Re: Personally I will not discount any reasonable ground scheme
Hi Oli,
I am sorry but your post is most confusing. What clock are you talking about?
The one in the Asynchronous Reclocker or the KWAK-CLOCK? The latter produces a square wave for sure but with an ordinary probe it will look like a distorted sine wave.
The clock in the ASR is kind of sine wave as no comparator is used to square it up. BTW, though a 100MHz crystal is used the frequency of oscillation is about 60-66 MHz. I looked up in the DM74ALS74 datasheet from Fairchild and the maximum clockfrequency is about 34 MHz. So I am afraid this part is not usable in the ASR.
I have tried resistors in clock, data and wordclock lines but did not hear any difference so I stopped using these.
Me using "Maverick" ideas??? Don't think so....😱
Oli said: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?
Hi Oli,
I am sorry but your post is most confusing. What clock are you talking about?
The one in the Asynchronous Reclocker or the KWAK-CLOCK? The latter produces a square wave for sure but with an ordinary probe it will look like a distorted sine wave.
The clock in the ASR is kind of sine wave as no comparator is used to square it up. BTW, though a 100MHz crystal is used the frequency of oscillation is about 60-66 MHz. I looked up in the DM74ALS74 datasheet from Fairchild and the maximum clockfrequency is about 34 MHz. So I am afraid this part is not usable in the ASR.
I have tried resistors in clock, data and wordclock lines but did not hear any difference so I stopped using these.
Me using "Maverick" ideas??? Don't think so....😱
Elso,
Your correct the ALS according to the TI data book is good for 100MHz clock max, and I bet that really pushing it.
Your correct the ALS according to the TI data book is good for 100MHz clock max, and I bet that really pushing it.
ALS logic
Huh,
then there is a big difference in max. permissible clock speed between Fairchild and TI.
I looked it up in the TI datasheet. The 100MHz is for the AS part. The ALS part has the same fmax as the Fairchild part.
jewilson said:
Huh,
then there is a big difference in max. permissible clock speed between Fairchild and TI.
I looked it up in the TI datasheet. The 100MHz is for the AS part. The ALS part has the same fmax as the Fairchild part.
Re: Personally I will not discount any reasonable ground scheme
Hi Oli
The value is the tradeoff: It defines the slope of the clock / data signal:
- higher slope means (in general) smaller chance of induced jitter
- lower slope means less current generated (also in groundplane)
Less RF current also means lower jitter
I findvalues between 22 ohm and 330 ohm in practice. Audible difference appear, so it might take a while to tweak them
succes
Oli said:
Hi Oli
The value is the tradeoff: It defines the slope of the clock / data signal:
- higher slope means (in general) smaller chance of induced jitter
- lower slope means less current generated (also in groundplane)
Less RF current also means lower jitter
I findvalues between 22 ohm and 330 ohm in practice. Audible difference appear, so it might take a while to tweak them
succes
Asynchrous clock Elso
The asynchronous reclocker Elso.
Interesting that you should hear no difference with resistors in the digital lines- I do want to keep it simple.
Out of curiousity- Are you a ground 'plane' man or a 'star' man? (excuse the pun)
Maverick- Only kidding!
The asynchronous reclocker Elso.
Interesting that you should hear no difference with resistors in the digital lines- I do want to keep it simple.
Out of curiousity- Are you a ground 'plane' man or a 'star' man? (excuse the pun)
Maverick- Only kidding!
Cheers for the info.
Guido,
Cheers for the info.
I feared it would be one of those 'listen to it' choices!
Thinking back to your ground plane theory, I intend to use a number of different power supplies to isolate analogue, digital, PLL and reclocker circuitry.
Q. Do I connect the grounds from these supplies at a single point on the plane?
Q. The idea is to allow return currents to flow to ground, but to avoid 'series type' grounding i.e. digital ground connections between PLL ground and ground supply terminals. This would lead to undesireable potential differences. Ideally each type of circuitry should in in line-of-sight of the ground. Is my understanding correct?
Guido,
Cheers for the info.
I feared it would be one of those 'listen to it' choices!
Thinking back to your ground plane theory, I intend to use a number of different power supplies to isolate analogue, digital, PLL and reclocker circuitry.
Q. Do I connect the grounds from these supplies at a single point on the plane?
Q. The idea is to allow return currents to flow to ground, but to avoid 'series type' grounding i.e. digital ground connections between PLL ground and ground supply terminals. This would lead to undesireable potential differences. Ideally each type of circuitry should in in line-of-sight of the ground. Is my understanding correct?
Cheers Jim
Jim,
I'll read through the info- thanks. I'm still deciding whether these resistors are a 'good thing' or not.
Jim,
I'll read through the info- thanks. I'm still deciding whether these resistors are a 'good thing' or not.
Re: Cheers for the info.
Hi Oli,
Q1: I'd say:
" connect the grounds from these supplies closest to the chip(s) they supply "
However, it depends if you add series beads and / or resistors in the supply lines. If you do that (reccomended) the RF supply currents will be greatly reduced, and so are the ground currents. In that case, it does not matter that much where to connect the grounds of the various supplies involved.
Q2: Understood correctly
cheers
Oli said:
Hi Oli,
Q1: I'd say:
" connect the grounds from these supplies closest to the chip(s) they supply "
However, it depends if you add series beads and / or resistors in the supply lines. If you do that (reccomended) the RF supply currents will be greatly reduced, and so are the ground currents. In that case, it does not matter that much where to connect the grounds of the various supplies involved.
Q2: Understood correctly
cheers
Re: Re: Cheers for the info.
However, it depends if you add series beads and / or resistors in the supply lines. If you do that (reccomended) the RF supply currents will be greatly reduced, and so are the ground currents. In that case, it does not matter that much where to connect the grounds of the various supplies involved.
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The Cho Drops in the post earlier are rubbish. I got some samples (they are super quick) and as recommended, connected to both signal and ground lines on a ringing (35MHz) SPDIF signal.
Distorts the wave form totally, removed the RF, but the signal is too poor to lock on! Perhaps they are better for PS lines.
I measured 0.7 uH, 0.9R, and for some reason 4.7 uF! Shall have a look inside one of them.
However, it depends if you add series beads and / or resistors in the supply lines. If you do that (reccomended) the RF supply currents will be greatly reduced, and so are the ground currents. In that case, it does not matter that much where to connect the grounds of the various supplies involved.
------------------------------------------------------------------------------
The Cho Drops in the post earlier are rubbish. I got some samples (they are super quick) and as recommended, connected to both signal and ground lines on a ringing (35MHz) SPDIF signal.
Distorts the wave form totally, removed the RF, but the signal is too poor to lock on! Perhaps they are better for PS lines.
I measured 0.7 uH, 0.9R, and for some reason 4.7 uF! Shall have a look inside one of them.
Re: Re: Re: Cheers for the info.
Hey Fred,
You might use them as a decap......
cheers
fmak said:
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The Cho Drops in the post earlier are rubbish. I got some samples (they are super quick) and as recommended, connected to both signal and ground lines on a ringing (35MHz) SPDIF signal.
Distorts the wave form totally, removed the RF, but the signal is too poor to lock on! Perhaps they are better for PS lines.
I measured 0.7 uH, 0.9R, and for some reason 4.7 uF! Shall have a look inside one of them.
Hey Fred,
You might use them as a decap......
cheers
Re: Cho Drops
See post by Oli under p1
--------------------------------------------------------jewilson said:
See post by Oli under p1
Frank,
I am not sure what you stating here, however to decouple HS logic can take multiple caps including a .1 and .01 and even smaller depending on ringing frequency
Of course there are other thing we can to to improve this.
I am not sure what you stating here, however to decouple HS logic can take multiple caps including a .1 and .01 and even smaller depending on ringing frequency
Of course there are other thing we can to to improve this.
How about using resistor values from a tried and tested example?
I wonder if I could use the resistor values directly from Guido's example:
The Audio Dac Page
It appears that 1k resistors are used in all 'standard' logic lines.
After the reclocker, the left and right latches use 100R resistors (for higher slew rate)
The clock uses 330R resistor
(compromise between slew rate and noise?)
Would this scheme have more general application?
I wonder if I could use the resistor values directly from Guido's example:
The Audio Dac Page
It appears that 1k resistors are used in all 'standard' logic lines.
After the reclocker, the left and right latches use 100R resistors (for higher slew rate)
The clock uses 330R resistor
(compromise between slew rate and noise?)
Would this scheme have more general application?
Oli,
You could but I would use smaller value from the application notes. A value from 50 to 100 ohm will work ok. Also, don't use a Metalfilm reisitor, they are sprial cut with a laser which causes some inductance, which is not good. Use a carbon film in this application.
You could but I would use smaller value from the application notes. A value from 50 to 100 ohm will work ok. Also, don't use a Metalfilm reisitor, they are sprial cut with a laser which causes some inductance, which is not good. Use a carbon film in this application.
Carbon film?
Okay, I'll try a lower value of resistor.... say 100R
Metal film inductive?
In your view is higher thermal noise of carbon film less of an issue?
Okay, I'll try a lower value of resistor.... say 100R
Metal film inductive?
In your view is higher thermal noise of carbon film less of an issue?
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