What to listen for when setting VTF?

Toufu,

Are you certain you're actually playing with VTF at a true 4.0g? How are you measuring? The dials on some tonearms are notoriously inaccurate. Some Shure balances were (idiotically) manufactured of magnetic steel, which exaggerates the measured downforce. Etc....

Unless you're weighing with a reasonably accurate scale, you can't be sure you're actually playing at that seemingly outlandish tracking force.

But if you are, I agree with Zenblaster. Something is very wrong if you have to play a Denon 103 at 4.0g to sound good. What happens if you play in the normally recommended range? What sounds "bad" about it?

Stop! In the name of love - for your LP's, not to mention your 103.

...for some classical recordings, the strings have some silbius or distortion, that are corrected by going to 4.0. I am still running it at around 2.2, but was curious why it is that way

There are several possible causes, including various setup parameters and phono stage slewing distortion, but here's one cause I'm certain is involved to some degree in your system.

Every stylus has a contact radius, which determines the minimum size of the groove modulations it can trace. When a stylus encounters modulations smaller than it is, all it can do is scoot past the tops, playing part but not all of the waveform at that frequency. This necessarily results in clipping of the waveforms at these higher frequencies and perhaps in the momentary loss and regaining of stylus-groovewall contact, all of which we hear as "sibilance". The larger the stylus, the lower the frequency where this will begin to occur.

The contact radius of the 103's conical stylus is much larger than the contact radius of styli in some more modern cartridges. Finer stylus profiles trace smaller modulations (ie, higher frequencies) cleanly, and do not start "scooting" past small groove modulations until higher frequencies.

Increasing your VTF to excessive levels will not make the stylus fit into modulations smaller than it is, but it may mitigate the resulting distortions in a couple of ways:

1. Increased pressure between stylus and LP assures that the stylus will not lose contact, which makes the (unavoidable) clipping of too-small modulations as smooth as possible.

2. Increased pressure between cantilever and suspension is smothering higher frequencies, much as soft earplugs block higher frequencies while letting lower ones through. In effect, you're using excessive VTF as a HF rolloff filter.

If you listen to a lot of this kind of music, and the distortion bothers you, I'd suggest that your next cartridge be one with a line contact or micro-ridge stylus. All else being equal, they reproduce HF's more cleanly than conical or elliptical styli.

Raul makes another good point. I'm not familiar with the Zu version of the Denon 103, but the normal versions of that cartridge are not an ideal match for lighter weight unipivots like the JMW 9. Compliance, while not actually as low as Denon's quoted 5cu, is still lower than optimal for this tonearm. That can affect tracking.