MagLev Plattenspieler - Page 1
Forum section: electronics / general

author: MT
author_rank: Super Contributor
timestamp: December 26, 2019, 06:32:51 pm
content: 30 years to late perhaps yet pretty neat!

author: VK3DRB
author_rank: Super Contributor
timestamp: December 27, 2019, 12:21:15 am
content: Yes, seems to be well made and quite innovative.But it costs $3,834 on special.https://www.apollohifi.com.au/catalogsearch/result/?q=mag+lev+audio&cat=0If there is money to be made selling these, they will have to compete with clones soon enough. But my guess is they won't sell many as demand will be low.The wow and flutter is quoted as <0.17%. I wonder if the caveat is when there is no breeze like when someone wants to use it at the next pool party or BBQ.

author: coppice
author_rank: Super Contributor
timestamp: December 27, 2019, 12:33:10 am
content: I can't remember who made them, but soon after direct drive turntables started to appear, someone introduced a levitated turntable like this. It didn't raise the turntable by a huge amount, like the one in the video, but you could clearly see under it.

author: Brumby
author_rank: Unknown
timestamp: December 27, 2019, 01:59:47 am
content: I absolutely love the idea - but the stability is an issue for me. I would prefer something that has locked position - such as you get with superconducting materials.Clearly the height of clearance is an overstatement and intended for someone who simply wants to show off. Any real benefits would be achievable at much lower altitudes. Still, if someone gave me one, I'd find somewhere to put it.

author: Nusa
author_rank: Super Contributor
timestamp: December 27, 2019, 02:48:42 am
content: Magnetic levitation turntables have been around for a few decades -- just not in the budget of the ordinary person. Here's a La Plantine Verdier turntable at the heart of this audiophiles system.

author: BrianHG
author_rank: Super Contributor
timestamp: December 27, 2019, 02:58:10 am
content: What horrible junk, with that VLF wobbly wave bouncing around as it spins.Also, even if the platter didn't wobble, without such countermeasures in the chassis, the tone arm's point at the rear would still receive up and down vibrations through the chassis.

author: BravoV
author_rank: Super Contributor
timestamp: December 27, 2019, 04:56:02 am
content: Simple noob question, just curious how the mechanism of the floating table, suppressed the vibration generated by the speakers through air wave, especially when playing loud music ?

author: Cyberdragon
author_rank: Super Contributor
timestamp: December 27, 2019, 05:40:58 am
content: These things have been debunked here before for being pretty mediocre (there was some fancy kickstarter or something). They are hard to start up and keep stable.

author: Gyro
author_rank: Super Contributor
timestamp: December 27, 2019, 03:32:25 pm
content: Quote from: coppice on December 27, 2019, 12:33:10 amI can't remember either, but I do remember there were two variations on the theme - both using opposing ferrite ring magnets around the centre spindle bearing.One actually kept the platter elevated slightly - rather frowned upon by most of the HiFi press at the time because it vertically decoupled the platter from the arm base. The other simply used the magnets to take some of the loading off the thrust bearing, thus allowing a heavier platter.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 27, 2019, 06:08:42 pm
content: Quote from: BravoV on December 27, 2019, 04:56:02 amDepending on how much feedback is used in the levitation control loop, the system can work like a relatively soft spring. So if the pattern is heavy enough it can dampen vibrations from the ground. However things like supply ripple and noise from the regulation (e.g. light effecting optical position detectors) can come in.Against loud music directly effecting the pic-up it needs the cover.Anyway this is something for the optics, not for the sound. It is nice looking, but with no special benefit for the sound.

author: coppice
author_rank: Super Contributor
timestamp: December 27, 2019, 06:15:29 pm
content: Quote from: BravoV on December 27, 2019, 04:56:02 amIt was a gimmick. It eliminated rumble from the bearings, but for every other aspect of reproduction it was worse.

author: German_EE
author_rank: Super Contributor
timestamp: December 28, 2019, 11:02:26 am
content: The only problem is that I either sold or gave away my record collection thirty years ago when the CD came out. This therefore gets filed in the 'looks good but it's useless to me' section.

author: tooki
author_rank: Super Contributor
timestamp: December 30, 2019, 12:10:30 pm
content: Quote from: coppice on December 27, 2019, 06:15:29 pmWould an oiled bushing not work? I'd think that'd be very good at eliminating bearing rumble. AFAIK oiled brass bushings are what tape capstans use, which need to be extremely stable.If anything, I'd think one could use maglev to levitate the entire turntable, so that both the platter and tone arm are decoupled from the floor. Not that I think it'd be likely to perform better than other solutions.

author: BravoV
author_rank: Super Contributor
timestamp: December 30, 2019, 12:57:03 pm
content: Quote from: tooki on December 30, 2019, 12:10:30 pmSo the next job would be tuning the whole floating thingy to have self resonance frequency "way-way" beyond 20-20kHz ?

author: wraper
author_rank: Unknown
timestamp: December 30, 2019, 01:08:55 pm
content: Since tonearm is not floating, it's just marketing gimmick. Also it's not stable at all on the video, so excessive wow and flutter distortion is almost guaranteed.

author: Jeroen3
author_rank: Super Contributor
timestamp: December 30, 2019, 01:58:26 pm
content: Of course it is not better. But it looks like magic.

author: Gyro
author_rank: Super Contributor
timestamp: December 30, 2019, 02:19:09 pm
content: Quote from: tooki on December 30, 2019, 12:10:30 pmIndeed, oiled bushings work extremely well in turntable bearings. Unfortunately the rumble comes from the vertical component, and it's the thrust bearing that is the most difficult to engineer.The Linn LP12 used to use a hardened point, bearing on an extremely hard thrust plate. Many turntables use a single ball bearing at the bottom of the bore, bearing on the hardened end of the spindle. All of these run the thrust bearing in an oil bath, but wear still occurs, leading to rumble as the contact area grows. Other designs use PTFE pads, but I remember these being unpopular in the hifi press due to their 'flexibility' (the aim being to make the coupling between the platter and arm base as 'rigid' as possible), but a good low noise option.Worst of all were the old Garrard turntables like the SP25, which had a full thrust race at the bottom of the spindle. This would quickly wear the thrust washers, causing considerable rumble as the balls grumbled around at low speed.As I mentioned previously, the best use of magnetic levitation was opposing permanent ring magnets to supportmostof the vertical load, considerably reducing load and wear on the thrust bearing. Even then, the magnets needed to be well centred to prevent cyclic speed variations (wow).These days, some form of fluid dynamic bearing (as HDDs) might be possible, although the very low rotation speed would be a design challenge.