Master Clock for your EtherREGEN

[DarqueKnight]

Many thanks to @MartinT , @Superdad ,  @JohnSwenson and others who contributed to this thread. Based on the good advice and personal experiences described here, I decided to forego playing "reclaimed cell tower clock roulette". I recently ordered an Afterdark Giesemann Triple Output (75 ohm square wave) OCXO with integrated linear power supply. A review will be posted in the Afterdark forum after it is received and settled in.

 

If my curiosity gets the better of me, I might order one of the cell tower clocks to compare it to the Afterdark Giesmann.

 

 

My EtherREGEN is configured as follows: TeraDak DC-30 linear power supply, Revelation Audio Labs Cat8+ 1.25m Ethernet cable B-side to Bryston BDP-3 digital player, Revelation Audio Labs Cat8+ Ethernet cable, A-side port 1  to Synology DS718+ NAS, Monoprice Cat8 Ethernet cable, A-side port 4 to Araknis AN-110-SW-S8 Ethernet switch. The Araknis switch provides the stereo system's networked components (BDP-3 digital player, PS Audio P10 AC regenerator, EtherREGEN) a wired connection to the home LAN's router.

 

The EtherREGEN is located on the top rear of a dCS Puccini U-Clock word clock.

 

Digital source components, left to right: dCS Debussy DAC, dCS Puccini word clock, Synology DS718+ NAS, Bryston BDP-3 digital player. The three main source components sit on PS Audio PowerBase isolation platforms and Black Diamond Racing isolation cones and pucks. The NAS sits on a 1/2" thick pad of Sorbothane. Twenty-two pound granite slabs anchor the DAC, word clock, and digital player to their isolation platforms. The NAS is powered by a TeraDak DC-150 linear power supply. Source components and preamp are powered by a PS Audio P10 AC regenerator, which is fed by a dedicated 20 amp AC circuit. Each monoblock power amp has its own 20 amp AC circuit, which are on separate legs of the breaker box's electrical service.

 

 

[DarqueKnight]

 

I was curious about the specs of the cell phone tower OCXO  clock currently offered on AliExpress for the EtherREGEN. I asked the vendor these questions:

 

1. What is the output impedance, 50 ohms or 75 ohms? The pictures look like 50 ohm outputs, but I wasn't sure if the picture was the actual product.

 

2. Who is the manufacturer of the OCXO?

 

Answers:

 

1. 50 ohms.

2. NDK 2525.

 

AliExpress OCXO item ordering page:

 

https://www.aliexpress.com/item/1005001705401580.html?spm=a2g0o.cart.0.0.4a913c00TOaaBw&mp=1

 

NDK2525 spec sheet:

 

https://www.ndk.com/en/ad/2013/001/pdf/c_NZ2520SD_e.pdf

 

 

[DarqueKnight]

3 minutes ago, MartinT said:

 

I think you've not read this thread fully. A few of us have asked for and received 75 ohm units. It's easy to verify by looking at the BNC connectors.

 

There are at least three brands of OCXO clocks used. Both my active and spare one use DAPU.

 

Also, some units are single square and dual sinewave, while others are triple squarewave. It depends on what you want.

I read the thread fully. I think you did not read, or understand, my post fully.

 

As my post stated, the pictures in the AliExpress ad I referenced showed 50 ohm outputs, but the ad specifically stated that the clock was for EtherREGEN owners. I wanted to ask about the output impedace to be sure. Product pictures in ads are not always representative of the actual product.

 

I recall reading that the DAPU OXCO stocks have been depleted, and that people were receiving clocks that had other brands of oscillators. That is why I asked the vendor in my referenced AliExpress ad about the OCXO brand in their clock.

 

Obviously, I am aware that there are several options for these type of  OCXO clocks and outputs, hence my references to not wanting to play "reclaimed cell tower clock roulette", and ordering the Afterdark Giesemann clock with integrated linear power supply.

 

Specifically, I was posting information for those who might be interested in that particular AliExpress OCXO option, as I had not seen the specs for it posted previously. My apologies if I overlooked it.

 

I am still interested in one of these inexpensive clocks to compare to the Giesemann, and possibly to use with my second EtherREGEN in my system at work.

[DarqueKnight]

Again, thanks for posting this thread and your results. I had been interested in better clocks for my EtherREGENS for quite some time, but did not want to spend thousands of dollars. I was not aware of Afterdark products until I read about them in this thread.

[DarqueKnight]

5 hours ago, James Stephens said:

Hi there,

 

Something might be amiss.

 

That spec sheet appears to be for an oscillator that will output a number of frequencies but not 10MHz, and that isn't an NDK2525.

 

Having said that, I checked NDK's website but I didn't see a spec page for an NDK2525.

 

Best,

James

 

Hi James,

 

That spec sheet was the closest I could find when doing a search for an NDK2525, either by search engine or on NDK's website.

When I saw the "2520" in the part number, I wondered if the 2520 might be a member of that family of OCXOs.  ALso, it could be that I was given the wrong part number by the AliExpress vendor.

 

When I searched for 10 MHz NDK OCXOs, most of those part numbers began with "NH". I have sent an email to NDK requesting clarification.

[DarqueKnight]

After the AliExpress seller confirmed that they could change the square wave output to 75 ohms, for an additional charge of $8 USD, I placed an order for one. I paid an additional $13.98 for AliExpress Premium shipping, with an expected delivery date of March 21, 2021.

 

My total came to $114.24 ($85 for the clock + $8.00 for the 75 ohm output + $9.26 tax + $13.98 premium shipping - $2.00 AliExpress discount coupon).

 

However, the order did not go through for security reasons. I was then led to an "appeals" page where I was asked to upload a photo of my credit card, a photo of a photo ID, and other identity confirmation. The appeals page said if everything checked out, the order would be released in about three days, at which time I could complete payment.

 

This, along with the difficulty in finding accurate specs, or even the accurate identity of the OCXO in this clock, were taken as "signs" that I should move on. I then promptly cancelled the order.

 

[DarqueKnight]

4 hours ago, R1200CL said:

Why aren’t you purchasing the same clock as the rest of us ?

 

@R1200CL, The three square wave output BG7TBL clock you purchased from HamRadioshop Store is no longer available. That unfortunate development has been mentioned a few times previously in this thread.

 

Three square wave output BG7TBL no longer available:

 

https://www.aliexpress.com/item/4001245799329.html?srcSns=sns_Copy&spreadType=socialShare&bizType=ProductDetail&social_params=20028087761&tt=MG&aff_fsk=_mNKlgzX&aff_platform=default&sk=_mNKlgzX&aff_trace_key=093f272f4474412f94cf5157972e514d-1614452691180-01472-_mNKlgzX&shareId=20028087761&businessType=ProductDetail&platform=AE&terminal_id=a79ff3b9eedb4287b15412a42a902112

 

The BG7TBL I attempted to purchase from TZT specifically said it was for use with the EtherREGEN. Based on that, I assumed that clock would have a low phase noise OCXO and that the seller might be agreeable to changing the square wave output to 75 ohms.

 

https://www.aliexpress.com/item/1005001705401580.html?spm=a2g0o.cart.0.0.4a913c00TOaaBw&mp=1

[DarqueKnight]

4 hours ago, R1200CL said:

What version did you purchase ?

How long time from order to receive ?

@R1200CL, I purchased the Prince level of the AfterDark Giesemann Triple Output OCXO. Adrian said the estimated delivery time is 5-7 days after the unit is built and shipped. Of course, things can get held up in customs on both ends.

[DarqueKnight]

17 hours ago, ambre said:

Vannot you use Paypal also insured shipment and risks. That working great with AliBaBa :-)

Yes, I reconsidered and placed the order again and paid with Paypal with no issues.

 

I have been ordering from AliExpress since 2017 and never had any issues paying by credit card, or with merchandise arriving in a reasonably timely manner from China. Maybe they have some new security protocols for credit card payments.

 

My order is supposed to ship within 8 days. I requested the square wave output and the middle sine wave output to be changed to 75 ohms. We'll see what shows up and when.

[DarqueKnight]

@MartinT What are those four silver cylindrical vibration damping devices?

[DarqueKnight]

1 hour ago, FIndingit said:

https://www.ebay.com/itm/333541364404
 

a premium alternative among the Chinese ocxos. 

The phase noise spec for the Morion OCXO is given for 5MHz,  (-130 dBc/Hz at 10 Hz). This would be equivalent to -124 dBc/Hz at 10 Hz. According to @Superdad "125dBc/Hz @10Hz is about what it takes for a 10Mhz clock to audibly surpass the EtherREGEN's 25.0MHz Crystek CCHD-575."

 

The Morion-based clock might not be an audibly superior alternative to the ER's Crystek clock.

 

On 1/13/2021 at 1:09 PM, Superdad said:

 

"The Crystal CCHD-575 [used in the EtherREGEN] 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.  (Crystek is very conservative and the graphs they post do not reflect these actual terrific production performance marks.) And remember, it is far easier to get better numbers from a 10MHz clock than a 25MHz clock, though they can be equivalent in terms of jitter/phase-noise.

 

-125dBc/Hz @10Hz is about what it takes for a 10Mhz clock to audibly surpass the EtherREGEN's 25.0MHz Crystek CCHD-575.  25.0MHz is 1.5 octaves above 10.0MHz, so its typical -110dBc/Hz (@ 10Hz offset) can be considered equivalent to -119dBc/Hz if it was a 10MHz clock (about 6dB/octave is safe to draw comparisons between frequencies). And it seems plausible that the adjusted-for-frequency difference of 6dB--between -119 and -125--would be about the threshold for what could be audible with our switch.

This assumes use of a good short clock cable, matched impedances, and use of square wave..."

 

 

[DarqueKnight]

6 hours ago, GMG said:

I was wondering about the longevity of OCXO in general. 
do they degrade over time?

how are they compared to “regular” audio clocks?

 

@JohnSwenson addressed that question here:

 

On 12/31/2020 at 8:47 PM, JohnSwenson said:

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 completely meaningless for digital audio. The time it will take to get a one second error is greater than the age of the universe, but that is meaningless for digital audio!

 

John S.

 

[DarqueKnight]

12 minutes ago, FIndingit said:

Does After Dark really claim their ocxo modules are brand new and unused? As far as I know neither Cybershaft or Mutec do that. 

 

AfterDark claims that their Giesemann OCXOs are a new design:

 

 

[DarqueKnight]

Now would be a good time to post a question to @AfterDark. on the AfterDark forum about the provenance of their OCXOs.

[DarqueKnight]

On 3/3/2021 at 9:22 AM, LewinskiH01 said:

HamRadioshop seller on Aliexpress has been out of stock of the BG7BTL clock, but now has it back. 75 ohm, 3 square wave signals.

 

I've inquired about the OCXO currently in use and received "SYMM" for an answer. Googling I found a Symmetricom STP2695LF 10MHz OCXO, but the seller hasn't confirmed if Symm means Symmetricom, nor the model. My intent is to check the phase noise specs, per this thread. Seller says "don't worry; it's the same high quality".

 

Does anybody have any insight that can help me? Anybody received a BG7TBL with a SYMM? Does SYMM=Symmetricom?

@LewinskiH01 I recently received two BG7BTL clocks, one purchased from Ham Radio Shop via AliExpress.com and the other purchased from TZT Store via AliExpress.com. The BG7TBL ordered from TZT Shop took 3 weeks to arrive. The BG7TBL ordered from Ham Radio Shop took 2.5 weeks to arrive. Both clocks had OCXOs that were Symmetricom part number 159-00057-000. I could not find any specs using that part number. I had some success finding phase noise specs using the model number 090-003861-13. A search on that model number lead me to an eBay ad for a GPS device that used that OCXO.

 

Link to eBay ad: https://www.ebay.com.au/itm/Symmetricom-LCD-GPSDO-Low-phase-noise-10MHz-1PPS-OCXO-GPS-Disciplined-Oscillator-/312533079686?mkevt=1&mkcid=1&mkrid=705-53470-19255-0&campid=5337590777&customid=&toolid=10001

 

The eBay ad provided the phase noise graph shown below and phase noise specifications for the Symmetricom 090-003861-13 of

-110 dBc/Hz at 1 Hz and -130 dBc/Hz at 10 Hz.  @Superdad said an OCXO would have to have phase noise performance of -125 dBc/Hz at 10 Hz to be audibly better than the clock used in the EtherREGEN.

 

Figure 1. Phase noise plot for Symmetricom 090-03861-13 OCXO. [Source: eBay ad]

 

Figure 2. BG7TBL from Ham Radio Shop on left. It has three 75 ohm square wave outputs. BG7TBL from TZT Shop on right. It has a 75 ohm square wave output, a 75 ohm sine wave output, and a 50 ohm sine wave output.

 

The metal cases, OCXOs, and circuit boards of both BG7TBLs were identical, as were the 12V/1A "wall wart" switch mode power supplies (Asian Power Devices model number WA-12M12FU).

 

Figure 3. Inside BG7TBL purchased from TZT Shop.

 

Figure 4. Closeup of BG7TBL OCXO purchased from TZT Shop. OCXO was manufactured the 49th day of 2011.

 

Figure 5. Inside BG7TBL purchased from Ham Radio Shop.

 

Figure 6. Closeup of BG7TBL OCXO purchased from Ham Radio Shop. OCXO was manufactured the 51st day of 2011.

 

Figure 7. Shipping box of BG7TBL purchased from TZT Shop.

 

Figure 8. Inside shipping box of BG7TBL purchased from TZT Shop.

 

Figure 9. Shipping box of BG7TBL purchased from Ham Radio Shop.

 

Figure 10. Inside shipping box of BG7TBL purchased from Ham Radio Shop.

 

Figure 11. The BG7TBL purchased from Ham Radio Shop was very well protected from shipping damage.

 

Listening Evaluations

 

I perceived no sonic difference between both BG7TBLs when listening to the 75 ohm square wave outputs of each. In both cases, there was a small improvement in clarity, detail, and image weight. This was with each clock's stock power supply and a generic 2 meter 75 ohm BNC cable made by ProSig. This cable came as an accessory with my dCS Puccini U-Clock word clock. Using better BNC cables and replacing the stock switch mode power supply with a TeraDak DC-30 linear power supply resulted in further improvements in sound quality.

 

Using either of the sine wave outputs of the TZT BG7TBL resulted in diminished sound quality. There was a small loss of clarity, detail and bass definition.

 

Figure 12. TeraDak DC-30 linear power supply, DC cable, and 10 AWG power cable made by Signal Cable (MagicPower cord).

 

Figure 13. Evaluation setup.

 

Figure 14. Evaluation setup.

 

Figure 15. Digital source components, left to right: dCS Debussy DAC, dCs Puccini U-Clock word clock, Bryston BDP-3 digital player.

 

Figure 16. Block diagram of digital source components.

 

Figure 17. BG7TBL in its temporary location between the dCS components. I have an AfterDark Emperor Double Crown clock on order. This BG7TBL will be installed in my system at work. The other BG7TBL will be kept as a spare and for experimental purposes.

 

I am very pleased with the improvements in stereophonic performance brought by the BG7TBL clock. I look forward to hearing what the AfterDark clock will bring.

[DarqueKnight]

I used a Tektronix TDS 2012 oscilloscope to see what the TZT Shop's BG7TBL's square and sine waveforms looked like. Measurements were taken using the following three 75 ohm BNC cables:

 

1. Prosig PSG00542 RG-59/U coaxial cable, 2 meter length. This cable came with my dCS Puccini U-Clock word clock. Cost $5.

2. Revelation Audio Labs Prophecy Cryo-Silver with Oyaide BNC connectors, 1.5 meter length, made in 2009. Cost $349.

3. Revelation Audio Labs Prophecy Cryo-Silver with Furutech BNC connectors, 1 meter length, made in 2015. Cost $449.

 

Figure 1. Top to bottom: Revelation Audio Labs 1 meter 75 ohm coax cable with Furutech BNC connectors, 2015 design, Revelation Audio Labs 1.5 meter 75 ohm coax cable with Oyaide BNC connectors, 2009 design, Prosig PSG00542 75 ohm coax cable.

 

Figure 2. Square wave output with Prosig PSG00542 cable.

 

Figure 3. Square wave output with RAL/Oyaide cable.

 

Figure 4. Square wave output with RAL/Furutech cable.

 

Figure 5. Sine wave output with Prosig PSG00542 cable.

 

Figure 6. Sine wave output with RAL/Oyaide cable.

 

Figure 7. Sine wave output with RAL/Furutech cable.

 

After purchasing the Puccini U-Clock in 2015, I experimented with different BNC coax cables between the U-Clock and the dCS Debussy DAC. I found that better quality clock cables resulted in better sound quality.

 

 

[DarqueKnight]

The RAL/Furutech sounded best, then the RAL/Oyaide, then the Prosig.

 

 

[DarqueKnight]

 

23 minutes ago, ambre said:

Less voltage and peaks in both waves.

How to interpret less is better ......??!!!

 

 

There is some amplitude inaccuracy due to the impedance mismatch between the scope and the source/cables.

 

10 minutes ago, JohnSwenson said:

What impedance did you have the scope input set to? A standard inputof 1 megaohm will give very different results than a 50 ohm input. (which is much closer to 75 than 2 megaohm is).

 

John S.

 

The scope inputs are 1 megaohm. This scope requires a 75 ohm feedthrough terminator to properly terminate 75 ohm sources and cables, which I don't have at the moment.

[DarqueKnight]

9 minutes ago, Superdad said:

 

After folks digest John's above-linked paper, and when he has a bit of time, there is much he will want to explain about the BG7TBL clocks. Their circuits are a bit bizarre and a HUGE compromise, but in the end if using their sine wave output with the filter recommended (got to read the paper), one could still get decent performance our of that very inexpensive clock.  

The AfterDark units (and others priced well above) really are better clocks. Sorry @MartinT.  But again, there is a great and cheap way to get better performance from them...

@Superdad , @JohnSwenson,

 

Thank you for the clock paper. It provided some explanation for the sonic results I mentioned in my initial post regarding experiences with square vs. sine outputs of my BG7TBLs.

 

I ordered my BG7TBLs out of curiosity, as I am waiting for delivery of an AfterDark Emperor Double Crown Giesemann clock. The stock BG7TBL was a small improvement over the EtherREGEN's internal clock. The addition of a better clock cable and a linear power supply took things to another level. Whereas the stock BG7TBL produced an improvement along the lines of "oh, that's nice", the "tweaked" BG7TBL produced an improvement along the lines of "let me stop what I am doing in the another room and go back to the listening room".

 

Thanks for the tip on the Mini Circuits filter. I will try one with my sine output BG7TBL.

 

 

[DarqueKnight]

@Superdad

 

I did not run into a $50 minimum when placing an order for one 50-ohm BLP-10.7+. The order came to $47.22 ($35.45 + $11.77 shipping).

 

As you mentioned...ordering the 75 ohm version is somewhat difficult.

 

[DarqueKnight]

19 minutes ago, PYP said:

From the main website, you do get the message about it being a non-catalog item, but you can use this link to the web store instead:  https://www.minicircuits.com/WebStore/dashboard.html?model=BLP-7-75%2B    I ordered one 

filter.

 

Since John mentioned this part number in his article, and previous to his article I was indoctrinated about matching impedances, I chose that part.   You can tell an audiophile something doesn't matter, but that call to logic will probably go unheeded. 

@PYP @Superdad

 

The filter @PYP ordered is a 75-ohm 7 MHz filter rather than the 75-ohm 11 MHz filter specified in John's clock paper.

 

Spec sheet for BLP-7-75+:

https://www.minicircuits.com/pdfs/BLP-7-75+.pdf

 

Spec sheet for BLP-10.7-75+

https://www.minicircuits.com/pdfs/BLP-10.7-75+.pdf

 

 

[DarqueKnight]

6 minutes ago, LewinskiH01 said:

@DarqueKnight

My BG7BTL from RadioHam arrived too. I had a similar experience to your. 

 

How do you know which [output] is which?

 

The Ham Radio Shop BG7TBLs are advertised as

"75ohm output by BG7TBL 10MHz OCXO FREQUENCY STANDARD 3 channel square wave clock Master Clock for your EtherREGEN"

 

Therefore all three of the outputs should be square wave. The only way to know for sure is to attach the outputs to an oscilloscope (which is what I did).

 

The BG7TBL I purchased drom TZT shop had, per my request, going from left to right:

 

Output 1 - 75 Ohm Square

Output 2 - 75 Ohm Sine

Outout 3 - 50 Ohm Sine

[DarqueKnight]

I placed an order by phone for the Mini-Circuits BLP-10.7+ 50 Ohm and BLP-10.7-75+ 75 Ohm filters.

 

 

 

[DarqueKnight]

2 hours ago, Rasputin said:

I’m very interested in your experience with the filters when you get them, hope you will share.

Of course I will.

[DarqueKnight]

I have received my Mini-Circuits filters. The people at Mini-Circuits were a pleasure to deal with. The order was placed mid-morning and it was shipped early afternoon the same day. It arrived three days later by FedEx.

 

Figure 1. The filters arrived in a sturdy box with copious amounts of protective paper padding.

 

Figure 2. Two of the BLP-10.7-75+ 75 ohm filters and one of the BLP-10.7+ 50 ohm filters were ordered. I have one BG7TBL with three 75 ohm square wave outputs and another BG7TBL with a 75 ohm square wave output, a 75 ohm sine wave output, and a 50 ohm sine wave output.

 

Figure 3. I did not pay attention to the filter size on the spec sheet. I expected them to be smaller.

 

Figure 4. I also received this accessory for my Tektronix TDS 2012 oscilloscope. It is a 75 ohm feed through termination for impedance matching of 75 ohm cables to the scope's 1 M-ohm input impedance.

 

Figure 5. Three 75 ohm BNC cables. Bottom to top: Prosig PSG00542 RG-59/U coaxial cable, 2 meter length. This cable came with my dCS Puccini U-Clock word clock, cost $5, Revelation Audio Labs Prophecy Cryo-Silver with Oyaide BNC connectors, 1.5 meter length, made in 2009, cost $349, Revelation Audio Labs Prophecy Cryo-Silver with Furutech BNC connectors, 1 meter length, made in 2015, cost $449.

 

Figures 6 through 8 show the waveform and amplitude distortions that occurred due to the impedance mismatch between the cables and the scope. The BG7TBL had been on for over 24 hours prior to taking measurements.

 

Figure 6. Square wave pulse train waveform with Prosig cable, impedance mismatch.

 

Figure 7. Square wave pulse train waveform with RAL 2009 cable, impedance mismatch.

 

Figure 8. Square wave pulse train waveform with RAL 2015 cable, impedance mismatch.

 

Figure 9. Square wave pulse train waveform with Prosig cable, impedance matched.

 

Figure 10. Square wave pulse train waveform with RAL 2009 cable, impedance matched.

 

Figure 11. Square wave pulse train waveform with RAL 2015 cable, impedance matched.

 

Figure 12. Square wave pulse waveform with Prosig cable.

 

Figure 13. Square wave pulse waveform with RAL 2009 cable.

 

Figure 14. Square wave pulse waveform with RAL 2015 cable.

 

The RAL 2015 was the best sounding of the BNC cables.

 

Figure 15. Unfiltered sine wave from 75 ohm BG7TBL output.

 

Figure 16. Sine wave from 75 ohm BG7TBL output with 75 ohm Mini-circuits filter.

 

Listening Evaluations

 

Figure 17. EtherREGEN with Mini-Circuits 75 ohm filter at its clock input. Both the EtherREGEN and the BG7TBL clock were powered with separate TeraDak DC-30 linear power supplies.

 

I cannot speak for anyone else's EtherREGEN, but mine, and my ears, much preferred the BG7TBL's square wave input. Switching to the BG7TBL's 75 ohm sine wave input caused a loss of bass detail, diminished tactile sensation, and diminished imaging properties. Inserting the filter caused a further reduction in sound quality, particularly in bass detail.

 

While my results with the Mini-Circuits filter were not positive, I would not discourage anyone from trying it, especially if you have a high quality sine wave clock. Results will vary based on your clock and cables.