Torsional vibration; Gimballed vs Unipivot

[James D]

Hi Jerry,

Actually the softer pivot points sound better The Morsiani uses a gramphone needle - this has a rounded point and is relatively soft. A knitting needle sounded better than a darning neddle that I tried...

I still have my 774 arm. It is the best gymbol arm that I have heard and it's awful when the damping is used... I have never heard a competant arm that sounds better with silicon damping. When it has improved the arms performance it has always been because something else wasn't set correctly or was just plain badly designed... Never add damping to tonearm - it just kills the sound...

Unipivots are great and aren't difficult to make. There are some rules to follow and reading the linked articules will give a good guidelines for building one.

Neal,

Thanks! Not sure why I linked the thumbnail!!!

James

[Greg.]

Hi James,

OK, so a knitting needle sounds better than a darning needle. Have you tried crochet and all the others? Then of course should we try a double knit in preference to one of those really chunky ones? I can see I'm going to need to research this very secretly. If I shared this with my other half, the men in white coats would probably shortly after arrive at the front door to remove me, kicking and screaming my sanity, yet never ever again free to drop a stylus into a groove. We need to keep this one quiet chaps; it could be the end for us all

Best wishes,

Greg

[Clive]

Doesn't a crochet needle have a hook at its end?

edited to make my posting readable!

[JerryT]

James

I prefer my Mission arm without damping, but others don't.

I'm intrigued as to why a 'soft' point should sound better then a hard one. I'll leave others to hypothesise. It seems counterintuitive to me, but I'll think some more!

Jerry

[Greg.]

Hi Clive,

Well yes, a crochet needle has a hook at one end, but the other end is a point. It's an education thing. I just hope that we don't end up knowing more about knitting than we do about unipivots

Best wishes,

Greg

[Clive]

Hi Greg,

Quite frankly I'm relieved that you know more about knitting than I do. It's not something I want to be educated about!

Cheers,

Clive

[James D]

Soft points verses hard points for unipivots is a relative thing... both are hard really but it seems that resonance control in the system is better with the softer points - this suggests to me that its an energy bandnpass or band stop effect that is the desired outcome at the pivot. this is inline with Mark's thoughts about torsional vibration control (I think!) and also partially explains why the Schroeder gets such good reviews.

James

James

[IslandPink]

Interesting links.

Some are amazingly simple ( the altman one for example ) and could be knocked-up pretty quickly . I couldn't see all of the links , here , due to the internet police, but will try to access the others in a few days when my new home computer is working .

I didn't see any of them with outriggers , like the Graham models. It seems to me, that one of the best ways to give better resistance to the 'twisting' torsional mode ( and maybe thereby improve bass ) is to have extra mass out sideways on outriggers , coming out from the pivot housing . This way you avoid having to sling the main counterweight too low, and the lateral eff. mass ( but not the vertical eff. mass ) is increased . It seems to me you're aiming to get the resonance freq of this torsional mode to be well below the audio band ?

Any pitfalls on geometry that cause limits on how you distribute the mass ? -
I imagine there are ways you can end up with bad results or cantilever damage if you try some weird set-ups ?

Must get some ebony and knitting needles, then .

Mark

[James D]

In the vertical plane getting mass slung too much below the stylus is a problem as when the stylus has to ride a warp it has to lift to lift this mass as well, this can lead to excessive compression of the cantilever as the inertia delays the arm moving in response to the stylus.

Ideal is mass below the pivot and inline with the stylus.

James

[ColinA]

:p Since I am using a Biro tip for a pivot I will experiment on whether Black, Blue or Red sounds better!