Is there any logical reason to use a tube as the oscillator in a DAC? - Page 1
Forum section: electronics / projects

author: Deactivated-1
author_rank: Frequent Contributor
timestamp: October 26, 2023, 05:03:02 pm
content: I came across a PrimaLuna DAC that uses a tube for the oscillator.Why? is there any logical reason for this? Is jitter of any concern at all with modern oscillators? Is there any feedtrough from the oscillator to the audio?

author: DimitriP
author_rank: Super Contributor
timestamp: October 26, 2023, 05:21:40 pm
content: Primaluna + DAC + Tube = a lot of dollars.How would YOU do it?Once upon a time in a place far away I was one told that signal from FM transmitters using tubes "sounds better" and "goes further".Using a tube solves most problems, if not from an engineering perspective, it gives the sales/marketing people something to talk about.Wouldn't you feel "wierd" if you paid almost $4K for a DAC and all it used was solid state components like everyone else's for a lot less ?I could have save me a lot of typing and said:Primaluna; I rest my case.But where would be the fun in that ?

author: ataradov
author_rank: Super Contributor
timestamp: October 26, 2023, 05:22:34 pm
content: It is an audio-fool device, of course it will have tubes in random places. How else do you justify $4K price tag?The construction looks like shit with random capacitors zip tied to the frame. But I guess this impresses certain audience.Audio review sites that come up in a search are hilarious. They all copy the same description text verbatim from the vendor site.

author: coppice
author_rank: Super Contributor
timestamp: October 26, 2023, 05:25:27 pm
content: Don't you know audio equipment only sounds good if it produces a nice cheery glow. If the natural glow of a filament is insufficient you can always supplement it with a bunch of orange LEDs.

author: TimFox
author_rank: Super Contributor
timestamp: October 26, 2023, 05:34:04 pm
content: Clock jitter in DAC systems for audio is more important than one might think, but low-jitter crystal oscillators can be made from either vacuum tubes or solid-state components.https://www.analog.com/en/technical-articles/analyzing-audio-dac-jitter-sensitivity.htmlThe military ended up with a huge stock of "subminiature" tubes, as shown in your photo, which can be used in audio applications.They can have advantages over larger tubes for microphonics, but transistors rarely exhibit microphonic problems.

author: ataradov
author_rank: Super Contributor
timestamp: October 26, 2023, 05:37:02 pm
content: It is not clear what that tube even does here. It sits next to 10 cent crystal and some Nuvoton MCU.There is a good chance that only the filament is connected to the power. It looks like there are traces from al the pins of the bulb, at least this is good.Quote fromhttps://www.hifinews.com/content/primaluna-evo-100-tube-dac-usb-tube-dac-tube-clock:Quote

author: coppice
author_rank: Super Contributor
timestamp: October 26, 2023, 05:40:43 pm
content: Quote from: TimFox on October 26, 2023, 05:34:04 pmAt 48ksps 1ps of jitter is of a similar order to dropping from 24 to 23 bits. So, low jitter is important, but 1ps is not hard to achieve these days. Just don't try using something the output of a PLL that's massively multiplying up from a low frequency clock source.

author: coppice
author_rank: Super Contributor
timestamp: October 26, 2023, 05:42:53 pm
content: Quote from: ataradov on October 26, 2023, 05:37:02 pmOf course its clear. It glows. People like a cheery glow. That's why so much vacuum tube kit now has orange LEDs with their light projected onto the vacuum tubes to increase the effect.

author: TimFox
author_rank: Super Contributor
timestamp: October 26, 2023, 05:45:39 pm
content: Quote from: coppice on October 26, 2023, 05:40:43 pmNaïvely, one would think that 1 ps of jitter with roughly 20 us/sample would be trivial, but the jitter from a bad oscillator can be measurable on an audio signal.As discussed in the Analog Devices app note above, when you get jitter into the ns range, it is important.

author: coppice
author_rank: Super Contributor
timestamp: October 26, 2023, 05:50:03 pm
content: Quote from: TimFox on October 26, 2023, 05:45:39 pmNaive means being unable to roughly divide 20us by 2^24 in your head and get a number around 1ps. In 2023 maths standards suck very badly.

author: TimFox
author_rank: Super Contributor
timestamp: October 26, 2023, 06:07:29 pm
content: The opposite of naïve is not having been born yesterday.In my day at high school, we used to compete with each other on doing binary powers quickly in our heads.However, applying random variations to signal degradation is a bit more complex than that.I believe it was in the 1990s that serious attention started being paid to clock jitter in digital audio systems.An article from 1993:https://www.stereophile.com/reference/1093jitter/index.html

author: ataradov
author_rank: Super Contributor
timestamp: October 26, 2023, 06:17:19 pm
content: The tube is 6S6B. 6J52P is huge and has rigid pins.It is there for marketing. All of this is achievable using solid state devices. But you have to use up old Soviet junk somehow, I guess.

author: coppice
author_rank: Super Contributor
timestamp: October 26, 2023, 06:30:51 pm
content: Quote from: TimFox on October 26, 2023, 06:07:29 pmWe were seriously applying ADC and DAC jitter analysis to radar signals in the 70s. Its not rocket science. Its the basic tradeoff of how far the signal can have changed within the jitter width. Perhaps you are thinking of the effects of dithering. That is more complex. and some aspects of it are far from obvious and intuitive.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 26, 2023, 06:33:17 pm
content: Noise is strictly worse, comparing devices of comparable ratings and bandwidth, more or less simply because the cathode is several times hotter than ambient (absolute temp). Which incidentally also determines the exponential cutoff slope (tubes, like FETs, have an exponential subthreshold cutoff region; above threshold for tubes goes as Iout ~ Vin^(3/2); FETs, ~Vin^2).A given device might have lower noise, or in a given frequency range (RF tubes can be quite good; TWTs are still a good choice for certain microwave applications, mostly aerospace; those might finally be getting displaced by GaN these days, I don't know), but pound for pound so to speak, transistors win; and cryogenically chilled transistors, even moreso.For anything audio, rest assured the exclusive and sufficient answer is: marketing. A case couldkindabe made for competitive purposes in things like guitar amps, where That Tube Sound(TM) is easier to produce,in terms of design effort, than designing a DSP filter of equivalent performance. But the DSP itself, ADC, DAC, and the chip amp following it, are far cheaper (and more efficient, and more mechanically robust, and more reliable..) in any kind of quantity (100s? 1000s?) where that design effort is amortized away.Tim

author: TimFox
author_rank: Super Contributor
timestamp: October 26, 2023, 06:59:47 pm
content: Quote from: coppice on October 26, 2023, 06:30:51 pmNo, I am just stating that historically, during the transition from analog to digital audio systems, the effect of clock jitter became apparent to the audio fraternity (not only the demonized audiophiles).

author: TimFox
author_rank: Super Contributor
timestamp: October 26, 2023, 07:17:59 pm
content: I did a quick simplistic calculation to see how 1 ps of jitter compares with noise.Assume 74HCT logic, with these performance parameters:VIH-VIL= 1.6 V guaranteed logic levelsVOH-VOL= 2.4 V, measuring the endpoints for the transition time specification.tt< 15 ns, for the rise/fall time between those endpoints.For noise purposes, we estimate BW = 0.35/tt= 23 MHz;For thermal noise, assume 50 ohms supplying noise (conservative) of 0.9 nV/rt Hz, or 4.3 uV rms in 23 MHz BW.The slew rate of the signal between binary levels is 2.4 V/15 ns = 160 V/us.Therefore, 4.3 uV rms of noise voltage would effect a time difference of 27 fs rms (using that slew rate).

author: jonpaul
author_rank: Super Contributor
timestamp: October 26, 2023, 08:03:54 pm
content: Tubes/Valves and jitter/clocks are two DIFFERENT topics.Mixed up herehttp://www.audiophilleo.com/zh_hk/docs/Dunn-AP-tn23.pdfhttp://www.nanophon.com/audio/https://benchmarkmedia.com/blogs/application_notes/12142221-jitter-and-its-effectsj

author: TimFox
author_rank: Super Contributor
timestamp: October 26, 2023, 08:10:07 pm
content: Yes, but the original question asked if the use of a vacuum tube in the crystal oscillator would improve the clock jitter in a digital audio system.Most of us believe that it would not improve the jitter, and that there are ways to generate a clock signal that have very bad jitter using either tubes or solid-state devices in a bad design.Over my lifetime, it took a while before practical solid-state devices had better noise than the best tubes, but for normal purposes there is now a better solid-state device (JFET or BJT depending on the application) than the best small-signal tubes, especially since no one is now improving the performance of tubes for this purpose.

author: vk4ffab
author_rank: Frequent Contributor
timestamp: October 26, 2023, 08:16:39 pm
content: An audio fool and his money are quickly separated. I wonder if they used Zero Oxygen copper on the board rather than that dirty filthy 0.0005% oxygen copper, because we all know that 8.30269534 × 10-30 moles can make your jitter do the chicken dance and the only solution is to listen to audio in the vacuum that surrounds the flat earth where the warm glow from the nearest star will induce a magnetic field in the flux capacitor and improve the carrion effect as ravens and others come to scavenge free electrons from the oxygen cloud surrounding the tube plazmaAs a former sound engineer, cant say I have ever heard jitter even on very early implementations of DAT recorders from Sony.

author: TimFox
author_rank: Super Contributor
timestamp: October 26, 2023, 08:29:33 pm
content: This kind of snarky comment about demonized audio enthusiasts without technical education is typical of these sites.Feel free to discuss absurd ideas about cables sold to the unwary by charlatans.However, the design of low-jitter clock circuits is a quantitative design problem.Yes, OFE copper is specified to be 99.99% pure copper with < 0.0005% oxygen.You may find it in Cat6 ethernet cables due to its mechanical properties, mainly resisting metal fatigue.When I used it in good vacuum systems, the informal test of an alloy was to take a flat piece and clamp it in a vise.Regular copper would fail after only a few flexes back and forth with a ViseGrips pliers, but OFHC could handle more than my boredom threshold.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: October 26, 2023, 08:30:21 pm
content: NJR (now Nisshinbo) make oscillator ICs, and they recently released a NJU6385 in DFN6 that is spec'd as a low jitter, low noise oscillator for Audio use.It's unclear if this is a new design die, or a marketing re-package of existing parts ?Their Icc/Vcc plots do not suggest any fancy regulation on-chip.https://www.nisshinbo-microdevices.co.jp/en/products/quartz-crystal-oscillator-ic/NJU6385Phase noise Phase noise (-103dBc/Hz(Typ.) @10Hz Offset -163dBc/Hz(Typ.) @1kHz OffsetRMS Jitter 0.05psec(Typ.) @12kHz to 20MHzOperating Current 9.0mA(Typ.) @CL=15pF.

author: TimFox
author_rank: Super Contributor
timestamp: October 26, 2023, 08:32:25 pm
content: 0.05 ps = 50 fs is comparable to the rough quantitative value of 28 ps (using probably a low estimate of the voltage noise) that I posted above.

author: SiliconWizard
author_rank: Super Contributor
timestamp: October 26, 2023, 08:47:17 pm
content: Of course this is just marketing. Bonus point if someone did a proper teardown and found out that the tube was actually not connected to anything.Not even talking about the microphonic behavior of tubes and how even small vibrations could throw it all off. Maybe you need to mount this equipment on 10 tons of concrete or something, like the very high-end turntables.If anyone here is able to design a tube-based oscillator that exhibits better frequency accuracy and lower jitter than a pure solid-state approach with modern ICs, I'll be happy to have a look at it.

author: ataradov
author_rank: Super Contributor
timestamp: October 26, 2023, 08:52:47 pm
content: There are a high-res pictures of it. It is connected. It does buffer the output of that 24.576MHz crystal oscillator. And the traces go somewhere else. No idea where it is used though.

author: TimFox
author_rank: Super Contributor
timestamp: October 26, 2023, 08:55:42 pm
content: An interesting historical article about the transition at -hp- from vacuum-tube to solid-state crystal-controlled frequency reference generators.https://www.hpmemoryproject.org/news/100e/hp100e_page_00.htmAt that time, there was little discussion of jitter: the improvements concentrated on frequency stability, which was more a function of the crystal and its oven than the good electronics that followed it.

author: vk4ffab
author_rank: Frequent Contributor
timestamp: October 26, 2023, 09:56:42 pm
content: Quote from: TimFox on October 26, 2023, 08:29:33 pmTrue, and while I was being humorous, not snarky, I made a very real point, and that is, in what situation will jitter be an issue in audio recording or playback? Arguing about the technical merits of the amount of jitter in a system is one thing, in certain situations this can be a huge issue, but in audio recording, I am doubtful anyone is going to hear any degradation in audio quality due to clock jitter for the DAC.So for a qualitative measurement of the detection threshold of jitter in digital audio, we are talking about 120ps random jitter on a 20khz tone with 16bit resolution for it to be accuralty reproduced. This is a value that is orders of magnitude over the jitter found in most consumer grade products.So, if you cant hear it, arguing about 5ps or 100ps in the clock is pointless and a manufacturer arguing their 5ps tube clock makes better audio is nothing more than pseudoscience.

author: coppice
author_rank: Super Contributor
timestamp: October 26, 2023, 10:01:49 pm
content: Quote from: vk4ffab on October 26, 2023, 09:56:42 pmLow jitter isn't really about reproduction. Its about recording. If you want something close to real 24 bit recording, so you have lots of headroom, and don't have to be hyper sensitive about record levels, you need really low jitter. Once its all mixed down, the dynamic range is a lot lower, and it matters less.

author: TimFox
author_rank: Super Contributor
timestamp: October 26, 2023, 10:06:04 pm
content: Quote from: SiliconWizard on October 26, 2023, 08:47:17 pmHere is an example of a high-grade vacuum-tube based 1 MHz crystal oscillator design from 1960 (US Navy Bureau of ships article). See page 19 for the 6AH6 pentode Meacham-bridge oscillator (with a transistor included in the thermostat for the crystal oven).https://www.navy-radio.com/journal/journal-freq-synth-6012.pdfAgain, jitter in time units is not discussed, but the short-term stability is quoted as 2-3 x 10-9per day. With the Meacham-bridge circuit, this should depend almost completely on the crystal itself and the passive circuit connected to it. Therefore, using the pentode instead of a modern solid-state device isnotthe magic in the circuit.

author: ataradov
author_rank: Super Contributor
timestamp: October 26, 2023, 10:12:31 pm
content: Quote from: coppice on October 26, 2023, 10:01:49 pmThis topic is about consumer DAC though. And their own claim is "By using a tube, we have significantly lowered the amount of jitter and noise, resulting in superior detailretrieval." There is also a lot of BS superlatives.They also claim "Here are a few real SuperTubeClock™ pictures of what it can do: experts will certainly like them. No other commercial clock on earth will produce a square wave as this one." This is accompanied by pretty mediocre looking scope captures.They also confuse units "mHz" and "MHz". But such details are above them, I guess.And their super clean (tm) clock still goes into the CMOS DAC where it has to pass though regular CMOS gates subject to the same variation in the edges.

author: vk4ffab
author_rank: Frequent Contributor
timestamp: October 26, 2023, 10:20:59 pm
content: Quote from: coppice on October 26, 2023, 10:01:49 pmTrue, but in playback, which is what we are talking about with this audio fool DAC, even trained listeners struggle to hear random jitter less than 500ns. If I remember rightly, even the high end recording sound cards back in the day had jitter levels in the low 1000's of ps and no one complains their favorite song from 00's has audible jitter on it.

author: langwadt
author_rank: Super Contributor
timestamp: October 26, 2023, 10:40:58 pm
content: Quote from: ataradov on October 26, 2023, 10:12:31 pma 10cent tiny logic gate will make sharper edges than that

author: TimFox
author_rank: Super Contributor
timestamp: October 26, 2023, 10:48:23 pm
content: Quote from: langwadt on October 26, 2023, 10:40:58 pmSharp edges are the easy part. A good design of the crystal and its oscillator circuit is more important.A sinusoidal-output crystal oscillator can have good jitter, but its edges are not sharp.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: October 26, 2023, 11:00:39 pm
content: Quote from: PCB.Wiz on October 26, 2023, 08:30:21 pmLooking for alternative measurements on CMOS gate oscillators, I find this app note from TI.https://www.ti.com/lit/an/scaa119/scaa119.pdfThat's old, but curves are similar but not quite as good as the NJU6385, tho I see NJU6385 specs a low 17.7 ohms crystal, with Q ~ 67,000Quote from: langwadt on October 26, 2023, 10:40:58 pmBuffers are easy,TI info gives 3.3-V LVCMOS Clock Buffer Family additive jitter of ~7.5 fs typical at VDD = 3.3 V (Sq in, Sq out)

author: vk6zgo
author_rank: Super Contributor
timestamp: October 27, 2023, 01:09:17 am
content: When "the rubber hits the road", we are perceiving the result of all this "wizardry" using sensors which had their last design upgrade tens of millions of years ago & are subject to wide variability in individual characteristics.On top of that, going back one step in the chain, the transducers which convert the electronic back to sound have characteristics which are much more variable than the electronic part of the chain.Of course, to many the measurement of small increments of difference in various characteristics is an end in itself, somewhat like those religious scholars who spent years in debate as to how many angels could dance on the head of a pin.Meanwhile, the audiophile "true believers" are happy, the scammers are happy, the wheels of commerce roll on, who are we to question?

author: antenna
author_rank: Frequent Contributor
timestamp: October 27, 2023, 02:00:33 am
content: Seeing a glowing filament next to an oscillator makes me immediately think of Jeri Ellsworth's video titled "Don't use lame parts". Maybe not related, but thats what comes to mind.

author: SiliconWizard
author_rank: Super Contributor
timestamp: October 27, 2023, 02:37:40 am
content: Quote from: langwadt on October 26, 2023, 10:40:58 pmThe tube can only get them worse results than a proper CMOS buffer here, including microphonic effects as I mentioned, which will add jitter unless again the whole thing was 100% vibration-free.This is absolutely not the same as using tubes in analog stages in the audio signal path - while many find that questionable these days, tubes do add a particular type of distortion and frequency response that are often considered "pleasing" to the ear, it's not about high-fidelity, but twisting the signal in a specific way which has been known to "work" for listening to music for a pretty long time now.Here they claim lowering jitter, and I do not buy that one second, I'm rather convinced of the opposite. So to answer vk6zgo, I personally rarely question this kind of things, people can well buy whatever they want at whatever price, even if they are just buying air. But if the overpriced designs actually make things *worse*, which I highly suspect here, then this is where I would personally put the line.

author: bdunham7
author_rank: Super Contributor
timestamp: October 27, 2023, 02:52:48 am
content: Quote from: ELS122 on October 26, 2023, 05:03:02 pmTo give this guy something to talk about.

author: bdunham7
author_rank: Super Contributor
timestamp: October 27, 2023, 04:45:57 am
content: Quote from: ELS122 on October 27, 2023, 03:30:28 amNo, I think that was covered, in Reply #28 for example. TLDR: having a tube doesn't offer any technical advantage, lower jitter or otherwise.

author: vk4ffab
author_rank: Frequent Contributor
timestamp: October 27, 2023, 07:06:28 am
content: Quote from: ELS122 on October 27, 2023, 03:30:28 amIts irrelevant when the jitter is less than 500ns because most normal people cannot hear it. The fact that the oscillator is in the 5ps range just means the 24bit dac is not reproducing the audio perfectly, for that it would require a jitter of 0.5ps. You know, math, 1 over 2 pi * frequency * 2 to the power of n or whatever it is for perfect digital reproduction. So either the manufacturer really does not know basic theory, or they are using a whole lot of spin to sell over priced tube things to the gullible.The science is out there for anyone who can read and there have been plenty of studies on the audibility of jitter in digital audio. There are a lot of other real things that effect audio quality, but you have to design a pretty bad oscillator for jitter to actually matter. You could toss an SI5351a into that thing, save a few thousand bucks by having a tiny tube that does bugger all and still not hear its typical 35ps jitter in the recovered audio. You could probably use the first xtal oscillator I built on copper clad board and have great audio as well as the joy of oscillation on the scope.Most of my electronics is based in the practical, not theory so 5ps or 100ps who cares when in practice its all wankery.

author: Haenk
author_rank: Super Contributor
timestamp: October 27, 2023, 08:14:52 am
content: I think all this has it's roots in early DAC implementation - which has indeed been mostly awful and was probably widely discussed (and is forever burnt as Eeeeevil into the brains of early enthusiasts and HiFi-magazine readers). Due to cost restrictions, most of the early CD players came with just *one* DAC (one DAC for both channels, that is). So the companies had the great idea to toggle the channels and to delay one output channel.This wasn't an issue any more at the end of the 80s, but seems to be still a concern. Probably someone heard about it when still a kid...Honestly, I think jitter is the smallest problem in a home audio setup. And so did all the engineers back then, obviously. Symmetrical construction for the audio path - yes, please. But those damned bits, some flying wires are good enough. And I guess, they were right...

author: radiolistener
author_rank: Super Contributor
timestamp: October 27, 2023, 08:42:16 am
content: Quote from: ELS122 on October 26, 2023, 05:03:02 pmYes, oscillator phase noise (jitter) is very important for high performance DAC. High phase noise leads to a dynamic range reduction for DAC.I'm not sure if that tube oscillator has low phase noise, but if you're using top end DAC, it requires to use ultra low phase noise oscillator for clock. Such oscillators are pretty expensive (20-40 USD). Here is example of such oscillators:https://abracon.com/Precisiontiming/ABLNO.pdfGood quality DAC requires oscillator with jitter about 0.1 ps or less. Most of Chinese TCXO cannot provide so low jitter.But I din't hear that tube oscillator can provide ultra low phase noise, so I'm not sure if this is marketing thing or not.Quote from: vk4ffab on October 26, 2023, 10:20:59 pmYes, in most cases the difference with usual good TCXO will not be noticeable, it requires to hear special sound patterns and have good ears to detect it.

author: Kleinstein
author_rank: Super Contributor
timestamp: October 27, 2023, 03:40:55 pm
content: The typical audio data are not 24 bit quality and the DAC used is likely also not true 24 bits. The quoted 0.5 ps jitter requirement would only be needed for a FS sine signal near the top of the frequency range. Actual audio has rather limited high frequency contend and the DAC is usually oversampling, which also reduces the requirements.Low jitter helps, but it is usually not that critical and other points more be more important. The ear can anyway not hear that much of imperfections. If at all one may be able to measure with really high end gear.I don't see a way why a normal tube should be low jitter or especially stable - more of the opposite: a tube is sensitive to magnetic fields and vibrations and not super fast. So one can expect rather high jitter from a tube based oscillator. Alone having the tube and crystal separated that far apart and not well shielded makes it susceptible to EMI.Chances are most of the 25 cent canned oscillators are better.

author: coppice
author_rank: Super Contributor
timestamp: October 27, 2023, 03:57:43 pm
content: Quote from: Haenk on October 27, 2023, 08:14:52 amCD players produced in the first 3 or 4 years were quite abysmal. They eliminated the hiss, rumble and scratches we had to put up with from LPs or tape, but the actual sound quality was poor. Any complex music had the muddiness you associate with a lot of intermod products. The DACs they used were only about 13 or 14 bits linear. It took several years before they cleaned things up. It was about 1990 before CD reproduction was outclassing LPs on every front. This was also about the date when sales of CDs really started to accelerate. I expect that was largely coincidence.

author: coppice
author_rank: Super Contributor
timestamp: October 27, 2023, 04:02:45 pm
content: Quote from: vk4ffab on October 27, 2023, 07:06:28 amI think you mean 500ps. Even the tone deaf would hear 500ns.

author: coppice
author_rank: Super Contributor
timestamp: October 27, 2023, 04:08:32 pm
content: Quote from: radiolistener on October 27, 2023, 08:42:16 amAnyone talking about the need for a TCXO or a jitter level of <0.1ps has seriously lost the plot. TCXOs, and rubidium clocks, have their place in recording, to allow multiple sources to be freely mixed and matched. They have no value for reproduction.

author: tszaboo
author_rank: Super Contributor
timestamp: October 27, 2023, 04:16:20 pm
content: You see this below? That's how it is recorded. There are no tubes there, just a bunch of NE5532s, and usually a muppet that will compress every single recording so it can be played back on a 3 dollar earphone sold by Apple for 200 dollars.

author: CaptDon
author_rank: Super Contributor
timestamp: October 27, 2023, 06:09:46 pm
content: I can't imagine any tube oscillator being better than a cheap TCXO. Thinking back to the military tube type crystal controlled reference oscillators where the crystal, the oscillator tube and the buffer tubes were all contained within a double oven where the inner and outer oven had separate controls. Even the glow tube oscillator voltage reference was inside the oven and the double ovens also blocked anything except cosmic rays to obtain very low phase noise. If you pounded really hard on the rack (these beasts were rack mounted) you could produce phase/noise/jitter modulation but even the outer oven was shock mounted. Mine was built by C.R.L. or something like that for military / Wallops Island Goddard flight center. Navy gray beast of about 25 pounds and taking a couple days to achieve final stability (but still, it had a crystal aging factor). So the end observation, they were selling magic snake oil in a box to audiophools.

author: floobydust
author_rank: Super Contributor
timestamp: October 27, 2023, 08:55:40 pm
content: From EVO 100 pics, you can see they use russian submini triode 6S6B, then AD8611 comparator to pick off the signal at the plate. I doubt the triode gets the ~120V, no idea about the source of clean HVDC for it.It's a straightforward xtal osc, using the cathode drive. But it's wrong to have any DC across a quartz crystal to prevent ion migration. So I see design errors, drive likely high as well.This is obviously forpsycho-acousticsa $4,000 DAC needs something to stand out from the others. It also keeps the 8051 warm lol.

author: SiliconWizard
author_rank: Super Contributor
timestamp: October 27, 2023, 09:02:56 pm
content: Yes $4000 is a ridiculous amount of money for even a very good and well-designed DAC, but I can certainly see much better use of money for the design nonetheless.The final price has to be put into perspective in terms of margin - for high-end/luxury items, a 80%-90% margin is not unusual. We're very far from commodity gear with maybe a 20% margin if planets are aligned.As I said, I'm pretty convinced this design does actually significantly worse than a simple CMOS TCXO - not even speaking of an OCXO which would still make it relatively cheap.

author: vk4ffab
author_rank: Frequent Contributor
timestamp: October 27, 2023, 09:33:01 pm
content: Quote from: coppice on October 27, 2023, 04:02:45 pmNo i meant ns. That is about the limit where most average people can no longer hear jitter on digital audio and when you get down to 250ns even trained sound engineers can no longer hear jitter. There is plenty of research that has been done in this field. This is just one often cited paper, but there are others and none of them claim the human ear can hear jitter on digital audio in the ps range. So, as long as the dac/adc is using a clock with jitter in the low ps range, there will be no detectable jitter in the recovered audio even with a 24 bit dac sub optimally clocked.Detection threshold for distortions due to jitter on digital audio ASHIHARA et al 2005There are also consumer grade dacs on the market for a lot less than the one in this thread that have perfect jitter responses, MOJO comes to mind here, and no one is ever complaining about jitter with these sorts of things, they complain about a lot of other more important reasons for audio degradation. Certainly not their clock needs a tube to improve jitterClaiming their low jitter tube clock somehow has improved audio from a dac is nothing more that pseudoscience audio foolery and not based in reality because their 5ps clock will sound identical to a 100ps clock as both will have jitter distortion we just cannot hear.

author: ataradov
author_rank: Super Contributor
timestamp: October 27, 2023, 09:37:35 pm
content: Capacitors are dancing all over the place. Must improve the sound too.Also, their claim that it uses "Military grade" components is wrong. That OTK stamp indicates it is a regular commercial part.

author: TimFox
author_rank: Super Contributor
timestamp: October 27, 2023, 09:43:24 pm
content: From a quick look at the PCB near the crystal, it looks like a normal Colpitts crystal oscillator circuit.The Meacham Bridge circuit would be better, if it mattered.

author: bdunham7
author_rank: Super Contributor
timestamp: October 27, 2023, 09:51:17 pm
content: Quote from: vk4ffab on October 27, 2023, 09:33:01 pmIt depends a lot whether it is random or correlated jitter, as well as the program material and other circumstances. Random jitter can be equated to noise floor. The level below which audibility is possible is probably debatable, but the lowest number I recall seeing from a reputable source is 5ns, and I think that was a theoretical argument vs a demonstration. 500ns is a bit high, I think 500ns of jitter correlated to 1kHz might be readily audible with the right program material.As has been pointed out, it isn't unreasonable to hold recording systems to a bit better standard, but single-digit or fractional picoseconds is probably a bit much. You can do the math for a 24-bit or 32-bit system, but no audio system has anywhere near the actual 144dB (or 196db!) dynamic range that these imply.

author: TimFox
author_rank: Super Contributor
timestamp: October 27, 2023, 09:54:58 pm
content: 144 dB of dynamic range would be excessive, since the threshold of pain is around 130 dB(SPL), the threshold of hearing is 0 dB(SPL) in an anechoic chamber, but you are very lucky if the background ambient sound level in your house is < 20 dB(SPL).

author: boB
author_rank: Frequent Contributor
timestamp: October 27, 2023, 10:08:21 pm
content: Dumb idea although the audio philes might like it

author: vk4ffab
author_rank: Frequent Contributor
timestamp: October 28, 2023, 03:34:22 am
content: Quote from: bdunham7 on October 27, 2023, 09:51:17 pmIf i remember rightly, Dolby did a bunch of tests back in the day and found jitter became audible in the low ns range on a single tone sine wave. Now other than CW operators doing morse code, I do not know anyone who listens to a single tone sine wave, so in a practical sense, a single tone is irrelevant because its not how anyone listens to or appreciates audio.But even in that worst case scenario, a clock in ps range is not going to add much, if anything to audible distortion because things like quantized noise, non linear distortions and even the noise of individual components have a greater impact on audible distortion on a typical audio stream. So I do not have a problem with Ashihara and others findings that trained sound engineers using their own studios could not hear jitter much below 500ns.So taking this back to the device this thread is about, raving that 5ps is great and makes the audio better because of tubes is nothing more than marketing wank, because its effect is so small that the jitter could be orders of magnitude higher and still we wont be able to hear it.

author: radiolistener
author_rank: Super Contributor
timestamp: October 28, 2023, 11:21:16 am
content: Quote from: vk4ffab on October 27, 2023, 09:33:01 pmit depends on sound pattern which was used for testing and conditions (volume level, etc). Maybe for usual music you will not be able to recognize difference with clock jittter less than 250 ns, but for special test cases it still can be detected. You can combine some signals in the source in that way so distortions caused due to clock jitter can be easily recognized.Human ear has pretty large dynamic range. Yes, it is not linear, but for perfect reproduce for all frequencies, your DAC needs for about 140 dB dynamic range. There is no DAC with so high dynamic range that can cover all cases for human ear, so... it's better to use 0.1 ps jitter if you want to build good sound DAC, in order to not loss DAC dynamic range.Quote from: vk4ffab on October 28, 2023, 03:34:22 amGood quality sound DAC has many use cases, not only listening sound. For example it can be used to produce test signals for measurements which needs to be clean enough.And maybe someone like to listening clean sines... who knows

author: radiolistener
author_rank: Super Contributor
timestamp: October 28, 2023, 11:47:09 am
content: Quote from: TimFox on October 27, 2023, 09:54:58 pmFor example rifle gun shot has about 160 dB SPL, helicopter has noise about 120-140 dB SPL.Some orchestral musical trumpets instruments produce sound level about 150-160 dB SPL.Such sound level is not comfortable for human ear, but don't cause pain. But can be unsafe for long exposure.By the way, with usual atmospheric pressure max possible sound level is about 192 dB SPL, so if you want to cover painful sound, there is no DAC that can cover 192 dB dynamic range

author: Gyro
author_rank: Super Contributor
timestamp: October 28, 2023, 12:03:02 pm
content: I suspect that, even if the DAC puts out 140dB+dynamic range, the components down stream are going to have severe problems in maintaining it!

author: Kleinstein
author_rank: Super Contributor
timestamp: October 28, 2023, 12:18:59 pm
content: The effect of jitter in the DAC timing is only relevant when there is a signal, especially a signal with high amplitude and high frequency. The ear may be quite good in the dynamic range with 1 tone at a time, but not when is comes to detecting a little noise in the presents of a very loud one. The dynamic range is pretty limited and it is easy to mask noise noise. So the test showing some 0.5-1 µs as the level where jitter get hearable sounds totally plausible.

author: radiolistener
author_rank: Super Contributor
timestamp: October 28, 2023, 12:32:03 pm
content: Quote from: Gyro on October 28, 2023, 12:03:02 pmyes, there is no amplifier that can handle so wide dynamic range.

author: radiolistener
author_rank: Super Contributor
timestamp: October 28, 2023, 12:37:05 pm
content: Quote from: Kleinstein on October 28, 2023, 12:18:59 pmThis is not true, human ear is more complicated and can hear many tones simultaneously and even more it can distinguish even very weak signals on background of very loud one. But it has non flat frequency response and non flat sensitivity level, it depends on many factors. Include individual properties of ear, age factor and ability to hear different aspects of sound which needs to be trained.Quote from: Kleinstein on October 28, 2023, 12:18:59 pmwith 0.5-1 uS clock jitter you will get bullshit sound with high distortions. Something like cheap Chinese kid toy.I can say it’s very easy to get used to high-quality sound, but then it’s hard to listen to cheap sound, because you start to hear all the defects that you didn’t notice until you heard high-quality sound...Just remember how we listened very distorted and noisy sound from tape in the past and it was "pretty good", but now, when everyone got used to better quality sound, the tape sounds like bullshit...

author: coromonadalix
author_rank: Super Contributor
timestamp: October 28, 2023, 01:24:57 pm
content: yeah the higher resolution / precision etc ... you will hear them more, im lucky to have very good hearing at my agesame for tv's or else loll you see more defects ... impurities ... artefacts ... i remember the complaints When Sony Trinitron came into market loll peoples saw too much lollyou get high end dacs, but now the amp doesn't follow and the speakers too ...i played with what they called high end stuff at the time, like DAT or high end cd players with external DACS, or the DAC chip ... ones you could buy and change them on the main pcb's etc ...You could hear the difference in the cds recording mode : digital digital etc ... digital analog .... on 20,000 $/ea speakers lollPlayed with Carver, high end amplifiers, wow, i had formation to repair them loooooong time ago lollYou have Mosfets based amplifiers with a bandwith and frequency response so incredibly straight from 10hz to 50 Khz ....you alway end up missing something, unless you buy an huge kit, once and for all lollFor the tubes, i always hear a tube is "warmer" in sound vs electronic ones (transistors / mosfets etc ... a class a-b class) even heard those who are called G - H class, or the D i think, it like an smps amplifier running at very high frequencies 1Mhz or more ...Tubes amp could take more "beating" than others ... some of my old friends whant tubes amps, tube guitar amps loll end of an era lolloh and yes like the previous thread, going down into normal "cheap stuff" is like .......... crying and banging you head on a wall

author: vk4ffab
author_rank: Frequent Contributor
timestamp: October 28, 2023, 09:56:26 pm
content: Quote from: radiolistener on October 28, 2023, 11:21:16 amThe thing to remember is that the device we are talking about in this thread is a high fidelity audio device, its not a special test case, its not theoretical, its entirely practical and it revolves around the subjective reality of listening to audio, most commonly music. So in that context and that context only, 5ps clock jitter does not improve audio because humans cannot hear random jitter much below 500ns. There are certainly cases where that much jitter will be detrimental but those cases are not audio.Its also not that hard to design a clock with 0.2ps jitter, which would be required for accurate reproduction of audio with a 24bit dac. Diodes Inc make them as a part off the shelf you can buy from mouser. Using that they could claim look at us, no jitter on our audio, but rather, they use a tube, have detectable jitter and claim their tube thing makes the audio better. Because its a sales gimmick for tube people, nothing more. The tube makes the jitter we cant hear sound warmer after allTo quote Jello Biafra, those dumb punk kids will buy anything.

author: jonpaul
author_rank: Super Contributor
timestamp: November 01, 2023, 08:17:49 am
content: rebonjour:Misc notes:Jitter audibility: See already referenced AES and AP papers by Steve HARRIS and Julian DUNN.Reason to use a tube:Nostalgia, appearance,Jon