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Master Clock for your EtherREGEN


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5 hours ago, MartinT said:

The output connectors are 50 ohm. I'm thinking of sourcing PCB mount 75 ohm sockets and swapping them.

 

Using short 75 ohm cables into 75 ohm ER and Mutec in sinewave mode doesn't seem to be harming the signal too much.

Just swapping the connectors to 75 ohm is not sufficient, the output circuit has to be adjusted to also be 75 ohm. It may just be just changing a resistor, it depends on what the output circuit is.

 

John S.

 

 

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That was the right choice. What the GPSDO brings is much better stability over very long time frames, something that is not needed for audio and adds a LOT of complexity and potentially more noise.

 

I have a good GPSDO (well actually two!) but that is for use as a time base for my very sensitive time measuring equipment, not as a clock for digital audio.

 

Yep getting a good signal to the GPSDO is a major pain. I just bought a new one because it has a MUCH better GPS receiver than the old one, which meant I didn't need an outdoor antenna, one in the window works fine.

 

John S.

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8 hours ago, MartinT said:

 

Thanks - I will try it once I've got the impedance sorted. I hope I'm right in thinking an impedance mismatch affects a squarewave worse than a sinewave.

Yes, a mismatch has a larger affect on a square wave than it does on a sine wave, BUT the sinewave is already significantly worse than the squarewave. i still think a single mismatch on the squarewave will probably be better than the mismatch on the sinewave.

 

But that is just a guess, I haven't actually done that test and actually measured the output of the clock circuit.

 

John S.

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18 hours ago, sakso136 said:

My etherregen is standard one .

The guy on starkaudio,hk told me go for 50 ohm bnc

I told him I m going for gpsdo clock first then may be for cybershaft.

I mentioned that I m using it with er also.

So will you confirm I need bnc 75 ohm?

Really thankful for answering...

 

If you have a standard ER then you definitely want a 75 ohm one AND a 75 ohm cable.

 

When we were getting close to releasing the ER we did a pole and almost everybody said they wanted 75 ohm, so that became the "standard" ER. Alex makes a few 50 ohm versions every now and them for people that specifically order 50 ohms.

 

John S.

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20 hours ago, RickyV said:

An other difference I noticed is that my clock uses the LT1764 wich is a 3A version but still with 40uVrms noise. 
On the other pictures I saw they used LT1963.

 

Now, I am a bit of a modifier so why not replace these regulators with a 2A or 3A Lt3045 ( 3x 1A  LDOvr  reg). @JohnSwenson would this be a good idea?

Yes, clocks ARE susceptible to supply noise. The LT3045s are much lower noise than the ones mentioned, BUT a LT3045 is only good for 0.5A, so you need to put a bunch in parallel to attain the current you mention.

Are you thinking about designing your own boards or using someone elses boards? If you use existing boards they either need to be a single board designed for that current, or lower current boards specifically designed to be paralleled. You can't just take two or three 1A boards and parallel them unless they were specifically designed for that.

 

John S.

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On 10/10/2020 at 9:09 AM, R1200CL said:


That’s nice to know. (Rember there’s an A after 1963😀)

 

So the clock itself requires 11 V then. Did you find any data sheets for clock saying anything about voltage requirements?

 

I wonder if we’re able to convince the Chinese to exchange that present regulator in use to LT3045. 
I think he’s reading this tread, but a bit reluctant to participate in any discussion. 
 

However there may be other changes that could be done. So maybe if we’re patient John maybe give some suggestions. 

Remember that the LT3045 is just 0.5A. Even 12V OCXOs take more than that when warming up the oven. So you would have to parallel two to three LT3045s, this CAN be done but is a bit more complicated, and WAY more expensive than the 1963A.

 

John S.

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5 hours ago, GMG said:

There are two possible meanings of that "Manufactured for", one is as you mentioned that Finisar made them and manufacturer listed sold them as their own. But the more likely possibility is that they contain that particular manufacturer's code. The SFP modules contain a code for a specific manufacturer, the equipment (switches etc) from many manufacturers will only work if you insert a module with THEIR code embedded in the module. So Manufactured for means they contain that company's code. None of this matters for the ER since it doesn't look at that code at all.

 

John S.

 

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6 minutes ago, RickyV said:


What do you think about the 75ohm adapters I used and the two extra contact passes, it is short. 9 posts up.

As long as they are the correct impedance I think it is a great idea. Those adapters almost always use teflon dielectric and are machined to tight tolerances. There is a high probability what you have will be better that an equivalent piece of short cable of any type.

 

John S.

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14 minutes ago, RickyV said:

@JohnSwenson I was wondering do you know of modules or small pcb’s for sale that have a 10Mhz input and have a relatively easy selectable output frequency, 24Mhz, 25Mhz etc audio frequencies?

I don't know of anything specifically for audio frequency use.

 

You could do it with the Si5340-D-EVB which is the evaluation board for the synthesizer used in the ER. BUT you need to have it connected to a computer via USB to program the chip every time it powers up. It is great for testing and exploring but not good for a board you put in a product. And it is a pretty big board as well.

 

John S.

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2 hours ago, manueljenkin said:

Thank you very much John. Is there any possibility of mitigating some of the cable limitations by using a carefully designed PCB (controlled parasitics) instead of a wire?

 

Curious about this because the uspcb sounds much better than any cable at similar price to me. The causation I guess is different though, the latter being more due to better ground plane right?

What I mentioned above ARE PCBs, to be precise flexible multilayer PCBs using very high quality thin flexible dielectrics between copper layers. With multi layers they can be shielded very well and have very high precision impedance control. They just cost a lot of money.

 

Back in my days as a custom chip designer we used such cables for very high speed connections between boards, they cost in the range of $900 to $1400 per cable and were about 7 inches long. Not exactly cheap cables.

 

John S.

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4 hours ago, GMG said:

The Cybershafts and Afterdark clocks are sine wave (as far as I could gather from the translation)

I thought the Etherregen prefers square wave

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.

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