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In Reply to: RE: At the risk of being attacked, using the plastic, Technics, overhang posted by alaskahiatt on April 30, 2021 at 15:03:39
I just installed an AT cartridge using that method on Wednesday. Then I checked it against the Bearwald protractor and it was spot on! I was very surprised and pleased.
Follow Ups:
... so that would be surprising if it was really spot on :)
The Technics nulls are 58.8 and 113.5mm
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
Sure, but it's pretty close to Stevenson-DIN, within 0.1 deg offset and 0.1 mm overhang, so close enough to align with a Stevenson protractor using DIN inner radius.
But if you use the exact 230 mm / 15 mm / 22 deg numbers they spec it for, yes, it's a custom alignment with the null points you list. The point was that it's significantly different from Baerwald if one is aligning with much precision.
I am not sure what you mean about Stevenson "DIN" since the DIN modulation envelope technically spans from 57.5mm to 146.3mm, although it sounds like you are referring to Stevenson 1C as the nearest match. Whilst it might seem pedantic of me, you will see from the link, that although the overhang and offset are similar, the resultant arcs are very different.
Most people are actually referring to 1B when talking about a Stevenson alignment.
It is a common misconception that is repeated over and over that Stevenson is an "alignment" where you put the inner null at the minimum radius for whatever envelope you choose. If you read the Stevenson paper, he does not specify the inner null at the minimum radius - he applies the standard Lofgren equations to generate 3 variants for a Universal solution suitable for the three main record sizes based on the following modulation envelopes:
For a 215mm pivot/spindle distance and applying Lofgren A equations to the following modulation envelopes (converted from the values in the Table given in inches in the paper), you get the corresponding overhang (H) and offset (O) rounded to 1dp.
1A: (57.89 -> 145.26mm) H=16.9, O=23.2
1B: (54.81 -> 145.26mm) H=15.8, O=22.6
1C: (51.77 -> 145.26mm) H=14.8 (14.76), O=22.0 (21.99)
Technics: (53.47 -> 140.6mm) H=15, O=22
Anyway, I have created a link to the VE calculator to show how different the resultant geometries are to the Technics alignment. There will be some errors in the calculations due to rounding for the length conversions from imperial to SI.
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
I just meant that if you choose Stevenson on the calculator and set inner groove radius to DIN standard, leaving outer radius at default IEC standard, you get very close to Technics specification, within 0.1 mm overhang and 0.1 degree offset angle, as shown below. No biggie, just an observation, but thanks for the information about the different Stevenson variations ...
It may be time to pick up a "real" protractor then. I've been using the download from Vinyl Engine for years. As you have to punch the paper manually it's very possible to get it wrong.
On the other hand I hit both null spots and it sounds good. The Audio Gods must be smiling at me!
I
The nulls for the Technics alignment (15mm overhang and 22° offset) are 58.8 and 113.5mm - it is impossible to hit the Baerwald (66,121) nulls having used the Technics gauge since the required overhang is ~2.5 mm longer (overhang 17.46mm) and the offset ~1.5° greater (offset = 23.46°) compared to the intended Technics alignment.
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
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