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A Simple Test

Maybe everyone is already doing this andI'm the last one to figure this out, but I've tried a simple test to determine the degree of motor noise that is transfered to the cartridge.

Find a good clean record which has a longer time between a couple of tracks and, while the record is playing between tracks, turn the motor off and then back on. You'll probably detect the disappearance and re-appearance of hum and/or rumble. Any noise remaining when the motor off will be from other areas (surface noise, bearing noise, etc.)

This has been quite useful in helping set proper belt tension (more tension= more noise) and also identify differences and problems in motors as well as quickly identifying whether a motor or belt tweek was useful in reducing noise.

It's been quieter around here lately....

Jim
jimbo3
jimbo3 OP
304 posts
 
El- I haven't been letting the platter come to a complete stop before switching back on. Motor noise differential seems to be most apparent immediately after switching motor off and again when the motor is turned on, so there is not much of a need to have the motor off for more that a second or two. I can usually cycle this test 2 to 3 times between tracks.

After adjusting belt tension using this method (adjuust to least amount of noise through speakers) one can discern the difference between electrical and mechanical noises in the motor/drive system and then fix whatever is causing it. One can also test various belt materials for differences in noise.

After a couple of hours of experimenting, I'm now using the OL DC motor and a #4 silk beading thread and have been able to reduce motor/drive noise to virtually imperceptable while minimizing belt slippage. (Automotive fan belt dressing seemed to improve "traction", too!) Background is blacker and presentation is much more dynamic as a result.

Now I'm on to fine-tuning the arm/cartridge alignment.....
dougdeacon
3,338 posts
 
Jimbo3,

Automotive fan belt dressing to improve drive belt traction? Now THAT interests me. Any idea how well it would adhere to a mylar drive belt? Could it wear off and leave a residue around the platter?
jphii
485 posts
 
Doud,

Don't try it. It will leave a nasty residue, which I am sure will piss you off! And it will probably eat the mylar.

Trust me on this.

Joe
jimbo3 OP
304 posts
 
Yes, it might eat up mylar- don't know for sure, though. In my case, the silk string rides on the platter edge, so cleaning it is easy. I haven't had a residue, yet. However, I put the belt dressing on the string and not on the pulley or platter, so there is very little to start with.
dougdeacon
3,338 posts
 
Thanks Joe. I'm not too worried about the mylar, I have a 100' roll of the stuff. But a nasty residue on my cocobolo platter? No thanks! Sounds like it would poison the cats too.

I don't have any motor noise (as you know) and it's not like I have any belt slippage either. But the improved coupling when I changed from silk thread to mylar tape was quite audible. Just thought I'd take another step toward direct linkage if possible. Where's Psychicanimal when you need him! :)

Jimbo3, sorry for the threadjacking. Whether you use dead grooves between tracks or on a test record it sounds like a good test to try.
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