DIY Schroeder Tonearm???

[mgreene]

Ummm...

The magnets are attracting eachother in the Schroeder - or I'm far dumber than I thought I was

My understanding is that the pivot is the "string" that the arm is hanging on and the mobile magnet (in the arm) attracting the stationary magnet (on the base) keeps the pivot stable.

Mike

[fdegrove]

Hi Mike,

As I said, I didn't really look into the design.
Only problem I see is the drainage of vibrations emanating from the cartridge which is probably why the designer uses all kinds of woods.

The attracting magnets are an interesting idea though, I guess I'll have to to my homework on this.

[Paul Ebert]

Originally posted by fdegrove
Only problem I see is the drainage of vibrations emanating from the cartridge which is probably why the designer uses all kinds of woods.

I thought about this (a Schroeder clone) prior to settling on my air bearing arm. Wouldn't the vibrations simply drain via the magnetic field (i.e. heat)?

One thought that occurred to me was using rare earth magnets to stabilize a unipivot. But, that's another thing all together.

Anyway, similarly to the Ladegaard air-bearing design, this approach has the benefit of quite low cost. You don't have to commit a lot of funds to experiment.

Someday, I may give it a try.

Paul Ebert

[mgreene]

Why can't the built up vibrations escape via the pivot string to the arm pillar?

I agree that it looks cheap to try. I've started to line up some parts.

Mike

[fdegrove]

Hi,

Why can't the built up vibrations escape via the pivot string to the arm pillar?

That's about the only path there is that would provide a little drainage.

Paul,

The magnetic field won't couple vibrational energy throgh the air.
With an airbearing the pressure field of the air provides a coupling path.
I used to know all the theory behind all that stuff but it's getting rustier by the day.

I agree that it looks cheap to try. I've started to line up some parts.

Good on you Mike.
Keep us posted please.

Cheers,

[Paul Ebert]

Originally posted by fdegrove

The magnetic field won't couple vibrational energy throgh the air.

I used to know all the theory behind all that stuff but it's getting rustier by the day.

Hmm, (dusting off my antiquated physics...)

The magnetic field creates forces that act to damp the components of any vibrations that are perpendicular to the field. It does this by inducing currents, in the magnetic material - not the air, which are then converted to heat in that material (unless they are drained in an electric circuit of some sort).

So, there is an energy coupling, but it's independent of the air.

Am I missing something?

Paul Ebert

[Paul Ebert]

Originally posted by Paul Ebert

The magnetic field creates forces that act to damp the components of any vibrations that are perpendicular to the field. It does this by inducing currents, in the magnetic material - not the air, which are then converted to heat in that material (unless they are drained in an electric circuit of some sort).

Thinking about this further, I'm not saying that the magnetic field drains all, or even a majority, of the vibration. I do think that the 'string' would drain quite a bit. Perhaps the way to think about this is that the magnetic field preloads the string 'bearing', by increasing the tension on it and thereby making it a more effective energy drain. But, I do think that some energy would be converted to heat.

The main point is, however, that this may not be any less effective at draining energy away from the cartridge than a typical physical bearing. It all depends on the strength of the magnetic field and the elasticity of the string. At least that's how I see it (which could very well be wrong...).

Paul Ebert

[fdegrove]

Hi,

The magnetic field creates forces that act to damp the components of any vibrations that are perpendicular to the field. It does this by inducing currents, in the magnetic material - not the air, which are then converted to heat in that material (unless they are drained in an electric circuit of some sort).

Interesting.
Are you sure about this?
If so, any idea on how to find more technical info on the net?

Cheers,

[fdegrove]

Hi,

In case we're both in need of a refreshment course:

ERIC WEISSTEIN

Cheers,

[Paul Ebert]

Originally posted by fdegrove


Interesting.
Are you sure about this?

Yes, this is interesting stuff. I feel fairly confident about it, but it has been over 20 years since I studied it in college.

Originally posted by fdegrove

In case we're both in need of a refreshment course:

ERIC WEISSTEIN

What an amazing resource. Thanks!

Paul