all those 'Americans' and 30 page inserts with all sort of disclaimers and claimers and rights and no-rights .. just to buy a coffee cup. This is one aspect not even Monty Python could sketch more absurdly
one thing is the record/LP = HW
the other the proc SW...(is likely code and not executables)
I am all for open source..why not pick one standard one, GNU or what ever .. this is free for private use only, any modification to the code must be made available to the public domain bla bla (seen some 'license' saying this in essence = )..
here in EU I'm not afraid being sued if somebody kills their dog while attempt playing Frisbee w the the 'damn' thing (the record that is)..
just would like it stated somehow : do not make business out of others works..and if you modify code/develop incremental knowledge based on this content = put this back into the community
one thing is the record/LP = HW
the other the proc SW...(is likely code and not executables)
I am all for open source..why not pick one standard one, GNU or what ever .. this is free for private use only, any modification to the code must be made available to the public domain bla bla (seen some 'license' saying this in essence = )..
here in EU I'm not afraid being sued if somebody kills their dog while attempt playing Frisbee w the the 'damn' thing (the record that is)..
just would like it stated somehow : do not make business out of others works..and if you modify code/develop incremental knowledge based on this content = put this back into the community
Actually, one can test for IGD pretty much anywhere on the record. Because the cause is mostly how steep the groove angle becomes for a given level of programme material.
My suggestion for test tracks includes a short suite of tracks which are triangle waves with progressively increasing angles. Representing progressively increasing velocity (but constant for any test) and programme level. The tracks are graded from 15 to 40 degrees, though one could go up to 50 degrees that's not necessarily trackable by all rigs.
This tests IGD. Every rig has a groove angle limit, beyond which trackability is impossible. It is worse in offset angle arms, because the line of friction drag force is not tangential, so there's an asymmetry and grooves angled away from the spindle are effectively 20 odd degrees steeper. It's affected by stylus alignment, sometimes critically, because alignment can significantly influence friction drag.
So that test, with graded angles, can go anywhere on the record and is a test for the rig's IGD performance.
There can be a second cause of IGD, which happens if acceleration gets too high for the stylus to track. In the suggested triangle wave test, the apex of the triangle has curvature which tests acceleration in a graded way. Again, this can go anywhere on the record, and tests the other principle cause of IGD. This has nothing (or little) to do with friction.
So suggestion is we include the two short test suites. Since there's space. Both are triangle shaped grooves. One with graded straight angles and a 50um amplitude. One with graded apex curvature, constant angle, and a 50um amplitude. They can go anywhere on the record, but we have to know where that will be so that the test files can be generated.
I'm very happy to define and document those tests, and provide the test files. I tried to add them to the candidate list, but I'm locked out so have kindly requested restoration of write access please?
The tests were suggested in post #654, briefly summarised here:
Groove angle/slew lateral rate test 50um : 15 deg 15s
Groove angle/slew lateral rate test 50um : 20 deg 15s
Groove angle/slew rate test 50um : 25 deg 15s
Groove angle/slew rate test 50um : 30 deg 15s
Groove angle/slew rate test 50um : 35 deg 15s
Groove angle/slew rate test 50um : 40 deg 15s
Triangle/ grooveshape curvature acceleration test 50um 20 deg 500G 15s
Triangle/ grooveshape curvature acceleration test 50um 20 deg 600G 15s
Triangle/ grooveshape curvature acceleration test 50um 20 deg 700G 15s
Triangle/ grooveshape curvature acceleration test 50um 20 deg 800G 15s
Triangle/ grooveshape curvature acceleration test 50um 20 deg 900G 15s
Triangle/ grooveshape curvature acceleration test 50um 20 deg 1000G 15s
Groove angle/slew lateral rate test 50um : 20 deg 15s
Groove angle/slew rate test 50um : 25 deg 15s
Groove angle/slew rate test 50um : 30 deg 15s
Groove angle/slew rate test 50um : 35 deg 15s
Groove angle/slew rate test 50um : 40 deg 15s
Triangle/ grooveshape curvature acceleration test 50um 20 deg 500G 15s
Triangle/ grooveshape curvature acceleration test 50um 20 deg 600G 15s
Triangle/ grooveshape curvature acceleration test 50um 20 deg 700G 15s
Triangle/ grooveshape curvature acceleration test 50um 20 deg 800G 15s
Triangle/ grooveshape curvature acceleration test 50um 20 deg 900G 15s
Triangle/ grooveshape curvature acceleration test 50um 20 deg 1000G 15s
I think it would be best to see the groove angle test suite with one more track upped to 50 deg, which represents about +10dB @1kHz ref 5cm/s in terms of level on an inner groove, or +18dB on an outer groove. Depends on whether we wish to risk damage to the test record in the event people's rigs can't track it? That's why I stopped at 40 deg, but 50 deg and 1000G would guarantee no IGD if the rig will track it. IMO , of course.
LD
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I like the sound of that. As we can put it on the inside where real estate is not being competed for that seems like a win win?
There is a 3rd possibility for this particular record, as I know it was played on a garrard SP25 before I was given it 🙂
There is a 3rd possibility for this particular record, as I know it was played on a garrard SP25 before I was given it 🙂
Hi Pano,
1) After having spent many many hours in analysing .wav files, I finally have some solid base to answer your question.
As you can see here Turntable speed stabilty there is a strong indicating that "waving" of the LP input signal, caused by Cart resonance, may be to a large degree responsible for the IM spectrum above 6Hz.
But since there are so much variables in Cart/Arm, TT and level of LP signal, all unknown at this moment, that it is almost impossible to jump to conclusions.
But nevertheless, something can be learned from this exercise.
The stronger the 3150 Hz signal on the LP, the larger the Cart resonance amplitude will be, causing the waving.
So the solution to proceed could be to have a very weak and a relatively strong 3150 Hz signal, or may be even one of medium amplitude.
The weak version will show in the IM spectrum without any attenuation eccentricity and other anomalies caused by the motor or whatever else and tell you the soundness of your TT alone.
The strong 3150 Hz signal will add to that the Waviness, now showing also the Cart/Arm characteristics in the IM spectrum.
Subtract the first spectrum from the second, and you will have a pretty good idea how your Cart/Arm is behaving.
2) Since the eccentricity of the Dr. Feickert Adjust+ isn't that bad after all, less then 0.1mm calculated from the same link above (>0.06% IM at a radius of 130 mm) someone could ask him where the LP was produced.
Hans
Thanks Hans. What do you think of 3 tracks of 3150 Hz at different levels, or would just 2 be enough? They could be locked grooves or 15-30 secs each which would be easy to record and analyze.
What levels do you think are needed compared to 5 cm/s?
What levels do you think are needed compared to 5 cm/s?
If space is no dealbreaker, I would opt for 3 levels of resp -20dB, -35dB and -50dB. Locked grooves and 15-30 seconds would be great.
That will give you a fairly good idea what the Arm/Cart is adding to the IM spectrum.
Hans
Bill,
I don't think it is as simple as that.
What is the IM distortion of a silent track ??
Hans
W&F meters need more time to lock and downrange. Maybe run the high level for longer? I'd like to see at least 30 sec, a little longer if possible.
-Chris
-Chris
There is a 30 sec 3150 Hz on side B. It could be 60 secs. For the software analysis, 4 secs is enough. 🙂
If we want to know the off center of both sides, we'd want the same 3150 on sides A&B.
If we want to know the off center of both sides, we'd want the same 3150 on sides A&B.
New IEC386 rules are at least 5 seconds, but in the past it was 30 seconds minimum.
I have tried both time windows and the differences weren't overwhelming.
But there is nothing against 30 seconds when the LP has enough space left.
I know that Adjust+ is measuring for the full 30 seconds.
Hans
Yes, when doing 2 LP revolutions. But IEC386 demands at least 5 seconds or 3 LP revolutions.
Hans
Hans: If you want to see what the frequencies of the arm/cart are, a silent track will allow you to extract them in terms of frequencies and Q. The contribution to the overall wibbly wobblyness of the output spectrum will be affected by input signal level.
If that track is on side B, I have no issue with the shorter track lengths on side A. Call me a happy camper!
-Chris
-Chris
That's not what I had in mind.
I wanted to see what the Arm/Cart is additionally contributing to IM distortion, which cannot be simply predicted by looking at the spectrum of a silent track.
Yes, Hans is correct IMO. Level in the candidate test list is unnecessary high and challenging for playback. -20dB ref 5cm/s would be fine for all versions of polar SW and meters, AFAIK. I think if we could choose a single level, that would save space and be fine.
The side A/B tracks 3150Hz tones tracks should be identical and need to go at exactly the same spindle radius. The track file itself should include the once per perfect rev marker, as per discussion on the TT speed stability thread. It's probably too much to ask to align the rotational markers between sides, and besides it probably depends on how the stampers are assembled at pressing time.
As proposed it should be more than long enough to cover IEC386 30s, so it could be shorter. But Hans is right, it might as well be inclusive for that standard.
LD
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Yes, a good silent track that's long enough to do spin-down tests would be multi-purpose. Ideally it would go on an outer track, (counter-intuitively) perhaps simply a long lead in for side 2 ?
LD
