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Upgrade for users of 1/2" mylar belt

This thread will be of interest to Galibier, Redpoint and Teres belt drive TT owners, or anyone using or thinking of using a drive belt made from 1/2" mylar. The belt material of choice on these tables for several years has been the silver holographic mylar streamers from sources linked on the Teres and Galibier websites. This outperforms everything else we've tried but like anything it's not perfect - and we've now found something better.

One of the silver holographic mylar's assets can also become a liability. That metallic layer, when new, gives the belt exceptional "grip" on the platter and motor capstan. Minimal slippage on transients is one reason the material works so well. Unfortunately, that layer can wear over time, leaving a silvery gray residue and allowing performance to deteriorate. The only solution has been a good cleaning and a new belt. No big deal, but if there was a better or more stable belt Paul and I wanted to find it.

I'll spare you a recounting of our many experiments and jump to the good news: thanks to (yet another) brainstorm by my resident genius/partner, we've developed a belt that both performs better and lasts longer. I've held off posting until we were sure, but after 4 months of steady use Paul’s idea is still working perfectly. The only negative is that making this new belt takes an hour or more of work spread over two days, but to us it's worth the effort.

HOW TO MAKE ONE

1. Cut a length of the silver holographic mylar tape sufficient for your TT, plus 3-4" extra.

2. Remove the silver metallic coating off the backside of the mylar. Paul used an acid etching cream popular with stained glass hobbyists to dissolve the metal - safe, quick and easy (use skin and eye protection).

3. Rinse thoroughly under running water, inspect to make sure you got all the silver off, wipe and hang to dry overnight.

4. Splice as normal to make a TT belt, making sure you tape on the OUTSIDE (which will be smoother than the now bare inside).

5. As always, the best splicing technique is to overlap the ends and cut on a 30-40 degree angle. Apply 1” video splicing tape (*not* tabs) across the belt at the *same* angle and trim away the excess.


WHY IT PERFORMS BETTER

Unlike any plain mylar ribbon you could easily buy, the silver holographic streamer has an ultra fine texture embossed on the back side of the *mylar* during manufacturing (*before* the metallic backing is applied). Once the silver layer is applied you can't see this texture, but that's what diffracts light like a million tiny prisms to produce the shimmery rainbow effect. Stripping the metal backing away exposes this texture, which becomes the contact surface of your new belt.

Paul realized this texture must exist and then hypothesized that using it for the working side of a TT belt might provide more “grip” on the platter rim and motor capstan than either plain mylar (which is extremely smooth) or the metallic backing. He was right. This belt produces more lifelike dynamics, both macro- and micro-, than even a brand new silver holographic belt - which heretofore was the best.

WHY IT LASTS LONGER

Removing the metallic backing exposes bare mylar, which is much sturdier than that fine layer of metal. Under normal use and assuming no accidents, one of these belts should last many, many months, perhaps years, while delivering consistent performance. Ours is going into its fifth month with few visible and no audible signs of wear.

Different motor capstan materials might interact with this belt differently, but I urge anyone with a compatible table to give this a try. Like all our favorite little tweaks, we'd find it hard to go back.

A FEW TIPS

1. Clean any silver/grey residue from your old belt off the motor capstan and platter before mounting the new belt.

2. As many of us have learned, the more inelastic the belt, the more critical motor leveling becomes. That is truer than ever with this new belt. Getting the motor set just right is touchy. Take care that your new belt is riding level in the center of the capstan before you start to play. You don't want it sliding up or down and mangling itself.

3. Motor distancing is also more critical than ever. Since this belt will not slip *or* stretch, tension must be perfect. The right amount is just shy of the tension that would tilt the motor off its feet.

4. Depending on your climate, the belt can build up static potential during use. Not enough to spark, but more than enough to attract airborne dust. I dust the belt's inside with my CF brush after each side before stopping the platter.

5. With this or any belt, always start your platter spinning with a helping push. Just pressing the motor's ON button creates lots of belt-wearing friction as the rapidly spinning motor tries to drag that heavy platter up to speed.

It all sounds like a pain, and it is! But the sonic and longevity results are worth the effort.

Cheers,
Doug
dougdeacon
dgarretson
2,598 posts
 
Doug,

I've acquired a spare VPI 300RPM delrin motor pulley to machine flat in order to compare 1/2" tape to the custom thread/pulley drivetrain on my modded VPI TNT. I have a lathe, but I suppose I would need to devise a special cutting tool to make a convex surface. Do you feel a convex surface is really necessary, assuming that guide lips have been added at the outer edges to keep the tape from wandering?

Also, one thing I've noticed with my thread drive arrangement, is that frequent retensioning is necessary as the thread stretches. You can really hear liveliness & bass improve after minor retensioning. Does tape drive stretch constantly and require similar maintenance?

I've had bad luck with completely inelastic materials such as braided Stren fish line. I believe a certain amount of elasticity is necessary to "spring-load" tension into the drive system. With zero elasticity fish line, the line needs to pulled as tight as piano wire to obtain grip(at which point it rings), and even then fails to grip well due to excessive slipperiness of the coated synthetic material.

So I suppose the optimal drive belt material should have some inherent friction, a bit of elasticity, and enough physical integrity not to break down and stretch to the point that it looses its elasticity. I can always hear the improvement of switching to a new thread. I assume this is because the old thread has given up its elasticity.

Finally to the matter of batteries. I've been using large 12V SLA batteries to power the VPI AC motor through Mark Kelly's AC-1 drive controller. The same Enersys Odyssey and Optimas Yellow Tops are used to power CDP and other line-stage components in my system. I've noticed quite of bit of improvement with very low-impedance batteries, and even more improvement after adding huge amounts of filtering capacitance. If you examine internal resistance specs for SLA batteries, you'll find that only the really large (and expensive) >50AH deep-cycle batteries like the ones above achieve impedance <3 milliohms. Whether these differences can be heard in your application is unknown, but perhaps worth a try.

Dave
frank_sm
112 posts
 
Thanks Doug, I made a couple of belts yesterday and used the 1/2" splicing tape since that's what I ordered. I think it will hold just fine. It's a lot stronger than the silver splices I was using. Thanks for your continued support!
dougdeacon OP
3,338 posts
 
Dave,

That seems like a great idea! Good out of the box thinking.

Do you feel a convex surface is really necessary, assuming that guide lips have been added at the outer edges to keep the tape from wandering?
I've never tried, maybe Thom or Chris Brady would know from the early days of the Teres development group.

It's worth a try, right? Worst case: you mangle a $.25 belt. Best case: you discover that the greater contact surface provides more traction (a thought that's occured to me, though we haven't tried it). Give it a try, you can always machine to convex later, right?

Also, one thing I've noticed with my thread drive arrangement, is that frequent retensioning is necessary as the thread stretches. You can really hear liveliness & bass improve after minor retensioning.
No doubt about it, fully agree.

Does tape drive stretch constantly and require similar maintenance?
Never. Motor positioning and levelling are critical and may need an occasional reset, but that's all. Mylar won't stretch under the loads we're applying. I've gone months without adjusting anything in the drive system, though last week the cat nudged the motor in the middle of the night. Grrr!

The problem with your non-stretch fish line isn't that it's non-stretch. The problem is that it's too fine in cross section to have enough grip on the motor pulley. Introducing elasticity might ameliorate that, but you'd be substituting one vice for another.

So I suppose the optimal drive belt material should have some inherent friction, a bit of elasticity, and enough physical integrity not to break down and stretch to the point that it looses its elasticity.
Yes, no and yes, at least IME. And that's the whole point of this tweak. The texture on the back of the holographic mylar is exposed by removing the silver layer. There's your friction. No elasticity, so no damage to musical transients. No break down either, mylar is a very stable material.

I've noticed quite of bit of improvement with very low-impedance batteries
That's been our experience too. Paul chose the battery we're using for precisely that characteristic. Yours might be even better of course. :-)

---

Comment to Galibier users:

Several of you noted that, unlike our setup, you don't need to tension the belt to the motor pod's near-tipping point. Makes perfect sense. A Galibier motor pod is notably heavier than ours and also more squat in shape, so the feet are more spread out. It would take a lot more force to tip your motor than ours, probably too much and possibly risking the life of your motor bearings.
dan_ed
2,451 posts
 
Thanks for confirming that, Doug, about the motor pod differences. That is the conclusion I reached based on what I remember your Teres motor pod to look like.

With the Galibier motor I find that if I go real tight with the belt it will almost immediately climb the capstan. So I start there and gently relax belt tension until the belt no longer climbs. That seems to be about the best tension.

And thanks for mentioning about the dust picked up by the belt. I neglected to brush the belt between plays for 3 or 4 sides. When I brushed the inside of the belt on the 5 side I was startled at how much immediacy came back. Maybe Paul's next breakthrough should be a way to eliminate or minimize the static buildup. ;-)
dgarretson
2,598 posts
 
Doug, I have not yet laid hands on mylar tape, but I find it difficult to believe this material has no elasticity or even approaches the inelasticity of braided fishline. If you hold a 50" length of mylar in your hands(typical length of a TT belt), you're saying it has zero stretch when pulled at the ends? I'm not criticizing mylar, but merely exploring the point that some elasticity is inevitable and perhaps even desireable.
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