Seems like I am dumb founded, that you've found the missing wide band decouple caps. I just have not seen that decoupling can completely reduce and absolve the switching noise at that components or across many circuits, even when their one per device.
Guido, to remove circulating ground currents they have to cancel if not they add. When you have multiple ground planes in a mixed signal, application cancellation becomes simple. You just cannot, compare a tube amps grounding scheme with a complex digital and analog systems.
As I stated before, one big fat ground plane layer can work, but it needs the proper circuit’s design and power low impedance power distribution and good decoupling. However, it is difficult to get their without expertise. A
Also, look up common mode rejection on the best opamp’s, it very poor in the MHz range.
Keep Build them clocks
Cheers
Jim
Guido, to remove circulating ground currents they have to cancel if not they add. When you have multiple ground planes in a mixed signal, application cancellation becomes simple. You just cannot, compare a tube amps grounding scheme with a complex digital and analog systems.
As I stated before, one big fat ground plane layer can work, but it needs the proper circuit’s design and power low impedance power distribution and good decoupling. However, it is difficult to get their without expertise. A
Also, look up common mode rejection on the best opamp’s, it very poor in the MHz range.
Keep Build them clocks
Cheers
Jim
Thanks for the info..
Thanks for the info Petter. I thought you could use a value lower than 2.5W, but clearly damage will occur if our resistor is not sufficiently robust.
🙂
Thanks for the info Petter. I thought you could use a value lower than 2.5W, but clearly damage will occur if our resistor is not sufficiently robust.
🙂
jewilson said:
Hello Jim,
I agree on your remark on expertise & opamps
My main point is to prevent currents through the plane, by
- applying, and physically correctly connecting, decoupling capacitance (or shunt regulator)
- adding series impedance (RF) in each supply line
By doing so, no low impedance power distribtion scheme is required, simply because "DC" runs through the supply lines
I agree that this philosophy does not fully take away any noise currents through the plane, but 15 years of experience have shown that this philosophy gives far better results on AD and DA designs, when comparing them with any demo board I have seen (TI, BB, Crystal, you name them). I am talking signal integrity, not even RF emissions..........
In the basics my philosophy does not differ from my favourite tube amp grounding scheme
thanks for your reply, interesting discussion
enjoy
Guido,
Your right, some of the demo boards are not so hot. You know, the engineers that design these demo boards are not the same people that design the chips and some don't have that much experience. Yea, I would not take my lead from a demo board from them either.
Regards
Your right, some of the demo boards are not so hot. You know, the engineers that design these demo boards are not the same people that design the chips and some don't have that much experience. Yea, I would not take my lead from a demo board from them either.
Regards
Are there any good examples of the ground plane technique?
My goodness
I appear to have sparked debate!
If I can summarise for my own sake....
'A big fat ground plane' is great, but only if you can successfully implement it.
Q. Guido, are there any good example materials on the web to illustrate your design ideals? e.g. layout photos or diagrams.
I intend to produce a DIY dac and lack your wealth of experience.
I simply design my PCBs by eye, with educated guesses as to where return currents flow. To date I have used split grounding methods with no audiable problems, but could I do better with your methods?
For my situation:
Is a single ground plane or split grounding a safer overall bet?
(I am sure both parties will make their case here, so please be gentle!)
My goodness I appear to have sparked debate!
If I can summarise for my own sake....
'A big fat ground plane' is great, but only if you can successfully implement it.
Q. Guido, are there any good example materials on the web to illustrate your design ideals? e.g. layout photos or diagrams.
I intend to produce a DIY dac and lack your wealth of experience.
I simply design my PCBs by eye, with educated guesses as to where return currents flow. To date I have used split grounding methods with no audiable problems, but could I do better with your methods?
For my situation:
Is a single ground plane or split grounding a safer overall bet?
(I am sure both parties will make their case here, so please be gentle!)
I am going to split everything, but the grounds will be connected at a point of my choosing. I am also using 4 layer boards and applying shield on several layers to try to keep the ground clean. Hopefully this will be adequate.
I have been doing layout around the DAC for the last few days (power only until today when I actually connected the outputs ....)
Interesting and timely discussion. Thanks to all contributors.
Petter
I have been doing layout around the DAC for the last few days (power only until today when I actually connected the outputs ....)
Interesting and timely discussion. Thanks to all contributors.
Petter
Resistors in the digital signal lines too...
This discussion has given me loads of ideas.
I have a prototype of my DAC with 'star' earthing. It has already suffered significant modification and wants to fall apart!
I believe it can survive some further tweaking with the grounding. I want to prove to myself that connecting the different grounds at many points will do no harm- perhaps hint at improvement. Only then will I know if a ground plane is viable for my application, or that I should stick to the familiar 'star' method.
I notice that Guido prescribes the use of resistors in the digital signal path as a method to reduce the demand on the supply lines and hence the size of return currents. I am using VHC flip-flops for reclocking with a 100Mhz asynchronous clock.
Q. As a rule of thumb, will 1k resistors do the trick with all my HC and VHC logic?
Q. Has anyone else had success with using resistors in digital signal lines, or do you feel it hampers the signal-to-noise ratio?
Cheers...
This discussion has given me loads of ideas.
I have a prototype of my DAC with 'star' earthing. It has already suffered significant modification and wants to fall apart!
I believe it can survive some further tweaking with the grounding. I want to prove to myself that connecting the different grounds at many points will do no harm- perhaps hint at improvement. Only then will I know if a ground plane is viable for my application, or that I should stick to the familiar 'star' method.
I notice that Guido prescribes the use of resistors in the digital signal path as a method to reduce the demand on the supply lines and hence the size of return currents. I am using VHC flip-flops for reclocking with a 100Mhz asynchronous clock.
Q. As a rule of thumb, will 1k resistors do the trick with all my HC and VHC logic?
Q. Has anyone else had success with using resistors in digital signal lines, or do you feel it hampers the signal-to-noise ratio?
Cheers...
Peter,
That is the best thing you can do for a DAC is multilayered grounds. What kind of dac are you using and what are you doing for the supply and filters. 🙂
Oil,
If possible you should stick to ALS logic. High Speed COMS will under shoot ground and ring, dumbing spike on ground. Of course You really don't need 100Mhz clock. Try using one of Jocko Homo clocks their really clean. I mean dam clean. Also, 1K ohm is to large more like a 100ohm or lower.
🙂 😀
That is the best thing you can do for a DAC is multilayered grounds. What kind of dac are you using and what are you doing for the supply and filters. 🙂
Oil,
If possible you should stick to ALS logic. High Speed COMS will under shoot ground and ring, dumbing spike on ground. Of course You really don't need 100Mhz clock. Try using one of Jocko Homo clocks their really clean. I mean dam clean. Also, 1K ohm is to large more like a 100ohm or lower.
🙂 😀
jewilson said:
Thanks for the encouragement. I will do exactly this - one layer is power, another is ground, and then I will likely fill top and bottom with ground as well unless you recommend otherwise (initial plan was ground one side, power the other).
I am using multiple PCM1794's per channel in mono-mode. Currently I have a setup of 2 units stomach to stomach. Filtering on analog ground is one 0805 multilayer ceramic on each pin, as well as larger organic polymer electrolytics, also in SMD with mininal distance to pins. For power I am using 1206 multi-layer SMD's but have not yet finalized the larger caps - I will probably end up with SMD's right on these as well, at least where I have space, but then again there is a power plane so impedance is low anyway.
Filtering on digital ground and power is identical: one 0805 SMD + one larger SMD also set up for minimal distances to pins.
I have not yet decided what to do with power nor where to hook up the grounds. My plan is to have at least 4 DAC chips per channel, but I may end up trying with two 🙂
Suggestions for both analog and digital power would be most welcome. I am considering using high-speed op-amps as well as low speed supplies. This one is tricky. I quite like the "isolation approach suggested on this thread.
I aim to have analog +5V, 0V and +-18V.
Initially the unit is a graft into Behringer DCX2496 and so I can likely work directly from l/RCLK, BCLK, MCLK, SDATA and I may well choose to reclock these.
Petter
Peter,
Check out this tread, I am using one a bunch of these regulators on my DAC. http://www.diyaudio.com/forums/showthread.php?threadid=20937&goto=newpost read through most of the thread.
Also, If you using +/-12 volts for the analog you will have a larger option for the part you can use. Many of the new Opamp will pop with +/-15.
The next important issue is the receiver interface.
On the power leads if you put regulators very close to the DAC and opamps you'll have more options, or you can have longer runs. However it best to have the power supply outputs as close as possible.
🙂
Check out this tread, I am using one a bunch of these regulators on my DAC. http://www.diyaudio.com/forums/showthread.php?threadid=20937&goto=newpost read through most of the thread.
Also, If you using +/-12 volts for the analog you will have a larger option for the part you can use. Many of the new Opamp will pop with +/-15.
The next important issue is the receiver interface.
On the power leads if you put regulators very close to the DAC and opamps you'll have more options, or you can have longer runs. However it best to have the power supply outputs as close as possible.
🙂
Thanks Jim
Jim,
Thanks for the info.
I am using VHC logic to accomodate a 100Mhz clock. The ALS data sheets I have read so far extend to only 80Mhz. I am using Elso Kwak's clock. It sounds fine and I do not wish to explore other options in this department yet..... (I realise that 100Mhz is not essential)
I will try some 100R resistors in line with the logic of my prototype. Can I put these in the clock line itself?
Cheers
Jim,
Thanks for the info.
I am using VHC logic to accomodate a 100Mhz clock. The ALS data sheets I have read so far extend to only 80Mhz. I am using Elso Kwak's clock. It sounds fine and I do not wish to explore other options in this department yet..... (I realise that 100Mhz is not essential)
I will try some 100R resistors in line with the logic of my prototype. Can I put these in the clock line itself?
Cheers
Oli,
Well use as few VHC gates and chips as possible. Tie all unused gate high through a resistor that the comon procedure. Decouple them with .01 and .001 caps. Also, If your using dip packages you can place the decoupling cap underneath and between the power and ground pins.
Well use as few VHC gates and chips as possible. Tie all unused gate high through a resistor that the comon procedure. Decouple them with .01 and .001 caps. Also, If your using dip packages you can place the decoupling cap underneath and between the power and ground pins.
Re: Are there any good examples of the ground plane technique?
Hi
you may look here
http://members.chello.nl/~m.heijligers/DAChtml/dactop.htm
and here
http://members.chello.nl/~m.heijligers/DAChtml/Supply_decoupling.pdf
succes, especially to those splitting groundplanes
Oli said:
Hi
you may look here
http://members.chello.nl/~m.heijligers/DAChtml/dactop.htm
and here
http://members.chello.nl/~m.heijligers/DAChtml/Supply_decoupling.pdf
succes, especially to those splitting groundplanes
No Luck Needed
Guido,
"We don't need no stinking luck" becuase it's the correct method. It's proven by Bell Labs, Analog Devices, Texas Instruments and others.😀
Guido,
"We don't need no stinking luck" becuase it's the correct method. It's proven by Bell Labs, Analog Devices, Texas Instruments and others.😀
Re: No Luck Needed
Sure, and these companies are right, by definition
You do not want to know how many of their famous demo boards I improved.....
Anyhow, I gave my backgrounds and reasoning, and all of you are free to try it, or do it differently
Ciao
jewilson said:
Sure, and these companies are right, by definition
You do not want to know how many of their famous demo boards I improved.....
Anyhow, I gave my backgrounds and reasoning, and all of you are free to try it, or do it differently
Ciao
Guido,
Maybe you should move to the US and teach us all how grounding must be implemented. It’s a amazing that us bunch of ignorant engineers at Texas Instruments were able to make $200 million dollars a year designing analog-digital acquisition with split grounds.
🙄
Maybe you should move to the US and teach us all how grounding must be implemented. It’s a amazing that us bunch of ignorant engineers at Texas Instruments were able to make $200 million dollars a year designing analog-digital acquisition with split grounds.
🙄jewilson said:Guido,
Maybe you should move to the US and teach us all how grounding must be implemented. It’s a amazing that us bunch of ignorant engineers at Texas Instruments were able to make $200 million dollars a year designing analog-digital acquisition with split grounds.
Hi Jim
Been a few times to Texas, love the food over there, it is too hot though.....
I learned that audio applications are highly sensitive, and there is a major difference between a working (functional) application, and a decent sounding one.
I hear it, and I can measure it, otherwise I would have come up with different philosophy.
Suggestion: Measure the voltage (Time domain, wideband, say 200 MHz) between 2 planes.
regards
-
Guido
Personally I will not discount any reasonable ground scheme
Personally I will not discount any reasonable ground scheme
(unless its too much hassle
)
I find it ironic that my 'good sounding' prototype is a culmination of the ideas of the big boys: Crystal Semiconductor, Philips, Burr Brown, Analogue Devices, Texas Instruments et al. It also includes the more 'maverick' ideas of individuals such as Kusunoki, Wildmonkeysects, Kwak, and now... Tent.
If it works for me I use it 😀
Back to more technical matters....
The sizes of resistor in the data lines and clock line must matter:
I was going to make a big deal about the pulse width a 100Mhz, but suddenly I remembered the output of Elso Kwak's clock looks nothing like a square wave- any resistor in the data line may distort the waveform and induce jitter. Agree? No resistor in clock line?
How can you calculate the correct resistor for a given frequency? (or is it more a rule of thumb?)
In particular I am concerned with the Sdata, Sclk, Bclk lines. Will 100R do?
Personally I will not discount any reasonable ground scheme
(unless its too much hassle
)I find it ironic that my 'good sounding' prototype is a culmination of the ideas of the big boys: Crystal Semiconductor, Philips, Burr Brown, Analogue Devices, Texas Instruments et al. It also includes the more 'maverick' ideas of individuals such as Kusunoki, Wildmonkeysects, Kwak, and now... Tent.
If it works for me I use it 😀
Back to more technical matters....
The sizes of resistor in the data lines and clock line must matter:
I was going to make a big deal about the pulse width a 100Mhz, but suddenly I remembered the output of Elso Kwak's clock looks nothing like a square wave- any resistor in the data line may distort the waveform and induce jitter. Agree? No resistor in clock line?
How can you calculate the correct resistor for a given frequency? (or is it more a rule of thumb?)
In particular I am concerned with the Sdata, Sclk, Bclk lines. Will 100R do?
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