Casey -
god damm it ....we have to pay for the privalage of slipping around on ice over here - it's called the 'Winter wonderland' skating park. Case, where on earth were your ice-skates dude ??!!!!??
Ok, so this is where you're at. Well, isn't it about time you have someone throw you an arm together, and then you can evaluate the sound of what you've done so far ?? I mean, look....all ur good for is sitting on your bruised pride and spinnin' yourself a couple-a-dozen discs for goodness sakes !
Then, when you've done further modifications you'll be able to have 'before- an-after' references.
I bet it sounds frikkin' awsome already !!!!!!!!!!
Come on......
the suspence is killin' me
god damm it ....we have to pay for the privalage of slipping around on ice over here - it's called the 'Winter wonderland' skating park. Case, where on earth were your ice-skates dude ??!!!!??
Ok, so this is where you're at. Well, isn't it about time you have someone throw you an arm together, and then you can evaluate the sound of what you've done so far ?? I mean, look....all ur good for is sitting on your bruised pride and spinnin' yourself a couple-a-dozen discs for goodness sakes !
Then, when you've done further modifications you'll be able to have 'before- an-after' references.
I bet it sounds frikkin' awsome already !!!!!!!!!!
Come on......
the suspence is killin' me
Guys,
Thanx for the well wishes.
Jess-
When I first started the project over a decade ago, A) cheap imports hadn't hit our shores yet, and all the heads I could find were over a grand, and B) I was naive as to the work involved (looked simple in theory). Had I to do it again today, I would certainly buy one.
I hadn't noticed the variation until I cut the strobe pattern (I know I should have, but didn't). It hasn't seemed to throw it out of balance much though...probably due to the massive size. I have been racking my brain trying to figure out a method to balance the thing. Anyone have any suggestions?
EC8010-
You don't know how happy I am to hear that. I've been telling everyone I know that the "easy access" of having the thing on your hip, isn't worth the potential damage.
Please do..I have about 13 more hole circles that need drilled
-Casey
Thanx for the well wishes.
Jess-
When I first started the project over a decade ago, A) cheap imports hadn't hit our shores yet, and all the heads I could find were over a grand, and B) I was naive as to the work involved (looked simple in theory). Had I to do it again today, I would certainly buy one.
I hadn't noticed the variation until I cut the strobe pattern (I know I should have, but didn't). It hasn't seemed to throw it out of balance much though...probably due to the massive size. I have been racking my brain trying to figure out a method to balance the thing. Anyone have any suggestions?
EC8010-
You don't know how happy I am to hear that. I've been telling everyone I know that the "easy access" of having the thing on your hip, isn't worth the potential damage.
Please do..I have about 13 more hole circles that need drilled
-Casey
Can anyone explain the mechanism by which an out of balance platter causes speed variations? It seems to me that the speed variation must be caused by a variation in either friction or load, but I don't understand how a constant extra weight on one side of the platter generates a varying load or varying friction. Is it because of interaction with a spring suspension? Does it have the same effect with a rigid suspension?
Oh cry me a river Mr. Oracle Delphi...you'll manage
-Casey
err, that's Mr Oracle Delphi "MkIII" if you don't mind !
Heh heh ...Ok....but I paid up the wonga for that deck mate (2nd hand, of course!)
But that TT of yours is gonna sound sooo good on account of all your hard work, AND the pleasure that will be all yours from making it-
I might have the Oracle...but you have your own creation & I am envious in that respect !!!
L8R dude.
James-
Interesting..I may be able to adapt this...Thanx.
Sheldon-
Would it be correct to say that..
1) The ratio of imbalance to total mass
2) The clearance of the spindle bearing
3) The rigidity (diameter) of the spindle
...would be the factors of how susceptable to an imbalance a platter would be?
I haven't balanced mine (I assume it's off a few grams anyway), but when I really whip it around, I can't feel any vibration in the plinth you would expect to feel if it were a real problem.
-Casey
Interesting..I may be able to adapt this...Thanx.
Sheldon-
Would it be correct to say that..
1) The ratio of imbalance to total mass
2) The clearance of the spindle bearing
3) The rigidity (diameter) of the spindle
...would be the factors of how susceptable to an imbalance a platter would be?
I haven't balanced mine (I assume it's off a few grams anyway), but when I really whip it around, I can't feel any vibration in the plinth you would expect to feel if it were a real problem.
-Casey
Well, casey, there is the static balance mode, then there is the dynamic balance mode...
Start with static balance, just suspend the platter on its spindle on a pair of LEVEL knife-edges (machinist's knife edges - straight) and give it a very gentle push to start rotation. The point where is settles (the bottom point) is the heavy side of the platter. Then, stick a couple grams of mastic (whatever is easily removed, but will stay in place - even play-dough works) on the high side and let it spin a rotation. If the mastic winds up on the bottom, then there's too much of it. If it stayed at the top, too little. You keep playing with adding and removing the mastic until the platter spins through a whole rotation without swinging past a point and back again - i.e. no heavy point. With patience, you can get it to within +/- 0.25g, which is pretty darn good and may well be good enough. The WOW function of the Wow and Flutter meter will be able to tell you if you need to go to from there to the Dynamic balancing stage or not.
The problem with an out-of-balance platter is that the weight difference is not a constant extra weight on one side of the platter - it rotates as the platter spins. The result is the transmission of kinetic energy into the spindle, bearing, suspension, plinth, etc... This energy has to go somewhere, so it resonates throughout the turntable and most often comes back to the platter. Believe me, it can be heard very clearly. If you want to prove it to yourself, scotch-tape a coin to the rim of your platter and play a record.
Actually, Sheldon, it will in any table that uses an elastic drive belt (most of 'em). The imbalance rythmically loads the belt and will amplify the effect even more
Jess
JesseG said:Actually, Sheldon, it will in any table that uses an elastic drive belt (most of 'em). The imbalance rythmically loads the belt and will amplify the effect even more
Jess
It's only a pedantic issue at this point, but I'd bet that it's not rotational speed variation per se, but more likely an orbital motion that is the issue.
Sheldon
Jess-
It'll probably take a while before the red hand print on my forehead fades from my slapping it when I read this..I thought "Of course!!". I had been spending all this time visualizing somthing on bearings, or between centers. This would work much better.
I'm thinking some hacksaw blades embedded in blocks, and ground with my setup I used to true up my pulley shaft, would work great. I ordered this expandable arbor to mount the platter on for the cutting of the strobe pattern. I will have to turn a collar for the small end so the O.D. matches the big end, then it would be perfect to "roll" the platter on the blades.
Excellent...thanks Jess
-Casey
It'll probably take a while before the red hand print on my forehead fades from my slapping it when I read this..I thought "Of course!!". I had been spending all this time visualizing somthing on bearings, or between centers. This would work much better.
I'm thinking some hacksaw blades embedded in blocks, and ground with my setup I used to true up my pulley shaft, would work great. I ordered this expandable arbor to mount the platter on for the cutting of the strobe pattern. I will have to turn a collar for the small end so the O.D. matches the big end, then it would be perfect to "roll" the platter on the blades.
Excellent...thanks Jess
-Casey
I decided to try an experiment. If a coin would demonstrate the effect, then something that weighs about a pound should demonstrate it big time, yes?
Something like a 1 pound roll of solder?
An externally hosted image should be here but it was not working when we last tested it.
So there's a problem. It sounds the same with or without the weight. I don't hear any change in the sound of the TT itself, when I put the weight on. I don't hear anything different on the lead-in. And I don't hear anything different when the music is playing. Also, I can't see any speed variation on the strobe bars. This is a belt drive TT. I built it from parts that I salvaged from one of those mass produced plastic turntables, can't remember the brand. Anyway.. it contains nothing special.
So.. huh?
I would imagine that most of the problem with unbalanced platters ic caused by the platter not being level. Then, the motor has to drive the weith 'uphill', and then it accelerates uphill, with the wow at approx. 0.5 Hz. (frequency of rotation).
If the platter is level, the only thing that will happen is that the bearing will have to provide a centripetal force. If the bearing is not won evenly (like a well-used bearing on a belt drive TT), this will cause a change in the friction in the bearing, at the same frequency.
James
If the platter is level, the only thing that will happen is that the bearing will have to provide a centripetal force. If the bearing is not won evenly (like a well-used bearing on a belt drive TT), this will cause a change in the friction in the bearing, at the same frequency.
James
Also, if the plinth is flexible, the tonearm geometry will change as the loading on the plinth changes. This will also cause a change in speed. So a good bearing, level platter and a solid plinth should sort it out.
However, an off-balance platter will kill the bearing much more quickly than an in- balance one.
James
However, an off-balance platter will kill the bearing much more quickly than an in- balance one.
James
It would seem that an imbalance in the platter, in of itself, isn't audible. However, it shows up any deviation from ideal, such as James has pointed out, ie, degree of levelness, and bearing wear. I would also suggest the condition of the belt, It's been my experience that an older rubber belt isn't as elastic as it should be.
That would explain why I couldn't detect any symptoms of imalance on my setup..it surely is imbalanced. If for no other reason than bearing life, I will balance it. I also suspect a reduction of overall bearing friction, as the spindle rides center in it's bushing, rather than "walking" around it.
-Casey
That would explain why I couldn't detect any symptoms of imalance on my setup..it surely is imbalanced. If for no other reason than bearing life, I will balance it. I also suspect a reduction of overall bearing friction, as the spindle rides center in it's bushing, rather than "walking" around it.
-Casey
From Pixpop
Thanks Pixpop - I love it when people experiment
As James and Casey have observed, the issue of bearing wear, elasticity of the belt and the levelness of the platter have some bearing on the matter. But, here's where my original assertion comes from:
Some years ago, I acquired a Wow & Flutter meter and, of course, I couldn't wait to try it out. Being a turntable freak, I had several to play with and wanted to get some emperical measurements of rim-drive vs belt-drive vs direct drive.
It all started because the audiophiles of the day alleged that direct-drive tabels didn't sound good because of the motor pole pulses imparted into the platter. I thought horse-droppings - the dd engineers couldn't possibly have made a mistage like that.
So, I got a Pioneer PL-51 table and put the WF meter on it - sure enough, the wow was in the region of 1.6-2.1% I was stunned. I took a look at the platter - an aliminum casting which, when held loosely by the rim and struck made a marvellous bell.
Then a friend told me about Duct Seal - a heavy mastic material used by furnace tech and plumbers to seal the cracks in ducting. I bought a pound and started spreading the stuff on the underside of the platter. After applying about half a pound of duct seal, striking the platter produced a dull thud - much better from a resonance point of view. Back on the table and measuring and guess what! the WOW had climbed to 3.5% And, the sound was clouded and muddy. I thought the duct seal treatment was a failure. The friend suggested that maybe the platter was no longer balanced. I popped it off and put a pin trhu it on a pair of knife edges and it swung to bottom so quickly it almost spun all the way 'round!
Fortunately, duct seal is easy to move (and remove) so after some redistribution, the platter was at least staticly balanced and back on the table it went. This time, the meter measured 0.01 - 0.03%. AND, the music was crisp, detailed and light as air - all this with no change at all in cartridge, tonearm or setup.
So, that is my adventure with balancing turntable platters and why I say that it can be easily heard when it is not balanced.
That's my story and I'm stickin' to it!
Thanks Pixpop - I love it when people experiment
As James and Casey have observed, the issue of bearing wear, elasticity of the belt and the levelness of the platter have some bearing on the matter. But, here's where my original assertion comes from:
Some years ago, I acquired a Wow & Flutter meter and, of course, I couldn't wait to try it out. Being a turntable freak, I had several to play with and wanted to get some emperical measurements of rim-drive vs belt-drive vs direct drive.
It all started because the audiophiles of the day alleged that direct-drive tabels didn't sound good because of the motor pole pulses imparted into the platter. I thought horse-droppings - the dd engineers couldn't possibly have made a mistage like that.
So, I got a Pioneer PL-51 table and put the WF meter on it - sure enough, the wow was in the region of 1.6-2.1% I was stunned. I took a look at the platter - an aliminum casting which, when held loosely by the rim and struck made a marvellous bell.
Then a friend told me about Duct Seal - a heavy mastic material used by furnace tech and plumbers to seal the cracks in ducting. I bought a pound and started spreading the stuff on the underside of the platter. After applying about half a pound of duct seal, striking the platter produced a dull thud - much better from a resonance point of view. Back on the table and measuring and guess what! the WOW had climbed to 3.5% And, the sound was clouded and muddy. I thought the duct seal treatment was a failure. The friend suggested that maybe the platter was no longer balanced. I popped it off and put a pin trhu it on a pair of knife edges and it swung to bottom so quickly it almost spun all the way 'round!
Fortunately, duct seal is easy to move (and remove) so after some redistribution, the platter was at least staticly balanced and back on the table it went. This time, the meter measured 0.01 - 0.03%. AND, the music was crisp, detailed and light as air - all this with no change at all in cartridge, tonearm or setup.
So, that is my adventure with balancing turntable platters and why I say that it can be easily heard when it is not balanced.
That's my story and I'm stickin' to it!
pixpop said:
I decided to try an experiment...
Something like a 1 pound roll of solder?
So there's a problem. It sounds the same with or without the weight. I don't hear any change in the sound of the TT itself, when I put the weight on. I don't hear anything different on the lead-in. And I don't hear anything different when the music is playing. Also, I can't see any speed variation on the strobe bars. This is a belt drive TT. I built it from parts that I salvaged from one of those mass produced plastic turntables, can't remember the brand. Anyway.. it contains nothing special.
So.. huh?
Hi Pixpop !
What kinda music were you listening to when doing your trial ?
I think that its accepted that piano is really suseptable to the detection of 'wow&Flutter' on a turntable. I've detected this myself...and it's always clear when the piano notes kick in !
-A-
I'm sure a suspension would compound the problem, but the PL-51 that Jess is talking about has ( I believe) a rigid mount as well. I think a better possible explanation as to why it was more pronounced on his table has to do with a drive coil imbalance. Unless every pole of the DD motor had it's driver transistor(s) matched (very unlikely in a mass produced Japanese mid-fi table), the speed would fluctuate relative to the strength of the field coil the heavy side was over at any given time.
The fact that your speed didn't change (according to your strobe) with the weight of the solder roll added is a testament to your motors speed control. Having a weight like that on one side of your spindle, it has surely cantilevered over so that it is hitting one side at the top of the bushing, and the opposite side on the bottom. This additional drag would swamp any “wow” forces you may be generating with the weight.
Good on you for not accepting blindly that balance is all that important (I'm sure that just “how important” depends on the table), but I believe the orbital forces generated from an out of balance platter couldn't be a good thing. It could manifest itself in any number of ways, and for me, after busting my hump ridding my table of motor noise, I won't knowingly let any energy back in..I'll be balancing my platter.
-Casey
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