Cartridge Alignment using Stevenson's protractor

[A K Bhattacharjee]

Although most of the fms are aware of the fact, even then for benefit of the beginers & to get opinions of experts, I want to share my experience. During alignment of a new cartridge recently, I found there is no such two points where the cantilever is parallel to the lines at two null points of stevenson protractor even after moving the cart forward or backward in the headshell. When cart is put at the extreme back the cart comes closer to alignment but not perfectly. Now if the cart is twisted a bit little in the headshell towards the spindle, the cart/cantelever is perfectly parallel/squre to the lines at two null points.
After the alignment what I observed is sound is very much clear than before. But I want to mention one thing that playing old records, pops have become more prominent than before(before alignment)
Images of alignment are attached.
Thanks

 

[sunder]

It's said that this Stevenson's Protractor alignment, hugely reduce the Inner groove Distortion. In which tonearm (TT) the cart is fitted? In some tonearms or with some carts, the slight twist may be needed. Well made Stevenson's protractors (made with thick board) not available. I doubt that the accuracy of the print out copy of the protractors. Thanks for the input.

 

[A K Bhattacharjee]

It's said that this Stevenson's Protractor alignment, hugely reduce the Inner groove Distortion. In which tonearm (TT) the cart is fitted? In some tonearms or with some carts, the slight twist may be needed. Well made Stevenson's protractors (made with thick board) not available. I doubt that the accuracy of the print out copy of the protractors. Thanks for the input.

Sherwood PM 9805. I have verified the alignment with original Shure protractor as well as with Fluance. Problem with this turntable is no protractor came with it like others hence alignment is difficult. Reason behind the post is to get opinion on alignment in cases where the manufacturer does not provide a protractor.

 

[sunder]

The effective length (overhang) of your Sherwood PM 9805 is :10mm. If you don't have the original overhang gauge for this turntable, please try to do this: Get the Overhang Gauge of the Technics turntable which is used in most of the 'S' shaped Technics arms with effective length of 15mm. it's easily available on eBay for $10. With that gauge, mark the thinnest line below 5mm of the overhang tip of the Technics Gauge. So ,that is the overhang point (10mm) of your Sherwood TT. Firstly, please set the cart by using this gauge, then you can verify with the protractor also. Hope this would help.

TECHNICS RMR2210 OVERHANG GAUGE

TECHNICS SERVICE RMR-2210-W overhang gauge.

www.soundservice.gr

 

[sunder]

Hello friends, I need a Stevenson's Protractor made out of thick board with clear printing and finishing. Please let me know the availability with details. Thank you. Regards.
Sunder.

 

[A K Bhattacharjee]

The effective length (overhang) of your Sherwood PM 9805 is :10mm. If you don't have the original overhang gauge for this turntable, please try to do this: Get the Overhang Gauge of the Technics turntable which is used in most of the 'S' shaped Technics arms with effective length of 15mm. it's easily available on eBay for $10. With that gauge, mark the thinnest line below 5mm of the overhang tip of the Technics Gauge. So ,that is the overhang point (10mm) of your Sherwood TT. Firstly, please set the cart by using this gauge, then you can verify with the protractor also. Hope this would help.

TECHNICS RMR2210 OVERHANG GAUGE

TECHNICS SERVICE RMR-2210-W overhang gauge.

www.soundservice.gr

Problem with this tt is" It's pivot to spindle distance is 205 mm, arm length 180" I do have Technics overhang gauge. I have tried what you said. I have already mentioned in one my previous post that if the cartridge could have been moved back by a few mm then I could have aligned it properly without twisting. I have many headshells starting from universal to technics none of them have such slots where the cartridge can be moved back further to get the desired effect hence I had to twist it. It is worth mentioning here that none of the specifications mentioned in the manual of Sherwood is correct.

Thanks for reply

 

[jls001]

Try the attached Stevenson A arc template. Pivot to Spindle distance is 205 mm.
Over hang should be 17.4 mm and the offset angle should be 24°07'8".

 

[sunder]

none of them have such slots where the cartridge can be moved back further to get the desired effect hence I had to twist it.

Have you tried with smaller size body cartridges like AT-91 , AT-95 or CN5625CL .?

 

[A K Bhattacharjee]

Have you tried with smaller size body cartridges like AT-91 , AT-95 or CN5625CL .?

Yes, I do have all. I have taken it as challenge. Why shall I not be able to align correctly in this tt.

 

[A K Bhattacharjee]

Try the attached Stevenson A arc template. Pivot to Spindle distance is 205 mm.
Over hang should be 17.4 mm and the offset angle should be 24°07'8".

I have aligned the cart as per Lofgren A arc protractor, which is almost similar to what you have sent. After alignment,I observed that Overhang was perfect but effective arm length did not match. Here also I had to twist the cart by a few mm towards the spindle.It is not possible to adjust the cart in the headshell(due to limited space)to achieve the desired specification.Otherwise no problem.
What I have seen in this tt is whatever protractor/headshell/cart is used, slight twisting is necessary which is not there in other tts.
Thanks for the template generation.

 

[jls001]

I have aligned the cart as per Lofgren A arc protractor, which is almost similar to what you have sent. After alignment,I observed that Overhang was perfect but effective arm length did not match. Here also I had to twist the cart by a few mm towards the spindle.It is not possible to adjust the cart in the headshell(due to limited space)to achieve the desired specification.Otherwise no problem.
What I have seen in this tt is whatever protractor/headshell/cart is used, slight twisting is necessary which is not there in other tts.
Thanks for the template generation.

Do you know the original overhang of the tonearm? If you know, assume that the curvature/bending of the arm already gives correct offset angle at the head shell so simply align the cartridge in the middle of the head shell (L/R, when seeing the head shell from front of TT) AND adjust the correct overhang. I believe this will give you an alignment closest to what was intended from the factory. It is sufficient to align cartridge on most Technics TTs using the steps described above. If the cartridge needs twisting as shown in your pictures, it means the template you arer using is not suitable for that arm.

 

[General_sound]

After reading your post, I revisited the alignment of an Ortofon Omega cart I had fitted, by guesswork, on a Sherwood PM 9805 tt. Using both Stevenson and Fluance protractors, the alignment was totally off. The best I could do was with Stevenson, by pushing the cart to the back of the headshell. Now it sounds much better. Inspite of being relatively inexpensive, the tt does sounds decent and has been running well since 2010
(used sparingly and with care).

 

[A K Bhattacharjee]

After reading your post, I revisited the alignment of an Ortofon Omega cart I had fitted, by guesswork, on a Sherwood PM 9805 tt. Using both Stevenson and Fluance protractors, the alignment was totally off. The best I could do was with Stevenson, by pushing the cart to the back of the headshell. Now it sounds much better. Inspite of being relatively inexpensive, the tt does sounds decent and has been running well since 2010
(used sparingly and with care).

Exactly. Lot of research & experiment have been done by me on this with different headshells & carts.
After a vigorous search, I came across the official measurements from Sherwood.
These are:
Effective length 220mm
Offset angle 22.5
Pivot to spindle 205mm
Overhang 15mm
Inner null radius 57.488
Outer null 110.893
So unless a shorter headshell or a headshell with longer gap is used alignment will be out. So it is better to place the cart at the rear end & adjust the cart according to the stevenson protractor or Fluance protractor. This what I have done. Try this with a good stereo record.

AKB

 

[General_sound]

Thanks a lot. Somehow I felt that overhang becomes leeser than 15 mm when cart is pushed to the end of the headshell. Is this correct?

 

[A K Bhattacharjee]

If you are using a headshell which have long gap then measure the effective length. It must be 220mm & if it is so, overhang will be 15mm. Otherwise measure the overhang accurately & place the cart in the headshell accordingly.

 

[General_sound]

Thanks a lot.

 

[General_sound]

I just revisited a Sherwood tt and Mr Bhattacharjee's suggestions as per photo number 1 dated May 24,2018. Set the Ortofon Omega exactly as shown, adjusted VTF and anti-skate. Much better sound. The Sherwood PM 9805 may be a low cost tt but I discovered that it has a heavier platter than many other Japanese/ Hanpin belt drives. Also the motor, to me, appears more torquey.

 

[A K Bhattacharjee]

I just revisited a Sherwood tt and Mr Bhattacharjee's suggestions as per photo number 1 dated May 24,2018. Set the Ortofon Omega exactly as shown, adjusted VTF and anti-skate. Much better sound. The Sherwood PM 9805 may be a low cost tt but I discovered that it has a heavier platter than many other Japanese/ Hanpin belt drives. Also the motor, to me, appears more torquey.