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Using Adjust+ for VTA

PostPosted: Tue Jul 09, 2019 2:27 pm
by Dorian
According to the Adjust+ user manual, the ideal setting is the point where both phase and crosstalk intersect. For some reason though (my own blindspot), I only ever focused on getting the crosstalk spot on, but not the phase.

Well I hadn’t been happy with the sound for the past couple of days, so last night I revisited my Adjust+ setup. See diagram below. First measurement is 0 degrees, last measurement is -2.5 (these don't actually reflect the degrees off-center, just each measurement).

My first measurement showed phase almost dead on, but crosstalk quite far apart. I then only adjusted azimuth (not VTA) for the second measurement, and got crosstalk almost dead on, but phase had moved further apart. For measurements 3-6, I only adjusted VTA, not azimuth at all. I finally got both phase and crosstalk aligned exactly on the 6th measurement.

I do of course realize that these measurements only apply to the test record, and that I may still want to adjust VTA somewhat during play. But nevertheless I thought it was pretty cool to see the differences in both phase and crosstalk from only making VTA adjustments.

I listened to two familiar sides after making these adjustments, listening very critically through headphones, and the sound was excellent top to bottom.

Does this seem like a valid approach to setting VTA?

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Screen Shot 2019-07-08 at 10.30.28 PM.png (74.61 KiB) Viewed 3808 times

Re: Using Adjust+ for VTA

PostPosted: Tue Jul 09, 2019 2:42 pm
by tony22
Seems like a good approach, but IMO I think what may really be going on here with the change in VTA is a slight change in zenith. I think that has more to do with phase changes than VTA - but with a non-conical or non-elliptical stylus, changing the VTA in effect may be enough to change the zenith slightly.

Re: Using Adjust+ for VTA

PostPosted: Wed Jul 10, 2019 1:36 pm
by Golear
Very interesting. Is it possible to play the test track through the speakers? What differences do you hear, in terms of:

a. minimum phase error, at the cost of higher crosstalk error;
b. minimum crosstalk error, at the cost of higher phase error;
c. both the same, as in your 6th configuration.

Thanks.

Re: Using Adjust+ for VTA

PostPosted: Wed Jul 10, 2019 1:58 pm
by Dorian
Hi Golear

I prefer not to change anything since I now have it spot on. FWIW, according to Dr Feikert, the human ear detects phase imbalances more than small crosstalk differences, and so he recommends prioritizing phase over crosstalk, if necesssary.

Re: Using Adjust+ for VTA

PostPosted: Wed Jul 10, 2019 10:08 pm
by Golear
Thanks for your reply. That's my personal belief, too.

Re: Using Adjust+ for VTA

PostPosted: Thu Jul 11, 2019 5:08 am
by kurtster
Dorian wrote:...
Well I hadn’t been happy with the sound for the past couple of days, so last night I revisited my Adjust+ setup. See diagram below. First measurement is 0 degrees, last measurement is -2.5 (these don't actually reflect the degrees off-center, just each measurement).

My first measurement showed phase almost dead on, but crosstalk quite far apart. I then only adjusted azimuth (not VTA) for the second measurement, and got crosstalk almost dead on, but phase had moved further apart. For measurements 3-6, I only adjusted VTA, not azimuth at all. I finally got both phase and crosstalk aligned exactly on the 6th measurement.

I do of course realize that these measurements only apply to the test record, and that I may still want to adjust VTA somewhat during play. But nevertheless I thought it was pretty cool to see the differences in both phase and crosstalk from only making VTA adjustments.

I listened to two familiar sides after making these adjustments, listening very critically through headphones, and the sound was excellent top to bottom.

Does this seem like a valid approach to setting VTA?



Most interesting. It would seem that the VTA is one of the adjustments that can help overcome the most problems with alignment once you are as close as your tools can get you to ideal. From all the reading I've done here lately it seems the azimuth changes with each VTA change. So I give up trying to tweak that any further. It only seems to be off about 1 dB at the most when I look at the wav files. I can fix that later.

Just trying to dial it in the rest of the way since getting set with the Mint Tractor. That has been the single greatest sonic improving adjustment that I have made to date. The wife has been impressed with the improvement. That leaves me with the VTA to do everything else I guess. I agree with the thought that being in phase is the more important adjustment.

In steps 3 through 6 which way did you go with the VTA ? Up or down and by how much ? I must rely on what my ears tell me for the VTA. I seem to start out low and adjust up in .25 mm increments and rarely do I ever take it down from my initial setting. I am always adjusting the VTA for every record, mostly for differences in thickness then adjust further as needed.

Then is it possible that with the VTA you can somehow end up with a setting that just happens to get where you are trying to get because enough of the angles are close enough on that tiny point of the stylus tip that it overcomes all or enough of the other errors to sound correct ?

Lastly, If I was going to try to play with the azimuth one more time should I err on the high side for the VTA or the low side ?

Re: Using Adjust+ for VTA

PostPosted: Thu Jul 11, 2019 11:56 am
by Golear
I agree with kurtster.

I also thought that adjusting the tonearm bearing height affects VTA/SRA only. But many other parameters are affected. In addition to azimuth, I think there will be changes to VTF and the angle of the wires in the magnetic field inside the cartridge. This would be true for linear tracking tonearms as well as pivoted ones. And with pivoted tonearms, we have azimuth changes. One sets it by ear, for a specific LP, a specific cartridge, arm and turntable, specific playback system, and listener. This is a cool feature, not a bug. Adjust a host of parameters with one control!

Perhaps we have to stop talking about adjusting "VTA/SRA". To adjust VTA/SRA (only), use shims between tonearm and cartridge. This may be appropriate if the the stylus mounting is very far off, when checked with the microscope method.

How about this: When we turn the knob on a VPI tonearm, we change the height of the tonearm bearing/pivot with respect to the bottom of the groove on an LP, when the LP is placed on the platter. Shorten this to... adjusting the "relative tonearm height" or RTH?

Re: Using Adjust+ for VTA

PostPosted: Thu Jul 11, 2019 12:46 pm
by Brf
Adjusting the VPI Vta tower (pivot height) affects the stylus as follows:

Azimuth (AZM): due to the tonearm offset

Stylus Rack Angle (SRA): sin(θ) = Opposite / Hypotenuse

Tonearm overhang : Pythagorean Theorem

Re: Using Adjust+ for VTA

PostPosted: Sat Jul 13, 2019 9:49 pm
by macster
Brf wrote:Adjusting the VPI Vta tower (pivot height) affects the stylus as follows:

Azimuth (AZM): due to the tonearm offset

Stylus Rack Angle (SRA): sin(θ) = Opposite / Hypotenuse

Tonearm overhang: Pythagorean Theorem



I never even thought about this.

Thanks.

M~

Re: Using Adjust+ for VTA

PostPosted: Sun Jul 14, 2019 4:02 pm
by Golear
I don't think Brf meant Pivot-to-Spindle distance. That would remain constant because the mechanism that adjusts the RTH will not move the tonearm's position and just move the bearing assembly in a vertical plane. (Or at least, one hopes so.)

I think Brf meant Pivot-to-Stylus distance when measured in the horizontal plane - this will be affected by the angle of the tonearm with respect to horizontal. I think a change in Pivot-to-Stylus distance will affect the cartridge alignment, as well as VTF. (And a change in VTF will likely have its own small effect on the SRA/VTA.)