Re: Have test jitter after add 50 ohm resistor ?
Hi
1 - Yes, you need the resistor (it reduces the currents, and series terminates the source)
2 - Jitter is the only thing that counts, I don't care about the waveshape but one that does have huge overshoot in general has higher jitter as it excites several kinds of ESD protection diodes, for example
3 - I measure using true 50 ohm system and 350 MHz analogue scope (no higher BW available at Tentabs) and come to about 2 ns rise / fall time
Again, steeper slopes are not a goal as sych as they generate more di/dt hence in turn will increase the jitter
cheers
vcch said:
Hi
1 - Yes, you need the resistor (it reduces the currents, and series terminates the source)
2 - Jitter is the only thing that counts, I don't care about the waveshape but one that does have huge overshoot in general has higher jitter as it excites several kinds of ESD protection diodes, for example
3 - I measure using true 50 ohm system and 350 MHz analogue scope (no higher BW available at Tentabs) and come to about 2 ns rise / fall time
Again, steeper slopes are not a goal as sych as they generate more di/dt hence in turn will increase the jitter
cheers
Hi Guido,
Thanks for your answer.
I have no equipments to measure the jitter performance. I raised these questions just based on my experiene. I know that add series resistor can reduce EMI which is caused by huge overshoot. That resistor can attenuate the signals reflected by the receiving end. But I am wondering if adding resistor will cause higher jitter. So far as I know that the jitter will be affected by trace width due to trace capacitane varies with width. Adding series resistor will reduce the rising and falling time. You can imagine that a clock source charges and discharges the (stray)capacitance of the trace through a series resistors which caused the signal rising and falling times varies from time to time and makes jitter worse.
The other question is I made a TDA1543A NOS DAC with 50MHz async osc to de-correlate the system clock. You know that using 50Mhz async osc will make the sound stage more open and wide but the truth is the jitter of the clock will become 20ns which is far worse than the original,but it sounds good even with such high jitter !
Is jitter really important ???
Vincent
Thanks for your answer.
I have no equipments to measure the jitter performance. I raised these questions just based on my experiene. I know that add series resistor can reduce EMI which is caused by huge overshoot. That resistor can attenuate the signals reflected by the receiving end. But I am wondering if adding resistor will cause higher jitter. So far as I know that the jitter will be affected by trace width due to trace capacitane varies with width. Adding series resistor will reduce the rising and falling time. You can imagine that a clock source charges and discharges the (stray)capacitance of the trace through a series resistors which caused the signal rising and falling times varies from time to time and makes jitter worse.
The other question is I made a TDA1543A NOS DAC with 50MHz async osc to de-correlate the system clock. You know that using 50Mhz async osc will make the sound stage more open and wide but the truth is the jitter of the clock will become 20ns which is far worse than the original,but it sounds good even with such high jitter !
Is jitter really important ???
Vincent
Re: Re: Have test jitter after add 50 ohm resistor ?
1 - Yes, you need the resistor (it reduces the currents, and series terminates the source)
2 - Jitter is the only thing that counts, I don't care about the waveshape but one that does have huge overshoot in general has higher jitter as it excites several kinds of ESD protection diodes, for example
3 - I measure using true 50 ohm system and 350 MHz analogue scope (no higher BW available at Tentabs) and come to about 2 ns rise / fall time
Again, steeper slopes are not a goal as sych as they generate more di/dt hence in turn will increase the jitter
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1. Depending on the processor, you may need to change the value for best wave shape and minimal overshoot. Some XOs even like a bit of capacitance across the output.
2. The waveshape may or may not affect jitter igenerated n downstream components. I do know that spdif outputs with parasitic osvillations and ground bounce sound worse than those without.
In the case of your relocker, GUido, there is quitev a lot of ripple on the top hat and a rather assymetric eye pattern. (Using 400 MHz Tek Scope).
3. Your rise time is probably correct; I measured 3ns or thereabouts.
Fred
1 - Yes, you need the resistor (it reduces the currents, and series terminates the source)
2 - Jitter is the only thing that counts, I don't care about the waveshape but one that does have huge overshoot in general has higher jitter as it excites several kinds of ESD protection diodes, for example
3 - I measure using true 50 ohm system and 350 MHz analogue scope (no higher BW available at Tentabs) and come to about 2 ns rise / fall time
Again, steeper slopes are not a goal as sych as they generate more di/dt hence in turn will increase the jitter
------------------------------------------------------------------------
1. Depending on the processor, you may need to change the value for best wave shape and minimal overshoot. Some XOs even like a bit of capacitance across the output.
2. The waveshape may or may not affect jitter igenerated n downstream components. I do know that spdif outputs with parasitic osvillations and ground bounce sound worse than those without.
In the case of your relocker, GUido, there is quitev a lot of ripple on the top hat and a rather assymetric eye pattern. (Using 400 MHz Tek Scope).
3. Your rise time is probably correct; I measured 3ns or thereabouts.
Fred
Re: Re: Re: Have test jitter after add 50 ohm resistor ?
Hi Fred, others
1 - The series r (value) is a tradeoff between jiter and EMI / reflections. I recall exhaustive listening sessions on the values we used in our DAC
2 - I know the ripple on that output is due to some groundbounce and will improve a far as economically feasible
3 - What scope do you use ? the 2ns is using 10%/90% levels
cheers
fmak said:
------------------------------------------------------------------------
1. Depending on the processor, you may need to change the value for best wave shape and minimal overshoot. Some XOs even like a bit of capacitance across the output.
2. The waveshape may or may not affect jitter igenerated n downstream components. I do know that spdif outputs with parasitic osvillations and ground bounce sound worse than those without.
In the case of your relocker, GUido, there is quitev a lot of ripple on the top hat and a rather assymetric eye pattern. (Using 400 MHz Tek Scope).
3. Your rise time is probably correct; I measured 3ns or thereabouts.
Fred
Hi Fred, others
1 - The series r (value) is a tradeoff between jiter and EMI / reflections. I recall exhaustive listening sessions on the values we used in our DAC
2 - I know the ripple on that output is due to some groundbounce and will improve a far as economically feasible
3 - What scope do you use ? the 2ns is using 10%/90% levels
cheers
Re: Re: Re: Re: Re: Have test jitter after add 50 ohm resistor ?
Hi Fred
Allright on the Tek
I'd like to rephrase: Groundbounce depends on the I/O currents (that is why I like series resistors too)
all the best
Hi Fred
Allright on the Tek
I'd like to rephrase: Groundbounce depends on the I/O currents (that is why I like series resistors too)
all the best
Re: Re: Re: Re: Re: Re: Speaking of the Tent Clock
Lay it on the line!
You are in charge.
Now what are you going to do about it?Kuei Yang Wang said:
Lay it on the line!
You are in charge.
Re: Re: Re: Re: Re: Re: Re: Speaking of the Tent Clock
Konnichiwa,
My point is that the main (22mH) choke has it's resonance at 80KHz. By adding high and medium permability ferrite beads on the wires of the choke you add impedance at high frequencies, where the hoke becomes in effect a coupling capacitor. What I am doing and suggesting is the choke equivalent of capacitor bypassing.
A handfull ferrite beads, a nice largish value AF choke and the right capacitor combo can provide a very large amounts of rejection of noise on the original supply line, without going active regulation and with minimal parts count.
Hence my suggestion to stick with the high value choke over a lower value choke with higher resonance, also because if you measure impedance the lower value choke does not really offer a lot more impedance at a given frequency, despite it's higher resonance frequency.
Ciao T
Konnichiwa,
Elso Kwak said:
My point is that the main (22mH) choke has it's resonance at 80KHz. By adding high and medium permability ferrite beads on the wires of the choke you add impedance at high frequencies, where the hoke becomes in effect a coupling capacitor. What I am doing and suggesting is the choke equivalent of capacitor bypassing.
A handfull ferrite beads, a nice largish value AF choke and the right capacitor combo can provide a very large amounts of rejection of noise on the original supply line, without going active regulation and with minimal parts count.
Hence my suggestion to stick with the high value choke over a lower value choke with higher resonance, also because if you measure impedance the lower value choke does not really offer a lot more impedance at a given frequency, despite it's higher resonance frequency.
Ciao T
Re: Re: Re: Re: Re: Re: Have test jitter after add 50 ohm resistor ?
Guido Tent said:
Hi Fred
Allright on the Tek
I'd like to rephrase: Groundbounce depends on the I/O currents (that is why I like series resistors too)
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Perhaps I should rephrase also; I/O current and XO or relocking circuit.
The Valpey Fisher XO I am using (VF140) on your PS really sounds good (balanced) and has an excellent wave shape.
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