction and a cleaner power delivery system.
Contiguous ground planes, one per signal/power plane layer, all signals where possible routed as stripline (buried on an inner layer, no air dielectric).
Isolate where possible all input and output signals, and employ the correct amount of EMC protection.
Use small MLCC capacitors for decoupling, X7R for general decoupling, COG on clock and oscillator devices.
etc.
For the digital side the standard reference "High Speed Digital Design" Howard Johnson & Martin Graham, also "Electromagnetic Compatibility Engineering" Henry Ott, covers the EMC side of things.
Here is also an eclectic mix of links and references I use for general reference and for others wanting to investigate the world of digital layout, especially high speed design, but should also give a good insight into the problems and solutions to look for.
http://www.elmac.co.uk/pdfs/Lord_of_the_board.pdf
Star Grounding Wars
http://www.cvel.clemson.edu/Presentation_Slides/PowerBus-Decoupling.pdf
PCB007 Quiet Power: Resonances in Power Planes
PCB007 Quiet Power: How Thin Laminates Suppress Resonances
PCB007 Do Not Perforate Planes Unnecessarily
http://www.ipblox.com/pubs/DesignCon_2011/11-TA3Paper_Weir_color.pdf
http://electrical-integrity.com/Quietpower_files/Quietpower-6.pdf
http://electrical-integrity.com/Quietpower_files/Quietpower-7.pdf
http://electrical-integrity.com/Quietpower_files/Quietpower-8.pdf
http://electrical-integrity.com/Quietpower_files/Quietpower-9.pdf
http://www.electrical-integrity.com/Paper_download_files/EPEP98_DET.pdf
Ground Pours: To Pour or Not to Pour?
http://www.goldphoenixpcb.biz/pdf/Loop_Area_Decoupling.pdf
beTheSignal - BTS-305 Battling Ferrite Superstition
http://www.speedingedge.com/PDF-Files/BTS006_What_Is_Inductance (2).pdf
MIL-STD-461: Requirements for the Control of Electromagnetic Interference Characteristics of Subsystems and Equipment - Advanced Test Equipment Rentals
http://www.sigrity.com/papers/Power Integrity Analysis December 2009.pdf
http://alicedcs.web.cern.ch/alicedcs/ElectrCoord/Documents/Gnd_gen/TIS_Grounding.pdf
Clock Jitter Cleaners | National Semiconductor ? Lowest Jitter LMK Precision Clock Conditioners
http://www.nalanda.nitc.ac.in/industry/appnotes/Texas/dsp/slyt012a.pdf
http://focus.ti.com/lit/an/slyt026/slyt026.pdf
http://focus.tij.co.jp/jp/lit/an/slyt319/slyt319.pdf
http://focus.ti.com/lit/an/slyt051/slyt051.pdf
http://www.designcon.com/2010/DCPDFs/TF-MP5_Lee_Ritchey.pdf
http://focus.ti.com/lit/ml/slyp167/slyp167.pdf
http://www.e2v.com/assets/media/files/documents/broadband-data-converters/doc0999B.pdf
Printed Circuit Design & Fab Magazine Online
EMC Testing etc
A Practical Interference Free Audio System (Part 2)
Designing for Interference-free Audio System Components
http://www.compliance-club.com/pdf/EMCTestingPart1.pdf
http://www.compliance-club.com/pdf/EMCTestingPart2.pdf
http://www.compliance-club.com/pdf/EMCTestingPart3.pdf
http://www.compliance-club.com/pdf/EMCTestingPart4.pdf
http://www.compliance-club.com/pdf/EMCTestingPart5.pdf
http://www.compliance-club.com/pdf/EMCTestingPart6.pdf
http://www.compliance-club.com/pdf/EMCTestingPart7.pdf
MISC
http://electronica.ugr.es/~amroldan/pcb/2007/modulos/temas/ReferenceDesignators.pdf
http://www.ucamco.com/public/RS-274X_Extended_Gerber_Format_Specification_201012.pdf
http://www.downstreamtech.com/support_cam/Advisories/IPCD356_Simplified.pdf
http://pcbtalk.com/data/upload/Designing_Balanced_PCBs.pdf
http://www.pcb3d.com/uploads/PCB_Design_and_Fabrication_Process.pdf
http://www.alternatezone.com/electronics/files/PCBDesignTutorialRevA.pdf
http://www.dnu.no/arkiv1/The CAD Library of the Future.pdf
http://www.ece.unh.edu/courses/ece7...onent Zero Orientations for CAD Libraries.pdf
http://www.smtnet.com/library/files/upload/The-Universal-PCB-Design-Grid-System.pdf
Screen and stencil printing
http://www.rakon.com/Products/Public Documents/Whitepapers/PHASE NOISE IN CRYSTAL OSCILLATORS.pdf
http://www.analog.com/static/imported-files/tutorials/MT-008.pdf
Right the First Time
RF
YO3DAC\Home Page
He He
http://www.edn.com/contents/images/243231.pdf
Printed Circuit Design & Fab Magazine Online
http://www.hottconsultants.com/techtips/split-gnd-plane.html
http://www.elmac.co.uk/pdfs/Lord_of_the_board.pdf
An intuitive, practical approach to mixed-signal grounding
http://focus.ti.com/lit/an/sbaa052/sbaa052.pdf
http://focus.ti.com/lit/ml/slyp167/slyp167.pdf
http://www.ieee.org.uk/docs/emc1206a.pdf
http://www.icd.com.au/articles/Split_Planes_AN2010_6.pdf
http://www.analog.com/static/import...gue/5467026043687049331665676350Grounding.pdf
http://www.analog.com/static/imported-files/tutorials/MT-031.pdf
Laid out the digital and ADC boards for Syntel for this project,
(unfortenatly Syntel is now defunct) all multi layer with ground planes.
http://accelconf.web.cern.ch/accelconf/e94/PDF/EPAC1994_1551.PDF
http://accelconf.web.cern.ch/accelconf/e94/PDF/EPAC1994_2333.PDF
But most of all have fun
Two sides of the same coin, signal integrity is EMC problems at board level, i.e. the circuits self generated noise, crosstalk, reflections etc affecting itself, and EMC is noise from and to the environment surrounding the circuit. These days all digital design can and should be considered high speed, not only is the ultimate clock frequency important but rise time is also a determinating factor as the faster the rise time the higher the knee frequency and thus the higher the harmonics a circuit and its layout have to handle. And anything that relates to a PC will have very high speed digital interfaces, the two main culprits being the DDR memory interface and Ethernet.
Be it either a PC or and "audiophile DAC" for them to work correctly you have to follow high speed digital layout guidelines, and solve the signal integrity problems. PC's are built to a cost, as is most commercial equipment, and this will have an effect on the end product, this will affect the final result, and while it will work as a PC, audio is not generally on top of the design requirements. Thus there will be a certain level of noise present (SMPS are not the only culprit, one of the main causes is "simultaneous switching noise" generated by the device during its normal functioning), this noise can be tolerated by the digital system, but may/will have an effect on audio output quality. To make things worse for determinating you own factors this will vary greatly from PC to PC, sound card to sound card and between PSU's. This applies to ALL commercial products sold, cost is quite often king... but this does not mean corners are cut, they can be and generally the cheaper (bargain!) the product more corners have been cut.
But there are many products and equipment built and designed that are Audio (also instrumentation, control and visual) based with digital that are designed and PCB laid out to the highest possible standards, where signal integrity and function is king, and not cost. A lot of these designs make your average PC look like a calculator with numerous BGA based FPGA's DSP's etc for the digital signal processing of the audio (or other analogue) signal. These designs and good quality motherboards for PC's are laid out using not only the ECAD system , but also a powerful set of simulation tools for signal integrity, power delivery system verification, EMC and thermal verification. So not only are the boards laid out but all the critical aspects are investigated and hopefully solved before the first prototype boards are made. This is an iterative process that involves the virtual simulation, checking the functionality and verifying the simulation results with physical prototypes, rectifying any problems etc.
PCB Electronic Circuit Simulation Software, Solutions & Tools | HyperLynx® - Mentor Graphics
CADSTAR: Price / Performance PCB design software: SI Verify | Zuken
To do this requires both a lot of expensive equipment and some very expensive CAD software, plus a team of engineers and layout guys. The software I use (Cadstar, full blown with all the add-ons) runs into the 50K (£) region, the hardware guys have lots of funky and expensive equipment, and quite a substantial amount of time, plus having the money to pay for multi-layer boards (mandatory with digital these days). Even then a suspected problem may be hard to find and isolate, as there are so many influencing factors.
But if I was laying out an "Audiophile DAC, or any ultimate performance digital or analogue digital design (which I do quite often) what would I do:
Clocks, the heart of any digital system. On any digital design once you place a FPGA, microprocessor or any device that requires a clock, you place the clock generating circuitry next, with the clock signal being as close to the clock input pin as possible (nor through wires, that are uncontrolled impedance), and make this track as short as possible and shield it on both sides with ground tracks or pours, with a contiguous ground plane underneath (or better still route it as a stripline with ground on all 4 sides). Also use a good quality OCXO based oscillator, with either a pi filtered power supply (COG caps, ferrite bead) or even its own linear LDO regulator.
Use controlled impedance PCB stack up.
Use HDI (high density interconnect) PCB layout techniques, with outer layers ground for shielding, for the ultimate design.
Follow high speed layout and EMC reducing layout techniques and verify results using simulation.
Use closely coupled ground and power planes for planar capacitance for increased noise reduction and a cleaner power delivery system.
Contiguous ground planes, one per signal/power plane layer, all signals where possible routed as stripline (buried on an inner layer, no air dielectric).
Isolate where possible all input and output signals, and employ the correct amount of EMC protection.
Use small MLCC capacitors for decoupling, X7R for general decoupling, COG on clock and oscillator devices.
etc.
For the digital side the standard reference "High Speed Digital Design" Howard Johnson & Martin Graham, also "Electromagnetic Compatibility Engineering" Henry Ott, covers the EMC side of things.
Here is also an eclectic mix of links and references I use for general reference and for others wanting to investigate the world of digital layout, especially high speed design, but should also give a good insight into the problems and solutions to look for.
http://www.elmac.co.uk/pdfs/Lord_of_the_board.pdf
Star Grounding Wars
http://www.cvel.clemson.edu/Presentation_Slides/PowerBus-Decoupling.pdf
PCB007 Quiet Power: Resonances in Power Planes
PCB007 Quiet Power: How Thin Laminates Suppress Resonances
PCB007 Do Not Perforate Planes Unnecessarily
http://www.ipblox.com/pubs/DesignCon_2011/11-TA3Paper_Weir_color.pdf
http://electrical-integrity.com/Quietpower_files/Quietpower-6.pdf
http://electrical-integrity.com/Quietpower_files/Quietpower-7.pdf
http://electrical-integrity.com/Quietpower_files/Quietpower-8.pdf
http://electrical-integrity.com/Quietpower_files/Quietpower-9.pdf
http://www.electrical-integrity.com/Paper_download_files/EPEP98_DET.pdf
Ground Pours: To Pour or Not to Pour?
http://www.goldphoenixpcb.biz/pdf/Loop_Area_Decoupling.pdf
beTheSignal - BTS-305 Battling Ferrite Superstition
http://www.speedingedge.com/PDF-Files/BTS006_What_Is_Inductance (2).pdf
MIL-STD-461: Requirements for the Control of Electromagnetic Interference Characteristics of Subsystems and Equipment - Advanced Test Equipment Rentals
http://www.sigrity.com/papers/Power Integrity Analysis December 2009.pdf
http://alicedcs.web.cern.ch/alicedcs/ElectrCoord/Documents/Gnd_gen/TIS_Grounding.pdf
Clock Jitter Cleaners | National Semiconductor ? Lowest Jitter LMK Precision Clock Conditioners
http://www.nalanda.nitc.ac.in/industry/appnotes/Texas/dsp/slyt012a.pdf
http://focus.ti.com/lit/an/slyt026/slyt026.pdf
http://focus.tij.co.jp/jp/lit/an/slyt319/slyt319.pdf
http://focus.ti.com/lit/an/slyt051/slyt051.pdf
http://www.designcon.com/2010/DCPDFs/TF-MP5_Lee_Ritchey.pdf
http://focus.ti.com/lit/ml/slyp167/slyp167.pdf
http://www.e2v.com/assets/media/files/documents/broadband-data-converters/doc0999B.pdf
Printed Circuit Design & Fab Magazine Online
EMC Testing etc
A Practical Interference Free Audio System (Part 2)
Designing for Interference-free Audio System Components
http://www.compliance-club.com/pdf/EMCTestingPart1.pdf
http://www.compliance-club.com/pdf/EMCTestingPart2.pdf
http://www.compliance-club.com/pdf/EMCTestingPart3.pdf
http://www.compliance-club.com/pdf/EMCTestingPart4.pdf
http://www.compliance-club.com/pdf/EMCTestingPart5.pdf
http://www.compliance-club.com/pdf/EMCTestingPart6.pdf
http://www.compliance-club.com/pdf/EMCTestingPart7.pdf
MISC
http://electronica.ugr.es/~amroldan/pcb/2007/modulos/temas/ReferenceDesignators.pdf
http://www.ucamco.com/public/RS-274X_Extended_Gerber_Format_Specification_201012.pdf
http://www.downstreamtech.com/support_cam/Advisories/IPCD356_Simplified.pdf
http://pcbtalk.com/data/upload/Designing_Balanced_PCBs.pdf
http://www.pcb3d.com/uploads/PCB_Design_and_Fabrication_Process.pdf
http://www.alternatezone.com/electronics/files/PCBDesignTutorialRevA.pdf
http://www.dnu.no/arkiv1/The CAD Library of the Future.pdf
http://www.ece.unh.edu/courses/ece7...onent Zero Orientations for CAD Libraries.pdf
http://www.smtnet.com/library/files/upload/The-Universal-PCB-Design-Grid-System.pdf
Screen and stencil printing
http://www.rakon.com/Products/Public Documents/Whitepapers/PHASE NOISE IN CRYSTAL OSCILLATORS.pdf
http://www.analog.com/static/imported-files/tutorials/MT-008.pdf
Right the First Time
RF
YO3DAC\Home Page
He He
http://www.edn.com/contents/images/243231.pdf
Printed Circuit Design & Fab Magazine Online
http://www.hottconsultants.com/techtips/split-gnd-plane.html
http://www.elmac.co.uk/pdfs/Lord_of_the_board.pdf
An intuitive, practical approach to mixed-signal grounding
http://focus.ti.com/lit/an/sbaa052/sbaa052.pdf
http://focus.ti.com/lit/ml/slyp167/slyp167.pdf
http://www.ieee.org.uk/docs/emc1206a.pdf
http://www.icd.com.au/articles/Split_Planes_AN2010_6.pdf
http://www.analog.com/static/import...gue/5467026043687049331665676350Grounding.pdf
http://www.analog.com/static/imported-files/tutorials/MT-031.pdf
Laid out the digital and ADC boards for Syntel for this project,
(unfortenatly Syntel is now defunct) all multi layer with ground planes.
http://accelconf.web.cern.ch/accelconf/e94/PDF/EPAC1994_1551.PDF
http://accelconf.web.cern.ch/accelconf/e94/PDF/EPAC1994_2333.PDF
But most of all have fun
Wow Marce!
I guess I know what I'll be doing today...that's a lot of reading to do, so I'll just give you a rather tentative "Thanks in Advance."
Just kidding, any information that gives even a clue as to what's going on is helpful. We've found, as others working independantly have, that somethings work well with PC audio, but the exact mechanism is somewhat(?) vague. IOW, you may know from experience that something works, but lack a scientific explanation as to exactly why. I do believe that the insistance on an airtight explanation, and a failure on the part of sceptical, or less motivated people (not necessarily the same people), to actually try some of the suggested methods has been counterproductive.
Best Regards,
TerryO
I guess I know what I'll be doing today...that's a lot of reading to do, so I'll just give you a rather tentative "Thanks in Advance."
Just kidding, any information that gives even a clue as to what's going on is helpful. We've found, as others working independantly have, that somethings work well with PC audio, but the exact mechanism is somewhat(?) vague. IOW, you may know from experience that something works, but lack a scientific explanation as to exactly why. I do believe that the insistance on an airtight explanation, and a failure on the part of sceptical, or less motivated people (not necessarily the same people), to actually try some of the suggested methods has been counterproductive.
Best Regards,
TerryO
So then using USB to isolate the signal from the computer to an external DAC is about as good as it gets, right?
Sounds a lot like an external DAC such as the Gamma 2:
The γ2 Compact High Performance DAC
I'm still wondering how much of a difference a single rail, audiophile grade power humpty might make. I bet the bitcoin miners would love a single rail behemoth as well.
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The USB interface by itself does not provide for isolation. If I were choosing (rather than as I currently am, designing) DACs I'd be looking for one that has taken significant measures to control common-mode noise from the PC. Isolation does not need to be of the currently fashionable 'galvanic' form to accomplish this. Yet PCs are a major source of EM hash so getting this right is no mean feat. If the transfer mode is async and the choice of USB cable makes a difference to the sound, that's a sign the isolation still is not optimal.
Hi,
However Galvanic is so easy to do. All but the main clock can use opto-isolators followed by re-clocking. The Audio Clock's are best located at the DAC and are switched by the USB device via opto-couplers and this clock can then be transformer isolated to feed the USB device. COst increase over non-isolated devices would be quite low.
Yes. PC's cause several very real problems in the Domains of EMC/EMI and ground noise that most do not account for. And then we get the idiotic representation that for example USB Cables (or Mains cables) cannot make a difference because "bits are bit's", when in reality we find that with real devices and real systems not only CAN they make differences, but in fact they must make differences.
But not to worry, the same people also have their ABX tests just to make sure they can prove to you that what you hear you do not hear, with as much real world reasonableness as their "bits are bits" comments that simply are not relevant in the context.
One thing that can be done to help a PC in system is to make a Power conditioner that uses a transformer with electrostatic screen and balanced 110V AC power output (PC's and other stuff with switched mode supplies can all handle this) and first of all pull the earth of on the PC (which can be safely with such a system) and to stop noise going anywhere to add serious power filtering.
While the PC still produces noise, it has now a much harder time to "circulate" around the grounds and earth, which is what is the primary source of our problems.
Ciao T
However Galvanic is so easy to do. All but the main clock can use opto-isolators followed by re-clocking. The Audio Clock's are best located at the DAC and are switched by the USB device via opto-couplers and this clock can then be transformer isolated to feed the USB device. COst increase over non-isolated devices would be quite low.
Yes. PC's cause several very real problems in the Domains of EMC/EMI and ground noise that most do not account for. And then we get the idiotic representation that for example USB Cables (or Mains cables) cannot make a difference because "bits are bit's", when in reality we find that with real devices and real systems not only CAN they make differences, but in fact they must make differences.
But not to worry, the same people also have their ABX tests just to make sure they can prove to you that what you hear you do not hear, with as much real world reasonableness as their "bits are bits" comments that simply are not relevant in the context.
One thing that can be done to help a PC in system is to make a Power conditioner that uses a transformer with electrostatic screen and balanced 110V AC power output (PC's and other stuff with switched mode supplies can all handle this) and first of all pull the earth of on the PC (which can be safely with such a system) and to stop noise going anywhere to add serious power filtering.
While the PC still produces noise, it has now a much harder time to "circulate" around the grounds and earth, which is what is the primary source of our problems.
Ciao T
Here's a crazy idea - why not rectify the mains external to the PC with power factor corrector and feed in 400V (200V US-side) DC heavily filtered? At least this will cut down on rectifier hash and SMPSUs will probably do better with nice clean DC seeing that's what they try to create anyway before chopping it up. I believe this approach is also used in server farms to save energy, so perhaps it has 'green' credentials too?
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