Anyone uses CD jitter meter here? - Page 1
Forum section: electronics / projects

author: dzseki
author_rank: Frequent Contributor
timestamp: February 19, 2014, 08:09:16 am
content: I got a Meguro MJM-6350 CD jitter meter. It is out of cal for 4 years now, I think that is not bad for a hobby meterI kind of figured out how it works, but I need more theoretical background to evaluate the readings I get...This is how I use it (just to be clear, if I do it wrong )So I measure the RF output of the laser amplifier, with a simple scope probe (1x attenuation) connected to the jitter meter input, I set the level range, and speed on the Meguro, and got a jitter reading.-What is the difference between setting the level for 3T or 11T, as they give different readings which one is better what makes the difference?-I can select the polarity of the measurement, to measure the falling or the rising edge, again it gives different readings, which is more important?-Anyway, what is a good level of jitter for a CD 1X speed? I can toggle between 60 and 30 sigma ns (full range), I got mostly readings between 30 and 40 sigma ns, is that good, bad or avarage? What is considered very good, and what is very bad?

author: oldway
author_rank: Super Contributor
timestamp: February 19, 2014, 01:31:14 pm
content: Have a look here: perhaps some interesting books to download.http://docsfiles.com/pdf_cd_jitter.html

author: dzseki
author_rank: Frequent Contributor
timestamp: February 19, 2014, 03:06:14 pm
content: Quote from: mojo-chan on February 19, 2014, 02:05:56 pmActualy CD jitter meter monitors the the data that is directly read by the pickup, so it has nothing to do with the DAC. Of course jitter is definied around DA conversion, but this is a different jitter here.

author: Marco
author_rank: Super Contributor
timestamp: February 19, 2014, 04:00:15 pm
content: AFAICS the only thing jitter at the pick up might tell you about is problems with the motor or bearings, but your ears can do that too.I'm relatively certain that the read circuitry won't give a toss about 30 ns, it's designed to deal with signals which are steady for microseconds (and of course anything after the async FIFO won't see the jitter at all). I wouldn't be surprised if the disc would tear itself apart before you could generate enough jitter to make life hard for the read circuitry.

author: fcb
author_rank: Super Contributor
timestamp: February 20, 2014, 04:09:23 pm
content: Quote from: dannyf on February 19, 2014, 11:54:25 amMeguro are an extremely well respected company in the T&M field and this piece of kit wasn't designed as a piece of whimsy...There were probably hundreds if not a few thousand of these in factories back in the day.

author: dzseki
author_rank: Frequent Contributor
timestamp: February 21, 2014, 08:57:00 pm
content: Quote from: mojo-chan on February 21, 2014, 11:19:54 amI wasn't thinking it has anything to do with audio quality. Recentely I had a case, a guy brought a CD player that had a broken spindle wheel, but the guy said the pickup was otherwise ok. Now I had to change the whole pickup assembly yet because the spindle wheel alone is not available, but turned out after 30mins of playing the player makes mistakes on certain discs, so how do you tell the dear customer that after replacing the whole pickup the machine tends to make "reading" mistakes. That's where the jitter meter comes in to the view, as I can monitor jitter and level right after the pickup, playing the same cd when it is working good and when it makes mistakes: they are the same, so there is an other problem in the player too, I CAN proove it with this equipment, so he can't call me swindler.I was just curious if there are any hard number that are considered generally good or bad, but as I see not many of you used this type of equipment either.