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Old 12th November 2009, 09:36 PM   #1
dobias is offline dobias  United States
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Default Lead Weights

Why hasn't there been any discussion about adding lead weights to turntable platters & plinths?
It seems it would be a reasonable alternative to making a heavy plinth by stacking plywood.
I have a belt drive Rek-O-Kut N-33H. I'm planning to add weights to the platter perimeter inside the rim. I'll also add lead weights to the bottom of the 15 3/4 x 15 3/4 inch steel mounting plate with double sided adhesive tape.
While polishing the rim of the platter I learned first hand how badly the aluminum platter can ring. I'm sure the steel mounting plate could ring as well.
I'll soon know if lead weights do what I hope they will.
Along with the lead, to stop any vibration, I've purchased a 12 x 12 x 1/8 inch piece of 40 durometer Sorbethane to set on top of the platter. Since it's so soft, I may have to keep the original rubber mat on top of it.
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Old 13th November 2009, 11:46 PM   #2
AVWERK is offline AVWERK  United States
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Lead is great stuff.

I used lead shot and 2 part epoxy to fill a machined groove under my acrylic platter.
It weighs 14 pounds and most of that weight is at the perimeter where you want it.

All of this is useless unless you rebalance the platter. You will make matters much worse if you don't.

There is a night and day difference in how your turntable will sound if you ignore this.

When was the last time you noticed balancing holes under your platter? Few do it and most others don't.
Even if you don't add lead, balancing your platter will transform your sound.
Most noticable on slow piano decay's. You should be able to hear more clearly the decay bounce off the recording venue walls.

Regards
David
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Old 14th November 2009, 05:48 AM   #3
kffern is offline kffern  Australia
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Quote:
Originally Posted by AVWERK View Post
Lead is great stuff.

All of this is useless unless you rebalance the platter. You will make matters much worse if you don't.
Is there a method to check or re-balance a platter?
The small lead weights used on motorbike wheels come to mind.
Kffern
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Old 14th November 2009, 12:42 PM   #4
dobias is offline dobias  United States
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David,
Thank you for the response.
I'm well aware of the necessity of balancing. In my former life I balanced countless items of large & small industrial equipment.
My platter is already well balanced & if I add lead it will
undergo further balancing.
Assuming all balancing is performed, what effects did you see with
added perimeter weighting? Did it noticeably improve smoothness? Did
it also help reduce the platter ringing?
Frank
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Old 14th November 2009, 01:02 PM   #5
dobias is offline dobias  United States
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Default balancing

kffern,
Assuming a lack of dynamic vibration analysis equipment, static balancing is much slower but just as good.
First, after securing the tonearm, I'd drain the spindle oil & temporarily replace it with a small amount of light sewing machine oil to reduce drag to a minimum.
At this point, the belt or idler pulley should be out of the way. I assume direct drive TT's don't have any brakes involved if they're turned off.
Prop the turntable up about 75-80 degrees on it's side.
Manually spin the platter & mark where the lowest point is when it stops moving. Repeat to confirm the heavy spot.
Either add a small amount of weight to the uppermost part of the platter, or remove some of the platter material from the heavy part at the bottom.
Repeat until there is no consistancy to any indicated heavy spot after spinning.
Replace the original oil of choice & the belt. Level the TT.
Enjoy.
Frank
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Old 14th November 2009, 07:12 PM   #6
AVWERK is offline AVWERK  United States
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Location: So Calif.
KF

You can make a knife edge balance rig.

If you think of a tuning fork with 2 blades on each end (Stanley utility knife blades) with your platter placed vertical inside the 2 arms.

The blades are attached to the ends of the "tuning fork" so
the spindle rides on top of the blade edges (horizontal and level)

Any weight diference will cause the platter to rotate on the blade edges. dobais's way is for gross weight differences and not quite sensitive enough since the oil now is not as effective since the platter weight has pushed the oil away and is laying on the bushing causing more stiction. I have tried this way also.
Try the knife edge for the best alternative that a diyer can build.

The arms can be made of anything stable, hard wood, aluminum, steel, whatever, and a way to attach the blades on the end. Real easy actually

Dobias

The last couple of sentences(first post) explains how you can hear the changes plus theres a sense of ease and musical flow that I will not babble on about.

Regards
David
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Old 14th November 2009, 11:45 PM   #7
dobias is offline dobias  United States
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Join Date: Jun 2007
Red face knife edges

David,
I agree that knife edges are the best way if they are very level. If I visualize your method correctly, I've used that method with motorcycle wheels between two saw horses.
Setting one up for a platter having a one sided shaft could be more than a little daunting for the average handyman (me included).
Frank
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