Actually it has been my partner(crwalpole) who has done most of the vibration isolation experiments. But some of what we did was just using grey putty on the boards or bees wax and then mounting them in diecast boxes. His last one was built in an aluminum enclosure which was built out of 0.75" thick aluminum and inside he had springs to suspend it from and I believe the board was actually weighted to stretch the springs slightly.
There's many ways you can come up with to add some vibration isolation to these boards. I would get some grey putty(get putty that doesn't harden over time) and just put 0.5" of it on the backside of the board and then stand the crystal up(90* from the board) and pack some putty on it too. Then mount it in a diecast enclosure, you could then even mount it with soft rubber feet to whatever enclosure you use for your system boards.
Did any of this make a difference in the sound quality, yes and maybe.
They used to make channel crystals for hams, but 1 or 5 is more or less the same work.
Ask THEM and tell us
Kontakt - Quarztechnik Daun
Gerhard
vibration
Lots of great ideas for vibration dampening. In my experience, well worth the effort. I have had clear improvements in sound whether it is simple like putty on the crystal to quite comprehensive as I have with Andre's WTMC. My approach documented earlier. https://www.diyaudio.com/forums/dig...itter-crystal-oscillator-185.html#post5887494 Perhaps some inspiration. Sand works well combined with large masses separated by dampening layers.
Lots of great ideas for vibration dampening. In my experience, well worth the effort. I have had clear improvements in sound whether it is simple like putty on the crystal to quite comprehensive as I have with Andre's WTMC. My approach documented earlier. https://www.diyaudio.com/forums/dig...itter-crystal-oscillator-185.html#post5887494 Perhaps some inspiration. Sand works well combined with large masses separated by dampening layers.
Vibration sensitivity for crystal oscillators is something you can research. Wenzel has some good info but keep in mind the vibration levels they are dealing with are much higher.
It's known that the crystal frequency is sensitive to position and turning it over will change the frequency. Certain axis is will have the high sensitivity.
As to vibration, if you don't want to create active correction (see the Wenzel article), then it's best to figure out the sensitive frequency of the system and design isolation around that. It's similar to turntable isolation. More mass, more compliance and make sure you have no suspension resonances that match sensitive frequencies.
You may be able to connect the crystal to a high Z input with lots of gain and directly see it's vibration sensitivity. Its pretty similar to a piezo accelerometer. And there may be microphonics in the rest of the electronics.
It's known that the crystal frequency is sensitive to position and turning it over will change the frequency. Certain axis is will have the high sensitivity.
As to vibration, if you don't want to create active correction (see the Wenzel article), then it's best to figure out the sensitive frequency of the system and design isolation around that. It's similar to turntable isolation. More mass, more compliance and make sure you have no suspension resonances that match sensitive frequencies.
You may be able to connect the crystal to a high Z input with lots of gain and directly see it's vibration sensitivity. Its pretty similar to a piezo accelerometer. And there may be microphonics in the rest of the electronics.
Hi all,
I have a question that I reckon might mainly be for Marcel and/or Terry Demol, if possible ... It relates to TI's PCM179* series of DACs which are described as advanced segment DACs. Quoting the datasheet:
... With this in mind would you then say that this DAC resembles a DS modulator DAC (with possible sensitivity to oscillator doubler sub-harmonics) or is it more akin to a multi-bit DAC?
Any thoughts welcome ;-)
Jesper
I have a question that I reckon might mainly be for Marcel and/or Terry Demol, if possible ... It relates to TI's PCM179* series of DACs which are described as advanced segment DACs. Quoting the datasheet:
... With this in mind would you then say that this DAC resembles a DS modulator DAC (with possible sensitivity to oscillator doubler sub-harmonics) or is it more akin to a multi-bit DAC?
Any thoughts welcome ;-)
Jesper
My educated guess is that it is sensitive to subharmonics, but 36 dB to 60 dB less sensitive than the simulation of post #2850.
The sigma-delta is a multi-level sigma-delta and could be dithered such that it has no idle tones to mix into the audio band. Whether this is actually done is not clear to me.
If the sigma-delta modulator does produce an idle tone at fs/2, its effect will still be some 36 dB less severe than in post #2850 because the highest 6 bits are handled in a different way. That is, the sigma-delta modulate is attenuated compared to a pure sigma-delta DAC.
If the sigma-delta modulator is dithered such that there are no idle tones, then subharmonics will only raise its noise floor a bit. However, depending on how exactly it is implemented, the data-weighted averaging might still be affected by subharmonics. Assuming that the mismatch between the DAC elements is of the order of 0.1 %, it should be some 20 dB*log10(1/0.001) = 60 dB less sensitive than what I simulated in post #2850.
The sigma-delta is a multi-level sigma-delta and could be dithered such that it has no idle tones to mix into the audio band. Whether this is actually done is not clear to me.
If the sigma-delta modulator does produce an idle tone at fs/2, its effect will still be some 36 dB less severe than in post #2850 because the highest 6 bits are handled in a different way. That is, the sigma-delta modulate is attenuated compared to a pure sigma-delta DAC.
If the sigma-delta modulator is dithered such that there are no idle tones, then subharmonics will only raise its noise floor a bit. However, depending on how exactly it is implemented, the data-weighted averaging might still be affected by subharmonics. Assuming that the mismatch between the DAC elements is of the order of 0.1 %, it should be some 20 dB*log10(1/0.001) = 60 dB less sensitive than what I simulated in post #2850.
@MarcelvdG: Thanks Marcel for your feedback, I will take a look at it ;-) ...
A couple of thoughts, however, comes to mind:
- Would you by any chance happen to know if there can be any internal dithering in the PCM179* if it is connected like the DDDAC,
( A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input) ),
i.e. there is no internal oversampling inside the PCM179* because the SCK & MCK legs are connected?
- Also, and this is just to be sure I understand you correctly, the sub-harmonics' issue is only relevant in relation to using the frequency doublers - not with the pure Driscoll oscillators - is that correct?
Cheers & have a good weekend,
Jesper
A couple of thoughts, however, comes to mind:
- Would you by any chance happen to know if there can be any internal dithering in the PCM179* if it is connected like the DDDAC,
( A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input) ),
i.e. there is no internal oversampling inside the PCM179* because the SCK & MCK legs are connected?
- Also, and this is just to be sure I understand you correctly, the sub-harmonics' issue is only relevant in relation to using the frequency doublers - not with the pure Driscoll oscillators - is that correct?
Cheers & have a good weekend,
Jesper
@ gentlevoice
two things . the way I connect it (no digital filter) this happens:
1. No pre-and-after ringing of the signal (square is square). Which I believe is key for the NOS sound....
2. yes there is dithering for sure. The mash (or whatever you call it) is doing the job. you can see that when you run a FFT on the noise of the DAC output
I spent a short "article" on this phenomenon at my DDDAC website:
second paragraph "Quantization noise floor"
DDDAC 1794 NOS DAC - Non Oversampling DAC with PCM1794 - no digital filter - modular design DIY DAC for high resolution audio 192/24 192kHz 24bit
two things . the way I connect it (no digital filter) this happens:
1. No pre-and-after ringing of the signal (square is square). Which I believe is key for the NOS sound....
2. yes there is dithering for sure. The mash (or whatever you call it) is doing the job. you can see that when you run a FFT on the noise of the DAC output
I spent a short "article" on this phenomenon at my DDDAC website:
second paragraph "Quantization noise floor"
DDDAC 1794 NOS DAC - Non Oversampling DAC with PCM1794 - no digital filter - modular design DIY DAC for high resolution audio 192/24 192kHz 24bit
@ gentlevoice:
Yes to both questions.
The dithering I wrote about is the dithering of the quantizer of the sigma-delta modulator. Whether the input signal goes through an interpolation filter inside the PCM1794 or not has no relation to that.
@ dddac:
When the quantizer is not dithered at all or not dithered according to dither theory, you will mainly see that in the output spectrum around half the sigma-delta clock frequency: with 1 LSB peak-to-peak uniform or 2 LSB peak-to-peak triangular dither, there will be no idle tone around fs/2, with partial or no dither, there will be one or two idle tones (two when there is an offset) around fs/2. It isn't clear to me how you can determine that from measurements that only span the audio band.
Yes to both questions.
The dithering I wrote about is the dithering of the quantizer of the sigma-delta modulator. Whether the input signal goes through an interpolation filter inside the PCM1794 or not has no relation to that.
@ dddac:
When the quantizer is not dithered at all or not dithered according to dither theory, you will mainly see that in the output spectrum around half the sigma-delta clock frequency: with 1 LSB peak-to-peak uniform or 2 LSB peak-to-peak triangular dither, there will be no idle tone around fs/2, with partial or no dither, there will be one or two idle tones (two when there is an offset) around fs/2. It isn't clear to me how you can determine that from measurements that only span the audio band.
@MarcelvdG: Thanks again for clarifying about dithering & NOS and the subharmonics & doubler relationship. Will ponder what to do in terms of TWTMC also considering your reply in #3108 ...
@dddac: Thanks for commenting as well & also linking to your measurements on the PCM1794 in DDDAC configuration. I cannot say much on Marcel's comments on where dithering can be seen/measured but in any case I like the way the DDDAC measures and not least the way it sounds ...
Cheers to you both ;-)
Jesper
@dddac: Thanks for commenting as well & also linking to your measurements on the PCM1794 in DDDAC configuration. I cannot say much on Marcel's comments on where dithering can be seen/measured but in any case I like the way the DDDAC measures and not least the way it sounds ...
Cheers to you both ;-)
Jesper
Andrea, did the measurements were done with the same crystal for driscoll and
differential or with 2 or more different crystals?
joël
This one seems to be a very good clock unit. Phase noise is even better than the 11mhz driscoll version.
They also mention that the best way to shield the clock from rfi is a steel enclosure not aluminium.
MUTEC - Professional A/V and High-End Equipment - REF10
They also mention that the best way to shield the clock from rfi is a steel enclosure not aluminium.
MUTEC - Professional A/V and High-End Equipment - REF10
At at the end of the day, a PLL synthesizer is required to get the various audio freq. and here ends the given measurements
Hp
At at the end of the day, a PLL synthesizer is required to get the various audio freq. and here ends the given measurements
Hp
This is the keyword. Units from the link are 10MHz and they could not be used like plug-and-play.
The final measurements should include device after the main 10MHz box.
GB is open
Yes, the GB is open, please see the GB thread at
The Well Tempered Master Clock - Group buy
Yes, the GB is open, please see the GB thread at
The Well Tempered Master Clock - Group buy
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