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The Well Tempered Master Clock - Building a low phase noise/jitter crystal oscillator
The Well Tempered Master Clock - Building a low phase noise/jitter crystal oscillator
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Old 10th July 2018, 10:24 AM   #1681
canvas is offline canvas  Taiwan
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Originally Posted by gentlevoice View Post
The latter did not really cause much change in the measurements, whereas paralleling/not paralleling the outputs caused an appr. 100% difference in the noise amplitude on the VDD pin of the inverter. Paralleling the outputs caused this ~ 100 increase in the noise amplitude.
I tried the single buffer by blocking the contact of pin10~13 on 7404 and there is definitely some improvement on the sound. The high & extreme high is more smooth now. I think the parallel output somehow impacts the performance of the clock. I have no equipment to prove it, but I can hear it.

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Old 10th July 2018, 10:45 AM   #1682
gentlevoice is online now gentlevoice  Denmark
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The Well Tempered Master Clock - Building a low phase noise/jitter crystal oscillator
Quote:
I tried the single buffer by blocking the contact of pin10~13 on 7404 and there is definitely some improvement on the sound. The high & extreme high is more smooth now. I think the parallel output somehow impacts the performance of the clock. I have no equipment to prove it, but I can hear it.

Poting
Hi Poting ... thanks for the feedback. It would also be my guess that it somehow affects the sound - I just haven't had the time to make a listening setup so helpful with your feedback ;-)

Cheers,

Jesper
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Old 11th July 2018, 02:50 AM   #1683
canvas is offline canvas  Taiwan
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Originally Posted by gentlevoice View Post
Hi Poting ... thanks for the feedback. It would also be my guess that it somehow affects the sound - I just haven't had the time to make a listening setup so helpful with your feedback ;-)

Cheers,

Jesper
Hi Jasper,

In my case, single buffer sounds better. I wish to hear more feedback from others. Before Andrea released his board, there was a discussion on this matter. I proposed PO74G38072A as the buffer. If you are about to design your clock board, you may consider a good clock buffer. It should have enough power to drive long cable.

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Old 11th July 2018, 06:36 AM   #1684
gentlevoice is online now gentlevoice  Denmark
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The Well Tempered Master Clock - Building a low phase noise/jitter crystal oscillator
@poting:

Quote:
I wish to hear more feedback from others.
... Yes, that could be fine to hear from others as well.

Quote:
I proposed PO74G38072A as the buffer.
This is an interesting buffer, however, my guess is that it would still show extra noise on the VCC pins because it has two outputs. Even if there is no load on the output the logic still switches and causes noise on the VCC (& likely output?). I think the best would be a suitable (low phase noise) single gate IC that is not too small.

Quote:
It should have enough power to drive long cable.
Thanks for the suggestion but I will place it in reasonable vicinity to the DAC/ADC so high drive capability should be less of an issue.

Cheers,

Jesper
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Old 13th July 2018, 02:03 AM   #1685
canvas is offline canvas  Taiwan
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Originally Posted by gentlevoice View Post
my guess is that it would still show extra noise on the VCC pins because it has two outputs. Even if there is no load on the output the logic still switches and causes noise on the VCC (& likely output?). I think the best would be a suitable (low phase noise) single gate IC that is not too small.

Hi Jasper,

Thanks for the tip. This is my final "single buffer" mod on Andrea's Driscoll borad. Only one inverter is used. Other pins (except VCC, Gnd) are blocked by heat resistant tape underneath. My initial impression, this mod improves the sound even further. More depth, more defined layers of sound...etc. There was substantial change in sound when I listened to Adele's 21 album last night. Her voice was clearly separated from the background. There was no harsh on high and extreme high. The bass was solid and defined than before. Very interesting.

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The Well Tempered Master Clock - Building a low phase noise/jitter crystal oscillator
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Old 13th July 2018, 06:25 AM   #1686
gentlevoice is online now gentlevoice  Denmark
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The Well Tempered Master Clock - Building a low phase noise/jitter crystal oscillator
Hi Poting ... Thank you also for your feedback ... BTW - on a side note - my name is "Jesper" and not "Jasper" ... I know that in the English speaking countries it is often spelled Jasper but being Danish the spelling is different ;-)

One comment on the way you have made your modification: I personally would connect the inverter inputs that are not used to GND. It is not unusual that unused gate inputs - like inverter inputs - can shift between high and low even if there is no signal on them. This in turn would cause the outputs to also shift high & low somewhat randomly which again would lead to noise on VCC and possibly/likely the used inverter output.

BTW it looks as if you are using a Potatosemi inverter, right? Can I ask you if you are using the "GU04" or the "04"? And have you tried both?

Cheers,

Jesper
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Old 13th July 2018, 03:49 PM   #1687
canvas is offline canvas  Taiwan
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Hi Jesper,

I apologized for the wrong spelling. ^_^
My picture was taken just right after I soldered the chip. The unused inputs are all connected to ground. Unfortunately, the 7404 is the buffered version. I heard that unbuffered version is better here. However, I acquired this chip more than 10 years ago from another project. Due to the small quantity and the shipping cost, I decided to use what I had in hand. Have you ever compared these two?

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Old 13th July 2018, 08:55 PM   #1688
1audio is offline 1audio  United States
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The Well Tempered Master Clock - Building a low phase noise/jitter crystal oscillator
Typically the fastest gates will have the lowest additive phase noise. Adding a buffer stage will slow down the gate but may be necessary to drive the load. The Potato architecture is supposed to have significantly less noise induced into the supply. Still treat everything around these like a microwave circuit with small windows, differential signals where possible with carefully matched trace lengths and close continuous ground planes adjacent to the signals.

A common problem is supply modulation from data getting back to clock signals and buffers. Isolation is important, even a small inductor may be enough.
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Old 15th July 2018, 08:24 AM   #1689
gentlevoice is online now gentlevoice  Denmark
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The Well Tempered Master Clock - Building a low phase noise/jitter crystal oscillator
@Poting:

Quote:
Unfortunately, the 7404 is the buffered version. I heard that unbuffered version is better here. However, I acquired this chip more than 10 years ago from another project. Due to the small quantity and the shipping cost, I decided to use what I had in hand. Have you ever compared these two?
Hi Poting ... No, I have not yet compared the two. Hmmm ... when reading your post I wonder if you are aware of potatosemi's online store on ebay? Here most all of potatosemi's components can be bought at ~ 3 USD + a little less for shipping. Just FYI in case you didn't know.

Cheers,

Jesper
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Old 15th July 2018, 01:40 PM   #1690
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@Demian,

Thanks for the tip on inductor. Andrea does include an inductor on VCC pin. I hope this will prevent the modulation.


@Jesper,

Yes, I found it and placed my order already. It seems they are sending the package from Taiwan, but I still have to pay the international shipping...
I will compare the two and report back. This is perhaps the most critical part of the entire audio system.

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Last edited by canvas; 15th July 2018 at 01:43 PM.
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