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About JohnSwenson

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  1. Hi Abolive, I'm not quite sure what you are trying to do here. Are you trying to select an Ethernet cable and you are asking if you should be using a plastic or metal RJ45 on the cable you buy? Are you building your own Ethernet cable and want to know what plug type to buy? Something Else? Thanks, John S.
  2. You have to be careful with doing that. If you are getting the clocks for the different ERs from the same clock box, you may be bypassing the ER moats by doing this. Some clock boxes have fully isolated outputs, but many do not, the grounds of all the outputs are tied together. John S.
  3. First off what is your DAC and what inputs does it have? Are you looking at an MC3, an MC3+ or MC3+ USB? The MC3 is the basic model, it takes in an S/PDIF stream (or similar streams), extracts the clock, uses that to synchronize a clock synthesizer, which is used to reclock the S/PDIF stream and send it out. The MC3+ adds a better clock synthesizer and some more output stream types. The USB adds a USB receiver that outputs an S/PDIF stream into the rest of the circuit. It also adds DSD over USB input. The output is an S/PDIF (or similar stream) that goes to your DA
  4. Hi guys, I just finished writing the first pass of my clock paper and sent it to Alex. He wants to do a little editing before posting it. He is on vacation with his wife right now, it will be sometime next week before he can get it posted. The information in this paper is very important for choosing clocks, cables etc. I strongly recommend you wait and read this before spending a lot of money buying clocks and cables. John S.
  5. The impedance is not going to mater as far as working or not is concerned. Have you tried all three outputs? Unfortunately there is no easy way to tell if there is actually output (well there is, but it takes an oscilloscope). If you have a multi-meter you can check continuity of the cable. Probably at least half the time the problems are caused by the cables. John S.
  6. What are you powering the clock with? It takes 12V. Does the green light on the box come on? The procedure is to turn off the ER (unplug ITS power, move the little slide switch on the back so the lever is near the BNC jack. Plug the BNC cable in between the clock box and the ER (it doesn't matter which jack on the box you use). Power up the clock box, make sure the green LED on the clock box is lit up. THEN plug the power back into the ER. This should work. John S.
  7. Please stop asking me to give a detailed breakdown and measurement of a whole bunch of different clocks, it is not going to happen!!!! Do I have to say it again? It is not going to happen. I simply do not have the money to buy a whole bunch of them nor the time to do a full analysis of every clock out there. I can say the AfterDark boxes do NOT use $20 used OCXOs, they are new modules, but I do not know which ones are used in the different models. That's it for the AfterDark clocks. I AM working on my detailed paper on differences between sine and square, 50 ohm and 75
  8. Hi Doc, The Rpi4 has a very different arrangement of io from previous versions, Rpi3 etc. Whatever image you install on the SD has to have been compiled to work with the Rpi4. My guess is you have installed images that were compiled for Rpi3 not Rpi4. John S.
  9. This is a tough one, there are a lot of different interactions involved, no simple "This is always the best". I've been thinking all night about the best way to present this, I think I have figured out a good way to present it, but it will take awhile to get it all written up, so be patient it may take a few days. John S.
  10. I just got an AfterDark clock that Alex sent me. It doesn't say what model it is, but the output is definitely a sine wave with 1.3V peak to peak. The output is 50 ohms so I loaded it with 50 ohms and used a 50 ohm cable. I have not had a chance to run it with an ER or do phase noise measurements. John S.
  11. Yes that really seems like an interaction via the shield in the cable. This sounds like a ground loop issue so we will need to get details about the mains connections for the system. First off what country are you in? Different countries handle safety ground etc differently so it is important to know where you are. Next for at least those devices you mention, how are they connected to the mains? Is it a three prong plug or a two prong plug? Are you using the manufacturer supplied power supply? Physically where are the devices? Same room, different rooms, all on the sam
  12. Wow, someone who gets this stuff! I'll make an attempt to answer this stuff. First off I forgot to mention magnetic fields. The whole process takes place in a strong magnetic field which tends to align spins making these lines easier to detect. #1, this is a gas at low pressure, it doesn't have to be ultra high purity, but that does help. Visual light is used to pump the gas to the particular line in question. So the gas is glowing at that color (line) that contains the hyperfine line in question. #2, YES! This is all about the wave equations for the atoms. But not just
  13. Aha, THAT as they say is a good question! The understand that you have to understand how they both work. The crystal oscillator is easy, quartz actually changes shape when an electric field is applied. It has a sharp "resonance" frequency where the expansion and contraction works extremely well. Same thing as a swing, if you "pump" a little energy into it at the right frequency you get large excursions. If you pump it at some other frequency not much happens. Same thing with the crystal. The oscillator circuit is just a high gain amplifier fed back into itself, which naturally osci
  14. I've said this many times before but I'll say it again. What matters for digital audio is the phase noise, the absolute accuracy, and the aging (drift over time) and temperature coefficient do not matter. These are all so good that they will not even come into the picture for digital audio. The lowest phase noise is produced by the best crystal oscillators, period. All these other types of clocks (mostly "atomic clocks" such as rubidium, cesium, hydrogen maser, cesium fountain) all have lousy phase noise, but great long term stability (fractions of a part per billion), which is com
  15. Hi yyz, The A side contains a switch chip which drives the 4 RJ45 ports and the SFP cage. The connection across the moat also goes to one of the ports on that switch chip. The B side just has the one RJ45 port, no switch chip. The isolation techniques are identical going from A to B and B to A. There is one difference, the clock circuitry is on the B side and has to travel through one of the isolation circuits to get to the A side. This isolator is VERY low jitter it adds a little extra jitter to the clock crossing the moat, but not very much. This is the difference in going
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