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P-Mount T4P tracking force

Kipskiddy

Kipskiddy

Member
Hello forum friends.

I have been messing around with some different setups on my turntable and have made some interesting observations.

Model: Hitachi HT-6 direct drive with p-mount. Non-adjustable tracking and skate.
Cartridges: Generic, AT85EP and LP Gear CFT4PSE
Mounting screws: large steel that came with the generic, small steel that I bought from LP gear and small aluminum which I bought specifically as a p-mount screw as recommended somewhere in these forums.

With a non-adjustable tracking force turntable I can get quite different resulting tracking force depending on which combination I use. However in all cases the minimum VTF I can get is greater than 1.5g.

The LPGEAR with no mounting screw had VTF of 1.56g and 1.66g with the aluminum screw which is slightly out of the 1.25g +/-0.25g spec.

The fit is snug so I don't really need a mounting screw.

I'm inclined to use the LP Gear with no screw but is it worth it to try and get the tracking force below 1.5g or closer to the 1.25g nominal?

The individual weights are shown in the photo below. Adding the 0.1g screw added about 0.1g to the tracking force
Cartridges.jpg
 
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Is your stylus height set as per service manual?
You can't move the counterweight, correct? You can still add weight to it.
 
The screws aren't really required if the cart mounts snugly.

Be interesting to see how well it tracks at 1.25, the 1.5g might have been the intent of the designers.
 
If my HT-6 wasn't in storage, I could run the experiment I'm about to suggest. Taking borchee's suggestion, add some mass to the far end of the counterweight to see if you can get the force at the diamond to get close to 1.25g. As loudnoises suggests, there were styli, including Technics styli, that tracked better at 1.5g, the upper limit of the T4P standard. With a removable counterweight-weight, you could accommodate both types.
Also, please let us know what you're using to measure tracking force.
 
The service manual says to set the height to 6-9 mm above the platter when the arm lifter is in the up position, and it is within this range.
The counterweight isn't adjustable, but I could add some manually.
I'm using a calibrated 10g load cell for the measurement with an arm that sits at about record height.
If I do the counterweight experiment, what should I be listening for?
 
The only thing I can think of to be listening for is mistracking if the reduction in VTF is taken too far, but with an accurate VTF gauge, this would be very unlikely.
 
Splitting hairs is what it might come down to. Get it close the suggested specs and if sounds fine, it is fine.
 
Some P mount tables also had a fine adjustment, not always user-accessible. Might be in the service manual though.
 
Kipskiddy said:
With a non-adjustable tracking force turntable I can get quite different resulting tracking force depending on which combination I use. However in all cases the minimum VTF I can get is greater than 1.5g.
Click to expand...

I wonder if there is a problem with your tracking force gauge. The AT cartridge, especially, should yield 1.25 gr tracking force, at least with a OEM stylus. Do you have a way to test the calibration of your gauge?
 
I used the (Ortofon's) VTF gauge to load the cantilever (of my Stylus 10 and Stylus 40) with the recommended (15mN) force - while looking for the IM (variable magnetic shunt) position within the armature (at the de-touched replacement bit - of course).
My observation is:
  • only at the recommended VTF the IM is perfectly centered.
This position corresponds to the lowest THD, correct VTA, and to the proper effective length of the tonearm+cantilever combo, that puts the needle/stylus exactly at the tracing line (tangential - if your TA is linear, or Baerwald's/Loefgren's - if your TA is pivoted).

Regarding the trackability check: one should use proper test record and oscilloscope/spectroscope rather than his bare ear.
 
sound hound said:
I wonder if there is a problem with your tracking force gauge. The AT cartridge, especially, should yield 1.25 gr tracking force, at least with a OEM stylus. Do you have a way to test the calibration of your gauge?
Click to expand...
+1. Check it out.

T4P is supposed to be "standardized" to produce the same tracking force. Key words there is "supposed to".

If your's is too heavy, then your scale is off, the cart is not to the T4P standard or there's a non standard stylus installed. That 85Ep looks stock to me though. I have teh same one and it scales out right where it should on my Technics.

When I installed a VMN40ML on my AT132 for my Technics SL-QL15, I went with the stylus suspension requirements of 2.0-2.2 g vice the T4P standardized weights. When scaled, the new stylus (with guard) brought the vtf to perfectly in range at 2.1g. I managed this by leaving the movable stylus guard on the cart, which brought the VTF to where the stylus suspension wanted to be without having to max out the weight adjust on the tone arm itself.

So if you're running a non-T4P standard stylus, your weights may be out because of it. Costs nothing to check.....
 
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Scaled my 85EP for comparison:

fr_6155 copy.jpg

Little hard to see, but that's 5.865 g. That 85EP is straight out of the package, bone stock. Bought new approx 12 months ago.

Scale is accurate to 0.025 on a 20g check weight.

So your 5.890 is right on the money really. 0.025 g difference is effectively nothing.

If yours is "out of spec" when installed on that non adjustable T4P arm, you're going to have to add some weight to the headshell or back behind the tone arm pivot to bring it in spec. I often use a little modelling clay to find the proper amount of weight and then find something that doesn't look quite so "buck shee" when added.
 
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T4p mount standard is 6 grams mass, 1.25 grams tracking force. Some turntables with this mount, have limited tracking force adjustment, as light as 1 gram tracking force, or 1.5 gram tracking force. Pro tip, Over 90% of generic styli available will not work for T4p mount, they require heavier tracking forces than this system will work under.
 
More specifically, there are styli that will fit your cartridge that aren't *t4p compliant*. It's something you want to check for.

Just avoid buying anything generic, they suck anyways. You can often find old pfanstiehl styli on the bay, or go to voice of music or another reputable seller. But those unbranded styli with 37 identical listing - run away.
 
Thanks for all the feedback!
In the vein of gross overkill and diminishing returns I'm using a $2500 load cell setup for the measurement.
I stuck a small washer to the back of the tonearm with a slice of 3M double-sided tape and got the VTF down to 1.291g
My intent is to compare the AT85EP to the LP Gear CFT4PSE which is supposed to be an upgrade. Both are brand new.
Like most of my projects, I likely won't be able to tell the difference, but it's fun to try.
VTF after counterweight.jpgload cell 2.jpg
 
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