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Old 16th February 2013, 10:18 PM   #1
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Default Tangential Tonearm on Suspended Turntable?

Hi folks

I've ordered an MG-1.1 Airbearing tonearm but a couple of folk have said putting a tangential tonearm on a suspended turntable is a mistake.

If the arm is attached to the subchassis in the normal fashion then in theory the weight transfer of the arm across the turntable might affect the level of the platter and arm. If everything is set level with the arm in the centre of the record a slight weight bias to the ouside would be present at the start of play and to the inside toward the end of the record.

In practice does this make a detectable difference?

I've got a solid concrete floor and spiked stand so foot fall is not an issue.

Thanks in advance.

Steve
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Old 17th February 2013, 12:33 AM   #2
andyr is offline andyr  Australia
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Quote:
Originally Posted by Steve Luck View Post
Hi folks

I've ordered an MG-1.1 Airbearing tonearm but a couple of folk have said putting a tangential tonearm on a suspended turntable is a mistake.

If the arm is attached to the subchassis in the normal fashion then in theory the weight transfer of the arm across the turntable might affect the level of the platter and arm. If everything is set level with the arm in the centre of the record a slight weight bias to the ouside would be present at the start of play and to the inside toward the end of the record.

In practice does this make a detectable difference?

I've got a solid concrete floor and spiked stand so foot fall is not an issue.

Thanks in advance.

Steve
It would help if you mentioned what suspended TT you have, Steve - some are set up differently to others and the fact you mention above may affect some suspended TTs less than others.

The degree to which this effect occurs also depends on the weight of the tonearm assembly and the weight of the slide.

I toyed with the idea of putting a "Terminator" on my LP12 but decided against it, for precisely the reason you stated. So I am modifying my Linn so it can take a 12" UP, instead!


Regards,

Andy
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Old 17th February 2013, 01:20 AM   #3
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Sytemdek IIX at the moment but i'm considering trading it in future or just upgrading it. Origin live motor or maybe a Pro-ject speed box. Just looking at all the options but if the tonearm isnt going to work on suspended turntables i'll have too look at solid plinth types.

I've seen the MG-1.1 fitted to Oracles, Systemdek, and an LP12 but no reports of how the owners got on.

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Old 17th February 2013, 01:27 AM   #4
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You can measure the deflection... a lot depends on the stiffness of the suspension and the mass of the TT. A high mass TT isn't going to deflect very much as the arm moves, because the mass is insignificant compared to the TT, so the springs (etc) don't move.

A dial caliper will do the trick, they're pretty inexpensive today. I get digital ones that cost only 10$USD.

Another solution is to solid mount the TT and buy some dynamic air suspension/isolation pods, the type that are used for optical benches. Once you do that, you can add mass to the base or put the whole thing on a high mass slab so that the traversing mass of the arm is quite meaningless, plus you get much more isolation for the TT.

Another possibility, since ur on a concrete floor is to change out the suspension for some rubber pucks, that will still give isolation (not as much as a spring, but good at mid and HF) and since ur on concrete there isn't going to be any <20Hz stuff from the floor moving as there would be in most situations - and that's what the soft suspensions are trying to work to get rid of...
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Last edited by bear; 17th February 2013 at 01:31 AM.
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Old 17th February 2013, 06:03 AM   #5
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Quote:
Originally Posted by Steve Luck View Post

I've got a solid concrete floor and spiked stand so foot fall is not an issue.
Great floor for a turntable. I have a MG-1 mounted on a heavy plinth Lenco and it works great. I have the standard and Ultra P arms for it. I stuck the compressor in basement and ran the air tube through wall. A push lock bulkhead fitting mounted in a phone/internet wall plate connects to expansion tank/filter then to arm.

Prior I had rigid tables with dual pivot arms. My rack sits on a suspended wood floor, and foot falls would disturb the tracking. So I got a Gingko isolation base, works great. Jump up and down, pound on rack, no skips. I put the Lenco with MG-1 on it. If the isolation base moves in the same direction as arm tube, I get skips as the arm tube slides in and out of arm. I'm thinking that could be another reason why some folks might say a MG-1 on a suspended table is not a good idea. If the suspension moves it could cause the same problem as my isolation base.
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Old 17th February 2013, 04:27 PM   #6
AVWERK is offline AVWERK  United States
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All good advice. One way to check any TT for movement while playing music without test equipment is to attach a small light weight laser pointer to the plinth and point it to the longest dimension of your room and just watch

You might have to build a stand off tree out of balsa for those tables that have no access to the plinth. In that case, you might hot glue one to the underside area of the plinth.

Having 3 different TT,s currently using tangently tracking arms, you want to stay away from closely spaced small spring designs like the linn, AR, Systemdeck, etc. And favor wide spaced serious designs like Basis, vpi TNT, Oracle, SOTA. With enough foam around the springs you could make one work however, slightly compromising the design of course.

I think I read somewhere the VPI TNT was made because of the tangent air arms.
The laser method will tell you alot about whats going on in stability for all TT/tonearm configurations

Regards
David
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Old 19th February 2013, 05:10 AM   #7
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Laser pointer is a great idea to check out the movment of a turntable. Dial gauge isn't bad either.
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Old 19th February 2013, 06:32 AM   #8
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Quote:
Originally Posted by Steve Luck View Post
Hi folks

I've ordered an MG-1.1 Airbearing tonearm but a couple of folk have said putting a tangential tonearm on a suspended turntable is a mistake.

If the arm is attached to the subchassis in the normal fashion then in theory the weight transfer of the arm across the turntable might affect the level of the platter and arm. If everything is set level with the arm in the centre of the record a slight weight bias to the ouside would be present at the start of play and to the inside toward the end of the record.

In practice does this make a detectable difference?

I've got a solid concrete floor and spiked stand so foot fall is not an issue.

Thanks in advance.

Steve

first linear tracking arm I ever heard was a Souther mounted on an LP12. It was Lou Souther himself wo did the demo which I still remember like it was yesterday. Lou had an LP which was the most warped think I had ever seen anybody attempt to play. If that was not bad enough he had drilled a hole 3/8' off center. So Lou hold this disk up with a twinkle in his eye and asks me if I thought that my current rig could play it. I look at him and smiling almost laughing said no and neither will yours. Lou just smiled back and I realized I had just made a fool of myself. He put the disk on the Linn and to my amazement the cartridge stays in the grove and it dances around. then Lou says lets have a listen. Well it played and no it did not sound good but it did not sound bad. So Lou takes that disk off and without touching a thing (so you know he di not have it rigged just for the demo) puts a flat one on and I heard music like I never did before. I own a Cantus tone arm by Bo Hanson (late) of Rauna of Sweden. Bo was Lou's first importer int Sweden and three years after designed his own version of a linear arm to deal with what he felt were short comings of Lou's design.
So yes a linear can work very well with a suspended table. In his later years Lou sold his designs to and did further design for Clear Audio in Germany who later went on to steal Bo's design though the did not copy it well they do a very fancy version of it at about $15,000.00 called the statement.
I had many lengthy discussions with Bo about linear's and I agree with him that a mechanical contact is important for arms and for main bearings. Hope this is of some interest. Best regards Moray James.




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Old 19th February 2013, 06:45 AM   #9
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My dual pivot arm had trouble with this LP. Not the MG-1 though.

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Old 19th February 2013, 10:33 PM   #10
AVWERK is offline AVWERK  United States
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Steve
You need the laser beam to act as a multiplying "lever" at a distance to increase sensitivity for movement.
I have Starret and other dial indicators and although I haven't tried them as you suggest, me thinks the slight tenson to compress the shaft might work against what your trying to observe.
It's worth a try I suppose.

Regards
David
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