Dual 510 overhang measurment

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Iloveali
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Re: Dual 510 overhang measurment

Post by Iloveali » 18 Feb 2019 23:11

Japi Roelofs wrote:
18 Feb 2019 22:03
I have been following this thread with interest. The one thing Dual manuals don't disclose is the overhang figure. The 'Ebay protractor' that was shown on the previous page seems to have it though. It says it's for a variety of Dual models, that supposedly have the same arm length. I looked at a Test Report from an old German hifi magazine (check the link here — sorry, it's in German) for a Dual 701, that has the same effective length and offset angle as the 510. The overhang figure of 18.9 mm, and spindle to pivot distance of 203.1 mm are mentioned there too. Can we assume they are correct? Who knows... in that same test report it is said that the null points are at 61.5 and 124 mm though. That doesn't correspond with the null points of the Ebay protractor. Interesting...

So let's assume the overhang figure is right. We now have these parameters:

Effective length: 222 mm
Overhang: 18.9 mm
Spindle to pivot: 203.1 mm
Offset angle: 25° 20'

Is it possible to make a custom arc protractor using Conrad Hoffman's program? Let's see...

Regular alignment methods and groove radius sizes all give a different outcome. The only way to make it so that it corresponds with the specs given by Dual is to use Baerwald / Lofgren A alignment, and a set of custom groove radius sizes.

Being the obsessed fool that I am, I worked the numbers and came up with these parameters, to be used in Conrad Hoffman's program:

Spindle to Pivot Distance: 203.1 mm
Inner Groove Radius: 57.643 mm
Outer Groove Radius: 158.885 mm
Alignment method: Lofgren A

The result looks like this:

Dual 510 arc.JPG

So this is the same protractor as the 'Ebay protractor'. The position of the null points is a little bit different, but we're talking less than a hundredth of a millimeter here. Even more fiddling with the groove radius numbers might correct that. The numbers are weird anyway, especially the Outer Groove Radius which is way out of the actual disc size. What's up with that?

I guess the only way to figure out if it is really correct, is to very accurately measure the spindle to pivot distance yourself. Not an easy task...
Hey thank you for jumping in!! The slight discrepancies I too noticed when generating the arc template. My other thought is, if there saying 18.9 for overhang, why does the dual gauge come out as 28.5? I gotta be missing something. And then in the dual manual, it says to add right angle once overhang is set. That also confused me, as others state straight in the headshell. We are gonna figure this out!!

Japi Roelofs
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Re: Dual 510 overhang measurment

Post by Japi Roelofs » 18 Feb 2019 23:23

The 28.5 mm or 1 1/8 " figure does not refer to the overhang, but rather to the position of the stylus relative to the back of the cartridge carrier. This then will provide the 18.9 mm overhang, which is the position of the stylus relative to the center spindle.

DSJR
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Re: Dual 510 overhang measurment

Post by DSJR » 19 Feb 2019 09:20

Chaps, you're drastically overthinking a VERY easy adjustment that within reason, is largely inaudible if it's slightly out using a stock elliptical stylus - and totally inaudible with a conical stylus as these things have more distortion anyway!

The ONLY time it might possibly be an anal issue is if you have a fine line or Shibata style stylus that needs very precise alignment, assuming the makers got it right in the first place. VTA can be fine tuned quite often with 1/10g downforce either way and that's rarely an issue as long as the arm is reasonably level when playing a single record in my experience. if the arm sloped down, I'd use a 3mm or 5mm mat on top of the Dual one, which back then, didn't offer best record support (nobody had analysed the resonant effects of hard ribs and sharply dished centre areas), but I'm deep into audiophool territory here, so shan't pursue the concept further.

Just enjoy the music the deck is trying to extract...

Japi Roelofs
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Re: Dual 510 overhang measurment

Post by Japi Roelofs » 19 Feb 2019 11:22

There's an insane amount of 'variables' in record playback. Do I have the right tracking force? Proper antiskating? Is my belt the correct one? Is my turntable level? Is my stylus worn? Is my cable capacitance too high? The list goes on and on and on and on...

All of these things can drive a person nuts. So why obsess over such a trivial thing as a couple of millimeters more or less in the process of cartridge alignment? Well, because if you do this correctly, there's one thing less to worry about.

I have aligned hundreds of cartridges, and the Conrad Hoffman program — that allows you to make your own custom arc protractor — is simply a work of genius. It takes out a lot of guesswork. Making the stylus follow the arc is very straightforward. It either follows the line, or it doesn't. Once it does, the overhang is correct. Now all you need to do is make sure the cartridge body (or cantilever, if you want to be more precise) is lined up with the grid. If one makes a protractor according to the tonearm manufacturer's specs, having the cartridge sit square in the headshell is all that's needed.