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Old 17th September 2017, 08:09 PM   #531
luckythedog is offline luckythedog  United Kingdom
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To understand it, I think one needs to know detail of the drive design intention. Which I don't, but I'm sure someone here might..........?

Here we're on a bit of a detour, examining the FG signal of a particular TT drive, which proves to be tricky to interpret - no surprise I suppose.

One feature is the triangular pattern in the FG polar plot that's not synchronous with rotation; another is a ~9Hz pattern which is synchronous.

If we were looking a polar plot of pitch variation, we might tag those markers and relate them to the mechanism. That's how diagnostics and fixes can work using polar plots, IME.

However, this case at hand is a healthy TT by standards. At least until the FG probe was introduced So really we're exploring how the TT drive works, and what (if any) residual artefacts of the drive might remain - which is ethereal stuff methinks.

LD
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Old 17th September 2017, 09:30 PM   #532
JP is offline JP  United States
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In broad strokes the phase of the motor's frequency generator output is locked to the phase of the reference. Phase difference produce an error voltage that the drive then uses to adjust the speed. The whole thing is essentially a PLL. The 100Hz signal is what we're interested in, the rest is noise.

I went down this path as another angle in the pursuit of isolating test record/arm/cartridge issues as the FG signal from the motor is an ideal method to do this. However, in this case the data is full of noise and the 'table isn't running correctly due to where/how I probed it.

Probably best to move on.
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Old Yesterday, 06:28 AM   #533
davidsrsb is offline davidsrsb  Malaysia
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A modification to the code with an example of HOME on a Linux PC and an option for a 45 rpm capture
Change the extension from "txt" to "py"
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File Type: txt polarplotrev3 .txt (2.6 KB, 13 views)
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Old Yesterday, 08:00 AM   #534
luckythedog is offline luckythedog  United Kingdom
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Quote:
Originally Posted by scott wurcer View Post
I increased the rez of the plot to .1Hz (I did fake the the maximum frequency since the code would have to be modified to not use only integer frequencies as the max). This is 10Hz and 20Hz filtering. The second seems like some 40Hz mains FM on the 100Hz?
Hi Scott, would be great to see a plot of the FM spectrum, don't you think ?

All one has to do is a fourier transform of the display data as a time series, and calibrate the x axis according to the time spacing.......... the y axis would FT bin magnitudes, corresponding to display content spectrum.

I think this is pretty much essential to interpretation and diagnostics, one can't get far without needing to indentify the contributing factors in all but the most obvious cases.

HTH !

LD
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Old Yesterday, 03:36 PM   #535
fasterbyelan is offline fasterbyelan  United Kingdom
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Quote:
Originally Posted by scott wurcer View Post
One more rev, I removed all dependencies on outside libraries and added a prompt asking for a .wav file to process (must be in quotes). All you have to do is change the HOME directory in the script to wherever your files are that you want to process. If you wanted you could make sure they are in the search path for Python or enter the full path name (I find this a pain).

Wicked fast now plots the instant you hit return, save for the first time where it needs to load all the libraries.
Many thanks for the code Scott. Finally managed to get to grips with the world of Python and get it to run. Out of interest, I will run some of my own Lenco .wav's tonight and compare them to the ones from the software I have previously been using.

Regards,
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Old Today, 07:27 PM   #536
scott wurcer is offline scott wurcer  United States
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Quote:
Originally Posted by JP View Post
Probably best to move on.
JP, Do you have a suggestion that works in both Python 2.7xx or 3.0xx for the input file name without quotes?

Raw_file by itself works in 2.7 but if quotes are used it breaks. I can't get eval() to work for single and double quotes if the input is already a string, while either single or double work for input(). I don't do much with user input usually just some simple numerical input. I don't have a way to check Python 3 but want to make sure everything works in both.

If the input can't already be an arbitrary string so be it (yes this is a sort of trivial matter).

The filter glitch went away with the initialization function.
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Last edited by scott wurcer; Today at 07:33 PM.
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