Dealing with MoFi Ultradeck motor vibration

That's what I also thought when I was buying the table but I doubt that their dampening approach is very effective. Since the motor top plate is rigidly mounted onto a solid MDF plinth, I'm not even sure what kind of dampening they're talking about

The DC motor on my previous table, Pro-ject Debut III, was mounted on a bunch of rubber bands. Not sure if that was the reason for the Debut to be absolutely quiet but it was, at least in my case. That said, the overall sound quality of the MoFi deck is so vastly superior that I haven't dropped a needle on the Debut in months.

 

Many of those Pro-Jects are noisy as hell. You got lucky with yours. You got unlucky with your MOFI. That's the curse with these decks and the type of motors they use.

 

Thanks!

 

I bought a Mofi studiodeck. I can hear low motor noise without music, but don't hear that motor noise with music. not sure this is acceptable motor noise or not.

 

follow up: I removed the belt and ran the motor and the rumbling noise of the motor got louder and worse.
Please watch the video :
IMG_1823.MOV
I love all other parts of Mofi Studiodeck except this motor noise. It looks good and sounds good, but can't tolerate the noise.
I decided to return this. I really love Mofi, but
I'm afraid of getting the same noisy motor if I replace this to a new Mofi Studiodeck.

 

Schiit mentions something to this effect when describing the Sol motor. Thing is, the motor's mounting flange is still bolted directly to the housing can, so there remains a direct path for vibrations to the can and platform below. As promising as it sounds, it's really only half baked. The solution I used to improve the isolation was very simple but perhaps not as bullet proof reliable for a mass market item built to a price point with warranty considerations. I suspect the problem with the UD is similar in origin.

 

Is the noise the same on all records? From your description it sounds like you are hearing rumble baked into the grooves from the cutting lathe. Some records have a higher or lower noise floor.

 

Yeah, the noise of my Ultradeck is similar but without the knocking sound I can hear in your video. Just a loud baseline of the motor running. Probably a good idea you returned it. Doesn't hurt to order another one to see if it's quieter. Despite the problems I had with the motor, I'm not sure what else I would buy in this price range. And it sounds like not all units are noisy.

Yes, groove rumble is to be expected and is certainly dominant between the tracks but behind it there also is a subtle baseline of the same motor noise I hear when standing next to the table with the platter spinning. Also, on dead wax there is no rumble, so I get to enjoy the sound of the motor purring in all its glory (until the needle lifts.)

 

I would contact your dealer or MOFI to replace the table. All TT motors make some noise, but you should not be able to hear it when standing away from the unit.

 

If it doesn't bother you, then you don't have a problem. It's the same for me with my Studiodeck; I hear it when starting the motor but it doesn't bleed into the music from what I can tell.

Did you get in touch with MoFi before returning the table? I've been in touch with them regarding a different issue, and they've been very helpful.

 

Please watch this video :IMG_1823.MOV
Is your motor noise like mine ?

 

It shouldn't be visibly moving back and forth like that -- looks like something wrong with how it's mounted. The belt probably stabilizes it a bit, which is why it's worse without it.

I'd get with your dealer or MOFI -- depending on why it's loose, it could get worse over time, and, noise aside, may affect speed stability, too.

 

I'm not sure how MOFI intended the design to be. Some belt drive motors will have the motor spindle glued in with adhesive so it doesn't move. Maybe MOFI is just pressing them in here. Either way the end result (noise) is crap.

 

Might find a stethoscope on the plinth would be a final diagnosis, ‘cause if it’s the same sound through the scope it is just traveling up through the arm and cart.

 

It's just mounted onto that circular sleeve, and the sleeve is screwed onto the plinth. Mine isn't as loose in the sleeve as that vid -- if I try to pull it back and forth, I get maybe a millimeter or two of give, and there's no visible movement or noise if I run it without the belt. I had it like that this weekend, and I actually had to touch it to make sure it was moving at all.

 

Did you take the motor out? And if so, how? Unscrew the top plate screws, and out it goes?

 

I have unscrewed the top plate and lifted it up a little to just peek inside. The motor is attached to that plate, but I didn't pull it up high enough to see how. Wires from the motor look like they are just plugged into some terminals in the plinth assembly.

 

Dc blocker is for toroidal (donut shaped) transformer hum, check to see if your amp has one. I can think of two blockers but have not tried either one:
https://www.amazon.com/iFi-SilentPower-DC-Blocker-Connector/dp/B08XWHJRZ1
or
CMX-2 Precision Common Mode AC Line Filter With DC Offset Eliminator

 

Thanks for sharing. Good to know (just in case).

Yes, I did plug iFi DC Blocker into the turntable - no effect whatsoever. On a positive side, later I plugged it into the power amp and it took care of the hum from the transformer inside.

 

As it happens, I decided to get in touch with MoFi support. I quickly got the response below:

"...it is totally normal to be able to hear the motor when you are near the turntable.
After testing many motors and mounting methods we felt the high torque Hurst motor being mounted on the plinth gave the best speed stability. The motor is mounted on o-ring dampers to help decouple it from the turntable body and keep vibrations that travel towards the stylus to a minimum."

Quite informative, IMO. I sat on this info for a bit and at some point it danged on me that if the o-ring dampers are over-compressed they will transmit more vibration and noise to the plynth than necessary. So, I loosened the four mounting screws a bit and immediately heard noticeable reduction in motor noise. Furthemore, I was able to to almost "tune" the noise by playing with the screws' tension to a point where the noise is a lot lower than before. If you experience the same issue, I would advise to keep the motor running as you "tune" and keep an eye on the rubber belt so it runs smoothly around the motor spindle without jerking. I also kept the screws not too loose so the motor is still mounted fairly rigidly.

Hope this helps.

 

It's probably a cheap AC motor. Even very good AC motors (like the Papst in my Gyrodec) are subject to noise and vibration.

Cheapest solution (but somewhat ugly and involves another step in playback and a slightly unsightly additional piece of equipment) to really attack the problem is to run the table off a variable output transformer. After starting the table at around 115V, the voltage can then be dialed down to anywhere from 55V to 70V depending on the quality of the main bearing of the table.

Both motor noise and vibration will be significantly reduced and the table will also sound better. Upgraded table power supplies like the Linn Lingo, VPI SDS and others designed for AC motors have this as an automated feature (and it is very possibly their most significant feature) at elevated audio prices (ie. $1000 +)

I've been running my original AC motor (early 80's) Gyrodec this way for about 10 years since reading a suggestion from Harry Weisfeld at VPI regarding this at Audioasylum.

With improvements to my turntable's main bearing (better quality oil and silicon nitride ball replacing the stock ball), I can drop voltage down to around 55V on my table post startup.

Great Tweak for Older Tables with AC Synchronous Motors - Sources - Analog • Canuck Audio Mart Hifi and Audio Forum

 

$2K for a deck with audible motor noise? Okay, this MOFI support person must have an advanced degree in slinging b.s.

That would be an auto-return for me.

 

Synchronous motor noise comes from the motor hitting its motor's poles while in rotation. This is common to all synchronous motors. The successful models incorporate a suspension for the motor or extreme mass to absorb or deflect the motor noise from its pole vibrations. I have built 2 turntables as a DIY project and both exhibited the same type of motor noise problem transmitted to the platter via the belt. I used an ungodly amount of non-hardening modeling clay to absorb the vibrations that ultimately brought the noise under control. I might suggest getting a direct drive, like one of the new Technics (SL1210g). My Empire 598 has no noise issues, nor my VPI Hw-19jr. if that makes any difference.

 

Is it still under warranty ? Uggg

 

Again, with proper adjustment, I was able to get the noise under control, more or less. In general, MoFi approach/design is solid because the deck sounds fantastic overall. But I think they would benefit from investing in a better QA process. Besides dealing with the motor noise, I had to adjust the crooked platter post/bearing, and the tonearm dropping way to quickly. The latter two problems were fairly easy to fix but they should not have had a place here or even on a much cheaper brand-new turntable.

You're probably right on both points.