Belts and speeds

[Mr.Crow]

I'm a bit perplexed, perhaps due to the era I grew up in. Why do some turntables require physically moving the belt to change between 33 1/3 and 45 rpm? I'm sure there's a very good reason - I'm no hi-fi buff so please excuse the newbie like question.

The turntables I've used/had all used switches to accomplish this.

EDIT: managed to post in wrong forum. Sorry!

 

[rainsoothe]

I think it's done to lower production costs. So greed, basically

 

[nopiano]

Purist turntable makers like Linn would prefer the belt tension to be optimised for 33.3rpm only. Stretching it to fit a 45rpm pulley is a compromise, and doing so can stretch the belt. An engineer will probably say the difference is well within the elasticity of any decent belt and therefore that argument is absurd.

Many traditional manufacturers like Pioneer and Dual made perfectly sound mechanisms to shove the belt from one diameter to the other. Or if you regulate the motor electronically a switch is all you need. As already suggested, relegating it to manual change is thrifty!

 

[Al ears]

Nopiano is correct, it's all down to cost. The idea of a constant speed motor and pulleys of two different diameters is not new and employed by Rega and others on their cheaper models. Cheaper and less to go wrong is OK for most people.

The switchable speed control needs a more sophisticated power supply / regulator arrangement that is obviously going to cost more assuming it is built to a high standard

 

[MajorFubar]

No particular fault of yours but this question has been a bit done to death recently and the answer is always the same: it's cheaper to leave out any speed-switching gear. It's a bit of a lame excuse though when the cheapest plastic shite from Steepletone / iON / Crosley can do three speeds with the flick of a switch, but something costing multiples more cannot. But that's the truth of it. It's penny-pinching.

 

[davedotco]

Most turntables use an a/c synchronous motor, ie it locks to the frequency of the mains, not the voltage. Such motors are accurate, reliable and cheap, if you choose well, they are virtually silent and vibration free.

To change the speed of the turntable platter, you either change the speed of the motor, which is complicated as you have to change the frequency of the a/c that drives the motor.

Or, you change the size of the spindel, which in effect alters the 'gearing', ie the relationship between the spindle and the platter/sub platter assembly. This can be done by switching a guide between the two different diameters on a stepped pulley, easy enough but it will compromise the condition of the belt.

Or you can swith the belt by hand which is easier on the belt, in some designs, early LP12s for example, an oversize collar is fitted onto the single diameter spindel, all of course done by hand.

Then the marketing guys get to work to make sure that you 'understand' that their choice is for the best possible SQ.

 

[MajorFubar]

This can be done by switching a guide between the two different diameters on a stepped pulley, easy enough but it will compromise the condition of the belt.

I reckon you'd have to be someone who switched speeds an awful lot before that happened, probably hundreds, inbetween time the belt has got to an age and condition where it should be changed in any case. However, clearly that's the perfect excuse which both the bean counters and the marketing department can hang their respective arguments on

 

[davedotco]

This can be done by switching a guide between the two different diameters on a stepped pulley, easy enough but it will compromise the condition of the belt.

I reckon you'd have to be someone who switched speeds an awful lot before that happened, probably hundreds, inbetween time the belt has got to an age and condition where it should be changed in any case. However, clearly that's the perfect excuse which both the bean counters and the marketing department can hang their respective arguments on

With some players the condition of the belt is quite important, flat 'ground' belts in particular. I accept that in most cases this is not the case and it is mostly marketing but not always.

The condition of the belt was crucial to the performance of the Xerxes for example ant that deck used electronic speed switching.

 

[Al ears]

Possibly a bit sad I know but when I had my old Planar 3 I used two belts, one for each speed, just to ensure the 33 1/3 one was never stretched further.

Seemed it be the obvious thing to do.

 

[MajorFubar]

Yeah that is a bid sad lol.

 

[Al ears]

Yeah that is a bid sad lol.

I know..... but I was just putting a spare to good use and not letting it perish in a drawer, so maybe not too sad.

 

[davedotco]

Yeah that is a bid sad lol.

I know..... but I was just putting a spare to good use and not letting it perish in a drawer, so maybe not too sad.

If you want your vinyl playback to be as good as it can be, then all aspects of your player need to be in tip top condition. From keeping the stylus clean to looking after the belt, all part of the discipline required.

 

[Al ears]

Yeah that is a bid sad lol.

I know..... but I was just putting a spare to good use and not letting it perish in a drawer, so maybe not too sad.

If you want your vinyl playback to be as good as it can be, then all aspects of your player need to be in tip top condition. From keeping the stylus clean to looking after the belt, all part of the discipline required.

You are correct Sir. Those that cannot be bothered to flip a belt to a different pulley simply bought the wrong turntable. ;-)

 

[andyjm]

I'm a bit perplexed, perhaps due to the era I grew up in. Why do some turntables require physically moving the belt to change between 33 1/3 and 45 rpm? I'm sure there's a very good reason - I'm no hi-fi buff so please excuse the newbie like question.

The turntables I've used/had all used switches to accomplish this.

EDIT: managed to post in wrong forum. Sorry!

Back in the day, the electronics required to generate two stable and switchable AC drive signals to run a synchronous AC motor at two speeds cost good money, and running the motor off the mains and using a pulley with two different diameters was cheap. So what if you customer had to fiddle with belts to change speed, fiddling was part of the fun, right?

There are engineering reasons why running a multi pole motor with higher frequency than mains 50Hz could have benefits (though unlikely to be audible) as this reduces 'cogging' - though a springy rubber belt and heavy platter would damp most of this out.

Frankly, unless you have an irreplaceable collection of 45s, why are you bothering to change speed anyway. Come to that, if you really want good sound quality, why do you have a turntable in the first place....