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Item Audio "Spoke" for the Linn LP12 anybody..?

how many frequencies and at what amplitudes do you think will be needed to cause the stylus drag to kick in?

wouldn't the stylus profile,polish and tracking weight also be relevant in your assumptions?

let me know what you think we may need to make a test recording to get pressed onto vinyl....

p.s. what's superpositive mean?
 
Darryl, what is the composition of the opening to a song like Blue Monday? Could you recreate something like that with a synth but only recorded in in one channel while a 3150 kHz tone is cut in the other channel. Analysis of how the 3150 kHz tone is played ought to reveal any evidence of instability. But I can see why that could be awkward to cut.


I'd prefer to see the record also include a stereo test tone as one track and a separate hefty stereo 'Blue Monday' style opening elsewhere on the disc to be played by 2 separate arms/carts for those that can use 2 arms at once. Mind you, most '2 arm capable' decks are not suspended and won't have the potential for wobbling that a Vilchur style suspended deck might.
 
you could have a say slow kick drum and large bass pulse but not on one channel of a stereo cut vinyl....bass is mono on vinyl otherwise the stylus will jump out of the groove.

it would be virtually impossible to cut at a reasonable loudness.

you could cut say 2 low mid tones on the right hand channel and one other higher tone that is pulsed on the left but again the cutting lathe will be affected by drag if a normal deck is....i still don't feel that different signals in the grooves causes a noticeable change in stylus drag..... plus pure tones also cause resonance problems within the cart and arm which can then set up resonances in subchassis and you can end up with a whole mess of buzzes and rattles.....i could chat to my cutting man and ask him about stereo bass cutting but i have always been told that bass gets summed to mono....full stop.
 
I can't believe an SP-02 is going to be overly troubled driving an acetate past a cutter even if there are two competing tones involved. Certainly not in the way a suspended belt drive tt would be. It's my impression that the spatial order in a recording tends to collapse when heavily modulated material is imposed on lower amplitude constant tones. ie that voice, flute or violin stage left gets muddled in to a greater degree than it should otherwise be. This occurs to my ears on most Vilchur type suspended decks but doesn't on fixed plinth or good quality DD decks whatever other flaws they might have. I think its because at those points, the isolation afforded by the suspension is more compromised and noise, either from the motor or external, then gets through. Your man may be able to advise what kinds of signals could be cut on one channel while the other carries a constant tone. Obviously not anything super low as that would be sent to both.
 
pure sound said:
I can't believe an SP-02 is going to be overly troubled driving an acetate past a cutter even if there are two competing tones involved. Certainly not in the way a suspended belt drive tt would be.
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that's what i was hinting at....;)

it's interesting that when a local dealer trashed my othello turntable bearing the problem that suddenly appeared was it wowing under sustained piano chords....not so much bass transients or percussive pulses just nice long chords.

never did get that pretty turntable repaired....:mad:

i think that pitch problems are more related to the belt drive condition or main bearing faults than suspensions....as when i have tried to find these problems in measurements i can't seem to make them show or correlate with what is sometimes heard.

but if i can help in anyway we will try to agree on a file to construct for the test....
 
I think drag will be proportional to the product of stylus velocity and frequency. So a low frequency won't necessarily trigger the effect we want. OTOH a 3150Hz tone cycling between low and high level extremes might be interesting.

Another way is to make a lot of marks on a piece of tape, wrap it around the platter, then use a photodiode to generate the speed signal. The test disc can then actually be Blue Monday or American Pie.

Paul
 
Paul R said:
I think drag will be proportional to the product of stylus velocity and frequency. So a low frequency won't necessarily trigger the effect we want. OTOH a 3150Hz tone cycling between low and high level extremes might be interesting.


Paul
Click to expand...

this drag must be affected by stylus size, shape, polish, tracking weight as well surely?!

do we have any idea how this is not overcome by motor torque?

like i mentioned before talking a bout the fly hitting the car windscreen...what is the ball park reduction in velocity we are talking about or expecting to discuss?

someone should ask arthur from funk firm into this thread too....he studied this a lot...
 
The effect of constant drag isn't what I'm interested in. Stylus shape, size, polish, tracking weights etc are constant. What I'm interested in is how the system as a whole behaves when the load changes.
 
do we have any idea how this is not overcome by motor torque?
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I'm pretty sure it is overcome by motor torque.

OTOH the belt/platter inertia resonates, flexibly mounted motors move and the suspension on a suspended subchassis wobbles.

What we'd (I guess) like to do is quantify the speculation on the LP12 (in particular).

Paul
 
the stylus profile may not change in shape but it moves according to the peaks and troughs of the excursions it follows so it's surface area changes with modulation.
so it's resistance will not be seen as a constant is this the drag you are suggesting is strong enough to deflect power away from the drive and into the subchassis? sorry just trying to clarify what everyone thinks is happening in the stylus/record interface and it's possible implications to the drag.....

sorry paul and pure can you both reply to this cheers fellas!
 
I can see no reason to split the tones between the left and right channels. This just introduces tracking problems for the cartridge. All cutting setups mono the bass below 50Hz anyway. I would suggest a mono cut with a constant 3150Hz tone at low level, plus a loud 20Hz tone that pulses on for one second, then off for one second etc. Running this on Feickert Adjust+ or with the Platterspeed app would give an instant readout of any pitch changes in the 3150Hz tone.
 
'Superpositive' means that the signals superpose, i.e. two small waves at different frequencies will produce a more complex wave where the amplitude occasionally sums to produce a peak with double the amplitude of the two individual waves. In wow terms this means that if you add a source of 1% wow to a source of 1% wow you will have intermittent 2% wow. Wow superposes, just like waves.
 
Paul R said:
I think drag will be proportional to the product of stylus velocity and frequency. So a low frequency won't necessarily trigger the effect we want. OTOH a 3150Hz tone cycling between low and high level extremes might be interesting.
Click to expand...

Drag will probably be a function of surface speed (i.e. groove radius) and signal power. As you say, with RIAA equalisation it's not obvious which frequency range will suck most energy out of the platter. Certainly absolute groove amplitude will be the main guide. But the most important factor may well be the cumulative exciting effect of dynamic stop/start music. I've just checked my Sondek and it looks like the natural frequency of lateral movement is about two or three Hz, so a bpm of 120 - 180 might be a big factor in getting it to rock a little.

Another way is to make a lot of marks on a piece of tape, wrap it around the platter, then use a photodiode to generate the speed signal. The test disc can then actually be Blue Monday or American Pie.
Click to expand...

I have often considered doing this. I have a Canon 7D which can shoot video at a sample rate of 50 or 60 Hz and 720p. Under a macro lens a carefully marked tape around the platter might reveal a bit of wandering speed in video. Can I be bothered?
 
So you think using two bits of Sellotape to attach a thread would be better than just using the Sellotape, really, think about it?

What do you think would be harder to pull off sideways, the string under a bit of Sellotape or the Sellotape?
 
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