Do You Have a Favorite Disk to Set VTA/SRA?

Peter,

Thanks for posting a link to that discussion, which I hadn't seen. Post #38 seems problematic in two ways:

1. He "doesn't get" how the timing between fundamental and its harmonics can change. If we were discussing the original sound itself, neither would I. But we're not.

The sound source of interest is no longer a trumpet or guitar. It's a modulated piece of plastic. We're extracting sound by tracing those modulations with a stylus. All manner of mechanical inaccuracies, including SRA deviations, can and do alter the original sound in ways that could never happen when listening to live music.

Have you ever heard a live musician and said to yourself, "He needs to be playing with higher VTF, or less antiskating?" Of course not. The poster is suggesting that recorded and reproduced sound must have the same characteristics as live sound, which is patently untrue.

If the SRA of the playback stylus differs from that of the cutting stylus, the contact surfaces of the playback stylus will encounter groove modulations "out of synch" with what the cutting engineer intended. This, to my ears, alters the perceived sound as Whart and I have described.

2. His recommendation to set SRA by minimizing IM distortion using a test record is 100% correct; provided that, all you ever intend to play is that test record. As soon as you change records, however, the validity of that "perfect" result goes out the window.

With respect to the unknown poster, his method is that of someone who prefers the certainty of numeric measurements, even when those measurements have no applicability to the real world problem - which is how to adjust SRA for the particular record I'm about to play.

Whart,

Totally agree that "thick/thin" sound is consistent with the fundamental/harmonics timing differences one hears in more sensitive setups.

Also agree that this is cartridge specific:
1) A cartridge with a spherical/conical stylus does not really change sound at all with SRA adjustment.
2) Shelter 901 has an elliptical stylus, and it sounds "thick or thin".
3) AirTight Supreme has a "semi" line contact stylus. Not sure just what that means, but it makes sense that it would be more sensitive than a 901 but less sensitive than a true line contact.
4) High end Lyra and ZYX cartridges use a micro-ridge stylus, which provides the shortest contact radius of any stylus I know (short of a cutting stylus). It makes sense that such cartridges change sound in subtler or more detailed ways.

Interesting pictures of stylus shapes.

http://www.vinylengine.com/turntable_forum/viewtopic.php?t=22894

Chayro, great link, thanks! The pics/diagrams help explain what I was attempting to describe.

During the cutting process, the cutting needle lasts about 10 hours and then must be replaced. A worn needle cuts a noisy groove. Many people don't know this but if the cutter needle is set up right, the resulting lacquer cut is so quiet that no matter how quiet your playback electronics are, they define the noise floor.

As a result the cutter head must be removed and the needle replaced fairly frequently. Then it has to be reinstalled, aligned and then one goes through the process of getting it to cut correctly. This is the case regardless of the fact that the settings of the cutter head were previously recorded.

The issue is that every cutting stylus is slightly different. As a result, the 92 degree cutting angle can be regarded as an average and not an absolute as the mastering engineer is looking to get the machine to cut properly and is not aiming for 92 degrees. This means that every LP is cut at a slightly different angle. IOW its not just the thickness of the LP that is a variable. Even if they were all the same thickness to get ideal playback the VTA/SRA would have to be adjusted.

Hence the utility of the VTA tower pioneered by Triplanar. There are several arms now that use a similar design; if you really want to hear everything on the LP such adjust-ability is really handy!