Re: Low Jitter clock
One other thing: I built the KWAK 5 clock using AD8561 and measurement wise it seems very similar to the guido tent osc. in cleanness of the clock output (at 11.xxMHz) as measured on my 20MHz scope. For sound, they actually are virtually identical. Good sound from both.
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I don't think 20 MHz scope is sufficient to see the 11.2986 MHz square wave properly and assess ground bounce and the eye pattern. You need `10MHz or more.
One other thing: I built the KWAK 5 clock using AD8561 and measurement wise it seems very similar to the guido tent osc. in cleanness of the clock output (at 11.xxMHz) as measured on my 20MHz scope. For sound, they actually are virtually identical. Good sound from both.
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I don't think 20 MHz scope is sufficient to see the 11.2986 MHz square wave properly and assess ground bounce and the eye pattern. You need `10MHz or more.
20 MHz scopes are not enough for viewing 11.2986 MHz precisely. I have a 4 channel 60 MHz scope ( which triggers far beyond 100 MHz ) that is good enough for viewing the waveform carefully. I do have troubles measuring Sony cdplayers with their 45.xx MHz clock though, I see a waveform but I am confident that what I see is not entirely according reality 
TKK1010, I thought you wanted a schematic for synchronized reclocking or did I misunderstand you ?
TKK1010, I thought you wanted a schematic for synchronized reclocking or did I misunderstand you ?
Re: Re: Low Jitter clock
I was just looking at a high speed comparator on my scope -- driven by a reasonably good power supply (but not a Super-Regulator) -- decided to see what was going on with the supply rails at the same time, so I switched to AC coupling and had a look.
It was interesting to see how the pulse (and load) of the comparator modifies the power supply ouput -- just a few millivolts, but it propagates through the entire system.
fmak said:One other thing: I built the KWAK 5 clock using AD8561 and measurement wise it seems very similar to the guido tent osc. in cleanness of the clock output (at 11.xxMHz) as measured on my 20MHz scope. For sound, they actually are virtually identical. Good sound from both.
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I don't think 20 MHz scope is sufficient to see the 11.2986 MHz square wave properly and assess ground bounce and the eye pattern. You need `10MHz or more.
I was just looking at a high speed comparator on my scope -- driven by a reasonably good power supply (but not a Super-Regulator) -- decided to see what was going on with the supply rails at the same time, so I switched to AC coupling and had a look.
It was interesting to see how the pulse (and load) of the comparator modifies the power supply ouput -- just a few millivolts, but it propagates through the entire system.
I have a 4 channel 60 MHz scope ( which triggers far beyond 100 MHz ) that is good enough for viewing the waveform carefully. I do have troubles measuring Sony cdplayers with their 45.xx MHz clock though, I see a waveform but I am confident that what I see is not entirely according reality
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What you are doing with a scope twice the bandwidth of the square wave is to look at the high pass characteristic of the scope amp/buffer; and you will miss all those things that are are the result of poor clock such as ringing, edge reflections etc.
I made that mistake sometime ago and now uses a 400MHz Tek for 45MHz. There is a world of difference when youuse a 60MHz probe and not a 400MHz one. In fact, using a soldered BNC lead correctly terminated is the answer!!
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What you are doing with a scope twice the bandwidth of the square wave is to look at the high pass characteristic of the scope amp/buffer; and you will miss all those things that are are the result of poor clock such as ringing, edge reflections etc.
I made that mistake sometime ago and now uses a 400MHz Tek for 45MHz. There is a world of difference when youuse a 60MHz probe and not a 400MHz one. In fact, using a soldered BNC lead correctly terminated is the answer!!
fmak said:I have a 4 channel 60 MHz scope ( which triggers far beyond 100 MHz ) that is good enough for viewing the waveform carefully. I do have troubles measuring Sony cdplayers with their 45.xx MHz clock though, I see a waveform but I am confident that what I see is not entirely according reality
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What you are doing with a scope twice the bandwidth of the square wave is to look at the high pass characteristic of the scope amp/buffer; and you will miss all those things that are are the result of poor clock such as ringing, edge reflections etc.
I made that mistake sometime ago and now uses a 400MHz Tek for 45MHz. There is a world of difference when youuse a 60MHz probe and not a 400MHz one. In fact, using a soldered BNC lead correctly terminated is the answer!!
One of these days I will buy a differential probe !
Williams discusses "probing" in the ApNote from Linear Tech that I cited above --
Re: Re: Re: Low Jitter clock
It was interesting to see how the pulse (and load) of the comparator modifies the power supply ouput -- just a few millivolts, but it propagates through the entire system. [/B][/QUOTE]
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You are right; hence the need for individual evaluation when fitting clock with use use of the right equipment.
I can't help wondering about the no of wrong conclusions drawn from inadequate measurements - I have made that mistake often.
If you look at the clock signal with limited bandwidth, you come to the conclusion that all is well and that there is no difference between clocks!
It was interesting to see how the pulse (and load) of the comparator modifies the power supply ouput -- just a few millivolts, but it propagates through the entire system. [/B][/QUOTE]
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You are right; hence the need for individual evaluation when fitting clock with use use of the right equipment.
I can't help wondering about the no of wrong conclusions drawn from inadequate measurements - I have made that mistake often.
If you look at the clock signal with limited bandwidth, you come to the conclusion that all is well and that there is no difference between clocks!
Re: Re: Re: Re: Low Jitter clock
You are right; hence the need for individual evaluation when fitting clock with use use of the right equipment.
I can't help wondering about the no of wrong conclusions drawn from inadequate measurements - I have made that mistake often.
If you look at the clock signal with limited bandwidth, you come to the conclusion that all is well and that there is no difference between clocks!
[/B][/QUOTE]
Yeah -- you will note from Williams piece that he uses a boatanchor or a scope -- probably an old 545 -- and expensive probes. A used TEK differential probe costs as much as a used TEK 2465 !
--------------------------------------------------------------------------------fmak said:
You are right; hence the need for individual evaluation when fitting clock with use use of the right equipment.
I can't help wondering about the no of wrong conclusions drawn from inadequate measurements - I have made that mistake often.
If you look at the clock signal with limited bandwidth, you come to the conclusion that all is well and that there is no difference between clocks!
[/B][/QUOTE]Yeah -- you will note from Williams piece that he uses a boatanchor or a scope -- probably an old 545 -- and expensive probes. A used TEK differential probe costs as much as a used TEK 2465 !
In my experience the waveform is not that important hence my underrated oscilloscope. Jitter is more important and nearly all replacement clocks I've seen/used have better waveforms than the original "74HCU04 clocks" anyway and offer less jitter.
It is nice to have a 400 MHz oscilloscope though, it really shows what's there ( if one knows how to measure those frequencies ). Understanding what's on the screen is another thing, let alone the measures needed to be taken to correct the "errors" that are there in case a discrete oscillator is built. Too much for me and for most I think. That is probably the difference between hobbyists and pros
It is nice to have a 400 MHz oscilloscope though, it really shows what's there ( if one knows how to measure those frequencies ). Understanding what's on the screen is another thing, let alone the measures needed to be taken to correct the "errors" that are there in case a discrete oscillator is built. Too much for me and for most I think. That is probably the difference between hobbyists and pros
tube-lover said:hi all,
I was used this TCXO Oscillator 30PPM for the reclock circuit.
I prepare used for my twins TDA1541a DAC, any suggestion?
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All good XOs I have come across are within 20 ppm of stated freq.
You want XOs with low phase noise. TCXOs have higher phase noise due to the added circuitry and are not necessary.
There are many discussions regarding what signal or all the I2S signals to reclock to reduce the jitter. I would suggets that only WS ( LRCLK ) is important. Help me understand if my logic below is sound.
Let's look into how the DAC works. The BCK clocks the data into an internal shift register. Unless the jitter is excessive ( very unlikely unless the clock implementatin is cr*p ), the correct signal only data line will be clocked into the internal shift register. At the transition of the WS signal ( rising and falling edge ), then the contents of the internal shift register gets latched onto the analogue ladder resistors. As desribed in many articles, this needs to be very accurate and jitterless so that there is minimal error in the output analogue signal. So only the WS signal needs to be be jitterless. The others - no much impact.
Would anyone agree or point out the fallacy or my arguement.
My current project is to tap out the EIAJ signal of a old cheap VCD mechanism with a Philips CDM12.1 mechanism, and to drive Torben's dual DAC1541 board via a EIAJ to I2S converter. It works but the sound quality is worse than my EIAJ direct signal from my Pioneer CD players, which benefited from a Kwak 7 clock.
Thanks.
CM
Let's look into how the DAC works. The BCK clocks the data into an internal shift register. Unless the jitter is excessive ( very unlikely unless the clock implementatin is cr*p ), the correct signal only data line will be clocked into the internal shift register. At the transition of the WS signal ( rising and falling edge ), then the contents of the internal shift register gets latched onto the analogue ladder resistors. As desribed in many articles, this needs to be very accurate and jitterless so that there is minimal error in the output analogue signal. So only the WS signal needs to be be jitterless. The others - no much impact.
Would anyone agree or point out the fallacy or my arguement.
My current project is to tap out the EIAJ signal of a old cheap VCD mechanism with a Philips CDM12.1 mechanism, and to drive Torben's dual DAC1541 board via a EIAJ to I2S converter. It works but the sound quality is worse than my EIAJ direct signal from my Pioneer CD players, which benefited from a Kwak 7 clock.
Thanks.
CM
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