Cartridge/Tonearm Theory Question

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abril
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Re: Cartridge/Tonearm Theory Question

Post by abril » 13 Jun 2019 15:21

Dont forget you also have multipivot arms :lol:
https://www.vinylengine.com/library/gar ... 00sb.shtml

WHAMMO_63
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Re: Cartridge/Tonearm Theory Question

Post by WHAMMO_63 » 13 Jun 2019 17:16

Solist wrote:
13 Jun 2019 10:17
The problems with linear tracking tonearms is that you need a different type of mechanism to move the tonearm across the record. And ideally if you think about it, good tonearms are those which are basically invisible, or have no effect whatsoever on the movement of the cartridge.

On a traditional tonearm this is "easily" achieved since pivoted designs are simple designs. The trade off with this tonearms is that they dont read parallel as the linear trackers. Protractors usually have 2 points, and there is where the distortion should be the lowest (ideally 0, but its hard to set the needle perfectly). You can pick longer tonearms 11inch, which if you imagine will have a lower tracking distortion. If you were to draw a bigger circle which imitates the path of the needle, you can see that the bigger the circle the flatter the curve is. The problem with longer tonearms is that they like to resonate, so some clever damping and tube construction is desired to minimize those resonances. Short tonearms have a bigger tracking error, but are much less sensitive to vibrations. Most manufacturers went with 9inch tonearms in the past, since its a compromise of those 2 worlds.

Now, you can choose different protractors for these pivoted tonearms which will distribute the distortion in a different way across the record, if your tonearm geometry allows it. If you have a short 8 inch tonearm, or if you listen to a lot of classical music, stevenson can be a good choice, since it prioritizes inner grooves to minimize the distortion. Shorter tonearms have more difficulty tracking the inner grooves, and with a lot of classical music there are those big loud crescendos at the end of a record which can cause distortion. The other popular option is Lofgren A, which will distribute the distortion more evenly across the whole record. You can also try to make your own protractor to see how different values have an effect on the tracking error and distortion.

In the library section there is a nice tool for this kind of things:

https://www.vinylengine.com/tonearm_ali ... or_pro.php

And then you have linear tracking tonearms, which ideally have no tracking error. The problem with this tonearms is that they require a different type of mechanism to move the tonearms freely across the record. The last thing you want is the needle to drag the whole mechanism behind it. This will impede the ability of the needle to track the grooves properly. Some use air bearings for this purpose, but air bearings needs to be refilled and they are prone to leaking. Some use motorized mechanisms. There are even more problems. The mechanism needs to be perfectly in sync, otherwise you end up with a loss of information. The complexity is much higher in comparison to the pivoted tonearms, so the price is higher, and the demand is low.

I think that overall pivoted tonearms if done properly are good enough or even better than most of the linear tracking tonearms, the price is usually lower which is a bonus (more money for records), and are less prone to failures on the long run.

This is my 2c. Would love to hear more opinions about this.
Thanks for your input Solist :)

I think all tonearms must be susceptible to resonance? The longer the arm, the lower the cutoff frequency (e.g. wavelengths that are twice the length of the tonearm and up). The other thought I had is that as far as things like the cannon burst we shouldn't confuse base groove width with needle displacement that necessitates certain passages take up more vinyl real estate.

WHAMMO_63
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Re: Cartridge/Tonearm Theory Question

Post by WHAMMO_63 » 13 Jun 2019 17:19

abril wrote:
13 Jun 2019 15:21
Dont forget you also have multipivot arms :lol:
https://www.vinylengine.com/library/gar ... 00sb.shtml
I'll just put this here:

[youtube]https://www.youtube.com/watch?v=W_4sooWCh_Y[/youtube]

Solist
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Re: Cartridge/Tonearm Theory Question

Post by Solist » 13 Jun 2019 17:46

WHAMMO_63 wrote:
13 Jun 2019 17:16

Thanks for your input Solist :)

I think all tonearms must be susceptible to resonance? The longer the arm, the lower the cutoff frequency (e.g. wavelengths that are twice the length of the tonearm and up). The other thought I had is that as far as things like the cannon burst we shouldn't confuse base groove width with needle displacement that necessitates certain passages take up more vinyl real estate.
Yes, everything is susceptible to resonances if you have a enough big magnifying glass.

I dont know enough about tonearms, I am still reading about this topic. There is a lot more than the length of the tonearm to consider.

True, about real estate.

Solist
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Re: Cartridge/Tonearm Theory Question

Post by Solist » 13 Jun 2019 17:48

abril wrote:
13 Jun 2019 15:21
Dont forget you also have multipivot arms :lol:
https://www.vinylengine.com/library/gar ... 00sb.shtml
You are forgetting leaf spring pivot tonearms:
ERA K3 leaf springs_zpsd2gxntqk.jpg
(125.49 KiB) Downloaded 44 times
I have heard they are excellent with warped records :)

Solist
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Re: Cartridge/Tonearm Theory Question

Post by Solist » 13 Jun 2019 17:51

WHAMMO_63 wrote:
13 Jun 2019 17:19
abril wrote:
13 Jun 2019 15:21
Dont forget you also have multipivot arms :lol:
https://www.vinylengine.com/library/gar ... 00sb.shtml
I'll just put this here:

[youtube]https://www.youtube.com/watch?v=W_4sooWCh_Y[/youtube]
I believe his background is from digital disc readers/ cd players, cant remember exactly.

I wonder how much of an effect the dust/dirt has.

Solist
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Re: Cartridge/Tonearm Theory Question

Post by Solist » 13 Jun 2019 17:52

And then you have the 45 degree gimbal tonearms:
Reed-1X-tonearm2.jpg
(20.58 KiB) Downloaded 42 times
I also have my doubts about these. A weird compromise. I think its one of those innovations for the sake of innovation.

billshurv
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Re: Cartridge/Tonearm Theory Question

Post by billshurv » 13 Jun 2019 21:23

Servo driven linear tonearms have a bad press as most examples crab their way across the record causing imagined horror. However RayK, who posts here from time to time worked out a very elegant solution to this problem 40 years ago when modifying his Rabco. This has never been used in a production arm as far as I know and they have died out mainly due to bias against them, although the Sony Biotracer linears still command good money on ebay.

lenjack
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Re: Cartridge/Tonearm Theory Question

Post by lenjack » 13 Jun 2019 21:31

That would be the PS-X800. I always wanted one, but never got around to it. Restored ones go for over $2200 on ebay. There's a repair service on ebay for $64.

billshurv
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Re: Cartridge/Tonearm Theory Question

Post by billshurv » 13 Jun 2019 21:32

Yup that's the one. Clearly there are a group of afficionados who understand something many others don't!

lenjack
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Re: Cartridge/Tonearm Theory Question

Post by lenjack » 13 Jun 2019 21:40

Thanks for calling me an afficionado. I'll wear that like a badge. :) 8) :wink:

Solist
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Re: Cartridge/Tonearm Theory Question

Post by Solist » 13 Jun 2019 22:01

billshurv wrote:
13 Jun 2019 21:23
Servo driven linear tonearms have a bad press as most examples crab their way across the record causing imagined horror. However RayK, who posts here from time to time worked out a very elegant solution to this problem 40 years ago when modifying his Rabco. This has never been used in a production arm as far as I know and they have died out mainly due to bias against them, although the Sony Biotracer linears still command good money on ebay.
So, what was his modification? I am honestly curious.

billshurv
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Re: Cartridge/Tonearm Theory Question

Post by billshurv » 13 Jun 2019 22:18

I don't have the link to hand, but basically most of the servo arms work on a flag interrupting a beam to trigger moving of the arm. He found that, if you use the right optical sensor you get an analog signal, not an on/off one and you can use that as the control input and keep the drive motor always running rather than stopping and starting.

This doesn't cope with disk eccentricity but you should try and minimise that anyway.

WHAMMO_63
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Re: Cartridge/Tonearm Theory Question

Post by WHAMMO_63 » 14 Jun 2019 19:01

Solist wrote:
13 Jun 2019 17:52
And then you have the 45 degree gimbal tonearms:

Reed-1X-tonearm2.jpg

I also have my doubts about these. A weird compromise. I think its one of those innovations for the sake of innovation.
But the cool factor is off the charts with that tonearm :wow:

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Re: Cartridge/Tonearm Theory Question

Post by WHAMMO_63 » 14 Jun 2019 19:03

billshurv wrote:
13 Jun 2019 22:18
I don't have the link to hand, but basically most of the servo arms work on a flag interrupting a beam to trigger moving of the arm. He found that, if you use the right optical sensor you get an analog signal, not an on/off one and you can use that as the control input and keep the drive motor always running rather than stopping and starting.

This doesn't cope with disk eccentricity but you should try and minimise that anyway.
An analog solution to an analog problem, I LIKE IT!