Recording with a smartphone

[aragorn723]

I have been battling speed/tonal variation in my turntable for a few months.  Was asked by the manufacturer to make a recording of the sound so they could troubleshoot.  The resulting sound has a lot of variation in volume that definitely makes it sound like the turntable has major issues, but in reality, it's not as bad as the video would suggest.  Is there a technical reason why this volume variation was created in the recording?

Here's a link:



Based on this video they asked me to test the turntable with other amplification (which I did, but again didn't sound that bad).  What am I chasing here?  They have ruled out the main bearings since those spun freely.  My thought is the belt since it is loose, though the mfg says that couldn't cause the issue.  Would like to get a second opinion here, this isn't making sense.

Dave

[Deluk]

That sound was inconclusive to me and I did have to turn the volume to max. The singers tremolo didn't help. A test record with constant tones is needed. Have you got a strobe you can put on the platter to check if it is steady? A slack belt needs changing. Just because the platter spins easily doesn't mean it's rotating smoothly and correctly. The motor maybe faulty. If your TT uses a wall brick for power try another one.

[aragorn723]

Thanks, seems like whenever I email their tech support they run thru the same list of questions.
  Didn't seem like it was going anywhere.  I ordered a new belt, gonna install that first.  IIRC one of the Bottle head guys Doc? posted a free scope download, will have to see if I can find it. 

They say the motor is ok since there's no play in the shaft while playing records.  The motor does run off a walwart, will have to see if I have one with the same voltage and polarity.  I'm starting to wonder if this is just a limitation of this particular turntable.

Dave

[Doc B.]

Belts can make a big difference. Definitely worth trying another. Might also clean the platter and the pulley really well too, to make sure the belt grips without slipping.

[aragorn723]

I bought a new belt, should be arriving soon..  Will have to clean the platter and pulleys really well, maybe some rubbing alcohol?  Nothing like a good experiment to keep this hobby interesting 😎

Dave

[Loggie]

Hi Dave,
 I was reading in another older thread that you had replaced the bearing and the shaft.
Although it was pretty weird it was damaged ... these should almost last a lifetime.
Did you add a few drops of oil?

Maybe the belt was the problem for the speed variation now but you will be able to find that out once you have received it.
Rubbing alc is fine.

[aragorn723]

I didn't add any other oil since the spindle spins freely, and I wasn't sure if motor oil would damage the plastic.

Dave

[Deluk]

What is the TT makers recommendation for lubrication? They often include a tiny bottle of something. A couple of drops of Mobil 1 0 sae synthetic should be fine, but you can buy small bottles of suitable oil. Sewing machine or watch oil isn't very boutique but will work fine. Very little is needed. Did you tell us what your TT is?

[aragorn723]

They didn't make a recommendation for any added oil..  The only instructions were to remove the platter, unscrew the bearing assembly, insert the new bearing assembly, and screw it down.  We might have some sewing machine oil laying around.  I was trying not to include the turntable mfg since a lot of people like them so much..  It's a Uturn Audio Orbit.  Been having trouble with this speed (or possible tone/volume issue) for a while, and also had a LOT of trouble getting a London Maroon cartridge working on this table too.  Maybe not the best pairing, but that's a whole other issue.

One interesting thing I noticed tonight is that the power supply brick is supposed to output 24 VAC.  Tested it tonight, and i'm getting 28.2 volts out of it, fairly consistently.  When the power does fluctuate, it's by a hundredth of a volt.  I sent that information to the co-founder of Uturn tonight, but i'm wondering if that could be a smoking gun.  That's a 17.5% increase over the spec'd voltage. 

Dave

[Thermioniclife]

If it is a regulated power supply than that could be an issue, having said that if it is an unregulated supply 28 Vdc is the unloaded supply voltage and will drop down under load.

[Deluk]

This does seem to be an issue the Uturn should have sorted by now. Their customer service does seem to be good though.
https://audiokarma.org/forums/index.php?threads/uturn-orbit-owners.573480/

[aragorn723]

Turns out the power supply checks out.  According to Uturn it should be 28V without load, and 24V under load.  I changed out the belt, and it seems to have corrected my issues!  Thank goodness for listening at home as it allows for long listening sessions to really test these things out.  Now if I can get my local shop to get my London Maroon cartridge working on this thing 

Dave

[Deluk]

The London Maroon is a very expensive and rather special cartridge. IMO it probably needs an arm and TT several grades up from the UTURN in order for it to work anywhere near its potential. Something in the $100-150 range would suit it better methinks. How does the original supplied cartridge perform?