Who tweaks VTF too?

Ideally the bearing of the tonearm should be at the same height as the LP surface, otherwise there will be changes to VTF as the cartridge goes up or down with record warps. The greater the vertical distance between tonearm pivot and LP surface, the greater the magnitude of the VTF modulation. The same thing is true for the tonearm's center of gravity, which, if changes to VTF as a function of height are to be minimized, should properly be at the same height as the LP surface.

VTF modulations as a function of cartridge playing height will then cause the angle of the signal coils to change within the field of the magnetic gap, and the SRA to change. Both can be a source of non-linearities or IMD.

Whether the changes in SRA will be audible or not are partly down to the stylus profile - usually a long-footprint line-contact stylus with a narrow side radius will be most sensitive, while a conical may not be sensitive at all.

The change in coil angle with VTF may or may not be so clearly audible - it depends on the cartridge. The reason is that with most cartridges, there are two different VTF "sweet spots", one higher, the other lower in value. The lower value VTF sweet spot will align the signal coils so that they are parallel to the magnetic gap, which gives best linearity (which may or may not be the same thing as maximum output), and the most equal values for horizontal and vertical compliance. However, the lower value VTF will usually not be sufficient for optimal tracking of the LP groove.

The higher value VTF sweet spot will allow optimal tracking of the LP groove, but will push the coils out of alignment with the magnetic gap.

This is why you typically see a quite large recommended range for VTF from the cartridge manufacturer - the wide range signifies that a compromise between two different requirements is occurring.

OTOH, a cartridge that has been designed so that the VTF value which aligns the signal coils to the magnetic gap coincides with the value required for optimal tracking, will have a quite narrow recommended VTF range from the manufacturer.

hth, jonathan carr

Hi Jonathan, thanks for injecting some authoritative input into the meanderings on this thread. What you say all makes sense to me, however I would still expect some session-to-session variation in optimal (or preferred) geometry to be probable with any cartridge, based on differences in prevailing environmental conditions affecting the suspension, as well as differences among the way records are cut (or from my perspective and ability to tell, simply in the way they sound). Do you disagree with my take that in all likelihood, there's no reason one should go really wrong as a listener by using the best tool we have available, namely our ears, to tweak these parameters, including VTF within reasonable limits, on a record-by-record basis?

BTW, I do realize (even though you chose for whatever reason not to say so as a disclaimer) that you are involved in the design and marketing of a cartridge line that is claimed to take into account the effect of tracking force on optimal coil alignment within the magnetic gap. This would of course seem to make obviously good sense -- in fact, so much so, that I actually have a bit of a hard time believing either that other manufacturers have never taken this factor into account themselves (whether they said so or not), or else that they didn't determine that it's in reality a relatively unimportant consideration as regards sonic performance. (One can't help but note that by implication, your cartridges too did not previously take this factor into account, or else that you knew about it but considered it to be fairly trivial.) Still, even if it's as much marketing as science, the concept does strike me as being a really good idea for a cartridge maker to tout, so bravo. Please feel free to comment!

FWIW: Yesterday I went ahead and made a bunch of VTF measurements using my digital gauge (the kind commonly selling for $80 from many outlets), for both the lowest and highest VTA adjustment settings possible with my tonearm, which amounts about an 8mm differential in height of the pivot point -- quite a bit broader an angular range than anybody would actually utilize for setup or tweaking of any individual cartridge.

First I confirmed the precision of the gauge (to within whatever limits are imposed by the quality of my tonearm bearings) by making many measurements without changing anything. As I have found before, despite the fact that these gauges have a readout to three decimal places, it's only to the second decimal place that readings are close to repeatable, to within an accuracy of about plus or minus two (i.e., a margin of error of about 4 hundreths).

I was pleasantly surprised but hardly shocked to find that, as I predicted, the variation in VTF (from a baseline setting of 1.5g) which accompanied the widest possible change in VTA, only amounted (on average, over about 30 or so repetitions of the readings for each VTA extreme) to approximately .02g (i.e., about plus or minus one hundredth from the force reading that could be expected at the middle of the arm's VTA range), which is of course within the gauge's margin of error. Despite there being some overlap in the force readings at each arm-height extreme, I do think this small average force differential is nonetheless real, due to the overall trends I observed over the course of the measurements, but that it is probably too small to account for any sonic differences, especially given that in practical use the actual VTA range will be quite a bit less than what I was experimenting with.

So my conclusion is that it's unlikely that adjusting VTA represents, consequentially speaking, a secondary adjustment of VTF as well. But I would welcome what any other posters' findings might be on this issue, if anyone cares to make the kind of measurements I did, perhaps using better tools and a more premium tonearm. Still, at the end of the day I didn't start this thread to get into such technical considerations -- I started it because of what I heard, and to see if anyone else had also heard and was doing the same thing in tweaking VTF to suit their listening of the moment. Continues to seem like not so much...

PS - All the adjusting and measuring I performed yesterday, along with subsequent listening, did have the beneficial effect of prompting to me to slightly raise my tonearm's baseline VTA setting in order to increase the SRA a bit, so as to offset the effect on the rake-angle of the somewhat heavier (on average) VTF I'm commonly running these days. My thanks to those posters who pushed me not to forget such interrelated considerations!

There are a lot of us who hear what small VTF changes do. But as you say, it is only one parameter of several in a dynamic situation. I don't think making absolute statements as to whether it is this or that is helpful because these parameters must be taken in consideration together at all times. Maybe Wally would be interested in that debate. Yes, a few tenths of a gram can make a difference in some circumstances, IME, YMMV.

Update: 800 page views now, but still no affirmative responses that anyone else tweaks VTF to suit individual records.

Hello Zaikesman,
After following this post I will give it a try. If it can make an improvement I'm all for it.
Do you find that it is by individual albums or by the lable, such as all EMI's are set one way and RCA's another?
I assume you keep a list of the settings. Sorry I have not read all the post's yet, so if you have already answered the question I apologize.
I'm glad that you have taken the time to get the most out of your record play back system. Thanks for sharing this tweak, it never occured to me.
I usally set the VTF on the HI side of the recommended setting and I will adjust the VTA as required.
I'm trying to listen to nothing but albums lately, so this would be the time to do some tweaking.
Respectfully,
Joe Nies