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Time to choose: Baerwald, Lofgren, Stevenson ?

I’ve managed Dr.Feickert Analog Protractor for a decent price (build quality is superb, such a great tool).

Time to play with Baerwald, Lofgren, Stevenson alignments on my Luxman PD444.
Need advice from experienced used of the following arms:
Lustre GST 801
Victor UA-7045
Luxman TA-1
Reed 3P "12
Schick "12

Baerwald, Lofgren, Stevenson ? What do you like the most for these arms?
Manufacturers recommend Baerwald mostly. 

Dedicated "7 inch vinyl playback deserve Stevenson alternative, maybe?
Since it's a smaller format than normal "12 or "10 inch vinyl, it's like playin the last track's according to position of grooves on '7 inch (45 rpm) singles. RCA invented this format, i wonder which alignment did they used for radio broadcast studios.   

Thanks

chakster
sampsa55
71 posts
 
Lewm & Fleib:

The RS-A1 is a bit different as the cartridge is able to rotate and (possibly) maintain tangency to the groove. In Viv Lab and the Yamaha YSA-2, the cartridge is held straight and thus the cartridge will at the beginning and end of the record be at a ~10 degree angle to the groove.

Some thoughts:

1) The distortion resulting from the stylus being at an horizontal angle to the groove is 2nd harmonic, which I believe is the least harmful distortion.

2) It is not clear to me how different stylus shapes affect the distortion resulting from being at angle to the groove.

3) The calculations only cover horizontal alignment and it’s not obvious to me what the resulting distortions in the vertical part of the stereo signal are and whether these are dependent on the frequency (highly likely) and stylus shape (also highly likely). In particular, it is not clear whether these are 2nd harmonic or something else.

4) This horizontal alignment is the only kind of distortion for which I have seen a calculated estimate. Does anyone know of estimates for the distortion resulting from skating forces or vertical misalignment and whether these are 2nd harmonic or something else? I recall reading a discussion of the design of the Viv Lab where the designers seem to have been concerned about skating forces and considered the related problems worse than those related to horizontal alignment.

5) I’ve only seen one graph claiming to show the actual measured distortion from playing a test record. I came across this on the web and do not know if it is authentic. It was claimed to be from a Yamaha test of their YSA-1 (~Stevenson) and YSA-2 (straight) tonearms. Does anyone know of actual measurements of the distortions?


fleib
1,124 posts
 

Sampsa55,

Interesting post. Vertical alignment error (SRA/VTA) can be measured with a test record and a distortion analyzer. I've never done this. It seems to me, it will vary somewhat from record to record and I adjust it by ear and on the fly. Most people hear this as an imbalance -bass to treble which seems more obvious than tonal and harmonic inaccuracies which I also hear.

You say alignment error causes 2nd harmonic distortion. Is this documented? While vertical error is readily heard, horizontal is not so obvious. Adjusting alignment provides clarity and focus. Is this measurable 2nd harmonic distortion? Conventional pivoting arms only have 2 nulls across the record.

It's the movements of the cantilever which trigger the generator. Reduction of torsional forces from anti-skate and offset is said to be responsible for increased clarity. The RS-A1 also addresses vertical torsional forces by aiming the cantilever at the pivot vertically. The rotating headshell seems a compromise between alignment and offset.

There was a Grado Signature Laboratory arm which had elevated pivots and fixed alignment - offset.

Regards,




sampsa55
71 posts
 
You say alignment error causes 2nd harmonic distortion. Is this documented?

It's in Baerwald's original derivation from 1941, where he shows the resulting distortion to be primarily 2nd harmonic.




fleib
1,124 posts
 

**It's in Baerwald's original derivation from 1941, where he shows the resulting distortion to be primarily 2nd harmonic.**

Not to be argumentative, but that's hardly convincing. The distortion analyzer wasn't invented until '41. What did he use as a test record, a steady tone on a 78 ?

For those unfamiliar with the history here, Baerwald didn't invent the alignment which bears his name. He popularized the Loefgren A alignment which has lowest average error. Loefgren B has lowest total error, primarily because nulls are closer to the center of the band where error is greatest.

Sampsa55, I'm not saying 2nd harmonic is wrong, I don't know. Perhaps there is a more recent testing?

Regards,

sampsa55
71 posts
 
I wasn't referring to a test, but to Baerwald's math models where he derives the distortion resulting from the stylus being at at angle to the groove and the results show the 2nd harmonic dominates. I don't have Loefgren's original paper, so I don't know if the result is even older. (Stevenson wrote his in 1966.) I'm sure it has been tested too.


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