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SME V arm: dynamic VTF or straight weight

I am using an SME V arm and wonder if anyone has compared the sound using the dynamic VTF (i.e. setting the dial to 2.0g) versus setting the dial to 0.0g and simply using the counterweight and an accurate scale to set VTF at 2.0g. Is there a sonic difference and what is the theory behind one versus the other?

I would think that using the latter method moves the counterweight closer to the arm's pivot point and effects how the bearing is loaded and possibly also the moment of enertia of the arm.

I have briefly tried to hear a difference, but couldn't and plan to do a more controlled comparison. Anyone's own experience would be appreciated. Thanks.

Peter
peterayer
jea48
4,446 posts
 
I am using an SME V arm and wonder if anyone has compared the sound using the dynamic VTF (i.e. setting the dial to 2.0g) versus setting the dial to 0.0g and simply using the counterweight and an accurate scale to set VTF at 2.0g. Is there a sonic difference and what is the theory behind one versus the other?

I assume the arm uses a spring for the VTF. With the dial set at 0.0g isn't the spring stretched out and more likely to vibrate? I would think you would want to set the dial to the maximum VTF and then use the counterweight to set the VTF. At least that is the way it is done on Rega arms with the VTF spring, when using the Heavy Weight counterweight.
Dynamic balance graduated vertical tracking force (VTF) control applies 0-3g x 0.125g through resonance controlled spring.
http://www.sme.ltd.uk/content/Series-V-1330.shtml
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peterayer OP
1,382 posts
 
The other difference between the two SME 12" arms is that the 312S has a detachable headshell for easy cartridge swapping and azimuth adjustment while the V-12 has a fixed headshell for greater rigidity. I don't know if this difference is audible per se, but the possiblilty of adjusting azimuth is certainly a benefit.
albertporter's avatar
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albertporter
4,949 posts
 
Jea48, interesting idea. I've read somewhere that best results with SME is splitting the difference. In other words, apply half the track force with spring and half with weight.

If I had one here I would do the experiment. My 312S has no spring so no choice with it.

The flaw I see with the new SME V-12 is the non detachable head shell does not provide for azimuth adjustment of the cartridge. I don't know if I can give that up to achieve the (supposedly) extra rigidity.
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rauliruegas
13,086 posts
 
Dear Peter: IMHO and due to my V and IV experiences the cartridge that you mount in the V performs better if the V is working in full static way where the " springs " are totally by-passed ( it does not make sense to " split ". ), in the static balanced way the spring can't resonate/vibrate and can't affect the cartridge quality performance.

Regards and enjoy the music.
Raul.
peterayer OP
1,382 posts
 
I have read that the spring is damped so it should not vibrate much anyway. But Jea48 raises an interesting question. I had assumed that the spring would be compressed, not streched out at the 0.0g setting. I wonder which is which. I have set my dial to 0.0 and will listen for a few days and than switch back and report if I notice any improvement. My PC-1 is on the heavier side, so the counterweight does move significantly in toward the arm's pivot point now that it is balanced statically. And that must be better for the arm's enertia, even if it isn't audible.
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