As getting a custom arc protractor used to be quite a pain for Mac users, I decided to write my own protractor generator. I spent the last two days researching the math and writing the code. Here it is: AlignmentProtractor – Custom arc protractors for better phono cartridge alignment I haven't implemented a scaling feature yet - is it really needed? When I tried the Hoffman app (using Wine and a very old computer) it was necessary, but strangely it doesn't seem to be an issue for me with this one? Please let me know what you think and if it works well for you.
If you want other's to use it, it is necessary. Without it you're not taking into account other's printers.
That's a great idea! Using a square was just the easy way of doing it, as calculating the corner points of the triangle takes quite a bit more effort. Updated!
I just updated the scaling feature to actually use %. That will hopefully make it easier to understand. Is 2% of range enough for everyone here?
Well done! Was just looking for something like this. Could anyone help me get the correct settings for Stevenson on my Technics SL1200GR? I think the pivot to spindle distance is 215mm.
Technics should be 215mm correct. If this is like Hoffman, the program should calculate the rest. I'll check it out this weekend! Edit- It doesn't auto calculate like Hoffman.
Technics doesn't use Stevenson so at best you can only approximate that alignment with this program since it doesn't have the option for a custom alignment with user entering offset and overhang. But if you want the standard Stevenson alignment, you would just enter a name, then the 215 pivot to spindle distance, and select Stevenson and the default IEC groove radius, then calculate.
Should I use something else for my Technics then? The standard alignment you get with the plastic jig seems a bit extreme to me.
I don't know, you'd have to define why you want to use something different from the Technics alignment, I'm not sure what a "bit extreme" means in this case. Normally one picks a different alignment than stock because they want to optimize a certain parameter, for instance minimizing average distortion. Or in the case of this or the CH generator, you can't actually use them to generate a Technics alignment protractor, so choose to align to one of the three common standards.
You could try this one in this thread.. Maybe do a Hoffman first and compare them. The Technics jig gives a satisfactory alignment. Stevenson and Lofgren A&B give priority to inner grooves. With Lofgren, the cartridge will often be slightly angled in towards the spindle when done. http://www.conradhoffman.com/TemplateGen.zip
I recall seeing a diagram where the second null point almost touches the label with that alignment, but maybe that was wrong.
The Technics specification is Pivot to Spindle 215 mm Overhang 15mm Offset angle 22 ° Inner null 58.8 mm Outer null 113.52 mm So yes, most vintage tables used something similar to Stevenson with the inner null point close to the minimum groove radius. You can generate the protractor for the Technics spec using Stevenson with inner radius set to 58.8 and outer radius set to 140.63, or Lofgren A with inner radius set to 53.47 and outer radius to 140.6. If you want something less "extreme", then use the standard Lofgren A with IEC values for the groove radius, but you will have to angle the cartridge in the headshell to align the cantilever to the grid lines at the null points, and the overhang will be quite a bit more than stock. It's all up to you, not really a wrong or right way to do it. I generally use Lofgren A on my tables since I don't have a ton of records that I listen to regularly cut close to the label.
For Stevenson, the inner null point equals the inner groove radius to minimize distortion there. Only the last couple of millimeters before the inner grooves actually benefit from this, as Stevenson will get you the most distortion of the three alignment geometries. If your records are not cut all the way to the specified inner groove, the point of maximum distortion may be pretty close to the end of the side.. Bearwald (=Löfgren A) is generally considered to be a good choice, as it keeps distortion low over the entire record side. Lofgren B has the lowest average distortion, but at some point may give you more distortion than Baerwald. Once you go past the specified inner groove, distortion will increase quite rapidly, so it's worth checking out how your records are actually cut.
Yeah, it's not designed to do backwards calculations. The overhang is a result of the parameters you choose. I guess I would have to set it up very differently to allow for all kinds of calculations. I don't know how to do that yet, but I could probably figure it out. When I started this project, I didn't know how to program an alignment template generator either. That would probably make it more complicated to use though. Maybe it would need a simple mode and an advanced mode..
Right, the Hoffman generator doesn't have custom options either except for the groove radius, like yours. The alignment calculator pro at vinyl engine does have a custom option for the alignment that lets you enter the overhang and offset angle, but it doesn't generate an arc protractor, just prints the parameter values, and graphs for the error and distortion.
Actually I tried it again with just the PV to spindle and it gave me a protractor! I'll check it out this weekend. Thanks!
There are images for the popular alignments, but one that adjust to a custom one would be really cool.
Below is a comparison using the Vinyl Engine Alignment Pro of the Technics using the custom alignment setting, versus Lofgren A, Lofgren B, and Stevenson, using the default IEC groove radius ...
Yeah, that kind of graph. Man, I had totally forgotten what ridiculous amount of distortion Lofgren B has at the inner grooves... yeah, that's the idea. I'll look into it.
