[AliG]

To all vinyl lovers,
   I have a simple question that I always wanted to ask but I always forgot about it. I recall during RMAF06 I went inside a big showroom housing a big Kharma speakers and there's a gorgeous looking turntable (must be at least $20,000++). I noticed however that when a record was spinned, the platter "wobbled" quite a bit - the record spinned like a wave..
 
   I recently paid a visit to a friend's house and he has a turntable and the platter "wobbles" a little too, but he said it wouldn't matter.

  So the question is, does this wobbling thingy really doesn't matter??


Thanks
barry

 

[twitch54]

If the Platter "wobbles" you bet it matters ! There's obviously something wrong, I can't say what the min. runout specs should be but from what you described something is not right. Problems of tracking, rumble, wow & flutter, etc are for sure present.

[TheChairGuy]

Barry,

A LOT of belt drive turntable makers are home-spun affairs - each piece is lovingly crafted on someone's bench, without benefit of precision tooling.  There is certainly both positives and substantial negatives to hand made, rather than machine made.

As is the case with my VPI HW-19 Mk. III.  It's made of some kind of rubber, lead & cork sandwich....a thick affair and heavy at over 12 lbs  Mind you, among belt drive makers, VPI is a BIG company in comparison to many...so my platter may be more machine made than hand-made, even 

When you look at it from the side view spinning around it looks like it's bobbing up and down (drives me insane looking at it - the impreciseness of it).  When you put a record on it it would appear that it would be bobbing up and down, too.  As the record is black, and thin, it's hard to really know by peering at it.

Fact is, it seems to just be optical illusion.  The underside (cork) of the platter was not made with as much care as the top, and is thus uneven in places.  While spinning, it looks like it's wobbling, or bobbing.  In fact at the platter surface, it's quite level  ....so long as the entire deck has been leveled with a bubble device.

Leveling, particularly with torque-challenged belt drive affairs (and paramount with suspended belt drive decks) is very important.  In fact, I'd have to rate leveling a belt drive deck a far more important geometry to get right than more talked about VTA for cartridges.

John

[lcrim]

An off center hole in arecord can appear to the eye as a "wobble" also.  Your eye can play tricks.
If the platter bearings are loose, its obvious that this could cause mistracking and could mess up the vinyl surface.  IMO, whatever the cause, if its bad enough to cause mistracking then you must figure out what's causing it and correct it.  If you can't hear a problem then its probably not a problem.  In your example, it would seem that you only noticed this on one LP, if it happens on all then there's too much play in the bearing and stop playing and get it resolved.

[BobM]

When I originally installed my VPI MK III platter I also saw a wobble. Most noticeable by looking at the bottom of the platter edge as it is spinning and judging the distance between that and the plinth. I called VPI and they said, take the platter off the spindle and rotate it 1/4 turn. Then re-seat it again and look again. Keep doing this bit by bit until the wobble disappears.

Apparently the milling of the hole is not always perfect, but with a little adjustment it can be seated correctly to reduce the wobble.

As for the original question, it sounds like a precision problem between your bearing shaft and the bearing housing. Then again, there are TT's that are made this way, namely the Well Tempered. They use the belt tension to pull the platter straight, so check the belt tension also and see if that makes a difference.

Enjoy,
Bob

[Vinyl-Addict]

Since I am in the business of making platters, mainly acrylic, I can say that it is a challenge to machine a platter with perfect concentricity and runout even using the correct process. There are several contributing factors, material type being one. Acrylic must be machined on all surfaces, otherwise there will be "wobble" guaranteed.
If you've ever measured the thickness of an acrylic blank (using a micrometer of course ) used to make a platter you will find the difference in thickness and parallelism quite large from one end to the other.
If you only machine the bore and O.D. the platter will wobble noticably up & down with every rotation.
To minimize or eliminate this, machine the top and bottom.

Multi-layer platters are much more complex. You must go to extreme levels of precision to build these types of platters. Taking shortcuts will only lead to failure. As has been noted, using cork or sorbothane or any other non precision materials will create their own set of challenges.

One last thing, the bearing hub, the portion of the bearing where the platter actually rests must be absolutely perpendicular and concentric (perfect cylindricity) with the axis of rotation to eliminate "wobble", then of course the platter must be made using the correct process. Make sense?

[twitch54]

Understood....thus the big $$$ "HW" charges for his "Super Platter" !!

[doug s.]

Barry,

A LOT of belt drive turntable makers are home-spun affairs - each piece is lovingly crafted on someone's bench, without benefit of precision tooling.  There is certainly both positives and substantial negatives to hand made, rather than machine made....

if your home brew deck wobbles, it's cuz ya didn't use a genuine harley-davidson shovelhead intake walve w/matching walve-guide!   




(courtesy of the altmann diy turntable site):
http://www.altmann.haan.de/turntable/

doug s.

[twitch54]

That is just "Too Cool "  !!!!

[Wayner]

As far as platter wobbling goes for VPI owners, the center spindle is removable and there is a  method to reinstalling the spindle to make it perpendicular to the platter surface, using the threaded platter clamp as the guide. It may take several attempts to get it to eyeball flat, but once you get the feel of it, you will eventally get an acceptable install. Mine has only the slightest wobble which I'm guessing if I had a dial indicator for checking surfaces would be around .005-.010 of an inch. Turning those dimensions into VTA is a very tiny plus or minus from 20 degree standard. Obviously, the greater the warble, the more wow and flutter applied to the LP, so it is somewhat important to get this problem resolved.

An off-center hole in the vinyl usually produces a flutter in speed detection as the records grooves have taken on a "cam action" where the speed of travel is in a constant flux of acceleration and deceleration, making the sound of a slipping belt or something of that nature.

I have noticed that if some LPs are warped and if the warp is gradual enough that it is almost inaudible in its nature, although watching the tonearm bob up and down is never an easy feeling. At the top of the warp, the stylus is wanting to leave the groove and at the bottom of the warp, it trys to eat it. Damn gravity and inertia.