Master Clock for your EtherREGEN

23 minutes ago, JohnSwenson said:

I can tell you what happens technically with the waveforms on the wire, but how that shows up as sound difference is  a completely different issue.

 

Every time you have an impedance mismatch there will be a reflection, the bigger the mismatch the bigger the reflection. The worst thing is a mismatch at both ends, this causes multiple reflections, each edge bounces back and forth, this is can definitely cause problems with reception of  signal. If say the source is matched (50 ohm electronics, 50 ohm connector, 50 ohm cable) but the receive side is mismatched, each edge will reflect at the mismatch back towards the source. But since the source is properly matched that reflection gets absorbed by the proper impedance match.

 

So if a clock box has proprer electronics and connectors and cable, a mismatch at the receive end probably will not make too much of  a difference. The edge bouncing off the receive end and winding up at the source can cause some distortions at the source itself, but how much and what they look like vary wildly from design to design.

 

John S.

Thank you @JohnSwenson It looks like this is the way to go, provided the design both ends is correct

49 minutes ago, MartinT said:

I now have a set of 75 ohm connectors to install.  I will then need to find how the oven output reaches the connectors.  It may be a simple resistor change, I don't know yet as I've been unable to find a circuit diagram.  If in doubt, I'll leave it alone as it sounds very good already but I will change the connectors.

@MartinT I understand from the seller that this is a 50 Ohm output impedance. That you will need a resistor or something to change the fixed output. 

Are you using any of your variable output for other uses?

I don't have variable output?  I use both sinewave outputs and am not using the squarewave output.

When I open it up to change the connectors to 75 ohm, I will see what I can find with regards to output impedance.

I'll say again: it's clearly not a major issue driving two devices using short 0.5m 75 ohm cables despite the clock being 50 ohms in stock form.

2 hours ago, MartinT said:

When I open it up to change the connectors to 75 ohm, I will see what I can find with regards to output impedance.

Another consideration will be to exchange a 75 ohm EtherRegen with a 50 ohm version.

35 minutes ago, k-man said:

Another consideration will be to exchange a 75 ohm EtherRegen with a 50 ohm version.

For me, that wouldn't solve the problem as my Mutec MC-3+ USB is also 75 ohm.

It works well now but I'll exchange the BNC connectors when I have a little free time.

There isn’t many resistors... 

3k ohm = R20, R30, R36, R40.

51K ohm = R21, R39. 

The rest are 0 ohms.

Either could potentially feed the BNC connectors, I would trace back using a meter to see whether they are the line impedance resistors.

I shall pull my board out soon, I'm just waiting for some ceramic decoupling caps to arrive.

If it have to be a resistor, it must be R36 and maybe R39,

both after the DUAL INVERTER GATE SOT-23-6 CO45 IC.

Some guys put neoprene isolation around the ocxo:

https://www.head-fi.org/threads/gustard-u16-the-first-usb-interface-featuring-ess-usb-chip.888947/post-15196665

6 hours ago, MartinT said:

I use both sinewave outputs and am not using the squarewave output.

Actually, the EtherREGEN prefers squarewave input.  Since you have both, why don’t you go ahead and compare them? 

3 hours ago, basillus said:

The rest are 0 ohms.

Zero Ohms?! That’s called a PCB trace—though even those have some resistance. 
I mean yes, one can buy 0-ohm resistors, their only purpose (AFAIK) being to jumper spots where the circuit no longer needs an actual resistor.

3 minutes ago, Superdad said:

 

Zero Ohms?! That’s called a PCB trace—though even those have some resistance. 
I mean yes, one can buy 0-ohm resistors, their only purpose (AFAIK) being to jumper spots where the circuit no longer needs an actual resistor.

I know 😉

Replace the 3 1000uf/16v with something better is also an option...

and skip the dc plug and solder the cable directly at the pcb if the psu and cable are specific selected.

7 hours ago, Superdad said:

 

Actually, the EtherREGEN prefers squarewave input.  Since you have both, why don’t you go ahead and compare them? 

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.

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.

John, I do believe you're right. I've just switched the ER over to squarewave, leaving the Mutec on sinewave. There is a little more soundstage 'presence' and low level detail and the bass is a touch tighter. This is still with the mismatch at the clock socket/cable boundary.

When I receive a BNC T-connector, I'll be able to get my scope on the waveform and see how distorted it looks. My ears tell me that it's an improvement, though.

On 6/9/2020 at 3:44 PM, Superdad said:

 

Actually, the EtherREGEN prefers squarewave input.  Since you have both, why don’t you go ahead and compare them? 

Out of interest, what is the technical reason for this?

21 minutes ago, Confused said:

Out of interest, what is the technical reason for this?

Let's let @JohnSwenson tackle that one.  He has explained it to me several times--including recently--but today I have the memory of a goldfish as well as a pile of e-mail to return. 

1 minute ago, Superdad said:

 

Let's let @JohnSwenson tackle that one.  He has explained it to me several times--including recently--but today I have the memory of a goldfish as well as a pile of e-mail to return. 

Well, there is no rush with this one, and an answer from John would be excellent.🙂

On 5/30/2020 at 5:41 PM, Superdad said:

AfterDark, UpTone's successful dealer in Hong Kong, is also a big Cybershaft dealer. And he will be doing bundles of their MA-OPxx clocks with the EtherREGEN and our JS-2 later this summer.

Interesting.  From the photo of the back of the MA models, it indicates 15V 1A (and 13.5 - 16v).  Isn't the JS-2 limited to 12V?  I ask because I have a JS-2 and am considering a reasonably-priced external clock.  

4 minutes ago, PYP said:

Interesting.  From the photo of the back of the MA models, it indicates 15V 1A (and 13.5 - 16v).  Isn't the JS-2 limited to 12V?  I ask because I have a JS-2 and am considering a reasonably-priced external clock.

Upon request we now offer to adjust and relabel one output setting of one of the JS-2's two rails to 15V. With 120/240V AC input it can deliver continuous 4.2A @ 15V (that's less than our 7.4A continuous from one output at 12V--with 120/240V mains). With 110/220V AC mains our 15V setting can deliver 2.2A max.  Plenty for a Cybershaft clock. Even loading the other rail with a modest load--say an EtherREGEN at 12V works out.

We have shipped a few units this way, and AfterDark in HK is starting to order all theirs with such.

By the way, I have been told that Cybershaft will, for top-of-the-line OP20A/21A or OP20A/21A-D units, be moving back to the same beautiful chassis series as JS-2, just like it had been for now discontinued Limited2 series. No need for heatsinks on top of chassis and stamped faceplate.  But that falls outside your definition of "reasonably priced clock." 

33 minutes ago, JohnSwenson said:

The specific reason: the clock input goes into a very low additive phase noise clock synthesizer and all its inputs are designed for square waves.

 

More general reason: all the digital circuits that use clocks actually use squarewaves so feeding a sinewave into the system either doesn't work at all or gives much higher jitter.

 

Technical explanation of the above: All clock receivers have some form of threshold circuit, it changes state when the clock voltage goes through that threshold voltage. NO signals are ever perfect, there is ALWAYS some form of amplitude noise on the signal, AND the receiver itself always has some form of fluctuations on the threshold voltage. So think of the clock signal rising towards the threshold, as it gets nearer to the threshold the amplitude of the noise comes into play, the threshold might get passed when the noise is at its peak or at its lowest point, or some place in between. This noise on the signal causes an uncertainty as to when it will actually get to the threshold, otherwise known as jitter. The faster the voltage rise of the signal the lower the time uncertainty for a given noise amplitude. Thus a square wave with very fast rise and fall times will have much lower jitter than a sinewave which has a much slower changing voltage. This is the reason a circuit designed for square wave input MAY still work with a sinewave, but the jitter in the circuit clocked by the signal will be higher.

 

There ARE some ways to convert sinewaves into square waves, but the simple ways actually increase the noise on the signal making the jitter even worse. There are some ways to do it well but they are complex and expensive and take a lot of power. Putting one of those on the clock input of the EtherREGEN would have at least doubled the cost of the device, not worth it in my opinion.

 

BTW these master clocks provide both sinewave and squarewave outputs for different applications. Radio systems that need a very stable frequency reference for running into mixers etc want a sinewave. Digital systems want a square wave. Either system CAN use the other type, but won't work nearly as well. So it is best to get the type of master clock that works well with what you want to use it for.

 

I hope that makes some sense.

 

John S.

Thanks John, you explanations and insights are always an interesting read.