Cartridge Alignment Protractors

Hi, as you have a much shorter than usual or common arm length, in the absence of a protractor specifically drawn up for that arm, I would simply set the overhang to 9.5 mm, square up the cart in the headshell and be happy with that. Providing Kenwood's figures are accurate, your cart will be aligned accurately. It is also possible to check alignment and tweak further by listening to a test record although that usually applies to fine tuning the VTF and anti-skate more than the actual alignment of the cartridge.

To be honest I'd be tempted to use an overhang gauge and stick with the standard overhang. Without knowing the original offset angle it's hard to know what sort of alignment they were aiming for, or what is possible within the current headshell?

Hi,
There seems to be some confusion about how to use these protractors? Neither type is kept stationary between points - for this you would need a specific arc protractor designed for your mounting distance.

Here are the basics for correct use of a two-point protractor:

(1) lower the stylus onto the inner null point (rotating the protractor as required), then adjust the for/aft position of the cartridge in the headshell until the cantilever/cartridge body is parallel with the grid lines when the stylus is placed back on the point.

(2) lower the stylus onto the outer null point (rotating the protractor as required). If the cantilever/cartridge body is not parallel to the grid lines at this point you should twist the cartridge in the headshell to adjust the offset angle (without changing the overhang set in the first step).

(3) repeat steps 1 and 2 making minor adjustments as necessary

The advantage of a sight-line type (such as the KWillis protractor) is that you set the overhang and offset angle at the first point, then you just have to rotate the protractor* to check the second point, so it should be quicker. However, it's not always easy to point the sight-line accurately at the pivot point so if there is misalignment at the second point you should then use it as you would a two-point protractor to correct it.

For each alignment method (Stevenson, Baerwald and Lofgren B) the two-point protractors above will give identical alignment to the KWillis protractor when used correctly.

Regards,
JaS

* note that the angle between the grid line radii on the KWillis protractor reduces the amount you need to rotate the protractor when checking the second point, but the correct angle between these points is different for every mounting distance so you shouldn't attempt to force alignment at both points while the protractor is held stationary.

Hi

I've just finished a paper about this tool... read it very soon here ;-)

best regards

Seb

Hi,
Used correctly the Stupid protractor works well - the Baerwald null points will provide the lowest peak error, while the Lofgren B will give the lowest average RMS error (with a slight increase at the inner and outer grooves). Alternatively you could use Conrad Hoffman's Arc protractor generator (see the thread in the cartridge forum) to print out an arc protractor specifically for your arm length - these are quicker to use than a traditional two-point type, but if you go this route be sure to read the instructions carefully.

Regards,
JaS

hi

i am a bit lost here.
what protractor to use with my combo, thorens 124 with a fidelity research 64fx arm.
the distance from spindle to pivot is 230mm.
this thorens doesn't fit the thorens profile protractor.
and what would the overhang come down to?
thanks in advance.

hartgas
-.-.-.-.-.-
go dutch

Hi,
Baerwald & Loefgren B produce very low levels of tracing error within the playing area. They don't have a 'sound' as such so if it sounds bad either something else is amiss or you need to double check how you're using the protractor?

The SL1210 mk2 has a mounting distance (pivot to spindle) of 215mm and an effective length of 230mm (stylus to pivot when using the standard alignment tool).

52mm is the standard distance from the back of the headshell mounting surface to the stylus tip, not the overhang. Overhang is the amount the stylus tip overhangs the centre of the spindle once aligned - standard this is 15mm, but using a Baerwald protractor you will end up with 17.8mm of overhang and the cartridge 3mm further forward in the headshell (but lower tracing error).

FWIW you don't need to measure the overhang or offset angle, just align to the protractor as described in the instructions and it will be set.

Regards,
JaS

Hi. That seems to be the mounting distance between pivot and spindle and your model is 3012R, right? Best overhang depends on your system that means: just measure distance from stylus to mid of screws. If approx. 9.5mm, you can use the normal IEC or SME protractor. I can send a special protractor/pdf if you like. regards, Alfred

Hi,
The 15mm overhang figure is only applicable to the original alignment method. If you want to keep the original overhang distance/offset angle you could try making your own two point protractor? According to Jelco's specs the original null points work out at 68.7 / 129.9mm so marking these on a piece of card would give you the radii at which the stylus should be perpendicular to the groove (if Jelco's figures are accurate).

Alternatively you would get slightly lower maximum and average tracing distortion by using the Baerwald Stupid Protractor, but you will end up with 13.4mm overhang and an 18 degree offset angle when aligned accurately to it. There should be room in the headshell but the cartridge will end up slightly skewed in the shell if that bothers you.

Regards,
JaS

Hi,
The Rega protractors are only suitable for arms with a 222mm mounting/pivot to spindle distance. Any of the universal protractors (Baerwald, Stevenson, Loefgren B) are suitable.

Regards,
JaS

Hi,
The scan of the original single point Rega protractor in the library is suitable, or you could use the Rega Baerwald/Stevenson arc protractors for alternative alignments which give theoretically lower tracking error/distortion.

Regards,
JaS

Hi,
For serial numbers below 439606 you can use the two-point 'Stevenson Protractor', for later arms the 'Baerwald Stupid Protractor' is suitable.

Regards,
JaS

There isn't a problem with the file. What error are you getting?

Regards,
JaS

Hi
Standard effective length for most 215mm Technics arms is 230mm (mounting distance + overhang). The arc protractor uses Baerwald geometry for lower distortion which requires more overhang (cartridge further forward in the slots) and hence a longer effective length.

Regards,
JaS

That is likely going to be difficult to find. I have a 20 and through a little deductive measuring I found where the center of the stylus should be from a reference point on the arm so it will be dead center of the platter pin