Non-Smoking Man

Can a 12" tonearm do without bias adjustment?

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I read on a Tonearm manufacturer's website that you don't need a bias adjustment mechanism if the arm is 12" long, (or longer,  by extension). What do the panel think?

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Super Wammer

Any offset arm needs some bias, but the longer it is the less you need. Some people run without bias, but I wouldn't. Why set up a cartridge exactly, and then get distortion because the cantilever is deflected because of a lack of anti-skate?

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I run a very small amount on my 12" Audio Origami PU7.

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Thankyou Ian and dave - any other contributions welcome..

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The way that I look at it is that the turntable has to be perfectly level in all planes and even then a bubble level is never perfect, so the way I deal with the bias is that once the weight of the cartridge has been set I then let the arm freely bounce and if it deviates either way l then make my bias adjustment accordingly so that the arm bounces plumb and then it's often very minimal bias adjustment.

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Super Wammer
1 minute ago, p147 said:

The way that I look at it is that the turntable has to be perfectly level in all planes and even then a bubble level is never perfect, so the way I deal with the bias is that once the weight of the cartridge has been set I then let the arm freely bounce and if it deviates either way l then make my bias adjustment accordingly so that the arm bounces plumb and then it's often very minimal bias adjustment.

It's the drag of the stylus on a rotating record that creates the turning moment that anti-skate counteracts. Your technique doesn't take this into account.

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19 minutes ago, Non-Smoking Man said:

Thankyou Ian and dave - any other contributions welcome..

It is a fact of physics - and I quote from the website "Vinyl me please" Anti-skate is a process by which a degree of “counter rotational torque” is applied to the arm to center the stylus in the groove of the record. “Counter rotational torque” is a posh way of saying that a mechanism pulls against the arm as it moves inwards, nullifying the force as it moves towards the center of the record. The amount of force involved is not particularly large- rarely more than two grams of weight in total.

So regardless of the length of your arm the rotational force is the problem requiring bias control.  In order to set it totally correctly you need a test disc like HiFi Sound ...  

Not sure that anything else can be added to this .. those are the facts.

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Super Wammer

Jack, I’d be interested who asserted this.  The distortion from ‘angular error’ is reduced in the longer arm. SME claim by as much as 27% versus their shorter model.  But I’ve never heard any suggestion that antiskate requirements are eliminated. 

That said, it’s quite feasible not to use any, though not optimal.  I wish my maths was adequate to calculate the difference, but it’s not by a long chalk!

In the last few months I’ve read a long discussion elsewhere about the SAT arm. I gather its maker says it sound better as a nine incher.  Lots of happy 12” arm users didn’t agree that was even possible. 

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With a heavyweight arm and low compliance cartridge...anti-skate may not be necessary.

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Nick - SAT arm?

And the answer to your question - Temaard Audio (NZ).

Edited by Non-Smoking Man

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Morsiani eschew bias adjustment in their Unipivot design. (A well regarded tonearm.)

We are really talking medium to high effective mass here. Historically a number of the vintage 12 inchers (ortofon, EMT etc) had no bias adjustement so I suggest a rider -  do medium to high mass arms (20gms and above, say) require bias adjustment?

The theory ('facts') may indicate bias mechanisms should be necessary but I believe I read somewhere that they are 'more trouble than they are worth'. I.e, they may take away as well as add.

Edited by Non-Smoking Man

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Correction - the Morsiani CM - 1 uses magnetic bias. It's VPI who dont have a bias mechanism as such but you should twist the phono lead out wires to create the sideways force required.

There seems no way to test the bias versus no bias using the same arm. Using different arms introduces other design variables. Tenouously the Temaard does provide an opportunity as you can have their Merlin with or w/o a bias thread and weight.. but nobody has one on have they?

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Super Wammer
42 minutes ago, Non-Smoking Man said:

Nick - SAT arm?

And the answer to your question - Temaard Audio (NZ).

Thanks!  

This one...https://swedishat.com/index.html.  I think it’s about $30,000 so I’m still saving!  

Click through to his ‘white paper’ and you’ll see this (my bold):-

“Many supporters of the 12 inch arms claim that one of the benefits of a longer arm is that, as the angular offset in the alignment is lower, the skating compensation needed is lower too - they see this as a positive side effect. This is one of the most unsubstantiated claims in vinyl playback that needs to be debunked once and for all.”

Edited by Nopiano

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Any arm that has an offset will need an anti-skating force applied to it, regardless of whether it’s 9 inches or 9 feet long. It’s simple physics.

Any arm manufacturer that claims otherwise should be viewed with suspicion, IMHO.

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The skating force you are trying to counter is a function of the offset angle, tonearm length and the frictional force generated by the stylus moving through the groove. That part is just basic physics and maths. What is not so predictable is that frictional drag, which will vary with many different factors, including stylus shape, the groove modulation (i.e. the actual music being played at that point) and the vertical tracking force.

It is correct that every tonearm with angular offset will generate some skating force but it will be less the longer the arm is.

Another aspect is that different cartridges have greater or lower sensitivity to the skating force. For example ,in my experience Van den Huls and Koetsus perform better with very little anti skate. Generally low compliance cartridges are less sensitive to skating force. So as practical consequence playing a low compliance cartridge on a 12" arm may well sound perfectly ok without any anti skate. There is also less need for it with a mono cartridge.

As a point of reference Jack, my mono set up that you have heard, Miyajima Zero on an EAT3012 arm has no anti skate provision and the stereo rig with the Io Gold on a FR64S had close to zero anti skate because I was using a specially made lightweight aluminium anti skate weight rather than the FR steel one.

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