HiFi Subjectivist ¦ Audio Forum ¦ NVA User Group

This is partly inspired by Richard's infamous 'belts are for holding trousers up' quote but I'm genuinely bemused too as to why some are so anti belt drive. It seems to me that the object is to drive the platter without transferring any sound, vibration etc. from the motor. I don't see how any of these different methods can be inherently better at that than others. I'm no engineer or designer though so perhaps fans of a chosen method might share their thoughts and enlighten me?

Many belt drives suffer from poor pitch and timing, ime. Listen to a recording of piano.

Belt drives have an inherent problem in that the belt must be flexible, but in being so it may cause speed instability. 2 belts, 3 spindles, 2 or 3 motors, are just some of the ways of combating this.

There is also the problem with the belt and the suspension fighting against each other.

Direct drives can cause speed fluctuation by hunting for the correct speed. Servo control means they are forever changing speed.

Listen and decide if it matters to you

The problem with belt drives is that the belt can stretch, this then means that there is stored energy which gets back to the platter and causes a speed fluctuation (faster). As the platter is turning, very slightly, faster than the motor the belt is then stretched on the other side and causes the platter to be slowed down. In theory this results in a very slight wow in the output and frequency fluctuations in the music. In practice manufacturers have found ways to minimise this by installing a clutch between the motor and motor pulley and by making the belts less elastic. This is also a good excuse to charge a high price for a replacement belt. A very heavy platter can make matters worse on startup but, once up to speed the flywheel effect results in a very stable speed.

Idler drive turntables don't suffer from the same problem but they aren't problem free either, the idler must be disengaged from the motor shaft when not in use because there is a risk of slight distortion to the edge of the idler. This distortion can cause a percussion each time the distorted area hits the platter. The damage can also cause minor speed fluctuations. Designers solve this problem by coupling the idler mechanism to the on/off switch so that when switched off the idler is not in contact with anything. A second potential problem is that there is a bearing in the idler and that can become noisy, such noise is passed via the rubber idler wheel to the platter and thence to the stylus.

Direct drive turntables, self evidently, don't have a belt to stretch or an idler to distort or suffer bearing problems but they are rarely driven directly from the mains, which in the UK has a pretty reliable frequency. Most are driven by an oscillator circuit which is then corrected by a feedback circuit. The feedback loop can behave very much like a drive belt, some early direct drive turntables did indeed suffer from those problems. Later models have massively improved feedback circuits with damping to prevent speed fluctuations. For the record there are DC driven DD turntables but the motor isn't the issue, it is the feedback/speed control circuit.

There is no perfect turntable drive system but the belt drive is the simplest and has the fewest components. DC servo driven motors in belt drive turntables have, potentially, the same issues as DD turntables for exactly the same reasons. Badly implemented DC motors can have the motor servo fighting the belt.
The idler drive turntable is slightly more complex, though it has been around longer, mainly because the materials technology needed to solve the problems with belts wasn't available until more recently.
DD turntables have the fewest moving parts but complex electronics.

Well implemented any of the drive mechanisms can provide a very stable speed and an excellent basis for a vinyl playback system. However, the cheapest and easiest to implement well is the idler drive which is why there are so many good idler drive turntables around, I always fancied a Garrard 401. A wouldn't mind a Thorens TD125 either.

One final note, many belt drive turntables have isolation suspension systems, basically they are hung from springs. A good number have foam inserts in the springs to, supposedly, damp oscillations. The foam is another spring and springs store energy. One reason for the distrust many have for belt drive turntables is that suspension systems are often more trouble than they are worth.

The good Doc used to say doubling up drive belts worked well. Never tried it but will give it a go on my fruitbox some time. Will have to glue them together with bison kit

Geoff, you get my post of the year award so far

My first proper turntable was a Garrard 401
With an SME 3012 12” tone arm.

I regret selling it, but it went to a good home in Japan. Would love to get another one day.

I’m using a highly modded Rega Planar 2 at the moment. Everything has been replaced on it, except for the tone arm. Though it’s had a wiring upgrade and better quality weight.

Sounds lovely to me

I also have a NAD 533 that’s completely stock. Sounds lovely too. love the Goldring Electra cart, very sweet. It’s for my daughter hi-if, I have a while NVA setup situ Tannoy Monitors to drop off when shielding ends.

Thanks for the very instructive posts - really enjoyed reading your post especially, Geoff.

TheMarlin wrote: ↑Sat Jun 27, 2020 8:11 pm
Everything has been replaced on it, except for the tone arm. Though it’s had a wiring upgrade and better quality weight.

Bit of a trigger's broom then ?

Berty bass wrote: ↑Sat Jun 27, 2020 3:01 pm This is partly inspired by Richard's infamous 'belts are for holding trousers up' quote but I'm genuinely bemused too as to why some are so anti belt drive. It seems to me that the object is to drive the platter without transferring any sound, vibration etc. from the motor. I don't see how any of these different methods can be inherently better at that than others. I'm no engineer or designer though so perhaps fans of a chosen method might share their thoughts and enlighten me?

Get a Pioneer Exclusive P3 or P3a. Then compare that to any belt drive you can get your hands on.

The proof of the pudding is in the eating.

Lindsayt wrote: ↑Sat Jun 27, 2020 8:27 pm Get a Pioneer Exclusive P3 or P3a. Then compare that to any belt drive you can get your hands on.

The proof of the pudding is in the eating.

Not the most practical of suggestions, if I may say...