LP 12 : the right torque

[yours in music]

Regarding the torque to be applied to different component of the LP12, In particular for proper vibration draining from the cartridge-arm-Keel to the plinth, I had this answer from extremephono:

With the Linn system, just make sure you use progressively more less torque moving up the mechanical path.

i.e. Cartridge bolt (higher torque ~9) > tonearm VTA screw (~8) > base screw (~7 i.e. tonearm-to-armboard screws). It makes a big difference, think about how the energy travels.

What do you think of this principle and how does it comform / reconcile with the torque vaues advocated in this forum?

From memory:
- 1Nm for an arkiv
- 1.6 for the tonearm VTA screw

[yours in music]

The unit used by extremephono is lbf/in (pound force inch).
The conversion value in Nm for the torques refered to by extremephono are:
1Nm for the cartridge
0.9Nm for the VTA screw
0.8Nm for armboard/collar interface

[lejonklou]

That's an interesting theory, but it doesn't fit very well with the values that Thomas, Paolo and I have come up with through experiments, evaluated with the Tune Method. We have calibrated our tools against eachother's and have shared values for several years. The values we find optimal and report to one another are remarkably similar.

I had never heard of anyone using a torque tool for adjusting turntables until Thomas OK told me about his work a couple of years back. Now I've seen it mentioned here and there. Using a torque tool gives you more precision, but what you accomplish depends entirely on the method of evaluation.

[ThomasOK]

I think Fredrik has stated things very clearly. I will add that I have not found this lessening of torque along the path to work at all. While the armboard screws are definitely well below the arm collar bolts, the arm height bolt is higher than any other except the bearing housing to subchassis bolts (which are much higher than any others and the Keel is slightly higher than the standard subchassis). Also note that 1.6Nm is only for certain arms with the Akito being closer to 1.4Nm and slotted pillars like the Ittok being closer to 2.6Nm! (A finding I believe Paolo made.)

One must be quite careful with the cartridge fixing bolts as the Akiva and Arkivs are the only cartridges I have found to prefer anywhere near that high a torque (a little below 1.0Nm). I believe this is due to the pressed in steel fittings. Many other cartridges would be literally destroyed by such forces, either crushing the mounting points or stripping the built in threads. Most other cartridges I have installed prefer a torque setting somewhere near .4Nm with the plastic bodied Grados and the Adikt being closer to .2Nm.

As Fredrik mentions the evaluation must be made by ear using the tune method in order to achieve worthwhile results. Screwdrivers vary from one to the next more than some of the differences we talk about so you really can't just go by the numbers - you have to adjust for your particular tool.

[k_numigl]

> less torque moving up the mechanical path

More than questionable. Think about it: Different scew sizes,
different thread angles, different contact areas,.....
By no means torque translates directly into contact force (better: pressure =
force per area), and under the given circumstances contact areas vary
greatly.
Regards, Klaus

[yours in music]

Thanks, this explanation makes sense; anyway experimentation with ears as ultimate tool seems the best