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In Reply to: Ping Mosin, Tubesforever et al re: idler noise reduction posted by texanater on April 28, 2007 at 14:52:12:
I have one of Tubes L34 idler projects. I got it about 2-3 months ago and had quite a problem with a low mechanical noise in the beginning. On quiet passages-classical usually-there was a real problem. I'm not sure where the noise originates from, whether it's the idlers or the motor, I just don't know. So I started with adding some Dynamat around the base of the platter, close to the spindle. I also experimented with different armboard materials, I have a Rega RB250-Incognito-Mitchell weight. I also added stick on foam to the perimeter of the metal base, where it makes contact with the plinth. It was a little better. The armboards made the biggest difference, I have a piece of baltic birch glued to a piece of MDF, which is screwed to a piece of acrylic that mounts to the plinth. That made a huge difference, dead quiet. I also use a neoprene spacer to get the arm level up, actually I also used steel washers and acrylic washers, didn't seem to make a difference, sound wise. I have been using an Iron audio mat, which I thought cut the mecahnical sound even further, but today I started using my spot mat, Olly spots stuck on to an old flat LP. Still dead quiet. I also use the silicon nitride bearing.I hope this helps somewhat.
Follow Ups:
I've thought about the iron audion matt, but $120 is a bit rich for me right now. Do you think its really worth the price tag? I didn't think about the arm board much. Right now its just a piece of scrap wood. I don't even remember what kind of wood. I have plenty of mdf left over from a recent speaker project. I'll tinker with the arm board tomorrow. Thanks, I wouldn't have thought of that.
I have been working on th LP 34 plinth, moving stuff for my Brother in Law and rewiring tonearms.First, you should back off the stop screws and play with getting just the minimum tire contact to drive the platter and no more. This keeps the motor from being stressed by the tire and platter which dramatically reduces the vibrations to the platter.
Once you know where that point is, then set the stops and you are good to go. Now it will be easy to get quieter playback.
Like Mosin said, it might be really impossible to know where you are at with unknown tires. So get a fresh set.
Also, I really like Tom's approach to using the Iron mat to kill the ringing of the aluminum platter and dis-associating the motor vibration from the record. There is a foam which isolates the platter from the acrylic mat. I think this is superb!
email me your physical address and I will send you some of Olly's foam cork spots. These are a poor man's iron mat. I am using these and I find them extremely neutral with excellent bass response.
I suspect that polishing the bearing will be critical to getting really silent backgrounds. I really feel that a stock Rek O Kut is basically a mid fi product. It is a closely machined beast, but there was no polish whatsoever on the shaft or the thrust surface. You have a lot of hills and valleys with close machining. To get them out you really need to get things polished.
The silicone nitride ball was Mosin's recommendation and it took me over a year to try it. What a waste of a year....Mosin thank you!
With the polished bearing and the nitride ball you are definitely in for a big treat.
The motor has sintered bronze bushings. So just make sure they have just a little clean oil and it should do fine.
I did not have a chance to mock up a Pabst motor to the LP-34 today. Hopefully I can get to it this week. I just don't know if the Pabst is driving at the same RPM as the shaded pole motors.
I suspect that they are not. I will do some computations on this during the week.
The AT 440MLA is very silent in my system. I did have to play with VTA in order to get the cartridge dialed in. If it is too high, you will pick up a fair degree of noise. Too low and the cartridge sounds flat and lifeless. Make sure you have the VTA right. Start with the tail way down and then inch up while listening to something you know well. When the midrange starts to pick up you know you are getting close, when the soundstage sounds life like then you are there.
This should quiet down the AT 440.
I am working with my brother in law and another inmate to build a decoupled platter mat that I hope will quell the last bit of idler motor noise on my next LP-34.
It is just a test, but I am hopeful that it does the trick. Then you can have all the idler magic with a silent background like a belt drive.
Mosin has this now with his project. He took every step imaginable and then another 100 or so!
Where can you get the nitride ball? I'm going to get the bearing on my B-12H polished per your recommendation.
Tubesforever recomends the MacMaster site. You get two balls (hehehehe) from there for a total of about 14 bucks. The boca site gives you five balls (hehehehe) for less. I don't know the difference. I assume they are the same balls (hehehehe) but I dunno. I went with MacMaster before the Boca site was mentioned. I probably would have gone with boca. Just do a search for silicon nitride bearings at their sites.
I think Mosin said he has a local source. I tried to find it locally in Reno...no go....Tried in Portland OR....no go....Mosin is lucky to have a good local source. For me its the internet for parts like these.
Cheers!
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