Reasonably pricing Rb & OCXO and OCXO-only 10 Mhz Master clocks...

[jdandy]

Mark.......That is a very interesting and enlightening post. Thanks for the links to the different connectors.

[ariess]

I just checked with an engineer at Stanford Research Systems who makes the clock for Esoteric (FS725) which has the 50 ohm output. He says 75 ohm or 50 ohm will make no difference. Whether this means no audible difference or no theoretical difference (as he indicated) I can't say.

[SCAudiophile]

I think it is no theoretical difference....

[SCAudiophile]

Originally Posted by CGabriel

The characteristic impedance of a cable has no relevance to signal transmission unless the cable is operating as a "transmission line". What determines the mode of transmission is based on two factors: transmission frequency and the length of the cable. For a cable to operate as a transmission line the length of the cable must be close to the wavelength of the transmission frequency.

So, to be clear, if a cable is not operating as a "transmission line" then the characteristic impedance (50 or 75 or any other) is irrelevant. If it does not operate as a transmission line then the normal characteristics of DC resistance, capacitance and inductance become the primary factors in signal integrity.

10 Mhz is a significant transmission frequency and it is very likely that the cable could be operating as a transmission line. Here is some sample math:

Frequency = 10 Mhz
Velocity over copper wire = ~70% C

It is well known that a cable that is 1/4 wavelength of the wavelength does operate as a transmission line. A cable that is 1/10 the wavelength MAY be influenced but this is at the outer limit of transmission line operation.

So given the above: A cable will definitely operate as a transmission line if the cable is 5.25 meters or longer. And it MAY be influenced with a length as short as 2.1 meters.

Summary: If cable the length is very short as in .5 to 1 meter you should have no problem using a 75 ohm cable. If the cable is longer than 2 meters I would be looking for a legit 50 ohm cable.

Hope this helps.

Guys...this is an excellent post and it states some very specific facts that helped me understand this issue alot more.

[SCAudiophile]

I'm going to wake this thread up (and the parallel thread where the same discussion is duplicated) as over the past 2 months I've been doing alot of testing that overlaps with subject of 50-ohm versus 75-ohm clock cables, their significance and their interchangeability. There is also another audiophile or 2 that I know doing similar testing for his own purposes with different equipment in terms of master clocks, music server versus player/transport/DAC, etc....

I've had the good fortune to have a 2nd OCXO-based 10Mhz Master clock here on loan that is a prototype with even better phase noise characteristics and even an improved (Schottky barrier diode based) power supply. More about why this clock has been here the last couple of months when the info can become public knowledge but for now, I can only share that the OP14 and better levels of precision and lower noise characteristics it brings are but a stepping stone to something even better and off the charts...

Well here goes...

Cybershaft 10 Mhz Clock#1 (very low phase noise) OCXO clock, 50-ohm output calibrated using Symmetricom (TSC5115A) and BVA (8607) reference units;
Phase Noise:
-111.3 dBc/Hz @ 1Hz offset *
-133.1 dBc/Hz @ 10Hz offset ***
-142.2 dBc/Hz @ 100Hz offset ***

Cybershaft 10 Mhz Clock #2 (very low phase noise) OCXO clock, 50-ohm output,
Schottky barrier diode-enabled power supply, calibrated using Symmetricom (TSC5115A) and BVA (8607) reference units;
Phase Noise:
-114.7 dBc/Hz @ 1Hz offset ***
-133.5 dBc/Hz @ 10Hz offset ***
-142.2 dBc/Hz @ 100Hz offset ***

*Dual listening test runs over a 1 month period with both Cybershaft clocks producing 10 Mhz and the OCXO clock in the Esoteric D-02
producing 22.xxx Mhz 75-ohm clock signals respectively.

*The phase noise specs. given above beat another manufacturer's Rb-oscillator based top 2 units based upon specs I was sent recently from that manufacturer of < -100 dBc/Hz @ 1Hz offset, < -130.0 dBc/Hz @ 10Hz offset and < -140.0 dBc/Hz @ 100Hz offset. This called out only to
underline the fact that the 2 Cybershaft clocks used for this test (for 10 Mhz signal production) are at least reference grade.

<Cybershaft 10Mhz 50-ohm output drives clocking accuracy baseline for D-02 DAC>

Esoteric D-02 DAC with 10 Mhz 50-ohm input from Cybershaft

<75-ohm output from D-02 DAC to P-02 Transport>

Esoteric P-02 Transport taking in 22.xxx Mhz "MCLK" frequency mode over 75-ohm connect slaved to master clock in D-02

Reference cables;

Wireworld Platinum Starlight 75-ohm BNC:BNC, Kubala-Sosna EMOTION 75-ohm BNC:BNC (1.5m)
Esoteric/MEXCEL 8N-A2000 50-ohm BNC:BNC (1.5m)
2 other 50-ohm high quality cable from 2 well-known manufacturers (1.5m, 2.0m)
2 other 75-ohm high quality cable from 2 well-known manufacturer (1.5m, 2.0m)
1 50-ohm high quality cable with a 75-ohm connector from a well-known manufacturer

Results (at a very high-level);

Please note this is NOT about which cable is better for 50-ohm or 75-ohm…

The only purpose of the tests written about here is to determine whether the thesis that use of 50-ohm or 75-ohm BNC clocking cables matters on a matching characteristic impedance circuit (or not) when the lengths are short for 10 Mhz, 22.xx Mhz (master clock frequencies) and frequency-multiple re-clocking frequencies (44.1, 88.2, 176.4, etc…)…

All of the above cables and clocks used in all possible combinations, testing occurred using a variety of audiophile reference material from genres ranging from pipe organ and taiko drumming to large ensemble and small ensemble classical, jazz, big band, vocal (male and female), hard rock and progressive rock…

Results (mine, your mileage may vary):

- use of 75-ohm and 50-ohm spec-compliant cables (i.e. cable and connector both of that characteristic impedance) judged equivalent on
75-ohm MCLCK circuit between the P-02 and D-02 in categories such as tonality, sound-stage depth, width and height, leading and trailing edges of notes, overall transients, voices and ensemble play, side to side and front to back image coherency, and musical impact of both low volume and high volume delicate as well as highly dynamic passages HOWEVER….

- 50-ohm spec-compliant cables judged superior and worked perfectly on a 75-ohm MCLCK circuit; small but noticeable advantage in pacing of complex passages (large-scale orchestral and driving big band full ensemble play showed this off best), and ‘image specificity’, i.e. the exact right size and location of a given voice, instrument, etc on the stage in all 3 dimensions as well as air around instruments and voices, etc…..….(very (nice) surprises here)

- 50-ohm cables judged superior in all categories on a pure 50-ohm circuit (10 Mhz); best result in every category including all those listed above;
best air around instruments, image and soundstage specificity, 3-dimensionality, tonality and musical realism and correctness…all around winner is to use a proper 50-ohm SOTA cable on a 10 Mhz connection (see below….)

- 75-ohm cables judged inferior and prone to pacing problems and some lack of image specificity, decrease in soundstage depth in particular and breadth secondarily on a 50-ohm 10 Mhz signal circuit. Also heard undeniable evidence of lessening of air around instruments and decrease in transients around sax, drum and cymbals,….several other areas where I did not like the result (musically) compared to better results above….

- surprise was the 50-ohm cable with 75-ohm connectors on a 75-ohm MCLK circuits. All tests worked out and showed the best of the results above in all categories EXCEPT one key area, bass & sub-bass impact and extension. For some unknown reason there was a shortfall, i.e. early roll-off of bass and lessening in intensity on several test tracks with pronounced single drum strikes of varying amplitude and frequency…No telling why and this will no doubt require alot more testing to try to nail down but it was undeniably present…

- 50-ohm cable with 75-ohm connector not testing on pure 50-ohm circuit for obvious reasons…

In short, even at shorter lengths, cable rating (50 versus 75-ohm) can make a difference but only in certain (positive or negative) ways depending upon configuration…

I’m sure this will generate some healthy dialogue and debate which is definitely appreciated!

[SCAudiophile]

Another user made me aware of another new 10 mHz master clock from Portugal that looks interesting; V-Acoustics MCLK-01. No real details on performance beyond the typical PPM/PPB marketing hype as yet; these details have been requested by a couple of users. Nice casework and reported to be solidly engineered...

http://www.theaudiobeat.com/audiosho..._acoustics.htm


***In a separate piece of news, I'm expecting a new 10 MHz 50-ohm output clock Cybershaft prototype to test that will be well above OP14 level in mid-late April. I will report back improvements if any and listening results (of my system) with this even lower phase-noise implementation as soon as I break it in.....

[Robert_Anderson]

Originally Posted by SCAudiophile

Another user made me aware of another new 10 mHz master clock from Portugal that looks interesting; V-Acoustics MCLK-01. No real details on performance beyond the typical PPM/PPB marketing hype as yet; these details have been requested by a couple of users. Nice casework and reported to be solidly engineered...

http://www.theaudiobeat.com/audiosho..._acoustics.htm


***In a separate piece of news, I'm expecting a new 10 MHz 50-ohm output clock Cybershaft prototype to test that will be WELL above OP14 level in mid-late April; this could potentially be well beyond OP17 and possibly OP20 level(!!!). I will report back improvements if any and listening results (of my system) with this even lower phase-noise implementation as soon as I break it in.....

Thanks for all the interesting information. I have the P-03/D-03 combination with the G-0Rb. The clock made a substantial difference. I even splurged and bought the godawful expensive Acrolink cables. I don't think I can hear much difference between them and a cheap pair of BNC cables, though. The clock brings out so much life in the system that I would not want the equipment without it regardless of the price. I would like to compare cheaper clocks. I work on a radar that uses a Symmetricom GPS with a 10MHz oscillator output used as the master frequency reference in our frequency synthesis and local oscillators for different stages of our receivers. The Symmetricom uses a really cheap and cheesy card with the oscillator on it compared to our old Truetime units that had a nice rubidium oscillator installed. I ordered a standalone expensive oscillator, and put that into the system. It makes a substantial difference. I think it would be fun to play around with some of these in my system on the ship. Thanks for sharing.

[SCAudiophile]

Originally Posted by Robert_Anderson

Thanks for all the interesting information. I have the P-03/D-03 combination with the G-0Rb. The clock made a substantial difference. I even splurged and bought the godawful expensive Acrolink cables. I don't think I can hear much difference between them and a cheap pair of BNC cables, though. The clock brings out so much life in the system that I would not want the equipment without it regardless of the price. I would like to compare cheaper clocks. I work on a radar that uses a Symmetricom GPS with a 10MHz oscillator output used as the master frequency reference in our frequency synthesis and local oscillators for different stages of our receivers. The Symmetricom uses a really cheap and cheesy card with the oscillator on it compared to our old Truetime units that had a nice rubidium oscillator installed. I ordered a standalone expensive oscillator, and put that into the system. It makes a substantial difference. I think it would be fun to play around with some of these in my system on the ship. Thanks for sharing.

Hello! Are you still running with the G-0Rb? I would imagine the answer is a definite 'yes!'.....out of curiosity, what clock rate have you found is best? When I had the P-03U & D-03 combo with G-0s, I found I like the result from 176.4 kHz best for both RBCD and SACD playback though Esoteric swears by simply using 44.1 in that generation of equipment....thoughts?

[SCAudiophile]

A fascinating read on what type of setup and care it takes to produce quality master clocking products and also what it takes to maintain the calibration and testing to do so;

http://www.cybershaft.jp/clockcal.html

Also,...I've concluded many months of testing with 2 additional OCXO clocks from Cybershaft whose OCXO circuit was even more refined than the OP13+ type 2 unit in my RBOCXO-01 and also with a loaned high-quality Rubidium unit (used to have the Esoteric G-0s but it is no longer in my system so I had to borrow its successor from a friend).

At each step of the way, the idea that lower phase noise (and thus lower harmonic distortion and better Allan Variance (measure of short-term stability) were fundamental to the best musical playback, imaging, sound-staging and realistic playback has been proven as a fact.

In side by side comparisons of OCXO and Rb-based clocking and keeping priceerformance ratio in mind, I found that I preferred, by a large margin, a high-quality OCXO clock circuit's impact on the musical playback experience every time. The exception to this is a Rb circuit with similarly low phase noise; there seem to be only 1 or 2 that have achieved that ( Esoteric Grandioso G1 and 1 other... )

[Robert_Anderson]

Originally Posted by SCAudiophile

Hello! Are you still running with the G-0Rb? I would imagine the answer is a definite 'yes!'.....out of curiosity, what clock rate have you found is best? When I had the P-03U & D-03 combo with G-0s, I found I like the result from 176.4 kHz best for both RBCD and SACD playback though Esoteric swears by simply using 44.1 in that generation of equipment....thoughts?

I still am, but I am back at work now overseas, so I will have to experiment more when I am home again. 176.4 kHz sounds best to me, and I run my XRCD's through a separate Reimyo DAP 999. I look forward to continuing this the next time I am home.