Analog versus digital oscilloscopes - Page 1
Forum section: electronics / beginners

author: j57H8I4
author_rank: Contributor
timestamp: March 08, 2017, 12:35:41 am
content: No digital oscilloscope could ever reach the graph quality of an analog oscilloscope. Like no compact disc could ever reach the sound quality of a vinyl disk.

author: retrolefty
author_rank: Super Contributor
timestamp: March 08, 2017, 12:39:04 am
content: Quote from: j57H8I4 on March 08, 2017, 12:35:41 amThat is one opinion, others might not agree. So, other then trying to raise a brouhaha, what is the purpose of your post?

author: j57H8I4
author_rank: Contributor
timestamp: March 08, 2017, 12:45:44 am
content: Quote from: retrolefty on March 08, 2017, 12:39:04 amThat is not an opinion that is a fact. The purpose of my post is to make people aware about this.Anyway I posted my thread in the wrong section, I should have posted this thread in the "Test Equipment" section.

author: ataradov
author_rank: Super Contributor
timestamp: March 08, 2017, 12:57:45 am
content: Quote from: j57H8I4 on March 08, 2017, 12:35:41 amOh, my.Also, were not you confused how to calculate resistor divider just yesterday? What exactly do you know about test equipment and its quality?

author: ataradov
author_rank: Super Contributor
timestamp: March 08, 2017, 12:59:47 am
content: Quote from: retrolefty on March 08, 2017, 12:39:04 amI see a pattern here. Newbie tries electronics. After day 1 it turns out electronics is hard. Newbie gives up and goes full on troll mode.

author: j57H8I4
author_rank: Contributor
timestamp: March 08, 2017, 01:03:59 am
content: Quote from: ataradov on March 08, 2017, 12:57:45 amI was, because I do not know electronics.Quote from: ataradov on March 08, 2017, 12:57:45 amI exactly know that a digital graph is always approximate, while an analog graph is real.

author: ataradov
author_rank: Super Contributor
timestamp: March 08, 2017, 01:08:43 am
content: Quote from: j57H8I4 on March 08, 2017, 01:03:59 amYou really better stop talking right now, and learn something about oscilloscope design.It is "smooth" (hence analog), but in many cases it has more linear and non-linear distortions than a digital signal. And with a digital scope you can calibrate that out without problems to a certain extent.Also, digital scope preserves more fine information about the signal. Phosphor of the display has persistence, so it acts as a low pass filter, so all your high frequencies are gone and not displayed.

author: naldo
author_rank: Contributor
timestamp: March 08, 2017, 01:12:54 am
content: Disagree: digital scope is more sensitive to reading gives more details! Here, good night everyone!

author: gildasd
author_rank: Frequent Contributor
timestamp: March 08, 2017, 01:19:45 am
content: I want both!

author: james_s
author_rank: Super Contributor
timestamp: March 08, 2017, 01:20:10 am
content: I have both an analog and a digital scope. Each has strengths and weaknesses, and which is best depends on what you are doing. I like the "real" feel of an analog scope, they're great for having a quick look at what's there. A digital scope's ability to trigger and capture is invaluable for transient events though. People get an almost religious faith in one or the other but the reality is that you can have and use both. For a hobbyist, I think you can get a lot more scope for the money with an analog instrument. You generally have to spend a lot more on a DSO because most of the budget models are very limited but once you get to a certain level the disadvantages become less significant. If you want to capture single shot or non-repetitive events though digital wins hands down. For a long time I had a good analog CRO paired with an inexpensive PC based DSO and that gave me a good compromise. Now I have a really good DSO and expect to use my analog scope less but I'm still going to keep it.I've never seen a digital scope that could come close to the ability of an analog CRO to display vector graphics in XY mode but that is a rather niche application.I also like and collect vinyl, but I can't say it necessarily sounds any better than a CD to my ears. Good vinyl on decent equipment sounds very good, but better? I don't think my ears are good enough to say. For me it's more about the collecting, finding obscure stuff in thrift stores, and it's a bit of a different experience to cue up a record and play it. I like the album cover art too, modern formats are too small to make good use of that.

author: xrunner
author_rank: Super Contributor
timestamp: March 08, 2017, 01:22:49 am
content: Quote from: j57H8I4 on March 08, 2017, 12:35:41 amWell as long as the analog scope CRT doesn't have burn in, and the focus isn't out of adjustment, and the brightness isn't low because of thousands of hours of use ... maybe.

author: james_s
author_rank: Super Contributor
timestamp: March 08, 2017, 01:24:25 am
content: Quote from: xrunner on March 08, 2017, 01:22:49 amTo be fair, there are plenty of things that can fail and deteriorate in a digital scope. Let's compare apples to apples here and assume both instruments are in good working order and not worn out or damaged.

author: xrunner
author_rank: Super Contributor
timestamp: March 08, 2017, 01:28:52 am
content: Quote from: james_s on March 08, 2017, 01:24:25 amComparing a digital scope to an analog scope is inherently apples to oranges though ...

author: Dubbie
author_rank: Unknown
timestamp: March 08, 2017, 01:31:43 am
content: This seems to be the most persistent misconception among audio enthusiasts - that analogue == infinite detail, and that the analogue output of a digitized signal looks like a flight of stairs with each sample having infinitely steep risetimes before locking in at a value until the next sample. I wish!

author: james_s
author_rank: Super Contributor
timestamp: March 08, 2017, 01:41:59 am
content: Quote from: Dubbie on March 08, 2017, 01:31:43 amWell I'm more of a visual person myself, so I guess a reasonable analogy here is comparing a digital video signal displayed on a TFT screen vs an analog video signal on a CRT. I would say that hands down the CRT looks far superior for the same resolution. I've got a 27" Trinitron XBR in my rec room that still looks fantastic despite the fact that you'd never even get a true 640x480 out of analog NTSC. If you could get a 27" 4:3 LCD screen that was only 640x480 it would look horrible in comparison. For SD content I think the old Sony looks nicer than a comparable HDTV upscaling SD content, although 1080p content on a 1080p screen does look better but that's vastly higher resolution.Could the same apply to audio? I don't know, seems like a reasonable assertion that it could. I could also believe that a subjective matter as music could sound "better" to someone despite being worse in quantifiable metrics simply because it's subjective.

author: BrianHG
author_rank: Super Contributor
timestamp: March 08, 2017, 02:24:06 am
content: Quote from: james_s on March 08, 2017, 01:41:59 amCareful, CRT, Sony XBR, had a million:1 contrast ratio & true soft RGB color gamut. I have a studio color grading grade accurate 21 inch computer CRT with 10 000 000:1 contrast ratio, auto CRT aging compensating electronics to keep perfect color & black level, 2048x1536 at 85hz with a color with obliterates any LCD technology PERIOD. (Studio grade organic LED tv's with infinity:1 contrast are the only displays I seen which beat it.) But, it is still being fed from a video card which has a digital source. So, the problem is your TFT display's color quality limitations, not that the Sony XBR was analog. (Well if you are watching low bit-rate TV from cable of dish or internet, there is nothing I can do to help here) Also, the Sony XBR2 used a digital comb filter to separate the NTSC's luma and chroma signal. So, even with that TV, the analog source video was first digitally sampled, digitally color luma & chroma separated, then back through an analog dac (an all in 1 IC device), then sent to an old fashioned analog Y/C to RGB decoder (yes, this is absurd, but it is how Sony did things at the time due to technology restraints) and achieved a better picture than the XBR.

author: yuzuha
author_rank: Contributor
timestamp: March 08, 2017, 02:30:11 am
content: Quote from: Dubbie on March 08, 2017, 01:31:43 amBingo. Human perception is quantized too, and neuron firing is considerably slower than many digital systems. Sample fast enough with enough bit depth and digital is just as good as analogue.

author: raspberrypi
author_rank: Frequent Contributor
timestamp: March 08, 2017, 04:54:05 am
content: Quote from: ataradov on March 08, 2017, 12:59:47 amEveryone is an expert until the learn a little bit and realize how much they don't know. Yes vinyl sounds better then CD but its not because ones digital vs analogue. I listen to vinyl myself but to get the sound quality you have to spend money on the needle (not to mention pre amp amp and speakers) to get the full effect out. I use an ortophone concord pro ($180USD) on a vestax turn table ($800USD). The turn table makes no difference in sound quality. As long as its spinning at the right speed it has no effect on the signal, you could use a lazy susan spun by hand and it would sound the same. The only reason I have such a top end one is because I do alot of scratching/ mixing and you need a high torque direct drive, very sturdy turn table. If you sample at a high enough rate and have enough bandwidth your ears become the limiting factor. Have you ever heard an SACD on really good speakers and amp? It almost sounds worse because it reveals the limitations of the recording. Sounded really harsh to my ears and I see why the SACDs never caught on; you pay more money for something that sounds better on paper but worse to your ears. Kind of like how tube amps sound better when really they are adding a harmonic that is by definition distortion. Just like your eyes become the limiting factor with a scope.

author: james_s
author_rank: Super Contributor
timestamp: March 08, 2017, 05:14:19 am
content: Quote from: BrianHG on March 08, 2017, 02:24:06 amIt's not just the color gamut though. With a low res TFT I can see the grid of pixels, especially if you were to make a 640x480 TFT that was 27", the pixels would look huge. The CRT being analog has approximately round "pixels" that blend smoothly together. It's sharp enough to see the scan lines but the horizontal resolution lacks discrete steps.Your mention of the contrast ratio reminds me of the absurdly bogus specs on monitors these days. The TFT I have on my PC prominently proclaims 80,000,000:1 contrast, what a joke! It's a decent monitor but in terms of contrast the old Sony CRT I had which was probably rated 1,000:1 absolutely blows the TFT out of the water. Unfortunately it weighed a ton, took up half my desk and was starting to get a little blurry.

author: technogeeky
author_rank: Frequent Contributor
timestamp: March 08, 2017, 05:17:34 am
content: This thread is nonsense, all the way down, and should be locked. Even good responses given into the teeth of a trolls' query should be sacrificed.

author: j57H8I4
author_rank: Contributor
timestamp: March 08, 2017, 05:21:58 am
content: Quote from: raspberrypi on March 08, 2017, 04:54:05 amA digital equipment takes samples of a wave then calculates the evolution of the wave among its two samples, that means that the digital equipment is inventing the evolution of the wave among its two samples, while the wave among its two samples could be completely different. And this is what happens with digital oscilloscopes and with compact disc players. Analog oscilloscopes, as well as vinyl disc players, do not invent anything, they just return the real wave.

author: ataradov
author_rank: Super Contributor
timestamp: March 08, 2017, 05:29:44 am
content: Quote from: j57H8I4 on March 08, 2017, 05:21:58 amSo what? Physics and mathematics are such that your equipment does not truthfully reproduce those fast changes.Quote from: j57H8I4 on March 08, 2017, 05:21:58 amThere is no real wave, it is always limited by the equipment used to observe it. And capabilities of modern digital scopes far surpass capabilities of the analog scopes.If you don't understand this, then there is nothing can be done here.

author: j57H8I4
author_rank: Contributor
timestamp: March 08, 2017, 05:36:28 am
content: Quote from: ataradov on March 08, 2017, 05:29:44 amIt is impossible that digital equipment can surpass analog equipment ever, because digital equipment will always approximate, analog equipments take and return the full signal, the real signal.

author: ataradov
author_rank: Super Contributor
timestamp: March 08, 2017, 05:38:59 am
content: Quote from: j57H8I4 on March 08, 2017, 05:36:28 amLimited by the input bandwidth of the scope. In both cases, in digital and analog. Except that digital has much better ability to display that bandwidth limited signal because it does not need to limit it even further because there is no phosphor.You really don't know what you are talking about, and just look silly.

author: daqq
author_rank: Super Contributor
timestamp: March 08, 2017, 05:41:34 am
content: QuoteBS. Neeeeext!

author: ataradov
author_rank: Super Contributor
timestamp: March 08, 2017, 05:43:06 am
content: Quote from: daqq on March 08, 2017, 05:41:34 amWell, to be fair we never defined what quality is. May be he is an artist and enjoys smooth curvesAnd if we are talking about truthful representation of the signal, then BS indeed.

author: innkeeper
author_rank: Unknown
timestamp: March 08, 2017, 07:36:25 am
content: it's gotta be a tube oscilloscope for the best fidelity

author: Unknown
author_rank: Unknown
timestamp: March 08, 2017, 07:48:54 am
content: Quote from: j57H8I4 on March 08, 2017, 05:36:28 amHopefully you still enjoy movies on VHS?

author: raspberrypi
author_rank: Frequent Contributor
timestamp: March 08, 2017, 08:18:39 am
content: This guy is just trying to make an argument. The more he posts the less he seems to know what hes talking about. Does he even own a scope? He totally missed the point people made where the digital sample rate is so fast that a human cant tell the difference. Plus an analog scope can't do screen captures which is a huge advantage.What is he testing that a the digital scope is not good enough?Rubbish.

author: JPortici
author_rank: Super Contributor
timestamp: March 08, 2017, 08:32:49 am
content: Quote from: j57H8I4 on March 08, 2017, 12:35:41 amand you are serious.too young?too old?too noob?or just trolling?

author: borjam
author_rank: Unknown
timestamp: March 08, 2017, 08:46:45 am
content: Quote from: j57H8I4 on March 08, 2017, 12:35:41 amVinyl sounds "beautiful" because we do like its distortion. Exactly the same happens with analog tape recorders. I don't have anything against purposefully introduced distortion, but that's what it is.Now you can buy emulations of analog gear in order to "spice" your digital recordings or "add warmth". Guess what do they do? Yes, add distortionThere's nothing wrong with it. It's just part of the creative process. But those "magical" misconceptions about sound recording won't help you. Really!So, what happens with an analog oscilloscope? It's been explained countless times. Analog scopes naturally display an average of many sweeps.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: March 08, 2017, 08:58:43 am
content: Well, analog scopes are generally heavier than their corresponding digital counterparts, so they make better doorstops. But I remember some years ago when I was using a LeCroy WaveSomething that was running its scope application on a Windows XP operating system, and was connected to our lab's LAN. I could watch YouTube videos and check my email on the oscilloscope! Try that with a Tek 7000 series..... I don't think there's a plugin for that.

author: Gyro
author_rank: Super Contributor
timestamp: March 08, 2017, 09:00:22 am
content: Why are you guys continuing to feed a Troll - you know they thrive on it!

author: tautech
author_rank: Super Contributor
timestamp: March 08, 2017, 09:20:36 am
content: Quote from: j57H8I4 on March 08, 2017, 05:21:58 amYes the reconstruction of the displayed signal from data points is called interpolation, the higher sampling speeds and memory depths used give better quality reconstruction but some DSO's do it better than others.Interpolation algorithms are more advanced these days but indeed there is the possibility of reconstruction errors BUT with a CRO and taking measurements from the graticules there is a higher chance of error from parallax error.I'd rather the uP did that work for me and display the result on the display.I've owned a heap of CRO's and I'm not going back.

author: djnz
author_rank: Regular Contributor
timestamp: March 08, 2017, 10:42:31 am
content: Harry Nyquist and Claude Shannon say "Hello".