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Old 26th December 2005, 07:27 PM   #61
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Hello kevinkr,

Quote:
I think the mass of your turntable is so great that small variations in load due to tracing forces will be so heavily integrated that your motor will never seem them..
Kinda the point of the exercise Actually, the tracing losses do need to be put back into the rotational energy...eventually. For all practical purposes, I do not expect to actually "hear" the speed drag due to any heavy passage (that would have to be one heck of a album to drag down my platter).

Casey
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Old 26th December 2005, 07:38 PM   #62
kevinkr is offline kevinkr  United States
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Quote:
Originally posted by valveitude
Hello kevinkr,



Kinda the point of the exercise Actually, the tracing losses do need to be put back into the rotational energy...eventually. For all practical purposes, I do not expect to actually "hear" the speed drag due to any heavy passage (that would have to be one heck of a album to drag down my platter).

Casey
Quite true, any energy lost has to be returned to the system, provided the overall energy lost is a small percentage of the energy stored in the system there shouldn't be any discernable change in speed during heavily modulated passages..

I had a Pink Triangle turntable which used a badly botched implementation of the technics belt drive motor and their own electronics, speed was not even stable from the beginning of the record to the end, and heavily modulated passages resulted in a very discernable reduction in pitch. Needless to say I hated it, and got rid of it very quickly. The above was true both with the original motor and electronics and the replacement electronics from PT. I tried to locate an old SL-23 to cannabalize the control electronics from, but this was pre-internet, pre- eBay and I was unsuccessful.
I finally sold it to a fellow in the UK who was able to get it upgraded with the latest drive electronics and seemed happy with it.
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Old 27th December 2005, 04:37 AM   #63
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kevinklr,

Quote:
provided the overall energy lost is a small percentage of the energy stored in the system there shouldn't be any discernable change in speed during heavily modulated passages.
A couple grams drag, at most, vs. a 25+ lb. flywheel...I know where I 'll be putting my money

Quote:
but this was pre-internet, pre- eBay
I shudder when I think about what this hobby was like "back in the day". I think the Internet is the biggest advance for our fetish we've seen.

Casey
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Old 27th December 2005, 11:26 AM   #64
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Quote:
Originally posted by valveitude
I think the Internet is the biggest advance for our fetish we've seen.
I think you'll find that the internet has been the biggest advance for
a lot of fetishes.
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Old 4th January 2006, 04:39 AM   #65
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I had a long weekend, which can only mean 1 thing…turntable progress. There are a lot of pictures in this post, so it may take awhile to load, if like me, you’re stuck on dial-up.

First order of business was finishing the bottom plinth profile. After grinding the last one, I really wasn’t looking forward to it. This time around though it wasn’t so bad, pre-cutting with the router saved a lot of time. In order to match up the profiles, I clamped the plinths together while grinding…

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…which enabled me to get a close match…

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… you can see that the metal in the bottom plinth has a lot of flaws, I was going to leave it exposed, like the top plinth, but covering it will look better. Next I drilled small pilot holes through both plinths, while clamped together, where I intended to mount the feet. I then cut holes with a hole saw in the bottom plinth…

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…I then fabricated some bottom covers out of Corian to cover the hole, and provide a mounting point for the bottom feet. Once mounted to the plinth, I glued threaded studs to the discs while a nut was screwed down with a shoulder washer to ensure the studs were square…

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…up to this point, everything took about as long to do as was expected…that changed.
I don’t normally post a “step-by-step” description of the work done, but in this I will case (well..kinda, its still compressed) in order to show how much effort went into the “feet”. First I cut off a piece of brass stock, and mount it on the lathe…

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…then its squared up with a couple of rough cuts, and a clearance hole is drilled…

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….then a start hole is bored to ensure the tap drill-bit drills true center, then the hole is sized for the thread tap with a 29/64’s bit…

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…then a 9/16’s shoulder is bored…

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…a ½-20 thread tap is ran through. This was the biggest PITA… you scrape brass, not cut it. A tap cuts..much fun ensued…

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…I then glued a slug of drill-rod into the shoulder hole…

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…next up was the most time consuming step. The cutting properties of brass and drill-rod couldn’t be any more different. I had to find a cutting tool that could do both. I found a small carbide tipped boring bar filled the bill..it cut the drill rod, and scraped the brass, but I could only cut .01” a pass…

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…once the point was cut, I sized, and polished the foot…

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..and cut to length…

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… between 2-3 hours (depending on breaks)after picking up the brass, I have a foot…

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…repeat as necessary…

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Once all the feet were mounted, I filled up the cavities in the bottom plinth with lead shot…

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…and covered the shot with discs that had holes with a profile that match the feet (60 deg.)…

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…I then ran a bead of RTV silicone between the discs and the plinth, and sat the top plinth on them. After tapping it around to get the two plinths aligned, I put the bearing and platter on. It has been left to cure overnight…

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Note the points on the bottom plinth have dug in around ¼” into the bench top…I think I will be making some discs for these feet as well.

After this run, I’m pretty sore, but I can’t help but smile at the progress.

Casey
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Old 4th January 2006, 02:47 PM   #66
DaveM is offline DaveM  United States
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That is awesome. You keep making me wish I had the time to be doing this myself. Too many projects, too little time.

Keep up the good work.

DaveM
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Old 4th January 2006, 05:39 PM   #67
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nah....
it's ugly !

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Old 4th January 2006, 06:35 PM   #68
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Hello DaveM

Quote:
That is awesome. You keep making me wish I had the time to be doing this myself. Too many projects, too little time.
Thanx. I wish I the time to do this . The sad truth is, if I had an accurate prediction of the work involved, I probably would have resigned it to the "someday" pile, and spent the energy elsewhere...good thing I didn't. I feel that this will most likely be my last TT, and I plan to be enjoying it a long time after the memory of the labor fades .

Hello choky,

Quote:
it's ugly !
...and yet, not
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Old 4th January 2006, 08:55 PM   #69
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I'm suffering a bit from "paralysis thru analysis" regarding the platter surface (mat). It is my understanding that a direct coupling is the sonic choice, hence my planning on using a "mat" cut out of a record laminated to the top surface.

I have been having second thoughts on this, and can't help but feeling I would manage to embed some crud into the grooves of the clamped record.

So the question...what are my options here ? I don't want to de-couple the record (the goal of virtually all commercial offerings), and I want enough "give" that if I miss a speck of dust, it will push into the mat, and not the album. This sounds like two mutually exclusive properties to me...thoughts ?
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Old 4th January 2006, 11:03 PM   #70
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just a thought-
top platter (or mat,in this case) for EMT927 and EMT930 in "everyday" version is made from plexi with scarf (hehe-franch hats material) on top;

but-"measuring" or "etalon" mat (made original in EMT factory) for these two workhorses is made from pure glass.

I see several times on net that some biggest EMT fans sayed that this sort of mat is ultimative and best solution ,at least for EMT.

anyway- EMT927 is Al chassis with Al base platter,EMT930 is bakelite chassis with Al platter.......

just for record ......

btw-did I say that I like exactly that sort of uglyness?
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