C2 headshell weight - Friday project

the jewel in the crown
amagasakii
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Re: C2 headshell weight - Friday project

Post by amagasakii » 03 Dec 2019 20:54

Right, time to bring the saga of the weight to a close: weight's been removed. :D

Proof is in the pudding, so I tested with the most damaged record I own. This required an extra gram of VTF to track with the weight compared to without. The lateral forces at play I was referring to are pretty noticeable...
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Anyway, with the weight, VTF of just over 4g required to stay in the groove; without the weight, 3.25g, which is with the range specified for the ATN3600L.

My lesson learned: Added weight affects all planes of motion; this is obvious to me in hindsight, but I originally thought the counterweight would only affect vertical motion. While bearing drag may help damp some lateral forces, it's no match for the forces and inertia that additional weight(s) suspended away from the pivot introduce(s).

A70BBen
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Re: C2 headshell weight - Friday project

Post by A70BBen » 04 Dec 2019 15:52

Cartridges whose lateral and vertical compliances differ (such as Deccas and other asymmetric designs) and tonearms with differing vertical and lateral mass can drive you nuts. A test record with s lla low frequency sweep and visual readout can help determine the resonant frequencies of the system. It appears that with the added weight, yours was too low. Also when you add weight to the tonearm head, that weight has more effect on the moving mass of the entire system than does the adjustment of the counterweight.

amagasakii
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Re: C2 headshell weight - Friday project

Post by amagasakii » 04 Dec 2019 20:43

A70BBen wrote:
04 Dec 2019 15:52
Cartridges whose lateral and vertical compliances differ (such as Deccas and other asymmetric designs) and tonearms with differing vertical and lateral mass can drive you nuts. A test record with s lla low frequency sweep and visual readout can help determine the resonant frequencies of the system. It appears that with the added weight, yours was too low. Also when you add weight to the tonearm head, that weight has more effect on the moving mass of the entire system than does the adjustment of the counterweight.
Lesson learned! Also, I discovered I have to solder all pieces at once, and it gave me an excuse to buy a needle file set, so nothing's ever a total loss of time. :wink:

Does Garrard's design of the counterweight (square with the bulk of the mass hung below the tonearm) mean this tonearm has differing vertical/lateral mass? Or is that moot, since it's all carried by the tonearm bearings? (It's been a long time since physics class for me.)

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Re: C2 headshell weight - Friday project

Post by DSJR » 05 Dec 2019 20:30

S'cuse language, but that is one s**t record!! I'm amazed the thing tracks it at all ;)

amagasakii
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Re: C2 headshell weight - Friday project

Post by amagasakii » 05 Dec 2019 20:51

DSJR wrote:
05 Dec 2019 20:30
S'cuse language, but that is one s**t record!! I'm amazed the thing tracks it at all ;)
LOL, I know! I used to just pull albums 3/4 of the way out of the sleeve and make sure they didn't have a huge gouge running across them. Want to hazard a guess as to which part of this album was lurking in the 1/4 left inside the sleeve? Another lesson learned.

It's not quite as bad as it looks; things settle down about 30 seconds in, or at least the lateral warping dies down. The fact that it tracks is one of the reasons I like this little Garrard. I tried playing it on my Dual 521 once; it was having none of it. (I'm sure the AT3600L does its fair share of work as well.)

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Re: C2 headshell weight - Friday project

Post by A70BBen » 06 Dec 2019 08:32

"...
Does Garrard's design of the counterweight (square with the bulk of the mass hung below the tonearm) mean this tonearm has differing vertical/lateral mass? Or is that moot, since it's all carried by the tonearm bearings? (It's been a long time since physics class for me.)..."

================

No. The underslung counterweight only lowers the center of mass, which makes the arm more stable and resistant to jarring. Garrard forgot about that when the counterweight was redesigned to a round one in the SP25 Mk V!

Dynavector is probably the best-known arm with differing vertical and horizontal moving mass.