Desperation is the mother of invention...

Posted by tketcham (A) on July 7, 2012 at 05:59:53

In Reply to: RE: Not sure I understand.... posted by dtut on July 6, 2012 at 15:18:09:

Hi, Doug,
You came up with a great solution without having to modify the original tonearm and headshell. As you discovered, trying to force a square alignment into a round geometry can be frustrating. (Pardon the lousy pun.) The photos are especially helpful.

Mr. Blue Sky - The slotted mounting plate acts like a sliding base similar to what SME uses for their tonearms. Instead of moving the cartridge forward or backward to get the stylus at the proper position you slide the whole tonearm. But the similarities to the SME tonearms ends there...

Modern SME tonearms are designed for the Lofgren A (Baerwald) alignment and you slide the tonearm to put the stylus at the proper null point position(s). The headshell is fixed because you don't need to slide or rotate the cartridge. The stylus will be at the right angle when it's at the right position.

But the S-120 tonearm is designed for a different alignment than the Lofgren A alignment. The tonearm has a different geometry (tonearm position/length and headshell angle). Just sliding the tonearm to put the cartridge at the Lofgren A null points gets you only part way there. You still need to rotate the cartridge to have the right geometry to fit the Lofgren A alignment. That's where the headshell adapter plate comes in; it allows you to rotate the cartridge to get the right stylus angle. You'll then have the correct combination of tonearm position/length and cartridge angle. (The headshell angle is still wrong but you compensate by rotating the cartridge.)

As Doug mentions, it's not going to be as easy as just sliding the tonearm like an SME. Once you find the right tonearm position (by sliding it) to put the stylus at the proper null points you'll need to rotate the cartridge to find the right stylus angle. But it shouldn't be any more difficult than trying to set up a cartridge in a slotted headshell, where you have to find both the correct position and angle simultaneously.

Enjoy the project!

Regards,
Tom

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Follow Ups Full Thread

Topic - Tonearm Mounting/Geometry Question.... - Mr Blue Sky 14:33:39 07/05/12 (18)

Yes, maybe... - tketcham 17:52:32 07/05/12 (10)

Forgive me if this is a dumb question, but... - Mr Blue Sky 18:15:09 07/05/12 (9)

RE: Forgive me if this is a dumb question, but... - dtut 10:02:01 07/06/12 (4)

Not sure I understand.... - Mr Blue Sky 12:06:32 07/06/12 (2)

RE: Not sure I understand.... - dtut 15:18:09 07/06/12 (1)

Desperation is the mother of invention... - tketcham 05:59:53 07/07/12 (0)

That is a... - tketcham 10:23:22 07/06/12 (0)

No dumb questions, only dumb designs... - tketcham 04:32:18 07/06/12 (2)

RE: No dumb questions, only dumb designs... - John Elison 07:15:27 07/06/12 (1)

Worst may be best... - tketcham 08:23:30 07/06/12 (0)

RE: Forgive me if this is a dumb question, but... - John Elison 20:13:49 07/05/12 (0)

RE: Tonearm Mounting - M3 lover 16:21:45 07/05/12 (0)

Sounds right to me... - John Elison 15:56:06 07/05/12 (5)

If I had known math ... - reelsmith. 17:27:56 07/05/12 (4)

CD players rule! ;-) /nt\ - John Elison 20:32:56 07/05/12 (3)

Oh, John.... - JimK 08:07:22 07/06/12 (2)

RE: Oh, John.... - John Elison 09:50:29 07/06/12 (1)

I miss my tubes. - JimK 12:56:56 07/06/12 (0)

Follow Ups

Desperation is the mother of invention... - tketcham 05:59:53 07/07/12 (0)

Desperation is the mother of invention...

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