560 NEWBIE WOES : HOW TO CLINICALLY MEASURE COUNTERBALNCE AND TRACKING WEIGHT

[sixtoo]

So, after getting my machine rewired because someone in either Fed Ex or Customs decided to cut the wires to the motor,
I finally got everything setup and did a lot of reading on basic setup (everything flat, cutterhead traverse square to spindle and travelling across perfectly when hand winding.

I calibrated meter to 0db following the published calibration instructions, and calibrated the meters using ortophon test LP with ortophon needles.
I built a buffered multi so that the unbalanced signal was showing a perfect mirror of what is being sent to the cutterhead.
I set the counterweight to 45 grams, horizontally oriented the cutterhead, accounted for the 5-8 degree rake over 90 degresss (it didn't need to be changed from when I used this machine at Souri's but I measured regardless) measured 15g tracking force (on the new stylus) to the cutter head, with weight measured from record, and confirmed multiple times. 35-38 degrees temperature on blanks.

First test I did no heat, as advised by Souri and forums : barely scratching the surface : no swarf, no playable signal.
Second test 1 gram more tracking weight to cutter head : no heat barely scratching the surface : no swarf, no playable signal.
Third test, slight heat, almost got swarf but unplayable results.
Fourth Test, increased heat while cut looked like it was -almost- cutting, tip went instantly red hot, I shut off, got junk all over the cutting stylus, and after a cleaning and inspection it looked like the stylus was still okay.
Fifth Test, less heat, 1 more gram, still nothing, except pink junk from the cleaning liquid, after cleaning,

1st Try, First stylus cooked.
I feel relatively confident that my setup was correct, and examined the stylus before cutting. I was also with a mechanical engineer and another savvy nerd, all of us were like "we missed something for sure".

Feel free to offer up any suggests here, and if someone has a sure-shot way for measurement other than setting a brand new stylus on a record, and adjusting weight, please feel free to share.

Photos for reference.

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[sixtoo]

Ordered another stylus and measurement reticule from Spinnertown : will give another shot when it arrives.

[spinnertownblanks]

Just seen your order, thanks!

Those look like modulated grooves, calibration should be with unmodulated grooves (no audio), either that or its just skating the surface and causing ripples. Just to make sure i understand correctly, you calibrated playback to 0 VU, but how did you calibrate what is being sent to the head? It is best to cut, and slowly raise the volume of the audio until cutting 0 VU, then you can calibrate cutting level. Never confuse 0 DBFS with 0 VU. Maybe i miss understood and you did it this way, but just wanted to check.

Also for rake angle, it looks like your diamond isn't touching the blank, make sure it is when taking the reading. Again maybe you did, but just checking.

It will be something simple that needs tweaking i'm sure, but let me know that info and we can go from there.

[spinnertownblanks]

With calibration of what is being sent to the head itself, your audio is likely going through the Main Unit, so if you take a reading, it must be after the Main Unit. Either that or go for a feedforward system and map your cutterhead, then your pre-emphasis is done in the DAW and then you can take a reading of what is being sent to the head.

[sixtoo]

I want to map my cutterhead using the main unit, and was using audio for the tests for that purpose so I could make an AB curve but maybe I am getting ahead of myself.
I calibrated my meters using playback from the turntable with the ortophon test record (using a dj mixer as trimmer) and am sending recording out from this mixer (unbalanced) to the cutterhead (- this made sense to me because the whole system is unbalanced : and as I remember from audio class there is about 6-12db difference in signal between those two, so I assumed it best to keep the whole system unbalanced).
When sending audio, I slowly turned up from zero to the calibrated meter level of 0VU (DB is arbitrary because of the trimmer) cutterhead seemed to be just skimming the surface of the blanks, and would not dig in, which is why I eventually added heat.
I also assumed the depth of cut to be determined by dashpot spring pressure, but maybe I am missing something in a third variable for depth adjustment of the stylus and groove width?

[spinnertownblanks]

In terms of the groove itself, that will cut regardless of audio. So likely best to start unmodulated and get to audio afterwards. For now let’s get cutting nice silent grooves.

If it’s skimming the top of the blank it’s definitely a weight issue. If your counterweight is set anywhere around 45g, then it’s all down to the dashpot spring. If it’s skimming you definitely need to adjust to add more weight here, the head isn’t lowering enough