4th Oct 2022, 11:02 am | #41 |
Nonode
Join Date: Jun 2013
Location: Surbiton, SW London, UK.
Posts: 2,801
|
Re: Demagnetizing CD's !!
As high frequency electromagnetic fields only form on the surface, it might be best to
demagnetize CDs in the microwave oven. This might also work with MiniDisc, providing the disc does not have the sliding metal cover. |
4th Oct 2022, 11:11 am | #42 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,947
|
Re: Demagnetizing CD's !!
Just in case the more literal minded are tempted to try this, you should *not* attempt to microwave a CD. There are plenty of Youtube videos showing people doing this - at the very least it destroys the CD, and it can wreck the microwave itself or even start a fire.
|
4th Oct 2022, 11:59 am | #43 |
Octode
Join Date: Jul 2011
Location: Staffordshire Moorlands, UK.
Posts: 1,477
|
Re: Demagnetizing CD's !!
I had always assumed that the IQ of the average forum user here was greater than that of a turnip - Paul's need to post (above) makes me realise that perhaps I am naive!
Steve.
__________________
Those who lack imagination cannot imagine what is lacking... |
4th Oct 2022, 12:33 pm | #44 |
Nonode
Join Date: Jun 2013
Location: Surbiton, SW London, UK.
Posts: 2,801
|
Re: Demagnetizing CD's !!
Sorry, I should have qualified it "with the timer set to 2 seconds" as I don't wish to
encourage any fires. Some years back I loaned out a basic "microwave leakage detector" (diode and edgewise meter) and it was returned with the meter pointer vapourised. The user did not realised it was meant to check the leakage outside the over door ! |
4th Oct 2022, 1:19 pm | #45 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,947
|
Re: Demagnetizing CD's !!
This is a public forum, and you don't need to be a member to access posts. People come to posts as a result of random Google searches, and often read them out of context or without an appreciation of the forum culture. We don't want to encourage halfwits to burn their houses down
|
4th Oct 2022, 2:50 pm | #46 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,876
|
Re: Demagnetizing CD's !!
I believe that the CD and microwave experiment was once carried out on television by a certain Mr Clarkson, whose engineering nous has been repeatedly shown (also on television) to be not too dissimilar to the aforementioned turnip.
David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
4th Oct 2022, 2:58 pm | #47 |
Dekatron
Join Date: Jan 2006
Location: Ramsbottom (Nr Bury) Lancs or Bexhill (Nr Hastings) Sussex.
Posts: 5,817
|
Re: Demagnetizing CD's !!
I'm staying away from magnetic fields and CD's but it makes me think about Eric Laithwaite and the Mag Trains [as demonstrated on yesterday's Look At Life film-on TPTV yesterday The coding info given here is very interesting [even if I don't really understand it-probably a turnip]
Further to cleaning CD's and DVD's [just to get them to play, not be "super enhanced" post 38*] All sorts of things have been recommended in the past eg toothpaste/metal polish and stranger suggestions, usually with a slightly abrasive action and worse [not as a Hi Fi product of course]. I've found methylated spirit applied fairly vigorously usually helps or at least if it doesn't nothing else will Not being very good at repair and maintenance I find that my CD and DVD machines now have to be treated with even more as they age. Strangely a bit like Steam Engines which have to be coaxed into action even though they might have been fully restored]. Discs seem to respond better with a meths when there a fault reported. Even if that clears electronically I still do a clean before returning the disc. Going back to the lack of digital awareness [mentioned by Paul Sherwin] I recall using VHS tape for audio at one point when I realised how superior the audio spec had become on VCR's. Is it possible that some unaware individuals have associated the magnetically based Video Cassette with digital media. Unlikely but possible I suppose! I think that, overall, audio recorded on CD or DVD is already of a pretty extraordinary quality [compared with a few decades ago] Leaving out the "Vinyl is always better view" everything is subjective in the end really. Dave W Last edited by dave walsh; 4th Oct 2022 at 3:17 pm. |
4th Oct 2022, 3:05 pm | #48 | |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,876
|
Re: Demagnetizing CD's !!
Quote:
So it can best correct scratches oriented radially. Scratches following the direction of reading destroy too much of the redundant coding population and correction performance is a lot poorer. By the time a radial scratch (or the famous drilled hole) comes around again, the decoder has built up a reserve of good data to allow the missing bits to be reconstructed. Some of the tricks played in the coding and error correction processes of the CD are quite impressive. For recording data, much more capable error correction is employed as the use of the output data is considered to be more fragile in terms of uncorrected errors. So the amount of redundancy coded into the data put on the disc is larger than the audio CD. This is why a data disc has lower capacity than you'd expect from the specs of the audio disc. David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
|
4th Oct 2022, 7:29 pm | #49 |
Nonode
Join Date: Jun 2008
Location: Coningsby, Lincolnshire, UK.
Posts: 2,819
|
Re: Demagnetizing CD's !!
So has anyone tried magnetising a CD yet?
|
4th Oct 2022, 8:04 pm | #50 |
Nonode
Join Date: Dec 2012
Location: Kirk Michael, Isle of Man
Posts: 2,350
|
Re: Demagnetizing CD's !!
A radial scratch is obviously shorter than a circumferential one, hence the latter being much worse.
I seem to remember there was a length (a mm or so) that could be recovered. More than that, you put your fingers in your ears. What the width of those radial marks Philips demonstrated would have been less than the correctable length. Les. |
4th Oct 2022, 8:08 pm | #51 |
Heptode
Join Date: Dec 2020
Location: Swaffham, Norfolk, UK.
Posts: 586
|
Re: Demagnetizing CD's !!
|
4th Oct 2022, 8:41 pm | #52 |
Nonode
Join Date: Jan 2016
Location: Stafford, Staffs. UK.
Posts: 2,532
|
Re: Demagnetizing CD's !!
I wonder if any of the 'phools, have considered the laser assembly? I have come across issues where a deck would appear to have failed because it was no longer able to read the (data) DVDs it was designed to, but was still happy to read CDs with similar data on. In fact it was such a well known issue that the test was for a failed drive, to try a CD. If it worked when the DVD didn't a laser replacement was a fix. Allegedly it was down to the damping fluid in the lens focus assy that thickened up. I don't know how true, but certainly I have such a drive that exhibited the failure, and a new laser fixed.
Could we sell some specially modified, demagnetised damping fluid? |
4th Oct 2022, 8:44 pm | #53 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,947
|
Re: Demagnetizing CD's !!
CDs and DVDs use different lasers. It's possible for one to fail while the other is OK.
|
4th Oct 2022, 10:53 pm | #54 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,876
|
Re: Demagnetizing CD's !!
Combining CDs, Magnetism and the mention of Eric Laithwaite. I used to have a Sony CDP302ES and one of the bullet points on its marketing brag-sheet was that the laser was moved across the deck by a linear motor.....
Hmm, there are quite strong magnets in the CD drive to do this, whatever sort of motor, and if CDs are susceptible to magnetisation... Oh dear! David David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
5th Oct 2022, 8:18 am | #55 |
Heptode
Join Date: Nov 2008
Location: Stockport, Cheshire, UK.
Posts: 712
|
Re: Demagnetizing CD's !!
lf you fancy a laugh then look at posh hi-fi interconnects.
Now l realise that better speaker cable can make a difference but there is a point at which there is no more to be gained. Not according to the cable manufacturers, who make all sorts of claims about their cables. lt's the prices that are shocking. One company sells a 1.5m mains lead for £30,000 Won't reach? No problem, the 5m one is £50,000 And £100 for a fuse. Apparently you'll get better blacks on your LED TV if you fit this fuse in the plug |
5th Oct 2022, 8:43 am | #56 |
Octode
Join Date: Sep 2020
Location: Thetford, Norfolk, UK.
Posts: 1,741
|
Re: Demagnetizing CD's !!
At risk of going OT, wonder if you can buy a £700 aerial for your DAB portable that improves the bit rate of the transmission?
|
5th Oct 2022, 9:19 am | #57 | |
Dekatron
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,984
|
Re: Demagnetizing CD's !!
Quote:
As I've said before, any audio product that uses the word "quantum" is by definition snake oil. Craig
__________________
Doomed for a certain term to walk the night |
|
5th Oct 2022, 10:05 am | #58 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,947
|
Re: Demagnetizing CD's !!
Can we stay on CDs in this thread please. Some OT posts have been trimmed.
|
5th Oct 2022, 12:13 pm | #59 |
Nonode
Join Date: Oct 2008
Location: Warsaw, Poland and Cambridge, UK
Posts: 2,677
|
Re: Demagnetizing CD's !!
I feel pretty well aware of how CD error correction works, but have noticed an interesting failure mode in the past. Back in the days when we used to record music on to CD-Rs, I found a couple which I'd recorded which had started to fail after a few years. When played on a standard domestic CD player they played without skipping or jumping (presumably because the 'track' is permanently written to the CD-R at time of manufacture) but the audio sounded like a weak FM radio station, with very noticeable white noise in the background. I never had chance to investigate further but am curious to this day about what was going on in the player's error correction circuits!
Chris
__________________
What's going on in the workshop? http://martin-jones.com/ |
5th Oct 2022, 12:16 pm | #60 |
Heptode
Join Date: Nov 2008
Location: Stockport, Cheshire, UK.
Posts: 712
|
Re: Demagnetizing CD's !!
l was always aware that CD was a digital medium but the sound you get from a CD player is obviously dependent upon the processing circuitry, l've had CD players that sound harsh (a bit like Windows Media Player)
And others that sound lovely, with a warmer sound more like vinyl. |