Cheap turntable upgrades

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Folsom

Cheap turntable upgrades
« on: 26 Aug 2016, 07:07 am »
So... you know how many of the non-uber expensive turntbales come with AC wall adapters?

Well, here's something to note. If you check your voltage on it, it may be MUCH higher than desired. This is an easy way to sell you a "speed controller".

How to check and adjust it?

1. Find the VA and voltage of your turntable motor. This may be listed on replacement motor specs, or on Music Halls like mine, you just unscrew the motor from top and look under it. If you have them it's VA/voltage. My motor says 2VA, and the adapter is "16v" aka 19.2v or so. This means it draws .125a, or 125ma. If you can't find these numbers you can use a multimeter's ampere settings to do this by inserting it between the the cable; refer to manual how to do this.

2. Now you can use this calculator to get an approximate resistor value to bring it back down to earth. Ignore the rest of the page. If you are ordering resistors and don't have a kit with many values, I recommend getting a range of them above and below; use the calculator to determine a range of around 2v up and down. You can just buy a resistor kit for $16 from Digikey, too. Hopefully none of you will need any very high values, or you may want a higher watt resistor. I presume the majority will be "16v" for everyone with the sub  $1k turntbales. If that's true you can use a potentiometer, too.

3. Use alligator test leads to insert resistors; you'll need 3 since your cord will be spit in two. Split in two, with the ends stripped far enough to attach alligators and test leads. Connect one side straight, the other with a resistor inbewteen. If using a pot, center and one leg either side connect to one end of wire from transofmer, and the odd leg to your other wire going to plug. Turn on motor and check voltage from one side without resistor, and to the resistor but on the side of the motor (the wrong email side won't change voltage by changing resistors, but will dip when motor turns on and off. Essentially "bypass" the motor with you voltage meter. Now find a resistor that gets you close to target voltage, make sure it's a little above, not below. I highly recommend hook test leads to make this easy.

4. Use electric tape or heatshrink and soldering iron to connect it all permanently. I'm sure some of you guys will find ways to make it hot swappable. That's a good idea because if your house voltage changes or you move the stereo, you may need to adjust resistor. I'm thinking about making a PCB board for this, that has a voltmeter, a swappable spot for the resistor, and a potentiometer to fine tune. So you can easily fiddle it correct. Or maybe a voltage regulator, but that's complicated by comparrison and doesn't come in real cheap.

Upgrade 2:

If your motor says the capacitor value on it that it uses (if it does) then check to see if it's film. On music halls it's under a small cap that the input for AC power is on. Mine had an electrolytic, which isn't great to start, but worse off their values are typically a long way from the given specification. For example my "8.2uf" measured at about 9.5uf. This causes imbalance in the motor, that says 8.2uf on it. In fact over a long time this will trash your motor. So once you know what you need, order a film version from mouser/Digikey, and make it a 1% or better tolerance. It's best to search for 100v and under to find the smallest one, since a speaker crossover sized one won't fit; lower voltage is always smaller, but make sure it's got at least 10v over required voltage.

Upgrade 3: buy a Herbies mat at the max thickness for Decoupling, raise your tone arm if needed to compensate. Don't be a chump, it's a huge upgrade.

If you correct these problems you'll be impressed. Seriously, subjectively people would assume you spent a lot more money. It's crazy how much better a properly operating motor sounds. There's nothing really wrong with the cheap motors unless they generate vibrations. They generate vibrations by being out of balance between magnets to coil, so correct that with a proper capacitor if yours is setup this way.

This is the stuff they don't want you to know. All the upgrades are suppose to come from piles of aluminium, extra boxes, etc... but the physics are simple, less vibrations the better, more accurate speed the better.

Folsom

Re: Cheap turntable upgrades
« Reply #1 on: 26 Aug 2016, 07:25 am »
I figured this out trying to fix a noise issue with my motor, btw, which I was about to spend $50+ shipping to just have more sub-par performance. It was just the cap way out of specification that gave me noise. It made my motor sound like it was trash. But the motor ran "fine" for a few hundred hours, originally. Except it was noisy by comparrison, even though it wasn't audible unless your ear was near it.

wushuliu

Re: Cheap turntable upgrades
« Reply #2 on: 12 Sep 2016, 07:22 pm »
I found similar results with vintage tables. Granted the caps were older, but even the tables that seemed to run perfectly fine benefitted from good quality cap replacement.

The more I DIY the more I learn it all boils down to the power supply...

Folsom

Re: Cheap turntable upgrades
« Reply #3 on: 12 Sep 2016, 07:28 pm »
Sadly I think my motor is too deteriorated. It probably would've lasted a lot longer on proper voltage and a better cap value.

There's a thread on DIYaudio about driving VPI/2 or 3 phase motors that's even better. You use cheap class D amps, a sine wave generator and maybe transformers depending on the voltage of your motor. The result is way more torque, way less rumble. You just adjust voltage by the volume of the sine wave.

undertow

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Re: Cheap turntable upgrades
« Reply #4 on: 12 Sep 2016, 08:23 pm »
I found most AC motor setups in general have less accuracy, and cause as many noise issues up the chain than even wall warts on DC motors. I had some strange hums, and speed issues all my life using any AC motor in the past. I highly suggest to anybody serious about really capturing the best of analog to update their motor using the DC kit by "Origin Live"... It is pretty reasonably priced for anybody with a 1500 to 15,000 dollar turntable honestly, and will jack the performance nearing competition with any top competitor. And yes it is sad most of the major manufactures to this day are selling 3000 plus tables with ZERO means of adjusting the speed via strobe on their motor, its just plug and play.

I think a lot of people give up on analog due to hearing all the isolation, and speed issues that plague recordings without even knowing it and of course Digital easily becomes superior in this scenario.

But, I also HATE wall warts. They make the rest of the system plugged into those circuits just as vulnerable to noise, and or speed fluxuation as well. So although origin live also offers a power supply upgrade to dump the wall wart as well its just as easy, and cheaper to build a custom linear one for it.

Trust me only best way to deal with any belt drive using an outboard motor you gotta have independent speed drive setup. Plus it's nice with the Origin live as you no longer have to stretch out belts changing pulleys either from 33 to 45... Most people have no use for 78 anyway, but not sure you can adapt that.

The music hall "Cruise Control" also exists, which has an AC 2 prong outlet, but its far less accurate, and actually you end up converting it back and fourth from AC to DC, back to AC anyway with it. And it will not change speed or turn on the motor for you anyway. Yes its cheaper if you have a 1000 dollar table to justify, but I still say go for the 500 to 600 dollar Origin live full replacement motor and DC controller setup that allows you to custom sink both your 33 and 45 RPM as well independently.

By the way this heavily simplifies all this "There's a thread on DIYaudio about driving VPI/2 or 3 phase motors that's even better. You use cheap class D amps, a sine wave generator and maybe transformers depending on the voltage of your motor. The result is way more torque, way less rumble. You just adjust voltage by the volume of the sine wave."

BobM

Re: Cheap turntable upgrades
« Reply #5 on: 13 Sep 2016, 12:17 pm »
Here's a tip #4 ... Try coupling the underside of your tonearm to the base the turntable rests on, if you have access to that location and you can. I read a Fremer review of a TT that did this, so I tried it myself and I heard an additional clarity that wasn't there before.

It could be tricky to find something that will fit in that space and still make sufficient contact top and bottom. I got lucky with an extra spike I had and a thin sheet of aluminum on one end.


S Clark

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Re: Cheap turntable upgrades
« Reply #6 on: 13 Sep 2016, 01:01 pm »
Depending on how you read the subject... Cheap turntable- upgrades     or    Cheap- turntable upgrades,  may determine if the following advise is appropriate.
But if you are upgrading a cheap turntable, one of the very best things you can do is add plasticene (clay) to the plinth, adding mass and reducing resonance.  Add 5+ pounds and you will hear a difference.