Experiments with VTF

Andrew,

Great post. Your VTF protocol is very similar to mine, as is your description of what to listen for.

Every MC I've used has responded well to this approach:

1. Set antiskating at or near zero. Excess antiskating will interfere with the VTF optimizing process.

2. Starting from a VTF that's known to be sufficient for clean tracking, reduce VTF in ~.05g increments until HF's begin to go fuzzy and/or audible mistracking "buzz" occurs on dynamic peaks. That "mistracking point" is your benchmark, and it changes with the weather.

3. From the mistracking point, increase VTF in .01-.02g increments. Listen for just the things you described, a filling in of midrange and upper bass weight without loss of HF speed, extension and "air". Go too far and you'll lose highs and microdynamics.

Most cartridges have a very narrow VTF sweet zone that balances heft vs. finesse. On my TriPlanar/UNIverse it's .02g wide or less, and never more than .04g above the mistracking point. Other cartridges have acted similarly, though not always with such precision.

4. Nudge antiskating back up in microscopic increments, using just enough to prevent R channel mistracking on very difficult passages. Excess antiskating produces sonic mud and slowness that sound quite similar to excess VTF.

Finding a cartridge's mistracking point and moving upward from there in tiny increments is a fast, repeatable and reliable method for dialing in VTF.

Best,
Doug

P.S. The VTF sweet zone can change during a session if you're playing alot of high energy music, especially if the cartridge was cold to begin with. As the suspension warms up, the optimal VTF goes down.

I've even had optimal VTF go back up during a break, since that allowed the cartridge to cool down again. This happened during Raul's visit. We stopped playing for about an hour to have dinner. When we came back the bass was weak. I replaced a thick O-ring with a thin one, adding about .02g, and everything was fine again.

Anyone for set and forget? ;-)

Do you make adjustments to VTF independent of VTA?

Yes. I agree with everything Aoliviero and Nsgarch wrote about that. The VTF tuning we're discussing is so small there's little practical effect on VTA (SRA, actually, as NSgarch said). Nor are the sonic changes from VTF fine-tuning at all similar to those of SRA fine-tuning. These adjustments sound very different.

Do you think that the differences you note are due to the change in the force the stylus is applying to the groove or to effective changes in VTA (which must change with VTF changes)?

No and no.

IMO the diffenences are due to the pressure that VTF applies to the cantilever/suspension interface. This is why excess VTF sounds so much like excess antiskating, as I mentioned above. They both apply too much external pressure and inhibit cantilever freedom.

The more pressure on the cantilever, the less free it is to respond. Its response to groove modulations will be slower and its peak amplitudes will be physically contstrained. The sonic result is smothered HF's and smothered dynamics and a general dullness or lifelessness.

OTOH, if VTF is too low, the arm and cartridge have insufficient inertia to resist moving when really big and slow transients (aka, bass notes) come along.
If the arm moves then some of the energy that should have deflected the cantilever relative to the magnets, doesn't. Result: softer bass with lower amplitudes.

Now where did I put that cartridge warming lamp? I actually suggested we use our Littlelite for that during winter months Neil, but Paul vetoed it for some reason. Oh well, another great tweak lost forever! I'm gonna design a tonearm with a built in heating coil and a thermostat. Should sound great!

For the record, it would take a 1,000W bulb to keep most cartridges warm in Ndoshi's listening room.

I presume that's why he uses a Koetsu. ;-)