With my VPI Classic 3 SE Sig/w 3 belts/ADS.... there's a constant need for adjustment between listening sessions.
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I do not think so testpilot. He is setting the motor speed when it is cold. It should be the same next time he checks it cold. dcaudio, next time you start up check the speed but do not change it. Get an idea of how many dots drift by a fixed point in 10 seconds. Lets say it drifts 5 dots in 10 seconds. Check the speed again when it has warmed up for 30 minutes. How many dots does it drift now. Let us know what happens!!
This is a common problem with BD tables. It is caused by a combination of belt slippage (which can be cured with proper tension) and belt creep which cannot be cured, but can be compensated for with feedback. No matter how accurate the motor speed, without feedback the platter speed will vary over time due to a number of variables that cannot be controlled.
SOTA now sells a PSU and tach with feedback that will keep the platter on speed regardless of variables such as belt diameter and durometer, stylus drag, bearing oil viscosity, temperature, belt creep etc.
one thing to consider is your power going to your house changes a few volts all the time that alone will throw off a turntable with out compensation.No, it won't. Turntables don't rely on AC voltage for speed regulation. The ones that use AC motors are synchronous to the line frequency, which is subject to only very tiny deviation by the very nature of AC distribution systems. Those that use DC motors employ regulation in the DC power supply.
AC motors are locked to the drive frequency, but the wall power frequency does vary a small amount over short periods. This will manifest itself as a wavering on single notes, but will not show up as speed drift over longer periods of time. Long term speed drift is caused by changes in the belt and bearing lubrication over time and changes in stylus drag from the beginning of a record to the end.
The speed of DC motors is more difficult to control than AC synch motors. Even with tight DC regulation of the voltage, the motor speed will be affected by torque load and temp. Some of the OL motor controllers compensate for speed changes with load variation (stylus drag), but without temp compensation, the speed of the motor will still wander.
A synthesized PSU will lock the speed of an AC synch motor to a quartz reference, but as I posted above, this does not guarantee constant PLATTER speed. Even with perfect motor speed control, the platter speed will drift over time.
I had stopped listening to albums because the speed fluctuations drove me nuts. It was very audible.
I finally bit the bullet and sent it back to Sota for a new motor, board, speed control and maglev bearing. The sound is now amazing. I can clearly see that it runs exactly at 33.3 and it sounds just as good.
My advice, stop playing games with your table. Either fix it or replace it. DC motors get old.
Testpilot, well then I guess origin live has some work to do. A turntable should be a set it and forget it device. Drifting motors and controllers is not acceptable in this day and age. Neither my SOTA or SME vary at all, cold, warm, upside down or sideways. The SOTA I check maybe once a year and it might drift a little. The SME not at all.
AC synchronous motors rely on stability of AC frequency, which before accounting for noise from other sources can vary by up to +/-2Hz, which is an error range of 6.7%. Noise that breaks the synchronization can increase this to 10% depending on the power factor of the source. Bottom line is to use a line frequency conditioning device for equipment that has AC synchronous motors. This is why quartz oscillator disciplined phase locked loop controlled DC motors maintain speed with much greater precision and reliability.
AC frequency, which before accounting for noise from other sources can vary by up to +/-2Hz ...Please explain how noise affects AC frequency and how you arrived at this spec.
Noise that breaks the synchronization can increase this to 10% depending on the power factor of the source.If that were true, the entire connected electric grid would collapse. The function of the AC frequency is to allow multiple electric sources to be connected and work simultaneously on the same grid.
AC is the preferred way of transmitting electricity to customers because it is way safer, more efficient and lower maintenance than DC.Oh no, AC is not safer than DC - that was Edison’s argument when he was battling it out over power distribution. That’s why Edison promoted the electric chair. It’s all in the history books.
Cleeds, As I recall, from reading those very same history books, Edison promoted DC electrical transmissionExactly. That’s what I wrote. Edison promoted the electric chair to warn about the dangers of AC. All of Edison's early electrification work was DC, such as in NYC, where he ran some of the wires himself.
Sorry for a bit of nothing, but you wrote, "AC is not safer than DC - that was Edison’s argument...." I interpreted that to mean that Edison argued that AC was safer than DC, which we both know was not the case. I had a feeling you merely made an error in syntax, but I just wanted to get it straight. Now I see how you meant it.
Just think: If Edison had won the point, we wouldn't need rectification in our audio equipment, but on the other hand the DC voltages available for B+ would in many cases need boosting. Also, it would have been difficult to assure that everyone got the same DCV at home.
@lewm I see now that what I wrote was completely ambiguous!
If Edison had won the point, we wouldn’t need rectification in our audio equipment, but on the other hand the DC voltages available for B+ would in many cases need boosting.We’d be in a different world if Edison had prevailed, for sure. For one thing, we’d probably be paying a whole lot more for electricity. I think the main reason AC prevailed is because of distribution efficiencies.
Oddly, solar electricity is DC. Edison would have liked that.
Thank you for that insight around speed fluctuations, phoenixengr!
In the later 90's, I had a full blown SOTA Star Sapphire with vacuum hold-down / electronic flywheel (line conditioner) - paired with a Fidelity Research fx64 arm with mid-priced Grados. The speed would hold only through a 3-4 hour listening session no matter what I tried, including swapping out for a new motor with an engineer friend. In the end, I simply lived with the issue. Two decades later, it's still comforting to know that something can be done.
During that experience, my rig was situated on a jouncy upstairs room, presenting a real challenge in isolating the turntable from footfalls, etc. I tried bladders, masonry (never have had any luck with that,) tiptoes, sorbothane, etc...but, the "cure" in that application was a sandbox with super dry play-sand from hardware store and a carefully leveled maple plinth atop the sand under the SOTA. Maybe this may help others.
Happy listening and More Peace, Pinthrift
A long time ago when I began to notice speed fluctuations on my VPI TT I cured it with a clean-out and lubrication of the bearing and a lubrication of the motor. So that might be an issue,
But phoenixengr, who apparently now licenses his inventions to SOTA, solved the problem forever initially for me and other VPI owners with his Falcon/Eagle/Roadrunner. Now sold together with a advanced design motor by SOTA. If they make it in a way that is compatible with your TT you might look into it. It's clearly the way to go for many reasons including better SQ, and it's quite low-cost for what you get..
Just wanted to point out that many of the posts seem to confuse long term speed stability with instantaneous speed stability. A turntable may measure out perfectly for speed over longer time intervals yet still create momentary episodes of pitch instability due to short interval speed errors. There's a difference.