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Old 3rd January 2013, 04:52 PM   #21
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Adding an EI isolation transformer to drop to 110V would remove a good deal of the HF noise on mains that would otherwise reach your motor. How much of a difference this would make I don't know. If you didn't ground a transformer secondary you'd also end up with a 'balanced power supply' to the motor, which might reduce the hum picked up by the cartridge and wiring (I speculate).
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Old 3rd January 2013, 07:26 PM   #22
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Haven't had an LP12 for ages but at the time i seemed to greatly prefer the Valhalla to a Geddon clone. Maybe the time is ripe for a retest on an ancient TD 150.
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Old 4th January 2013, 12:21 AM   #23
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The resistor drops 110V at 50 Hz. The harmonics, which modern mains has high levels, are attenuated much less as the motor is an inductive load. These harmonics cause vibration.
Using a transformer attenuates these harmonics at least as much as the 50Hz power
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Old 4th January 2013, 09:12 AM   #24
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I had an Armageddon clone, a Valhalla and a modified Hercules all available at the same time and tested back to back and measured. The Armageddon displayed the best speed stability of all of them. Whether a listener actually prefers greater speed stability is another issue altogether. A lot of LP12 owners that I know seem to actually prefer the 'rolling' speed instability of the Valhalla.

Here are two FM speed demodulations of a 3150hz test tone track. They are plotted out so that each 360 degrees of the graph equals one rotation of the platter. The same five rotations of the record are shown for each sample. Speed variation is shown as any deviation from a perfect circle. The difference between them is that the red version uses the standard 0.22uf capacitor value and the green uses 0.2uf. Nothing else was changed, the green track is marginally more accurate. The two tracks are 5 degrees out of sync.

Click the image to open in full size.

Click for none distorted version.
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Old 4th January 2013, 10:19 AM   #25
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How did you do the plot. It looks like Linux, so Octave?

The two phases are not of equal amplitude or exact quadrature. The phase via the capacitor is usually at greater voltage than the more direct one. Small changes in capacitance have large effects, as you have plotted.
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Old 4th January 2013, 10:53 AM   #26
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Just to clarify. The plots are not the two phases, they are two separate plots of the record rotation speed as captured through an A/D with different caps used for the lag phase.
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Old 4th January 2013, 12:00 PM   #27
gk7 is offline gk7
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Quote:
Originally Posted by sharpi31 View Post
Adding an EI isolation transformer to drop to 110V would remove a good deal of the HF noise on mains that would otherwise reach your motor...
Yes, thats what I thought too, removing HF (and DC sometimes present on the mains);
to accomplish this an EI isolation transformer like you said or probably a r-core
would be best.

Quote:
Originally Posted by sq225917 View Post
Regulation, regulation, regulation.
Yes, but then no resistor should be used, correct ? BTW, from your picture
in post #8 it looks like you do not use the resistor (R1, 3.3k).


Quote:
Originally Posted by sq225917 View Post
... The difference between them is that the red version uses the standard 0.22uf capacitor value and the green uses 0.2uf. Nothing else was changed, the green track is marginally more accurate. The two tracks are 5 degrees out of sync.
...
Is there a way to calculate this ? I ask, because my Thorens uses 0.33uF (?)
Which transformer did you use ?

Quote:
Originally Posted by The Space Egg Corp View Post
...
I haven't checked out the insides of the new Thorens TD160 MKII that I have to 'soup up'...
...but...
...does anyone know if I could benifit from ARMAGEDDON on this turntable.
...
Doesn´t the TD160 use a "wall wart" type AC adapter (16V) ?
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Old 4th January 2013, 12:56 PM   #28
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GK7.

I use no resistor.
You can calculate it from the motor winding resistance and the inductance. I didn't, i just used a trimmer cap (+ additional capacitance) and held the motor until I could feel the least vibration.
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Old 4th January 2013, 01:19 PM   #29
gk7 is offline gk7
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Thanks for the information. :-)
Can you recommend the minimum VA rating for the transformer ?
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Old 4th January 2013, 02:32 PM   #30
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sq225917
If you synthesise the quadrature drives in software, you could vary the nominal 90 phase shift and relative amplitudes - not done in the commercial units but easy enough to do at home.
The analogue approach probably depends on the mains waveform and I know mine varies drastically through the 24 hours as the domestic load changes.

I understood your plot correctly, It would be great if you could share how you did it.
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