The Null Tester - Page 1
Forum section: electronics / general

author: Shock
author_rank: Super Contributor
timestamp: February 01, 2019, 10:56:49 pm
content: Not a lot been posted about null testing, anyone test their Audio or Test Equipment cables? Whats your technique to A-B?

author: German_EE
author_rank: Super Contributor
timestamp: February 02, 2019, 09:59:48 am
content: At audio frequencies I can't see this being a problem and I've never tested for it, I'm also unlikely to do so.At RF frequencies this can be an issue, especially if you are working with I Q signals where the 90 degree phase difference must be preserved. There's also stuff like LVDS where one signal is the inverse of the other so in theory they should null each other out if summed together.Edit, a couple of extra points after watching the video for a second time:1 Having to adjust the null after changing a cable is not a problem. If a cable made a true difference to the audio signal then the depth of the null would be lower and he would have been unable to totally eliminate the test signal.2 I suspect (although I cannot prove) that this video was made so that he can sell his testers. I hope he makes his fortune because, if nothing else, he has destroyed the myth of 'directional' audio cables

author: Shock
author_rank: Super Contributor
timestamp: February 04, 2019, 11:32:54 pm
content: Quote from: German_EE on February 02, 2019, 09:59:48 amEven if he is wanting to promote his tester I still think it's a noble cause. There is going to be plenty of people holding onto the dream regardless, but it's a good educational video to get people back to science rather than just repeating what "the other guy said".The last audio sin I committed was going to the electrical wholesalers to get some flex power cable to wire a speaker cabinet up. It's bright orange and looks great, can also be repurposed later as an extension cable and all the electrons will be perfectly aligned from all that fine audio.

author: Electro Detective
author_rank: Super Contributor
timestamp: February 04, 2019, 11:57:20 pm
content: A bigger sin you didn't use welder flex for those speaker cabsThese cables can be re-purposed to tie up and flog Audiophools with,when their BS degenerates into sheer audio untruths and sonic blasphemy

author: stj
author_rank: Super Contributor
timestamp: February 05, 2019, 11:23:16 am
content: i used to use the orange flex for pro speakers on a mobile sound system.some guy said something once about some crap - audio phool related.i asked him, what's the average bass frequency - he said about 40Hz.then i asked the frequency of mains, he said 50Hz.then i said, so what's the problem??? - HE SAID NOTHING, JUST LOOKED AT ME LIKE HE WANTED ME DEAD!

author: German_EE
author_rank: Super Contributor
timestamp: February 05, 2019, 06:31:13 pm
content: For years I used to wire up 'large' speakers (bigger than 100W) with 40A shower cable and fit massive spade terminals at each end. I never got any complaints apart from those who wanted them in black (all power cables were either gray or white on the outside).

author: Shock
author_rank: Super Contributor
timestamp: February 06, 2019, 11:30:28 am
content: Shit just got real hehehe, gloves are off. This needed to happen years ago. Been so many crooks in audio over the last 40 years. Add this to output power rating shenanigans that seem to still exist and exaggerating download speeds.

author: Shock
author_rank: Super Contributor
timestamp: February 06, 2019, 11:44:05 am
content: I remember having a conversation over output tube biasing and distortion with someone and groaning, their method was to just use their ears because ultimately it came down to listening what sounded best.I said well I agree a listening test is important, but if you are keeping an amp within original operational spec wouldn't you at least want to know that it is running according to how the amp was manufactured and at least eliminate potential performance issues you cannot possibly discern with your ears.Anyway to this day they are probably still cooking the tubes of every amp they touch.

author: Electro Detective
author_rank: Super Contributor
timestamp: February 08, 2019, 12:35:09 am
content: There is NO WAY the other dude will dare accept Mr. Winer's challengeA public trashing like that will be bad news for any audiophool vendor or halfway styled (some facts/physics mixed with BS) audiophool businessNull tests, with the nulled result played through loudspeakers, is the final judge, jury, and executioner in audio challengesIf no one can hear it, there is no audible difference !No analyser displays required, even though nice to watch the proceedingsi.e. time for audiophools to break out their platinum coated harmonic enhanced shovels with noise cancelling, pure oxygen free, graphite compostite handles,and bury the BS

author: German_EE
author_rank: Super Contributor
timestamp: February 08, 2019, 06:01:19 pm
content: Let@s think about this for a moment, if you wanted to test everything in an audio signal (or maybe compare it to a reference) then what would you test? Here's my list:Amplitude over 3 x audio rangePhase difference over 3 x audio rangeBackground noise levelTHD or maybe an intermodulation distortion measurementTransient response using a fast pulseIf two amplifiers are identical after testing that lot then I doubt that the human ear can hear a difference, or should we add another test to the list?

author: Shock
author_rank: Super Contributor
timestamp: February 08, 2019, 06:40:48 pm
content: No expert, but you would probably have to do the initial transient response, steady state and decay over a range of signals to profile the amps response.

author: RandallMcRee
author_rank: Frequent Contributor
timestamp: February 08, 2019, 07:25:09 pm
content: The listed tests are quite insufficient.Remember you have two ears and a left and right channel. To get a convincing stereo (not to mention 5.1 + channels) you need to have matching preamplifier and amplifiers. So a bunch of tests to make sure they are matching.Then, when left is loud, right may need to be soft, socrosstalkmust be measured.Its not all about distortion at all. Of course, the speakers are where most of the bad stuff happens.

author: Shock
author_rank: Super Contributor
timestamp: February 08, 2019, 08:36:09 pm
content: Quote from: RandallMcRee on February 08, 2019, 07:25:09 pmWait a sec I need to do a litmus test, do you own a record player and collection of records?

author: RandallMcRee
author_rank: Frequent Contributor
timestamp: February 10, 2019, 06:22:06 pm
content: QuoteUmm, I did once--all gone now, sold for good money to the collectors out there.Just for reference, I've built every single thing in the signal chain including speakers (the drivers themselves). So, I did learn some stuff from experience.My last project was a direct drive turntable with a self-designed motor and magnetic bearing. I listened to my whole collection for the last time and then sold it off.

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: February 11, 2019, 07:01:08 pm
content: Quote from: German_EE on February 05, 2019, 06:31:13 pmHow comes? All the rubber ones are black. Such as H07RN-F (NSSHÖU) in former times.

author: stj
author_rank: Super Contributor
timestamp: February 11, 2019, 11:46:42 pm
content: it's all BS anyway in the end,listening to some model with no voice cleaned up with "AutoTune" and treaked on a recording desk and eventually terminating in imperfect ears!!