10 Mhz reference for audio LHY OCK-1, used in lab instead ? - Page 1
Forum section: electronics / general

author: ytterligare
author_rank: Regular Contributor
timestamp: March 17, 2023, 12:28:29 am
content: Hello there, what do you think about this kind of OCXO reference that supposedly should be used for High End Audio System purpose ? Would it fit well in a lab with Signal Generators / Counters / Spectrum analyzers with 10 Mhz ref in ?Construction seems superb, at least for the power section : all filtered, ultra high quality caps and so on, but, although it is an Oven Controlled Crystal Oscillator, I cannot find a lot of info about the precision and stability.Here's the link :https://www.beatechnik.com/lhy-audio-ock-1Oh...and there's also a superior model that cost twice the OCK-1 :https://www.beatechnik.com/lhy-audio-ock-2All Master Clock devices can be purchased with 50 or 75 Ohm optionCiaoAndrea

author: J-R
author_rank: Super Contributor
timestamp: March 17, 2023, 07:19:36 am
content: I say just the typical audiophile quackery. Just get a GPSDO instead.

author: ytterligare
author_rank: Regular Contributor
timestamp: March 17, 2023, 08:45:05 am
content: Quote from: J-R on March 17, 2023, 07:19:36 amI know, I know the way it's been used there may be not as useful as they claim it is, but I have two GPSDO, one Chinese and one European, both alternatively attached to an high quality antenna and since I live in a historical quarter of the city, first floor, the GPS signal struggle to get me a stable lock : usually I get 4 -5 sats, rarely I get 7 or 9...I know Rubidium or even Cesium references could help, but they're on another price league...

author: jpb
author_rank: Super Contributor
timestamp: March 17, 2023, 06:44:56 pm
content: I looked into this a bit when some were going on ebay.The impression I got that some had good specifications but were very expensive. You are paying a lot of money for some pre-filtering (I mean pre-selecting by this) of ocxos and a decent linear power supply. They probably start with an OCXO which is good, perhaps costing several hundred pounds and then the unit is sold for several thousand pounds.For example the Mutec top-of-line one :https://www.mutec-net.com/product_ref10_se120.php#dataHas very good phase noise and an Alen Deviation of less than 10^-12 so I guess the OCXO at its heart probably costs around £1000 if the specs are to be believed but I think the new price of the unit is close to £5000.Also they tend to operate at 75 ohms rather than 50 ohms.I think if one is going on ebay cheap then it might be worth getting but I think it is unlikely as someone who has paid £5k for something would expect to sell it for £3k which is still over-priced.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: March 17, 2023, 07:49:46 pm
content: Too much money me thinks. What about an HP?http://etoysbox.jp/Memo/3_Test_Equipments/HP_10811_OCXO/HP_10811_OCXO_Spec.html

author: jonpaul
author_rank: Super Contributor
timestamp: March 17, 2023, 08:29:03 pm
content: Audiophiles should read,the classic jitter papers,from1970s..1980s, eg AES AES.ORG by Dr Steve Harris and from Audio Précision AP.COM by Dr Julian Dunn.So, even at 24..32 bits an ordinary can XO for $10 will give,same sound as these products if a double blind ABX test is made. You can measure the clock, jitter with a time Analyzer like Yokogawa TA720.We have seen 20 PS, near the Analyzer spec.The xtal Q is so high, 20,000..100,000 that the sideband noise is nil.We have used the excellent Leo Bodnar GPS DSO £120 for years as,a master clock.Number of,satellites is irrelevant for audio clock use as long as the GPS locks.Main source for jitter in digital audio is,not the master clock, but CM noise entry or locally,contamination of the DAC, ADC, clock.Careful isolation with low capacité transformers, good PCB ground plane practice and use Shielded cables, can improve the noise and reduce jitter.Bonsoirjon

author: J-R
author_rank: Super Contributor
timestamp: March 17, 2023, 09:06:17 pm
content: From what I've seen for myself and from other reviewers, the Leo unit has been shown to be pretty good, among the OCXO-based GPSDO products. I don't see how those other OCXO-only products by themselves can ever be as good unless you can regularly verify them against a more precise reference standard. Which seems pointless if you have that already available.Yes, as with other test equipment, sometimes you luck out and get far better performance than expected, but without that better reference standard you would never know!I think this is one of the pillars of the audiophile industry, make something that most people can't easily check for themselves, so they can get away with selling whatever quackery they want.

author: jonpaul
author_rank: Super Contributor
timestamp: March 17, 2023, 10:23:30 pm
content: Any digital audio DAC or SRC is dependent on the input signal for the clocking.Only an ADC required a clock of exact frequency.For example an AES/EBU or SPDIF décoder has clock extraction from the Manchester code, and a PLL which recreates the original clock frequency.So most use for audiophiles does not need a GPS locked accurate clock, just a low jitter clock locked to the sourceJon

author: ytterligare
author_rank: Regular Contributor
timestamp: March 18, 2023, 07:35:16 pm
content: Quote from: J-R on March 17, 2023, 09:06:17 pmJ-R, not that for the level of my knowledge on the subject this could make a difference, but aren't Leo Bodnar unit TXCO and not OXCO ? Isn't it a "step-down" in terms of quality ?A.

author: jonpaul
author_rank: Super Contributor
timestamp: March 18, 2023, 08:05:45 pm
content: Leo Bodnar GPS DSO is an ordinary XO clocked, GPS disciplined synthesizer.The système has a VCO, PLL and feedback loops.Phase noise and jitter are well controlled and defined.User Selected output frequency is adjusted according to the GPS so that the frequency, 450 Hz....800 MHz is exact to GPS accuracy.All specs....http://www.leobodnar.com/shop/index.php?main_page=product_info&cPath=107This model is £165, another is £110Bon SoiréeJon

author: ytterligare
author_rank: Regular Contributor
timestamp: March 18, 2023, 10:58:51 pm
content: Quote from: jonpaul on March 18, 2023, 08:05:45 pmMerci, Jon, though I already own a couple of GPSDO ( a chinese one and an european DXPatrol) I'm trying to get as much info as I can about the dual output unit, also because one of the output can be programmed to feed my Icom 7300 equipped with LB reference interface.A question : given that the output is a square wave instead of a sine one, how does one cope with the various 10Mhz Ref in which I often see accepting sine wave instead ?Generally speaking, are sine and square waves interchangeable when used to feed a REF 10 Mhz in of a device ( e.g. SA, Frequency counter, function generator and so on...) ?

author: J-R
author_rank: Super Contributor
timestamp: March 18, 2023, 11:55:34 pm
content: Yes, my mistake the Leo unit is a TCXO-based GPSDO unit, not an OCXO! Sorry!I still see it as a step up from just an OCXO because of the main reason I stated, which is not having a reference to check it against.Last year I picked up an HP5334B with the OCXO option and it shows my point that long-term stability can be a major concern with OCXO. It was quite a bit out when I received it, but calibrating it to the Leo unit means it has been quite good after that and only needs minor tweaks every few months or so if I am really bored...

author: jonpaul
author_rank: Super Contributor
timestamp: March 19, 2023, 12:55:43 am
content: Rebonjour à tous !I,have been involved in professional digital audio for high end and cinéma since 1980s, and have gone into jitter and master,clocks.Not yet a,"time nut" but at least accumulated a fine laboratoire with HP 5370B, 5372A, Yokogawa TA720, EIP 545, and,5 pcs,the classic HP OXOa moment please for a few notes..1. histoire.....Morrisons at NBS, BTL pioneered the low TC cut xtal forward Télécom and broadcast frequency controls and time.clocks,in1930s, like the G cut. The BSTJ papers are,worth reading2. scientific American magazine Amateur Scientist column had a,homemade vlace,Morrison clock in 1960s.3. to Signorie Yitterlagari (?), Salut Paisano !Most HP and other instruments RÉF,CLK 5..10,MHz input are very forgiveining in waveshape and level.We found the input buffers and comparateurs/ Schmidt triggers can lock on any sine/ square/ waves from50 mv...5V.We created,a totally passiv master house réf clock years agoLeo Bodnar GPS DSO set to +32 output V (max level), 10.0000 MHz.Output to Mini-Circuits splitters, 2,4 or 6 X.Splitters then gaged to distribute 4..6 outputs,50,Ohms on RG58/U BNC to each instrument ( counters, time Analyzers, synthesizer, HP4195A, HP RF générateur 8640B, and a utility bench BNC.Despite the attenuation of many splitters, the system locks ,fine!To JR, calibration of the HP OXO module is a fine exercise, they need,some days of power to settle out, and they are supplied in various grades of TC and drift.With the correct PCB edge,connector and a few,power supplies, we built a frequency test jig, to compare 5 of,the HP 10544A and a,Wenzel, and others.After the Leo Bodnar GPS DSO, we never returned to the TCXO OXO.4.for deeper information See the "time nuts" lists for the real pros.Our old friend Magnus Danielson is an IEEE fellows, and major time/ frequency expert.Leo Bodnar is happy to respond to technical support on his,excellent website. His 40 ps pulse generator is another classic,and highly recommended.5. See previous référence papers on effect of clocked jitter on noise and digital audio.Have an absolutely fantastic weekend!AmicalementJon

author: Sighound36
author_rank: Frequent Contributor
timestamp: April 07, 2023, 11:51:20 am
content: Have only just seen this post so apologies for the late reply.The LHC OCK-1 is quite possibly one of the worse so called master clock's I have not just seen, measured and listened to, it has a fundemental flaw which I' sure will be obvious to you chaps.First image is a 10Mhz Function generator output, nxt is the LHC OCK-1 then a basic Mutec Ref 10The Leo Bodnar absolutely makes a mockery of this clock for both lab standard reference & audio

author: Sighound36
author_rank: Frequent Contributor
timestamp: April 07, 2023, 05:45:14 pm
content: Hello jpbSecond attempt at a reply here!!!We have many clocks here over 50 from basic clock pulse generation to a caesium standard, plus many Rb models. The Leo Bodnar we have used for many years both in audio (pro studio & domestic) plus the Mutec items as well.We use the SE-120 models in the lab for reference synchronization of the main R&D scopes Lecroy Wavepro HD’s, RT spectrum analysers from both R&S & signal analysers from Keysight, they also used with 7 & 8 digit DMM’s etcThe LB has 50 Ohms output only the Mutec ref 10’s has both 50 Ohm lab and test equipment based impedance and some are 75 Ohm for broadcast & audio standard fitment.While the Bodnar doesn’t have a super desirable PN plot from memory its about -70dbc @ 1Hz, however from our experience the amount of spurri /noise deviation on the plot curve itself has a greater effect on the result imho.Jonpaul's astute observations regarding audio clocks are on the money, having the main oscillators/synthetic etc close to the point of data conversion. Carefully layout and veered ground return paths, board stack up, quiet supply rails minimal impendences, corrected matched connects etc are all very valid observations for quality audio playback. I would further suggest that the supply voltage rail noise is as at least as important as the quality of the oscillator.Jonpaul’s posts on diy audio are legendary 😊I thought you would interested in how a SE-120 looks like in the lab, but also some measurements for the unit as well.Test instrument is a Lecroy Wavepro 404HD with the Mutec SE-120 providing the 10Mhz ref.A full wave form analysis, stand-alone jitter kit perspective (Plots are using cycle to cycle attribute), individual eye & digital X/talk plus full serial data break down.

author: metebalci
author_rank: Frequent Contributor
timestamp: April 07, 2023, 06:01:25 pm
content: Quote from: jonpaul on March 17, 2023, 10:23:30 pmIsnt many DAC playback devices buffer and reclock the buffered data to DAC ? So actually the input jitter is irrelevant for playback but actually the internal clock to DAC matters ?

author: metebalci
author_rank: Frequent Contributor
timestamp: April 07, 2023, 06:10:19 pm
content: Quote from: ytterligare on March 17, 2023, 08:45:05 amMy limited knowledge and a little bit of search in the past ended like this. A good DAC has internally a low PN XO, TCXO, or OCXO. An improvement over this (on paper) can come from things like SRS PRS-10 or Mutec REF10 which have very low PN but still not sure if this will be an improvement over internal clocks because the internal ones are purpose built not generic 10Mhz and it is on the same PCB. So my conclusion, better spend money on a good DAC then an external clock.For lab purpose, I managed to get a used FS 725 at a good price, it is more than enough for many. I use a ublox F9T PPS output to monitor/calibrate it but not so often. You can do same with a PRS-10.

author: jonpaul
author_rank: Super Contributor
timestamp: April 08, 2023, 08:21:23 am
content: Bonjour cher ytterligare (OP)I was a studio/pro/high end/Cinema audio equipment designer in 1970s..1990s. Work and Connections at Dolby Labs, THX/Lucasfilm, Sequerra, Marantz, Goldmund, etc.I have worked on very low C very high CMRR transformers and TX/RX optimizations, as in my SMPTE/AES/NAB papers.I refer you to the pioneering works on jitter and clocking of digital audio signals and DAC/ADC....1/ 1980s Dr Steve Harris (Crystal/Cirrus Logic ) AES papers eg effects of jitter on noise2/1980s.,..1990s Dr Julian DUNN AES and AP papers ,3/ Audio Precision app notes 1980s..1990sMany others ....Since these papers, there is no fundamental changes in the math or engineering of jitter effects on ddital audio.Jitter reduction has improved with use of fast DSP, double clocking and SRC.With a bit of research you can learn a lot and see the true issues.Bon Recherche!Jon

author: jpb
author_rank: Super Contributor
timestamp: April 08, 2023, 02:57:23 pm
content: Thank you SignalHound36 for the posts. It is interesting to see results of real measurements. I'm a hobbyist so don't have the budget to buy expensive references (at least not new), but I'm also an electronic engineer by training so am interested in them anyway.The audio industry is so full of hype it is difficult to assess claims or even to find proper data, mutec seem better than most on this as they do show phase plots.Another company that sells (expensive) references for audio is Cybershaft - they claim some very low adev values as well as very low phase noise. Have you measured any of their devices?Occasionally such devices appear on ebay but it is hard to find concrete specifications and any reviews are of the audio variety which don't seem very scientific (the human ear doesn't seem to be an optimal measurement instrument even if it is the most relevant is you are a hifi buff - I'm not).

author: Sighound36
author_rank: Frequent Contributor
timestamp: April 08, 2023, 03:46:05 pm
content: Hello JpbThank you for your comments, audio I dabble in now and again, we are more ultra quiet power supplies, IoT wearable tech, EV's and aerospace control motor devices, but it is very insightful to 'view' the actual end results of the say the clock entering the DUT at board level, we have some great board level ability packages we can use to obtain closer to the real world results. Coupled with the digital audio decoding we can view all serial data lines, clocks very accurately plus analogue channel output also in the frequency domain so can quickly ascertain any correlations between circuit board issues (Which is where the TDR, de embedding both cables and strip lines plus virtual probing comes in very handy) to enable to further refine down to the real issues that can affect audio.Cyber shafts, we have two of them and the observation I would make would be this, tacky off self-casework and hardware but performance is good, in audio terms if your system is typically audiophile all air, space and polished presentation, then the cybershaft maybe a more satisfying fit, the SE-120 is far more suited to even handed system. In the lab, I would take the Mutec. Or if I was starting out the Leo Bodnar is also a quality item.

author: Leo Bodnar
author_rank: Frequent Contributor
timestamp: July 25, 2023, 07:12:07 pm
content: I have recently bought both OCK-1 and OCK-2 to use as uncorrelated reference sources for phase noise measurements at home. I have a few Wenzels that I wanted to retire in favour of something in good enclosure and mains power. The price in the UK was £300 for OCK-1 and £500 for OCK-2.This did not work out how I hoped.OCK-2 sales information says it should have -115dBc/Hz:QuoteI have measured only -90dBc/Hz which is, well, 300 times worse than promised.OCK-1 phase noise is just as unexciting. It has a bump around 30kHz which reminds me of ENE3311B. I think it's exactly what is used inside OCK-1.

author: jonpaul
author_rank: Super Contributor
timestamp: July 26, 2023, 06:06:51 pm
content: Leo! Very fine to see you join this interesting dscussio.Both the Leos I have, the 40 pS gen and your GPDSO are still chugging reliabily after many years.BRAVO for your excellent work and designs!Jon

author: fourfathom
author_rank: Super Contributor
timestamp: July 26, 2023, 07:20:27 pm
content: Quote from: ytterligare on March 18, 2023, 10:58:51 pmA note on the dual-output Bodnar: Apparently there are some frequency pairs that just can't be achieved with perfect accuracy. You can set one, or the other, to be exactly on frequency, but in some cases not both. The error is for most cases small enough to be inconsequential, but people I am involved with are running multiple SDR receivers for ionospheric propagation measurement (where frequency accuracy in the sub-milliHz range is desired) and they have resorted to using multiple single-channel Bodnars. I wish I could give you more details about the two-frequency issue, for example I don't know if this is a limitation of the software or the underlying hardware. If the dual-output Bodnar has just a single PLL then I would suspect the hardware. I've not personally tried to use the dual-output Bodnars, but I do have three of the small single-output ones and am quite happy with them.

author: rhb
author_rank: Super Contributor
timestamp: July 27, 2023, 12:30:49 am
content: Take a look at these threads:https://www.eevblog.com/forum/metrology/low-cost-lt1-ppb-10-mhz-oxcos-on-ebay/msg4815059/#msg4815059https://groups.io/g/HP-Agilent-Keysight-equipment/topic/cheap_and_simple_oxcos/98188455The phase noise is a little high compared to some of the best available, but because of crystal aging, these should drift less than 0.4 ppb/yr.The bare OXCOs are $3 if you want to design your own board to take the best advantage of the OXCOs. The major limitation on stability is supply and voltage reference noise.Of the 4 of this board layout (note location of trimmer) that I tested, 2 set to within 0.1 ppb. The other 2 had drifted outside the range of the voltage divider. Those simply need the resistors changed to make the trimmer span the correct voltage range.The 0.1 ppb units were boxed up as a BNC and a SMA version. I'll eventually change the resistors on the other 2.Have Fun!Reg

author: Leo Bodnar
author_rank: Frequent Contributor
timestamp: August 14, 2023, 07:10:39 pm
content: If anyone cares, I have re-tested OCK-1 on R&S FSPN and got the same results than earlier — which should not be surprising.I did not have time to let FSPN to fully warm up but at that PN level this should not be necessary.Leo