Flutter!

[Mr. dB]

My turntable has suddenly developed a case of flutter.

The turntable is a Rega Planar 2. I put the Rega P2 motor upgrade kit on it in October 2009. The tonearm is an RB300, cartridge is a Denon DL103R.

Until recently it sounded steady. A few days ago I pulled out a Neil Young record and thought "I don't think he's supposed to be THAT shaky...". Other records confirm that it's fluttering.

I have already tried a new belt, which made no difference.

Anyway, I'm looking for ideas on how to troubleshoot this problem. I've already eliminated the belt. That leaves the motor, the subplatter, or the center bearing as possible sources for the issue. The bearing "feels" good -- if I take off the belt and spin the platter, it goes for minutes. But I suppose that doesn't really tell us much.

What's the best way to clean and lubricate a Rega bearing? I suppose that should be my next step, since it's almost free and doesn't require any replacement parts. Is it okay to use alcohol and Q-Tips? And after it's clean, what lube does it require? Is there a special Rega lube?

There is no local Rega dealer, so I'm pretty much on my own to figure this out and execute the solution, apart from whatever long-distance help I may receive from my friends at DIY. Thanks for any ideas.

My gut tells me that the shaft bearing in the motor is the most likely source of flutter in a belt-drive turntable, but the motor is the newest part of the whole system apart from the cartridge.

[Michael Bean]

I'm not familiar with that particular TT, but I think you're on the right track. Try running the motor without the platter in place, it should run with no discernable vibration or noise.

Mike

[indianajo]

You want a non-detergent oil with no additives. Sewing machine oil is usually good.
Is the motor a synchonous line voltage AC motor or is it a dc motor controlled by a circuit board with a set of stripes on the underside of the platter read by a photodiode? If a circuit board is involved, it could be almost anything. Even dust on the photodiode or illuminator device. Could also be a servo-motor reading internal windings for speed like a VCR. How many wires go to the motor?

[speaker dave]

Flutter is more likely to be related to the motor than the platter, just because flutter tends to be a higher rate of irregularity more in line with the faster motor rotation. Check for any gunk on the motor pulley. While it is running let your fingernail scrape on the drive surface and see if you feel anything. If not, and if it has electronic drive, then I would be suspicious of that (as Indianjo suggests).

David S.

[Mr. dB]

The motor in the Rega is an AC synchronous motor, driven by a capacitor phase shift circuit from line voltage AC. There are four wires. It's the same Premotec motor as used in many other British belt-drive turntables, including older Linn Sondeks.

I did try cleaning both the drive pulley and the driven pulley with q-tips and alcohol. The q-tips came out clean. The drive pulley is aluminum, and there is no visible gunk on it either. Besides, the motor and pulley are only a year-and-a-half old. The driven pulley/subplatter is plastic on the Rega turntables. I would suspect wear, but there is no wear line or any visible indication of where the belt rides on the driven pulley.

These turntables use a belt with a circular cross-section, essentially it's an o-ring.

I'm beginning to suspect that what I have is a resonance problem with the tonearm/cartridge combination. The Rega RB300 arm is a medium-mass design, my phono cartridge is a Denon DL103R which is a low-compliance MC that requires a 2.5-2.7g tracking force, and the cartridge body itself is also rather heavy. It's heavy enough that if I were using the standard Rega counterweight, it would have to be almost all the way out to the end of its travel to achieve balance. However, Rega makes a heavy counterweight available as an accessory, and I have one of those, so that it can achieve a balance with the weight closer to the pivot. Anyway, I'm thinking that there's a possibility that the combination may have a resonance that is high enough that it might be "fluttering" on small surface irregularities.

[speaker dave]

Originally Posted by Mr. dB

Anyway, I'm thinking that there's a possibility that the combination may have a resonance that is high enough that it might be "fluttering" on small surface irregularities.

This could be the case. Look to see if the cartridge seems to be continuously "bouncing" a bit. You might even be able to see corelation between what you hear and the bounce. If so do a search on "tonearm damping". There have been some oil trough dampers done by DIYers in the past. You might also consider one of the Shure cartridges with the built in damping brush.

David S.

[Mr. dB]

I don't see any bounding or other weird motions when this happens, but I've confirmed with enough records that whatever issues I'm having are not happening with flat records, and the driveline doesn't seem to be the source.

I got a very nice phone call from Chad at the US Rega Importer's office. Among other things, he told me that Rega uses regular 80 or 90 weight hypoid gear oil for the turntable bearing, and that it's okay to clean the bearing with alcohol or brake cleaner.

[Groove-T]

Normally its the pulley which is no more in closed contact with motor axis, one small portion of loctite or similar will fix the issue.

[speaker dave]

Originally Posted by Mr. dB

I don't see any bounding or other weird motions when this happens, but I've confirmed with enough records that whatever issues I'm having are not happening with flat records, and the driveline doesn't seem to be the source.

I got a very nice phone call from Chad at the US Rega Importer's office. Among other things, he told me that Rega uses regular 80 or 90 weight hypoid gear oil for the turntable bearing, and that it's okay to clean the bearing with alcohol or brake cleaner.

But you've already confirmed that it isn't a drivetrain issue, it is related to flatness of your records.

All phono cartridges/tonearms bounce at the tonearm resonance. If you ever look at the electrical output on an oscilloscope you will see a low frequency wobble of the signal related to any unflatness of the record. A slow warp isn't the issue here. The slight sharp ripples are what are closer to the tonearm resonance frequency.

Now with some cartridges this doesn't matter. They can bounce around and you don't hear much. Others are very susceptable to motion. I believe in their case the cantilever is going in and out of the magnetic field nd the tonearm bouncing is converted into a very noticaeble tremolo (amplitude modulation).

The answer remains: try another cartridge or try to add some tone arm damping, or buy a cartridge such as the Shure that adds damping.

David S.

[Groove-T]

Originally Posted by Mr. dB

I'm beginning to suspect that what I have is a resonance problem with the tonearm/cartridge combination. The Rega RB300 arm is a medium-mass design, my phono cartridge is a Denon DL103R which is a low-compliance MC that requires a 2.5-2.7g tracking force, and the cartridge body itself is also rather heavy. It's heavy enough that if I were using the standard Rega counterweight, it would have to be almost all the way out to the end of its travel to achieve balance. However, Rega makes a heavy counterweight available as an accessory, and I have one of those, so that it can achieve a balance with the weight closer to the pivot. Anyway, I'm thinking that there's a possibility that the combination may have a resonance that is high enough that it might be "fluttering" on small surface irregularities.

Sorry, i have not realized you use the DL 103.

Thus you have to add weight on top of the cartridge( at least 10 gramms) to get the resonance where it should be. The RB 300 has not enough mass by itself. Maybe you have to use a heavier counterweight to compensate.
Tracking force should not be adjusted with the spring, adjust it with the counterwight.

Then you will have no more problems, more bass and more dynamics.