Classic Cartridges

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Nick
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Re: Classic Cartridges

Post by Nick » Thu Oct 01, 2020 4:34 pm

Overhang is the distance the stylus is from the spindle at the centre of the record. In the arc across the record, the stylus is 90 deg to the line from the centre of the record at two points in the arc, the null points of the chosen geometry. The inward force is caused by a combination of the offset angle between the stylus to pivot point and the cantilever and if the stylus is before or after the null point. One is fixed, the other varies. Therefore the bias required changes. Also as the speed of the stylus in the grove changes, the friction and so the force changes across the record.

Shown in https://www.analogplanet.com/content/to ... ometry-101

Between the null points the stylus is behind the 90 deg point, outside them its ahead of them.
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Nick
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Re: Classic Cartridges

Post by Nick » Thu Oct 01, 2020 4:43 pm

On that cartridge (a Shure something or other), I had a bent cantilever (skewed towards the middle of the record) at the end of the month
As the arm was lowered, was the arm free to move inward as soon as the stylus hit the lead in groove, or was there a small time each repeat where the groove pulled the stylus in against he friction of the arm lowering device?

Would the bias which pulls out, not increase the twisting force on the cantilever rather than reduce it if you believe the skating force was what bent the stylus?
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Re: Classic Cartridges

Post by izzy wizzy » Thu Oct 01, 2020 5:16 pm

Nick wrote:
Thu Oct 01, 2020 4:34 pm
Overhang is the distance the stylus is from the spindle at the centre of the record. In the arc across the record, the stylus is 90 deg to the line from the centre of the record at two points in the arc, the null points of the chosen geometry. The inward force is caused by a combination of the offset angle between the stylus to pivot point and the cantilever and if the stylus is before or after the null point. One is fixed, the other varies. Therefore the bias required changes. Also as the speed of the stylus in the grove changes, the friction and so the force changes across the record.

Shown in https://www.analogplanet.com/content/to ... ometry-101

Between the null points the stylus is behind the 90 deg point, outside them its ahead of them.
The link above is to do with geometry relating to cartridge alignment. Got nothing to do with skating forces.

A pivoted arm is always ahead of the tangent due to overhang so skates in. The previous videos link demonstrate exactly this.

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Re: Classic Cartridges

Post by rowuk » Fri Oct 02, 2020 4:26 pm

Nick wrote:
Thu Oct 01, 2020 4:43 pm
On that cartridge (a Shure something or other), I had a bent cantilever (skewed towards the middle of the record) at the end of the month
As the arm was lowered, was the arm free to move inward as soon as the stylus hit the lead in groove, or was there a small time each repeat where the groove pulled the stylus in against he friction of the arm lowering device?

Would the bias which pulls out, not increase the twisting force on the cantilever rather than reduce it if you believe the skating force was what bent the stylus?
Actually, it was simply those circumstances that have "biased" my view since those early '80s. Maybe I just hit a limit for cantilever "hit the groove" stress? 4 weeks is around 1800 repeats.

For my simplistic mind, record playback is very primitive and complex at the same time. If microns can create high quality sound, how much horizontal force would affect that and how stable can a system be that has to allow the arm to be positioned by the stylus. If we want a "solid" mechanical ground to allow the cantilever to transmit as much of the signal as possible, what happens with even slightly off center holes? Even if the situation is not audible what does repetitive stress do to the cantilever and suspension over time.
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Re: Classic Cartridges

Post by Nick » Fri Oct 02, 2020 4:45 pm

what does repetitive stress do to the cantilever and suspension over time.
I would think unflat records will apply much higher repetitive forces.
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Re: Classic Cartridges

Post by vinylnvalves » Fri Oct 02, 2020 5:32 pm

There are a few pivot linear trackers some more successful than other, I bet someone owns a Garrard Zero. The best example I have seen after you discount the Thales arm ( to much to go wrong) is one from Frank Schröder the LT... details here https://darklantern.proboards.com/threa ... lt-tonearm This could be the final chapter in tonearm design, I do question why different arm lengths are available though...

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Re: Classic Cartridges

Post by Nick » Fri Oct 02, 2020 5:48 pm

I spent some time at Munich watching the Reed 5T working

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Re: Classic Cartridges

Post by Ant » Fri Oct 02, 2020 5:51 pm

vinylnvalves wrote:
Fri Oct 02, 2020 5:32 pm
I bet someone owns a Garrard Zero.
Yes.
Never used it thought because its build quality seems to be completely crap. Its not in bad nick but there seems to be loads of slop in all the pivots. Dunno if they were like that new, but it does not inspire confidence
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Re: Classic Cartridges

Post by IslandPink » Fri Oct 02, 2020 6:02 pm

Nick wrote:
Fri Oct 02, 2020 5:48 pm
I spent some time at Munich watching the Reed 5T working
So, is the floating pivot bit sensed and moved electronically ?
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Re: Classic Cartridges

Post by vinylnvalves » Fri Oct 02, 2020 6:40 pm

The Reed isn’t a passive system... as far as I am aware Franks is the only passive one which is elegant from my perspective as a mechanical engineer, however if you design control systems.. your view of beauty maybe different. Frank has the patent, a few companies make it under license. KT and Thales have pantograph type ones, with lots of bearings etc.

I always thought that Dynavector missed a trick with their unique arm, not doing something similar.

Some of these patents sit for years before the technology to implement them has matured. Take the Air Blade, as a fan of AMT’s it’s getting close to that ultimate speaker driver. Taking 40 years since Oskar Heils patent to make one commercially.

Eccentric bearings would be another way of achieving it, but would be a PITA to align/time the bearing... many styli broken I feel.

Obviously a laser reading system - similar to what they have at Livermore Labs, in the analogue data storage systems would get around the whole problem. Vinyl straight to digital at a phenomenal sampling rate... via the DSP to D class AMS amps .... the weakest link is still the speaker at the end :(

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Re: Classic Cartridges

Post by Nick » Fri Oct 02, 2020 9:50 pm

IslandPink wrote:
Fri Oct 02, 2020 6:02 pm
Nick wrote:
Fri Oct 02, 2020 5:48 pm
I spent some time at Munich watching the Reed 5T working
So, is the floating pivot bit sensed and moved electronically ?
Yes, there is a laser mounted on the tonearm pointing backwards. That shines on a CCD mounted on the rear part. the disk the arm pivot is mounted on controlled by a servo system that keeps the beam centred on the CCD.
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