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Setup Methodology: SRA vs. Azimuth

Puzzled Look

We knew that peeling the wrapper off Version 1 of AnalogMagik software would lead us down the rabbit hole of studying setup parameter interactions.  This is a topic we continually think about without any prodding, and any new tool has us revisiting and challenging our assumptions. 

If you’ve downloaded one of our setup guides, you’re well aware of our contention that all setup parameters interact with each other. 

The relationship between SRA and azimuth is a particularly challenging one for many, since (absent sophisticated tools) each one involves guess work, and this is compounded by their mutual interaction. 

I have not found any quantitative studies on how closely the two are coupled - at least in practical terms that would facilitate setup.

Zeno’s Paradox …

The “danger” such as it were, is that our experiments will mandate an exhaustive, recursive setup routine:  adjusting SRA, then azimuth, followed by SRA, then azimuth, ad nauseum – never reaching an end point, like Zeno’s paradox of Achilles and the Tortoise.

Our aim is to strike a balance, in both our lives, as well as those of our customers, so that our hi-fi systems are a source of fun, and not drudgery, frustration, and angst.  

Zeno's Paradox

Sometimes this means we have to go into uncharted territory, and someone needs to draw a map. 

I'll take this analysis to the extreme, and if I get sucked into a black hole ... well ... at least we'll know where the event horizon is.  Consider me, your cartologist.

Here There be Dragons

Galibier Design - Dragon

The most notable commentary I've found on this SRA/Azimuth relationship comes from our dear, departed analog-maniac Wally M.  I fail to see the utility of this calculator, and in true Wally fashion, his language can be flabbergasting (therein lies his charm). Perhaps the planned azimuth gauge would have shed some light on this.

Version 2 of the AnalogMagik software promises to once and for all, address the interrelationship between SRA and Azimuth, with a single test track.  I have trouble believing this, but I'd love to be proven wrong.  At present, I'm finding the AnalogMagik (version 1) software's independent VTA and azimuth tracks to be puzzling at best, but I'm open to the possibility that I have a blind spot. 

The map I'm trying to draw, will quantify the relationship between the two parameters, and we can hopefully get on with the business of enjoying our recordings.  Life is too short for endless, unnecessary fiddling. 

Some Working Assumptions

The setup perfectionists (you know who you are ... you SRA "twiddlers") seem to ignore one key point - that we have no idea how records have been cut.  Because of this, adjusting SRA based on record thickness accomplishes nothing other than perhaps a placebo effect.

I find myself repeating myself, but this is important:  in my AnalogMagik introduction, I reference Lyra designer Jonathan Carr's comments that there's no documented cutting standard for SRA.

Galibier Design - Stylus Photo: SRA = 91 Degrees

SRA = 91 Degrees

Galibier Design - Stylus Photo: SRA = 92 Degrees

SRA = 92 Degrees

In discussing this with a recording industry professional, he concurs with Jonathan.  So, if cutting angles range from 91 to 95 degrees (with a statistical mean of 92), then how are we going to establish a "set and forget" SRA alignment?

If we can't set SRA "permanently", then our carefully set azimuth will be wrong, every time we change the SRA.  Will this endless cycle ever end so we can kick back and listen to our records?

Finally!  Some Good News.

Thought we'd never get to this point, eh?

In our experience over a broad range of cartridges, we've found a baseline SRA setting of 92 degrees has served us well, having established this using a USB microscope.  

We rarely have to vary our initial setting by more than plus/minus 1/4 degree.  This equates to 1mm of bearing height change on a 9" tonearm.

Galibier Design - Stylus Photo: SRA = 93 Degrees

SRA = 93 Degrees

The Plan Unfolds

Based on our observed "stability" of a 92 degree SRA, we decided to take a series of azimuth readings with our Feickert Adjust + software at 3 SRA settings:  91, 92, and 93 degrees.  These extremes of 91 and 93 seem to be valid boundary conditions, based on the small variance from 92 degrees we've observed to be necessary during fine tuning.

The attached azimuth plots show the subtle shift over these rather large SRA changes.  Click the images to expand them.

Observation and Interpretation

Note that a negative angle on the horizontal axis represents the headshell rotating counterclockwise from horizonal when viewed from the front.  Likewise a positive angle represents a clockwise deviation from horizontal.

For phase angle, the L/R curves intersect as follows (approximate):

  • SRA = 91: 1.2 degrees CCW
  • SRA = 92: 1.4 degrees CCW
  • SRA = 93: 1.6 degrees CCW

The crosstalk intersections similarly drift in a counterclockwise (negative) direction as we move from 91 to 93 degrees.

Analysis and Conclusion

The big takeaway is that an SRA change of 1/4 degree will require a minor azimuth change.  You can think of this as the "fine tune by listening".  if you're a truly tortured soul, you can break out your Feickert or AnalogfMagik sofdtware, oe your mono summing cables, and have at it.

With a line contact stylus, you will hear a 0.1 degree difference, but the good news is that you can play with this as the urge strikes.  Your setup won't fall off a knife edge if you raise your bearing pivot by 1/4 degree (1mm on a 9" arm).

The key to this involves establishing a high degree of confidence in your SRA setting.  This is where danger of falling into the false nulls trap I discuss in our setup reports lies.  I wish I could advise you otherwise, but I've yet to find a better tool than a USB microscope.  Perhaps Version 2 of AnalogMagik will unlock the puzzle.

One point I would make relates to Jonathan Carr's comments about stylus variance of plus/minus 1.5 degrees.  Assume this to be the case if you're adjusting by ear.  For a 9" tonearm, plus 1.5 degrees translates to raising the arm at the bearing by 6mm from the starting position of a level headshell.  You likely wouldn't be inclined to experiment to such an extreme, but perhaps this example will encourage you to do so.

One thing I would emphasize is to somehow, keep track of your baseline settings so you can return to them should you get off track.  For SRA, this depends on your tonearm.  A Vernier scale like the one on TriPlanars or some Kuzma 4Poinrs is nice, but not necessary.  For "simpler" arms, a spacer like the one shown here will work.  Absent feeler gauges and such, a stack of business cards will work.  It's a good idea to keep track of the measured thickness, using a dial indicator.

Returning to an azimuth baseline can be a bit more tricky.  Even with our azimuth gauge, we can only re-establish azimuth to about .25 degree accuracy.  This is the best we can do, absent firing up our Feickert Adjust + software.  One thing I must warn you about:  even with the most sophisticated azimuth adjustment we've encountered (the Kuzma 4Points and Stogi Reference), you will be amazed at how little movement results in a 1/4 degree change, and we're after much smaller changes than that.

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