4 ms·

> Of course, it turns out there aren't that many home applications for an atomic clock For all the people who have a rubidium standard at home, 70% are using

> Of course, it turns out there aren't that many home applications for an atomic clock For all the people who have a rubidium standard at home, 70% are using it for electronic lab, amateur radio, or NTP at home. But the remaining 30% is another large userbase too - audiophiles. Many audiophiles claim jitter and phase noise in the clock signal significantly affects audio quality, and the most extreme audiophiles use a lab grade frequency standard, rubidium or better, and feed it to all their Hi-Fi gears. P.S: Given all the factors that affect audio quality, is the phase noise from a PLL synthesizer of reasonable quality really a major factor? Even if it is, does a rubidium standard really have any benefit beyond diminishing return over a crystal oven? Well, of course, these are the questions that are never answered by audiophiles. > You can buy a used rubidium frequency standard on ebay There is a continuous source of used rubidium standard coming from retired telecommunication and lab equipment, they are the cheapest atomic standard available. The catch is that the rubidium inside the discharge lamp will eventually get depleted during operation, usually within 10 years, once its life ends, it's useless and needs to be rebuilt completely by the manufacturer. So read the manufacturing date if you are going to power it 7x24. The real expensive ones are the Cesium Standard, such as the HP 5061A. Recently, the Hydrogen Standard also saw some uses.

JackMcMack 7y ago
The rubidium does not deplete (it's a closed system), but does settle on the glass. Supposedly you can heat the glass to turn all the rubidium into gas again, giving you theoretically infinite lifetime. I picked up a used PRS-10 on ebay for $250. It's a small but great oscillator, still made today. The manufacturer SRS claims 20 years lifetime, and mine has had 13 years of runtime, so I should be able to get 7 years out of it hopefully. The 11W1 DSub connector they used on the other hand is stupidly expensive. Cesium oscillators on the other hand do deplete their cesium (by design), as mentioned by CuriousMarc in the video. The tube in his unit was probably replaced at least twice, at a cost of >80k. The high performance tubes fare even worse because they "burn" through their cesium at a 3x rate. The 5071 successor by HP-Agilent-Symmetricom-Microsemi is the most frequently used COTS clock that contributes to UTC.
- segfaultbuserr 7y ago
  > Supposedly you can heat the glass to turn all the rubidium into gas again, giving you theoretically infinite lifetime. Thanks for the tip, that's interesting. I never know that they can be renewed in this way. > Cesium oscillators on the other hand do deplete their cesium (by design), as mentioned by CuriousMarc in the video. The tube in his unit was probably replaced at least twice, at a cost of >80k. Sad story. Recently I was browsing a web store that sells decommissioned U.S. military equipment. I was here to search for some cheap RF power meters, and I was surprised to see a HP 5071 in the listing. The vendor noted that he knew nothing about the equipment and information was welcomed. For a moment, I was thinking about sending him a service manual from the HP archive, before I realized it was simply impossible to get it up and running again without replacing the tube :( > The 5071 successor by HP-Agilent-Symmetricom-Microsemi Aha, the old Hewlett-Packard was truly a unique company. Its electronic technology has at least three separate chains of succession. Test Equipment: HP-Agilent-Keysight Semiconductor: HP-Agilent-Avago-Broadcom (Broadcom ended production of most HP parts, so now it's mostly dead, RIP...) Frequency Standard: HP-Agilent-Symmetricom-Microsemi
  - CamperBob2 7y ago
    And now: Frequency Standard: HP-Agilent-Symmetricom-Microsemi-Microchip
bogomipz 7y ago
Could you explain how one integrates a rubidium device in their hi-fi audio setup exactly? This sounds kind of fascinating. This is the first I've heard of this.
- Dylan16807 7y ago
  Lots of audio devices can take an external clock for synchronization and avoiding jitter. So you might have it output a 10MHz master clock signal and distribute it with coax cables.
- segfaultbuserr 7y ago
  We begin with Pulse Width Modulation. In PCM, an analog audio signal is digitized by an ADC, which performs digitization by measuring its instantaneous voltage, and convert it to a n-bit integer that represents this voltage level, such as 16-bit, at a fixed sampling frequency, such as 44.1 kHz. This process is reserved to playback the audio. "To properly digitize and re-construct digital audio it's relatively important the sampling intervals be as accurate as possible between the recording process and when it's played back." If the timing is not exactly one sample per 1/44.1k second, the signal will be distorted, it's being frequency-modulated by the unstable timing and it produces additional unwanted distortion. Like any digital system, a clock signal produced by an electronic oscillator provides the timebase, also known as the reference clock. Usually, the ADC and DAC chips needs a clock frequency commonly used in digital circuits, from 5 MHz to 30 MHz, and the internal circuitry inside the chip use this frequency as the reference clock to derive all the timings needed by the chip, including the sampling or reconstruction of PCM. Same applies to all other digital encoding formats. Ideally, the clock frequency should be as stable as possible. Unfortunately, all clock oscillators have inherent short-term instabilities, long-term instabilities, and non-zero temperature coefficient. Short-term instabilities, known as phase noise (in the frequency domain), or jitter (in the time domain) is a particular concern. As long as the audio system is properly optimized and characterized, jitter is not an issue. A good DAC will normally have a jitter around -90 dBc or lower, and it's probably negligible. NwAvGuy (an audio engineer known for his criticism of baseless audiophile practice), has a good explanation of clock jitter: https://nwavguy.blogspot.com/2011/02/jitter-does-it-matter.html https://nwavguy.blogspot.com/2011/02/jitter-does-it-matter.h... But of course, some audiophiles want to power their Hi-Fi gears with the best oscillator available, so that it'll have the lowest jitter and the minimum absolute frequency error and temperature coefficient, even if the benefits is dubious to other people. And they realized that a rubidium frequency standard is the best clock oscillator they can find. First, it's possible to DIY. All you needed to do is understanding how the digital part of the Hi-Fi system works and find the crystal responsible for generating the system/ADC/DAC clock. You simply remove the crystal and inject an external clock signal from the rubidium standard to the chip. 10 MHz is a common output frequency from a standard oscillator, if the audio circuit also has a 10 MHz clock, the rubidium standard output can be used directly. If it's not, if the frequency radio of the two is a integer, it's possible to use a frequency multiplier or a divider to generate the needed clock frequency from the rubidium standard output. If it's not an integer, a PLL frequency synthesizer can be used. Second, in an electronic lab, many gears have a "10 MHz Reference Input" port, their internal timings can be derived from the reference input, so that all signal generators, frequency counters, spectrum analyzer to a master clock oscillator (can be crystal oven, WWVB radio, GPS, or atomic) for consistency, so that all equipment's frequencies don't drift to different directions, all get a good clock with constant performance, and there won't be a disagreement between equipment. In some professional audio equipment for music production, it also allows an external reference to be used for the same purpose. One can simply plug the 10 MHz standard oscillator, including a rubidium standard, into the BNC connector of the audio gears.

JackMcMack 7y ago

The rubidium does not deplete (it's a closed system), but does settle on the glass. Supposedly you can heat the glass to turn all the rubidium into gas again, giving you theoretically infinite lifetime. I picked up a used PRS-10 on ebay for $250. It's a small but great oscillator, still made today. The manufacturer SRS claims 20 years lifetime, and mine has had 13 years of runtime, so I should be able to get 7 years out of it hopefully. The 11W1 DSub connector they used on the other hand is stupidly expensive. Cesium oscillators on the other hand do deplete their cesium (by design), as mentioned by CuriousMarc in the video. The tube in his unit was probably replaced at least twice, at a cost of >80k. The high performance tubes fare even worse because they "burn" through their cesium at a 3x rate. The 5071 successor by HP-Agilent-Symmetricom-Microsemi is the most frequently used COTS clock that contributes to UTC.

segfaultbuserr 7y ago
> Supposedly you can heat the glass to turn all the rubidium into gas again, giving you theoretically infinite lifetime. Thanks for the tip, that's interesting. I never know that they can be renewed in this way. > Cesium oscillators on the other hand do deplete their cesium (by design), as mentioned by CuriousMarc in the video. The tube in his unit was probably replaced at least twice, at a cost of >80k. Sad story. Recently I was browsing a web store that sells decommissioned U.S. military equipment. I was here to search for some cheap RF power meters, and I was surprised to see a HP 5071 in the listing. The vendor noted that he knew nothing about the equipment and information was welcomed. For a moment, I was thinking about sending him a service manual from the HP archive, before I realized it was simply impossible to get it up and running again without replacing the tube :( > The 5071 successor by HP-Agilent-Symmetricom-Microsemi Aha, the old Hewlett-Packard was truly a unique company. Its electronic technology has at least three separate chains of succession. Test Equipment: HP-Agilent-Keysight Semiconductor: HP-Agilent-Avago-Broadcom (Broadcom ended production of most HP parts, so now it's mostly dead, RIP...) Frequency Standard: HP-Agilent-Symmetricom-Microsemi
- CamperBob2 7y ago
  And now: Frequency Standard: HP-Agilent-Symmetricom-Microsemi-Microchip

bogomipz 7y ago

Could you explain how one integrates a rubidium device in their hi-fi audio setup exactly? This sounds kind of fascinating. This is the first I've heard of this.

Dylan16807 7y ago
Lots of audio devices can take an external clock for synchronization and avoiding jitter. So you might have it output a 10MHz master clock signal and distribute it with coax cables.
segfaultbuserr 7y ago
We begin with Pulse Width Modulation. In PCM, an analog audio signal is digitized by an ADC, which performs digitization by measuring its instantaneous voltage, and convert it to a n-bit integer that represents this voltage level, such as 16-bit, at a fixed sampling frequency, such as 44.1 kHz. This process is reserved to playback the audio. "To properly digitize and re-construct digital audio it's relatively important the sampling intervals be as accurate as possible between the recording process and when it's played back." If the timing is not exactly one sample per 1/44.1k second, the signal will be distorted, it's being frequency-modulated by the unstable timing and it produces additional unwanted distortion. Like any digital system, a clock signal produced by an electronic oscillator provides the timebase, also known as the reference clock. Usually, the ADC and DAC chips needs a clock frequency commonly used in digital circuits, from 5 MHz to 30 MHz, and the internal circuitry inside the chip use this frequency as the reference clock to derive all the timings needed by the chip, including the sampling or reconstruction of PCM. Same applies to all other digital encoding formats. Ideally, the clock frequency should be as stable as possible. Unfortunately, all clock oscillators have inherent short-term instabilities, long-term instabilities, and non-zero temperature coefficient. Short-term instabilities, known as phase noise (in the frequency domain), or jitter (in the time domain) is a particular concern. As long as the audio system is properly optimized and characterized, jitter is not an issue. A good DAC will normally have a jitter around -90 dBc or lower, and it's probably negligible. NwAvGuy (an audio engineer known for his criticism of baseless audiophile practice), has a good explanation of clock jitter: https://nwavguy.blogspot.com/2011/02/jitter-does-it-matter.html https://nwavguy.blogspot.com/2011/02/jitter-does-it-matter.h... But of course, some audiophiles want to power their Hi-Fi gears with the best oscillator available, so that it'll have the lowest jitter and the minimum absolute frequency error and temperature coefficient, even if the benefits is dubious to other people. And they realized that a rubidium frequency standard is the best clock oscillator they can find. First, it's possible to DIY. All you needed to do is understanding how the digital part of the Hi-Fi system works and find the crystal responsible for generating the system/ADC/DAC clock. You simply remove the crystal and inject an external clock signal from the rubidium standard to the chip. 10 MHz is a common output frequency from a standard oscillator, if the audio circuit also has a 10 MHz clock, the rubidium standard output can be used directly. If it's not, if the frequency radio of the two is a integer, it's possible to use a frequency multiplier or a divider to generate the needed clock frequency from the rubidium standard output. If it's not an integer, a PLL frequency synthesizer can be used. Second, in an electronic lab, many gears have a "10 MHz Reference Input" port, their internal timings can be derived from the reference input, so that all signal generators, frequency counters, spectrum analyzer to a master clock oscillator (can be crystal oven, WWVB radio, GPS, or atomic) for consistency, so that all equipment's frequencies don't drift to different directions, all get a good clock with constant performance, and there won't be a disagreement between equipment. In some professional audio equipment for music production, it also allows an external reference to be used for the same purpose. One can simply plug the 10 MHz standard oscillator, including a rubidium standard, into the BNC connector of the audio gears.