Noticeable Wow with New Belt

bane.oh

Active Member
Hey guys,

I have a Rotel RP-900 (the newer version) and I just replaced the belt with one I bought off ebay. After 15-20 hours of listening I started to notice audible wow where there was none before. When I put the old belt back on the wow seems to go away. Is this possible or am I going crazy? Can a belt cause more noticeable wow or was it always there and a new belt allowed me to hear it? I put on The Steve Miller Band - Book of Dreams, because it has those long synth notes at the beginning, and after switching back and forth a few times I am convinced I am right. It's so bad that I notice it with rock even. Did I get a faulty belt?

Thanks,

-bp
 
Usually it is the speed that is affected by a belt that might be out of spec. The width, thickness, length are very important for correct speed...I am not sure about how it would affect wow, but I'm guessing that a belt not in spec could possibly cause this problem. It seems you might have received a faulty belt.
 
Usually it is the speed that is affected by a belt that might be out of spec. The width, thickness, length are very important for correct speed...I am not sure about how it would affect wow, but I'm guessing that a belt not in spec could possibly cause this problem. It seems you might have received a faulty belt.

Thanks. The problem is my turntable is so rare that no one can tell me the correct replacement belt. The one I got looks to be the same other than the fact that it was a bit shorter than the old one. After a few weeks of use it has stretched to be about the same length. It was only a tiny bit smaller anyway. I figured it was because the old one had stretched out, it's at least 6 years old, probably much older.
 
Thanks. The problem is my turntable is so rare that no one can tell me the correct replacement belt. The one I got looks to be the same other than the fact that it was a bit shorter than the old one. After a few weeks of use it has stretched to be about the same length. It was only a tiny bit smaller anyway. I figured it was because the old one had stretched out, it's at least 6 years old, probably much older.

Have a look at the following site.
http://www.turntablebasics.com/belts/rotel.html

You may want to gamble on the FM 25.00 belt. :dunno:
 
My opinion (and purely that):

The new belt may be too tight, creating drag on the motor. As 6DZ7 says, a belt that's too tight can cause wow. Perhaps try stretching it a bit and see if that helps.
 
My opinion (and purely that):

The new belt may be too tight, creating drag on the motor. As 6DZ7 says, a belt that's too tight can cause wow. Perhaps try stretching it a bit and see if that helps.

I don't think that is the problem simply because the new belt is now almost identical in length to the old one. Maybe a mm or two shorter but it's definitely not "tight".
 
FWIW: I had this problem with a new belt I installed a few months ago. I was irritated. Then I realized I didn't have the belt centered 100% on the motor's spindle. It was catching on the upper lip of the spindle.

This probably isn't the issue, but it won't cost you anything to check.

Good luck!
 
Might try putting some talcum powder on the belt and running it again. I would also clean with alcohol the platter rim and the motor pulley prior to powdered belt. But a too tight belt could cause your problem as well as a whole list of other issues.
 
I went through this several years ago when I had to install a new belt on my RCA Selectavision CED player. I ordered a new PRB-Line belt which was supposed to be the correct size, but the platter speed was too slow. It turned out that the modern belts are made of a stiffer rubber than what RCA originally used. I found a supplier who had some NOS RCA OEM belts, and installing one of those solved the problem. Before the OEM belt was found, it was suggested to me that stretching the modern belt might help bring things back in line. I'm not entirely sure how that would be accomplished, but it's something to think about.
-Adam
 
I am not sure about how it would affect wow, but I'm guessing that a belt not in spec could possibly cause this problem.

Well, that could be caused by uneven thickness. One needs to consider that belt thickness is a part of the transmission ratio, due to the belt basically compressing on the inside and stretching on the outside, when it goes around the pulleys, so that the actual linear speed of the belt could be observed roundabout at the middle - hence the transmission ratio would basically be (radius of pulley 1 plus half the belt thickness) to (radius of pulley 2 plus half the belt thickness). And as the motor pulley usually is quite a bit smaller than the platter pulley, not only a constant deviation in belt thickness will have an impact on absolute speed, but also a variable deviation in belt thickness will have an impact on wow & flutter - unless one would have one of the few belt-drive designs with a motor-speed regulation that includes actual platter-speed sensing, like for example the Braun PS550(S), Philips' family of DirectControl turntable models and a few Dual models like the CS750 and CS750-1, which thus can actively compensate for such deviations.

And as usual at such an opportunity, I'll add my usual "et ceterum censeo" - namely, that I deem it a pity that today, in the era of cheap electronics, there are next to zero current belt-drive models with such a superior motor-speed regulation.

Greetings from Munich!

Manfred / lini
 
Manfred, I always learn something new from your posts, but let's not bring Carthage into this.:rflmao:

And furthermore, de gustibus non est dispundandum!
 
Well, alright, Larry,

though I really think that the current turntable manufactors should be bashed more frequently for being such lazybags and cheapskates. I mean, just look for example at the current Fehrenbacher-Duals: Most of these only make use of comparatively cheap DC motors, which do not even sport a frequency generator for motor-speed sensing and are controlled by comparatively simple regulator-ICs like the LA5530. Considering that a "simple" Technics SL-BD20 for ca. 150 Euro already sported a better motor-speed control with FG and PLL servo regulation, I can already hardly accept a simpler approach on a CS455-1 for in the meantime already ca. 400 Euro and even less on a CS600 for 1300 Euro.

So personally I'm quite disappointed by the current situation on the market for new turntables, after now already ca. ten years of "vinyl revival" - most so in the segment up to ca. US$ 1000 (or respectively 1000 Euro incl. VAT): Simple designs, that lag behind the state of technology of the late 70s/early 80s, often enough sport next to zero comfort features and then often enough are plagued by build quality/quality control issues on top - and many of these not exactly cheap for that...

Greetings from Munich!

Manfred / lini
 
Well, that could be caused by uneven thickness. One needs to consider that belt thickness is a part of the transmission ratio, due to the belt basically compressing on the inside and stretching on the outside, when it goes around the pulleys, so that the actual linear speed of the belt could be observed roundabout at the middle - hence the transmission ratio would basically be (radius of pulley 1 plus half the belt thickness) to (radius of pulley 2 plus half the belt thickness). And as the motor pulley usually is quite a bit smaller than the platter pulley, not only a constant deviation in belt thickness will have an impact on absolute speed, but also a variable deviation in belt thickness will have an impact on wow & flutter - unless one would have one of the few belt-drive designs with a motor-speed regulation that includes actual platter-speed sensing, like for example the Braun PS550(S), Philips' family of DirectControl turntable models and a few Dual models like the CS750 and CS750-1, which thus can actively compensate for such deviations.

And as usual at such an opportunity, I'll add my usual "et ceterum censeo" - namely, that I deem it a pity that today, in the era of cheap electronics, there are next to zero current belt-drive models with such a superior motor-speed regulation.

Greetings from Munich!

Manfred / lini
Hi Manfred. I concur with your explanation, but could such a belt cause a regulated drive system to go slightly "nutsie" at some time?
 
I have an RP-900 and yes it is a Systemdek clone with some Rega also. The subplatter and bearing well are Systemdek but the synchronous motor is the same as Rega (Premotec/Airpax). The pulley and belt are compatible with Rega, as a matter of fact I upgraded to a Tangospinner brass pulley and silicone belt. The stock plastic pulley might not be grabbing the motor shaft tight enough anymore and you are probably having some slippage resulting in WOW. That's the reason why I went with the Tangospinner.
-Matt
 
wj: Oh, I'd think that uneven/variable slip (e.g. due to a somewhat loose belt or one with greasy spots) could confuse such a regulation. But at least on a modern, microprocessor-controlled implementation with both motor- and platter-speed sensing I'd expect that the designers would add protective plausibility limits (you know, like "if motor turns alright, but corresponding platter-speed doesn't fit to motor-speed within certain limits, something must be wrong => switch motor off (and possibly signalise the error condition via flashing speed indicator LED or something...)"), as these would seem easy to include.

Greetings from Munich!

Manfred / lini
 
I have an RP-900 and yes it is a Systemdek clone with some Rega also. The subplatter and bearing well are Systemdek but the synchronous motor is the same as Rega (Premotec/Airpax). The pulley and belt are compatible with Rega, as a matter of fact I upgraded to a Tangospinner brass pulley and silicone belt. The stock plastic pulley might not be grabbing the motor shaft tight enough anymore and you are probably having some slippage resulting in WOW. That's the reason why I went with the Tangospinner.
-Matt

Thanks for the advice! I think you are the first person that actually has the same turntable as me. Those upgrade kits from Tangospinner look pretty cool! Is there a reason you didn't go for the kit and just got the belt and pulley?

EDIT: I just re-read your post and saw that the subplatter is different.
 
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