Master Clock for your EtherREGEN

Who here is using an external master clock with your EtherREGEN?  If so, what are you using and how would you describe the changes to sound quality compared with using the internal clock?

Used to have a Paul Pang 10MHz reference clock : great improvement in terms of soundstage and fluidity in transition compared to the internal clock. A good improvement seen from me. 

3 hours ago, MartinT said:

My thinking was that the ER, with its notorious Crystek 575 oscillator, would be the better component to respond to an external clock although I have no knowledge of the clock used in the Mutec.

Not sure what you mean by "notorious" Crystek 575.  The CCHD-575 is one of the lowest phase-noise production XO available (about $10 each at 500 piece qty,), and our 3 original 25MHz (random production) samples came with plots showing 10Hz-offset phase-noise of -108, -110, and -112 dBc/Hz.  (And remember, its easier to get better numbers from a 10MHz clock than a 25MHz clock, though they can be equivalent in terms of jitter/phase-noise).

To do better than that you have to either spend $400-$800 on an OCXO (the OXCO alone, not in a case), one specifically meant and measured to have ultra low phase noise, or buy--and screen with an expensive analyzer--selected surplus OCXOs (as Cybershaft does for some of their models). 

Plus we position the CCHD-575 just 3mm from the EtherREGEN's Silicon Labs clock synthesizer and power it carefully with an ultra-low-noise LT3045 regulator.

So an external clock better be darn good with both its phase-noise and its cable if it is going to outperform our internal clock.

Quote

I am pleasantly in shock that £70 worth of Chinese made amateur radio clock (well, to be fair, a pretty accurate oven controlled clock made for telecoms use) could achieve anything very much, let alone what I’m hearing.

I am really glad you are pleased with what you are hearing, but inexpensive OCXOs, while fine for stability (lack of frequency drift which is what telecom stuff calls for) are terrible with regards to phase-noise at low offsets--which is all that matters for our applications.  So unless your BG7TBL clock is performing some miracle, I'm not at all convinced that it measures any better than our internal clock. And certainly not at the end of a modest clock cable.

Sorry, great OCXO clocks don't come cheap! 

This is the inside of your unit. No markings on the clock to attempt to look up its specs. It is inexpensive enough that I might order one and have John run a full phase-noise plot of it with his new $17K Jackson Labs Phase-Station.

Cybershaft does have a new entry level line, and for the price (about $1,500 for the base model MA-OP13) they are exceptional.  Note that their phase noise specs (for which one receives a individual graph for each unit) are listed at 1Hz offset. All their model numbers correspond to the dBc/Hz figure at 1Hz offset. -113dBc/Hz @1Hz is terrific! As mentioned, I think they accomplish this by having sources for--and then screening, measuring, and sorting themselves--surplus clocks.  Nothing wrong with that at all.

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.

I found the specs for the DAPU OCXO. Would very much appreciate your thoughts on phase noise and the other specs.

http://dptel.com/products-detail.php?ProId=2895

3 hours ago, Superdad said:

If the O55A is really the clock module in your box then it’s a good bargain for $100.

Yes, it's my photo of my unit.

On 5/31/2020 at 8:19 PM, MartinT said:

 

Yes, it's my photo of my unit.

Would you mind posting where you bought it, if that's not against the rules...

9 minutes ago, Ponkbutler said:

Would you mind posting where you bought it, if that's not against the rules...

From AliExpress.

https://www.aliexpress.com/item/4000152539910.html?spm=a2g0s.9042311.0.0.795e4c4dGTiyce

Mine is the latest BG7TBL variant, dated 2019-12-09 and contains the DAPU OCXO.  No guarantees that others will be the same!

Thanks. Yes: you may have been lucky. There's no indication of whether it is 50 or 75 Ohm either...

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.

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.

It is starting to make more sense now.  John told me he runs into the Chinese DAPU OCXOs surplus on eBay all the time. Pulled from PCBs in older 4G towers. Typically about $15-20. Probably less in China.  
Here it is on Taobao:

https://www.taobao.com/list/item-amp/574299443769.htm?spm=a21wu.10013463.3.11

Now I dig a little further to understand that BG7TBL is the call sign of a Chinese ham radio operator who some years ago began producing a whole series of 10MHz clock units for ham amateur radio. Well covered here:

https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/
Fascinating.  I wouldn’t mind finding one with a nice Morion clock in it. 

40 minutes ago, Superdad said:

 
Here it is on Taobao:

https://www.taobao.com/list/item-amp/574299443769.htm?spm=a21wu.10013463.3.11

 

That one's about $42, extremely high temperature stability, low ageing.

But with the same (1kHz) phase noise spec there are these which are only $3 a pop : https://item.taobao.com/item.htm?spm=a230r.1.14.10.6ad93b6ex8TOly&id=567999133115&ns=1&abbucket=2#detail

I may be wrong but I deliberately did not select a GPSDO because the complexity is tenfold. All that digital circuitry and ground plane noise for the immaterial benefit of zero long term drift. I didn't want any more noise on the clock outputs than absolutely necessary. There is also the faffing around with a GPS antenna out to the window.

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.

Any of these above 75ohm off the shelf, - & worth the expectation of a substantive uptick with the ER?

I've not seen any of the BG7TBL designs with 75 ohms off the shelf. Even with 50 ohm output I'm getting a substantive improvement and I'm going to try adapting mine for 75 ohm operation.

Hmm interesting... I have the same BG7TBL Connected to my Gustard U16 and haven't tried it on the etherregen, because I figured it wouldn't be an improvement there.

Ok, now it must be tried, but just needed one more bnc cable ;0) and a better psu...

40 minutes ago, basillus said:

Hmm interesting... I have the same BG7TBL Connected to my Gustard U16 and haven't tried it on the etherregen, because I figured it wouldn't be an improvement there.

Ok, now it must be tried, but just needed one more bnc cable ;0) and a better psu...

You must try it!  I found the effect of external clocking both my EtherREGEN and Mutec very impressive.  You should hear a similar doubling of the effect.

I agree too. I am still using a 50 Ohm cable, would like to try the 75Ohm one soon, to see how much gain is available from impedance matching?

I wonder if It would also be worthwhile to use the two other output for clocking other things, say the DAC, Sadly my Lampi GG does not support this....

24 minutes ago, zerung said:

I agree too. I am still using a 50 Ohm cable, would like to try the 75Ohm one soon, to see how much gain is available from impedance matching?

I wonder if It would also be worthwhile to use the two other output for clocking other things, say the DAC, Sadly my Lampi GG does not support this....

BTW the connector is still 50 Ohm.

@JohnSwenson@Superdad

How much difference would you find - with the impedance matching? Thank you

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.