Turntable speed stabilty

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Jump to Latest
Hiten

Hiten

Member
Joined 2010
niffy said:
I have not heard this one. Adding mass at the headshell will not damp vibrations/resonance. It will lower the frequency at which the arm/cantilever system resonates but the peek of this resonance will tend to be of a greater magnitude.
Click to expand...
Thanks very much for the reply Niffy.
I read about headshell mass in Wireless World June 1959. Am copy-pasting the same below. Mind you this is 50 year old article. 'So many grooves have passed below stylus' since then :). But I think basic physical concept remains. And I gather in old days there used to be high verticle force but still do we need filmsy headshell. Example.

"Calculation of both bending and torsion of a tubular arm shows that extremely large diameters are required to put all arm resonances above the audio range. It would therefore be desirable to have sufficient lateral and torsional inertia in the head alone if arm resonances are to be minimized. If the pickup is a one -gram tracker with a compliance of 15 x 10-' cm /dyne, and the bass resonance is required to be 15 c /s, then, to inhibit the lateral arm resonances, the total mass of the head should be (152 x 4,2 x 15 x 10 -e) - = 7.5 gm. Likewise, considering that the compliance is usually inversely proportional to the tracking weight, about 40 gm would be required for a 5 -gm tracker. Accurate vertical pressures are ensured by balancing the arm and then inserting a calibrated pellet into the head"

Also kindly tell what does the auther mean by inserting calibrated pellet in to the head. That looks interesting.
Thanks and regards.
 
billshurv

billshurv

Member
Joined 2014
Paid Member
Thing is the actual demodulation software isn't available, which was done in labview. I believe it's the same basic principle as LD's but with some added cleverness missing.

In theory something like octave should be able to chomp this easily, but I've not done any of this stuff for 30 years so rusty as a rusty thing!
 
M

mkc

Member
Joined 2002
Paid Member
Yeah, we should really get LDs software made available.

@LD: I'm a software guy. How can we do this if you are interested. I do have limited time at the moment, but would be happy to help out.

Btw. having an old Thorens TD320 here that I will restore so I would be very interested in having the software.

Mogens
 
M

mkc

Member
Joined 2002
Paid Member
It would be great if we could collaborate on this. I for one would be happy to help out as much as time permit.

For starters I think it would be a great step to get it on Github or bitbucket and next I would suggest to port LDs implementation to Python, which should be possible to run on Linux, Mac and windows.

Mogens
 
M

mkc

Member
Joined 2002
Paid Member
scott wurcer said:
I posted a link to a seminal paper on the subject a couple of weeks ago and LD confirmed that the basic technique was in there somewhere. If he does not want to share his last trick I respect that.
Click to expand...

Me too. I was just under the impression from a post by LD earlier in this thread that he was willing to open-source the code. But, it could be a misunderstanding on my part.

As an alternative LD could decide if he would like this to be made available as an application but closed source and just make his IP available to a few trusted developers.

Mogens
 
M

mkc

Member
Joined 2002
Paid Member
Yes, license can be an issue.

If cross platform support is to be maintained and closed source, one option could be to use Qt and program it in C++. But, also here the Qt license model could be an issue as the Qt tool is free to open source projects, but not for commercial. I'm not sure in this case with perhaps free application, but closed source or at least LDs IP as closed source. All the GUI stuff is likely not needed to be closed source.

Alternative Python could still be used with LDs IP as an library.

Perhaps others here have better ideas or experience?

Mogens
 
scott wurcer

scott wurcer

R.I.P
Joined 2004
billshurv said:
Of course there is the option of having the 'trick' pre-compiled so not available as source code. But even that's a step ahead as the copyright framework (GNU, Apache etc) would need to be agreed and that in itself is a minefield!
Click to expand...

The Analog Discovery uses a .dll and provides an API (with C++ conventions) that works like a charm in Python. AFAIK the source for the .dll is not available. Sometimes it's a bit of a pain to keep track of C vs. Python variables, etc. but if I can do it anyone can.
 
Hiten

Hiten

Member
Joined 2010
I know in polar plots deviation from center point denotes eccentric records. But how does the software do it and displays in polar plots ? I guess since one single frequency is used to record, could it be that software measures amplitude on both groove walls and displays it ?
Regards.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Top Bottom