Lessons Learned Setting up VPI Scout - VTA interacts with VTF

I have gained a lot from this forum and thought it was time to make some sort of contribution. Although, for some of you this is probably nothing new and I welcome any corrections or additional thoughts.

Here are some lessons l’ve learned from setting up an Ortofon 2M Black on my VPI Scout with JMW 9 tonearm.

Initially when I was setting up the 2M Black I started with a vertical tracking force (VTF) of about 1.6 grams and started searching for the right VTA. I gradually lowered the back of the tonearm and reached what I thought was the right VTA. The sound “locked in” with a very balanced tone top to bottom. Going any further made the sound muddy. Raising the arm made the sound bright. I had found the optimum VTA, right? Not yet. Turns out that as I lowered the VTA the VTF was increasing. I had found the optimum VTF, but was not yet at the right VTA. When some records still continued to sound edgy I started experimenting.

Here’s what I started realizing….

1. Lowering VTA increases the VTF (unique to VPI JMW9 ?)
As you lower the back of the tonearm (decreasing the VTA) the VTF increases. This phenomenon doesn’t exist on my SME Series III Arm or my older Pioneer Arm. It may exist on other tonearms (don’t know) but it is quite pronounced on the VPI JMW 9 tonearm due to the geometry of the counterweight. The counter weight is oblong making it’s centre of gravity (CG) well below the centerline of the arm tube and quite a bit below the tip of the stylus itself. I believe this is done to stabilize the unipivot design but it also means that changing VTA changes the VTF. (I did some approximate math and satisfied myself that this geometry causes this phenomenon - see detailed explanation at the end).

2. Vertical Tracking Force (VTF) - You need a digital stylus force gauge
For me the sound quality was dramatically impacted by slight changes to the tracking force, in some aspects more dramatic than by the changing the VTA. On my 2M Black there was a very specific point where the sound was exceptionally good. This was at a VTF of approx. 1.70 – 1.75 g. Any increase above that point and the sound suddenly drops off and becomes muddy/veiled and lacking in dynamics. Below 1.70 the sound was thin and bright. (Note: the actual gauge readout was 1.95 – 2.0 grams; more on that below).


3. Stylus pressure gauge readout higher than actual VTF
The stylus pressure gauge readout was about .25 grams higher than the actual VTF at the surface of the record. The amount of error is dependent on the height of sensor on the gauge above the platter / record surface. This is related to item 1 above and there is a detailed explanation at the bottom. For now the key lesson learned is to trust your ears and don’t worry if your optimum VTF is slightly higher (+10%) than manufacturer’s recommendations

4. Use Blue Tack on head-shell to quickly adjust VTF as you change VTA
Newer JMW-9 arms have a fine weight adjustment in the end of the arm tube so you may opt to use that adjustment. My older arm doesn't have that feature so I used some Blue Tack on the head-shell to quickly adjust the VTF as I changed the VTA. I set the VTF at about 1.5 grams (1.75 indicated) and then added a small dollop of Blue Tack to the head-shell to get the VTF up to 1.70 grams (1.95 readout). As I lowered the VTA I checked the VTF and removed a small amount of Blue Tack to maintain the VTF around 1.70 (1.95 indicated) grams.

5. Measure the arm height as accurately as possible to set VTA
I used a dial caliper to measure the distance between the surface of the arm rest beam and the plinth. I also used this dial caliper to measure the thickness of various records (OK maybe I’m an OCD candidate but it does make a difference).

6. Rotating the counterweight changes the Stylus Azimuth.
Because the CG of the counterweight is below the centerline of the arm-tube it can be rotated slightly about the arm tube to adjust the azimuth angle of the stylus. Because of the relatively large mass of the counterweight you only need a slight rotation to make a difference. I’ve used a test record in the past but found it better to adjust this by ear. The soundstage opens up and the bass notes become tighter and more defined. You may need to tweak the VTA after setting the Azimuth. (I realize that due to the offset headshell this approach also affects the Zenith but the impact is very small and you can go back to fine tune this parameters if necessary). Also beware that unless you are very careful rotating the counterweight you may also change the VTF. Re-chececk the VTF again and adjust as necessary with the Blu-tack on the headshell.

7. Adjust VTA and VTF using records with vocals and a louder, high frequency passage on the inner track.
I used side 2 of Bill Conti’s original “Rocky” soundtrack (Liberty Records) to set up the VTA/VTF & Azimuth. Two reasons:
a) The first track on the side 2 has a duet with male and female vocals and higher frequency horn passages. The tone and harmonics of the vocals really locks in at the right VTA/VTF /Azimuth settings.
b) The last track on side two has a string ensemble playing the music used for the end credits. The high frequencies and occasional high amplitude of the violins causes significant inner groove distortion (tracing distortion) on a non-optimized set-up. The sound is a muddled fuzzy sound. When the VTA, VTF and Azimuth are optimized (and cartridge is aligned properly) the IGD disappears and each instrument can be clearly distinguished and the sound very sweet yet detailed (no edginess)
(BTW: Choose a VTA set-up record that you won’t mind getting sick of)


The result of all this obsessviness is that my Ortofon Black went from being a good cartridge to being a spectacular cartridge (IMHO). I have another JMW 9 arm- wand with a Clearaudio Maestro Ebony V2 and can quickly swap the arms to compare the two cartridges. Properly set-up the Ortofon 2m Black was significantly better than the Maestro, at least on my set-up. Note, however, I have what some would consider a laid-back system (e.g.: Mullard NOS CV4003 tubes and Cardas Golden Reference interconnects) so the liveliness of the Ortofon may just be the perfect match.


For the especially eager or those struggling with insomnia …

Detailed explanation why changing VTA impacts VTF on JMW-9 and therefore also impacts the digital force gauge read-out.
Most people set up their turntables by initially starting with a level tonearm. In the above notes I refer to reducing the VTA by lowering the back of the arm. As you lower the back of the arm, changing the angle of a tonearm from level, there is a corresponding reduction in the horizontal distance between the counterweight and the pivot point. However, there is also a reduction in the horizontal distance between the stylus and the pivot. If both the stylus and the counterweignt CG are approximately the same vertical level (i.e. they both have approximately the same vertical distance to the pivot point) than the percentage reduction in horizontal distance will be the same for both and there won’t be a change to the VTF. On the Scout/JMW-9 combination, the CG of the counterweight is quite a bit lower than the tip of the stylus. Thus when the back of the arm is lowered, the horizontal distance between the counter weight and the pivot decreases at a faster rate than the stylus to pivot point distance. More precisely, the percentage reduction in horizontal distance between the counter weight and the pivot point is higher than the percentage reduction in the stylus to pivot point distance. The net result is as the back of the arm is lowered (decreasing the VTA) the off-centre counterweight moves closer to the pivot point and increases the VTF.

This phenomenon also impacts the readout on the digital stylus force guage. The readout on my force gauge was higher than what is actually seen by the stylus when it is on the record surface. The reason is that the surface of my gauge where the stylus rests sits ≈1/8” higher off the platter than the surface of a 180g record. This higher gauge surface was effectively changing the arm angle and increasing the VTF. When I was setting up the VTF and VTA there was a clear optimum sound VTF at 1.95 – 2.0 grams. I was troubled by the fact that this was higher than the maximum force recommendation for the 2M Black. During my measurements I determined that the VTF would increase by ≈ 0.2g for every .100” that I lowered the back of the arm. The thickness of the gauge being .125” thicker than a 180g record meant that the VTF indicated on the gauge was about 0.25 grams higher than the actual VTF at the record surface. (In my case 1.95 - .25 = 1.70 grams meaning my optimum VTF was in line with recommended level – happy days !! )

 

You have the basics correct. Always check VTF without a record sans mat.
Arm height can be checked with a file card, the kind with horizontal lines on it.
You can also use o-rings on the tail of the tonearm to change VTF

 

O-Rings is an interesting idea. I'll look into that. Thanks

For arm height when adjusting VTA there is a range of optimum settings depending on the label. I measure the arm height using a dial caliber between the plinth and the arm rest. For quick reference I have placed a mark on the collar used to dial in the VTA. A 1/4 turn of the collar corresponds to a change in arm height of about .030" (the thread pitch is about .120") . The nice thing about the Scout JMW-9 is you can change the VTA on the fly. Once the sound "locks in" I record where the collar mark is positioned is in terms of hours and minutes. "12:00 pm" the collar mark points towards the back of the plinth; "3:00 pm" pointing to the RHS of the plinth, etc.. My lowest setting is for late '70's A&M pressings (e.g. Supertramp) is around 8:00 am ( approx. 0.250" tail down from the arm horizontal position). The highest arm setting for AP 45 RPM (e.g. Brubeck's Time Out ) is at "11:30 pm" (about 0.160" tail down from horizontal)
I've also noticed that 45 rpm on average seem to like a slightly (0.015") higher VTA than 33 rpm from the same label.