John Swenson tutoring paper: "Considerations regarding usage of external reference clocks" (EtherREGEN and other): Sine vs. square, impedance, cables—and a money saving surprise at the end.

[soares]

On 3/28/2021 at 3:34 PM, Superdad said:

As well, and perhaps as important, the filter (again, only for sine wave clocks—don’t put one on a square wave!) will assure a very clean, free from harmonics and noise sine, regardless of what might have been transmitted by the clock or picked up the cable.

Hi Alex, 

From what I’ve been told this is a squarewave output 75 Ohms. It performs very well with my eR but went to an upper level with a 50Ohms filter. When you to use the filter with just the sinewave is because it isn’t effective with a squarewave output? Because if it so my findings contradict it. Unless the version I have it is after all a square wave. 😂

Also I am not sure why just the 10MZ output is working. Do you know what is the purpose of the other outputs? 
Finally accordingly to @DarqueKnight the eR performs better with a squarewave irrespectively of the filter ( he was also using a Chinese cheap clock). All this makes me wonder if I I took the right decision by ordering an AfterDark clock sinewave version (emperor giesemann 75 Ohms). Any views? 🤗
Thank you and have a nice Easter!

Jorge

[MartinT]

2 hours ago, soares said:

Also I am not sure why just the 10MZ output is working. Do you know what is the purpose of the other outputs? 

 

Jorge, it looks like you have the RS-232 programmable version. Those two other outputs have their frequency programmable via the serial port.

[soares]

Just now, MartinT said:

 

Jorge, it looks like you have the RS-232 programmable version. Those two other outputs have their frequency programmable via the serial port.

Yes I have. Thank you so much Martin!

Gosh... 😂

Cheers Jorge

[James Stephens]

1 minute ago, soares said:

Yes I have. Thank you so much Martin!

Gosh... 😂

Cheers Jorge

And which is in turn sine wave, 50 Ohm .... no?

[DarqueKnight]

3 hours ago, soares said:

Finally accordingly to @DarqueKnight the eR performs better with a squarewave irrespectively of the filter ( he was also using a Chinese cheap clock). All this makes me wonder if I I took the right decision by ordering an AfterDark clock sinewave version (emperor giesemann 75 Ohms). Any views? 🤗

 

1 hour ago, MartinT said:

 

Jorge, it looks like you have the RS-232 programmable version. Those two other outputs have their frequency programmable via the serial port.

@soares @MartinT @R1200CL

 

Due to the apparent variation in BG7TBL clock configurations, I am not sure that one owner's experience is indicative of what someone else might experience with this clock, unless they have the exact same clock. There are differences in OCXOs, board versions, and features. In addition to all that confusion, the clock cables, clock output waveform (sine vs. square), and use of far end filters can have significant impact on sound quality.

 

Finally, I expect that best results with the BG7TBL will be achieved in systems that already have some implementation of master clocking. In the case of my home stereo system, the DAC and digital player are locked to a dCS Puccini word clock. I have not (yet) taken the Puccini word clock out of the chain and re-evaluated the BG7TBL's performance in that scenario. However, I did evaluate the BG7TBL (with a linear power supply) in my more modest stereo system at work, which does not have a master clock.  I was very impressed with the improvement. I will provide details of that evaluation in @MartinT's master clock thread.

 

 

[soares]

10 hours ago, James Stephens said:

And which is in turn sine wave, 50 Ohm .... no?

75 Ohms

[James Stephens]

28 minutes ago, soares said:

75 Ohms

Hi there,

 

Ok. For the BG7TBL I purchased from the same selller it stated clearly in the listing that is was 75 Ohm square Wave clock but I don’t see that listed for yours which made me think it might be a sine wave clock.

 

The filter is for sine wave clocks only. A square wave is comprised of a fundamental frequency plus its odd-order harmonics; the filter will attenuate those harmonics and the effect wil be to damage the wave. If it was even a square to start with, it certainly won’t be afterwards.

 

Best,

James

[DarqueKnight]

2 hours ago, James Stephens said:

The filter is for sine wave clocks only. A square wave is comprised of a fundamental frequency plus its odd-order harmonics; the filter will attenuate those harmonics and the effect wil be to damage the wave. If it was even a square to start with, it certainly won’t be afterwards.

The filter did not just damage the square wave, it changed it back to a sine wave!

 

Figure 1. Scope setup with unfiltered BG7TBL square wave output.

 

Figure 2. Scope setup with filtered BG7TBL square wave output. The square wave became a sine wave.

 

Figure 3. BG7TBL's unfiltered square wave pulse train.

 

Figure 4. Frequency domain (Fast Fourier Transform) plot of the BG7TBL's square wave output. This square wave is composed of the fundamental frequency at 10 MHz and odd order harmonics at 30, 50, 70, 90, and 110 MHz and the attenuated even order harmonics at 20, 40, 60, 80, 100, and 120 MHz.

 

Figure 5. BG7TBL's filtered square wave output - converted back to a sine wave.

 

Figure 6. Frequency domain (Fast Fourier Transform) plot of the BG7TBL's filtered square wave output.

 

Figure 7. BG7TBL's unfiltered 75 ohm sine wave output.

 

Figure 8. Frequency domain (Fast Fourier Transform) plot of the BG7TBL's unfiltered 75 ohm sine wave output.

 

Figure 9. BG7TBL's filtered 75 ohm sine wave output.

 

Figure 10. Frequency domain (Fast Fourier Transform) plot of the BG7TBL's filtered 75 ohm sine wave output.

 

[JohnSwenson]

1 hour ago, DarqueKnight said:

The filter did not just damage the square wave, it changed it back to a sine wave!

 

Figure 1. Scope setup with unfiltered BG7TBL square wave output.

 

Figure 2. Scope setup with filtered BG7TBL square wave output. The square wave became a sine wave.

 

 

Figure 3. BG7TBL's unfiltered square wave pulse train.

 

 

Figure 4. Frequency domain (Fast Fourier Transform) plot of the BG7TBL's square wave output. This square wave is composed of the fundamental frequency at 10 MHz and odd order harmonics at 30, 50, 70, 90, and 110 MHz and the attenuated even order harmonics at 20, 40, 60, 80, 100, and 120 MHz.

 

 

Figure 5. BG7TBL's filtered square wave output - converted back to a sine wave.

 

 

Figure 6. Frequency domain (Fast Fourier Transform) plot of the BG7TBL's filtered square wave output.

 

 

Figure 7. BG7TBL's unfiltered 75 ohm sine wave output.

 

 

Figure 8. Frequency domain (Fast Fourier Transform) plot of the BG7TBL's unfiltered 75 ohm sine wave output.

 

 

Figure 9. BG7TBL's filtered 75 ohm sine wave output.

 

 

Figure 10. Frequency domain (Fast Fourier Transform) plot of the BG7TBL's filtered 75 ohm sine wave output.

 

That is exactly what it is supposed to do. The purpose of that filter is to get rid of everything above the fundamental. The reason I mentioned it was to use with a sine wave which is much more susceptible to AM noise, either from the clock itself or picked up in the cable. Most of that noise gets taken care of by the filter.

 

If you already have a good square wave the filter is not appropriate.

 

John S.

[soares]

Thank you for all your replies! I probably also have the BG7TBL sinewave. Meanwhile I also received the AfterDark EG clock. It is also a sinewave. In both cases the filter did an amazing job! 

[James Stephens]

 

7 hours ago, DarqueKnight said:

The filter did not just damage the square wave, it changed it back to a sine wave!

 

 

 

Absolutely. The filter specs show that insertion loss rises above 40dB around 22MHz. Every single odd-order harmonic falls above that so is attenuated at least 40dB (i.e at least 100x from a voltage perspective) whereas the fundamental remains untouched.

 

Thanks for working these up and sharing.

 

 

[PYP]

1 hour ago, soares said:

Thank you for all your replies! I probably also have the BG7TBL sinewave. Meanwhile I also received the AfterDark EG clock. It is also a sinewave. In both cases the filter did an amazing job! 

Jorge, what clock cable do you use?  

[soares]

On 4/4/2021 at 10:21 AM, PYP said:

Jorge, what clock cable do you use?  

Blue Jeans Cable Company 75 ohm Canare LV-77S.

[PYP]

On 4/4/2021 at 5:51 AM, soares said:

Thank you for all your replies! I probably also have the BG7TBL sinewave. Meanwhile I also received the AfterDark EG clock. It is also a sinewave. In both cases the filter did an amazing job! 

Works for the Cybershaft (sine wave) too, Jorge!  Very, very nice.   Additional, effortless and natural detail and tone.  

Didn't expect this from a $50ish little filter.  I'm using the 75 ohm version.   The eR is happy and so am I.  

 

Thank you, John, for the informative paper and for this recommendation.   Good stuff!

[soares]

4 minutes ago, PYP said:

Works for the Cybershaft (sine wave) too, Jorge!  Very, very nice.   Additional, effortless and natural detail and tone.  

Didn't expect this from a $50ish little filter.  I'm using the 75 ohm version.   The eR is happy and so am I.  

 

Thank you, John, for the informative paper and for this recommendation.   Good stuff!

Indeed Philip. It was a great surprise! Glad it worked.🤗

[jamesg11]

So ... what have people been doing with their BG7TBL 75ohm sq wave clocks ... ?

 

 

[LewinskiH01]

On 4/4/2021 at 2:05 AM, DarqueKnight said:

The filter did not just damage the square wave, it changed it back to a sine wave!

 

Figure 1. Scope setup with unfiltered BG7TBL square wave output.

 

Figure 2. Scope setup with filtered BG7TBL square wave output. The square wave became a sine wave.

 

Figure 3. BG7TBL's unfiltered square wave pulse train.

 

Figure 4. Frequency domain (Fast Fourier Transform) plot of the BG7TBL's square wave output. This square wave is composed of the fundamental frequency at 10 MHz and odd order harmonics at 30, 50, 70, 90, and 110 MHz and the attenuated even order harmonics at 20, 40, 60, 80, 100, and 120 MHz.

 

Figure 5. BG7TBL's filtered square wave output - converted back to a sine wave.

 

Figure 6. Frequency domain (Fast Fourier Transform) plot of the BG7TBL's filtered square wave output.

 

Figure 7. BG7TBL's unfiltered 75 ohm sine wave output.

 

Figure 8. Frequency domain (Fast Fourier Transform) plot of the BG7TBL's unfiltered 75 ohm sine wave output.

 

Figure 9. BG7TBL's filtered 75 ohm sine wave output.

 

Figure 10. Frequency domain (Fast Fourier Transform) plot of the BG7TBL's filtered 75 ohm sine wave output.

 

 

Hello DarqueKnight.

 

If I'm interpreting correctly, your measurements above show a BG7TBL with square output unfiltered (Fig.3) and same square output with the addition of the filter (Fig.5). Have you had a chance to compare how these alternatives impact sound through the eR?

 

I have a 75 ohm square wave BG7TBL, like jamesg11 above, and wonder if adding the filter should be expected to improve sound. BTW, what cable were you using when you ran the measurements?

 

Thank you!

[DarqueKnight]

 

5 hours ago, LewinskiH01 said:

 

Hello DarqueKnight.

 

If I'm interpreting correctly, your measurements above show a BG7TBL with square output unfiltered (Fig.3) and same square output with the addition of the filter (Fig.5). Have you had a chance to compare how these alternatives impact sound through the eR?

 

I have a 75 ohm square wave BG7TBL, like jamesg11 above, and wonder if adding the filter should be expected to improve sound. BTW, what cable were you using when you ran the measurements?

 

Thank you!

@LewinskiH01

 

The cable was the Prosig PSG00542, a $5 cable that came with my dCS Puccini word clock. I compared the following:

 

1. The sound of four 75 ohm BNC cables with square wave output.

2. The sound of 75 ohm sine wave output with and without the filter.

 

The sine wave outputs, with or without the filter did not sound as good as the square wave output. Others have had the opposite experience.

 

I did not listen to the square wave output with the filter...I just wanted to see what the waveform looked like. The filter should not be used with square wave outputs, only sine wave.

[LewinskiH01]

1 hour ago, DarqueKnight said:

 

@LewinskiH01

 

The cable was the Prosig PSG00542, a $5 cable that came with my dCS Puccini word clock. I compared the following:

 

1. The sound of four 75 ohm BNC cables with square wave output.

2. The sound of 75 ohm sine wave output with and without the filter.

 

The sine wave outputs, with or without the filter did not sound as good as the square wave output. Others have had the opposite experience.

 

I did not listen to the square wave output with the filter...I just wanted to see what the waveform looked like. The filter should not be used with square wave outputs, only sine wave.

 

Thank you!

 

That Prosig cable is the same one that displayed best behavior from the three cables you posted on April 2. I wonder what the magic sauce is in it?

 

[DarqueKnight]

The Prosig cable produced the best classic square wave shape on the scope, but it was not the best sounding.

[LowMidHigh]

32 minutes ago, LewinskiH01 said:

 

Thank you!

 

That Prosig cable is the same one that displayed best behavior from the three cables you posted on April 2. I wonder what the magic sauce is in it?

 

 

Built to spec. 

 

A lot of the exotic cables don't meet the spec, and aren't property tested. 

 

[LowMidHigh]

28 minutes ago, DarqueKnight said:

The Prosig cable produced the best classic square wave shape on the scope, but it was not the best sounding.

 

Maybe you like little distortion in your music. Tubes add distortion, and many audiophiles swear by them. 

[DarqueKnight]

Just now, LowMidHigh said:

 

Maybe you like little distortion in your music. Tubes add distortion, and many audiophiles swear by them. 

No. I prefer neutral sounding gear. I do not own any tube gear.  The Prosig cable had the least clarity and detail.

[LewinskiH01]

3 minutes ago, DarqueKnight said:

No. I prefer neutral sounding gear. I do not own any tube gear.  The Prosig cable had the least clarity and detail.

Interesting. Which cable sounded best?

[DarqueKnight]

 

 

Just now, LewinskiH01 said:

Interesting. Which cable sounded best?

In my system, a Revelation Audio Labs Prophecy-Cryo (2015 version) sounded best.