VR: voltage to LPI info needed

[boryo]

Hi, I remember someone posted such a table long time ago but can't find it anymore. Does anyone have it or maybe if someone knows the formula how to calculate it myself? Thanks!

[spinnertownblanks]

A rough way to do it yourself would be to use a reticle ruler with a microscope and measure groove spacing, although this would be in cm not inch if in Europe, but will work. Hopefully someone has a table though!

[farmersplow]

Markrob and grooveguy have written several posts about this. Enter "voltage LPI" into the search function and you'll find something.

[dubcutter89]

Hi Bo!
Hope you're doing good

I have a Volts/LPI table for the Vinylrecorder somewhere, but I personally would recommend specific measurements on your unit - still I'll send to you for reference.
I also would recommend NOT to use a microscope - unless you have a very dedicated precise device the reading error will be quite high...

If I would have to figure out I would do the following:
- Attach a voltage meter across the (stock) pitch motor of the VR (potentially install a fixed unit, then you can always read the actual voltage in the future)
- Feed a set of voltages (0,5V 1V 1,5V 2V ...)
- For each voltage measure the time (stopwatch) it takes for the cutter to move a defined distance, for example 100mm (the long distance will make the reading error small - a lazy reading between 97...103mm will be only 3% error / same with time, if the measurement takes long - let's say 10mins - then a few seconds error will be very little in %)
((Sidenote: the 100mm distance is close to the max availabel surface on a LP -> the measured time will be a good indicator for the maximum playing time later. No need to do LPI or R/mm conversion if you don't want to!)
- Make a spreadsheet you feed with the measured values and do some math to get the LPI or R/mm values for 33 or 45 rpm that is related to the motor voltage.
- You can also check if the voltage and speed has a linear relation (double Voltage => half recording time...)

This way you can generate a very precise table for YOUR machine, and using the fix installed meter you can recall settings more precise in the future if needed..

Hope this helps!
Lukas

[PLD]

I did something similar, but wanted something where I entered a side duration and it gave me a voltage so that everything fit perfectly in the cuttable area. I measured the RPM of the feedscrew at various voltages and used the 'forecast' function in Excel (or similar) to fill in the gaps. There is a 100% linear relationship between RPM and VDC (of course!) and knowing that the pitch of the screw is 1.75mm, it's quite easy to get to what/where you want with a bit of maths (even for a dope like me). I've tried my resulting calculator with three different VRs and they've all had pretty much identical results.

[mikale]

This is from sawasounds pitch controller manual but no voltage settings just the dial but at least something to reference. Worked on our machine before we upgraded the motor controller.

[Dub Studio]

Here is the chart I use in the studio. I timed how long it took the motor to travel 10mm at 20 different speeds, came up with a janky formula to extrapolate times for all pot settings and then plotted them (very roughly) across the different disc sizes. It's not 100% accurate, but it gives a good ballpark setting to use. I always err on the side of caution and go a couple of ticks under the pot setting, so I definitely don't crash at the end. Bear in mind, this doesn't factor in label sizes, so you might have extra time left if your label is smaller than 100mm.

How to use:

1) decide what disc size you are gonna use (7 inch has to be in the red zone, 10 inch can be red/yellow, 12 inch can be red/yellow/green)
2) select the track time along the top (round it up to the nearest minute)
3) go down that column to the lowest cell in your colour band
4) check the corresponding Pitch for that cell on the left

For example, you have a 3:30 tune, you decide it's going on a 7". Round it up to 4 minutes, find that column and go down to the lowest red cell (marked 28.9 in this case), then check the Pitch setting for that row (45).

Dub Studio VR Pitch Controller Calc.pdf

Changes I would make in future: establish more accurate settings for specific lead-outs and label sizes.

Obviously this doesn't help to work out the loudness level you can hit, its just ensures you fill each side, but the u/rev@45 and u/rev@33 columns give a rough idea.

Merry Xmas!

[Vinylfan]

Did something similar in a table, where the input data are:
disc diameter, label diameter, rpm, program lenght, no of tracks, width of track separation, width of lead in/lead out.

The result is the distance the head travels in 1 min, in 1 rotation and LPI.

Obviously this works only without automatic groove speed controller. It gives no information about the poti setting (nor the voltage) and the loudnes level. Maybe helpful anyway.

_Disc Recording Yardstick Groove Speed Calculation Neu.xlsx