Turntable speed

[Paul R]

What I meant was, were you a collector of early 78s, you'd soon find that not all were actually cut at 78rpm.

Played at 78rpm, early Caruso (68 to 70rpm), for example, would sound like a castrato; this before we take into consideration that there were no standards for recording equalization.

I'm not a collector but I've dabbled. When dabbling I used Audacity to equalise and adjust effective speed. This does become a maze of tiny passages. I do have a 12" single sided recording of Caruso that is pre war. Great War that is. There's something profound about that direct mechanical connection from the sound in the room then to the movement of the stylus now. Then it goes digital and some of the mystique disappears.

The 78.26 thing is a useful confirmation that the speed measuring technique I've been messing with is working a bit. I hadn't noticed that it was the notional 'standard'. My aim is to look at variations while actually playing a record at quite a fine resolution. The average rpm just falls out. Anyway we'll see.

 

[Craig B]

My Rega Planar 2 runs at 34.10 RPM, LP12’s are likely calibrated at the factory. My LP12 is running at 33.33 using a calibrated iPhone app called RPM.

So, if you arrive a wee bit early, John, folk should assume that you had been listening to the Planar 2 before departure.

Your LP12 is more likely to have been calibrated at the dealers. This is part of the initial setup procedure, and something that is routinely checked during service and/or upgrades.

 

[John]

So, if you arrive a wee bit early, John, folk should assume that you had been listening to the Planar 2 before departure.

Your LP12 is more likely to have been calibrated at the dealers. This is part of the initial setup procedure, and something that is routinely checked during service and/or upgrades.

The Rega has been sitting unused for 10 years with the same belt that was on it when I purchased it used. So who knows how old the belt is, it’s a 1988 vintage model. Not sure how much different the results would be with a new belt and a clean pulley.

 

[Mike & Van]

Is there an app to test the app?

 

[Big Tabs]

I think I have some pre 78’s that are 80 rpm. From 1928

these


More images

Handel* : Conducted By Sir Thomas Beecham With Dora Labbette, Muriel Brunskill, Hubert Eisdell, Harold Williams (3) And The BBC Choir* – The Messiah - Volume I
Label: Columbia – 9320, Columbia – 9321, Columbia – 9322, Columbia – 9323, Columbia – 9324, Columbia – 9325, Columbia – 9326, Columbia – 9327, Columbia – 9328
Series: Columbia Masterworks
Format:
9 x Shellac, 12", 80 RPM, Album
Country: UK
Released: 1928

 

[John]

Is there an app to test the app?

I have two apps on my iPhone that test turntable speed. “Turntable Speed” is the one I’ve been using for the tests and screen shots I’ve provided in this thread. It’s a free app and it works great but there is no way to calibrate it to the gyroscope in the iPhone.

The other app I have is called “RPM”. It is also free for 10 uses and those are not calibrated to the iPhone. They have a paid version for $15 that has provisions to calibrate the app to the iPhone. I purchased the app and found that the calibrated results differ from the uncalibrated results.

I did find that the uncalibrated results of both apps agreed with each other. Hope that helps.

 

[sonddek]

Here you go taken with my 8 year old genuine LP12 belt.

Very interesting - thanks!

 

[hockman]

Using a conventional strobe disk, I cannot detect any stylus drag with my turntable. I was a bit surprised TBH, expecting the drag to slow down the speed. Perhaps it is very little.

 

[davidsrsb]

I have two apps on my iPhone that test turntable speed.

I doubt that the Apps go near the phone sensor hardware. If the OS API is flawed, they will have the same error.

 

[Craig B]

The Rega has been sitting unused for 10 years with the same belt that was on it when I purchased it used. So who knows how old the belt is, it’s a 1988 vintage model. Not sure how much different the results would be with a new belt and a clean pulley.

At that age it is likely that the motor suspension belt is past needing replacement too. This affects motor alignment and combined with an old belt could easily have the speed off by nearly a whole percentage point (+0.98%, rounded up to 2 decimal places). A bit of TLC and you could have that down to a maximum of 0.5%.

 

[John]

At that age it is likely that the motor suspension belt is past needing replacement too. This affects motor alignment and combined with an old belt could easily have the speed off by nearly a whole percentage point (+0.98%, rounded up to 2 decimal places). A bit of TLC and you could have that down to a maximum of 0.5%.

So does the speed of the Rega increase when these parts age or does the speed slowdown?

 

[Craig B]

So does the speed of the Rega increase when these parts age or does the speed slowdown?

It all depends upon the lay of the land. For example, if the motor suspension has shifted enough such that the spindle/pulley lists inward toward the main bearing/spindle then the likely to be already stretched belt may ride higher in the pulley groove enough for there to be a whole percentage point speed increase. One would think it would slip and therefore run slow, but the result is more akin to the belt riding within a very slightly larger diameter pulley.

Although it may seem finicky at first, the old O-ring motor suspension can easily be realigned such that the tension of a fresh belt pulls the motor spindle into vertical alignment with the platter bearing. The second biggest mistake* folk make here is thinking that they need get the motor siting level sans belt tension. With a grooved pulley this alignment need not necessarily be perfect, with the usual worse case scenario being the belt wandering up/down on the drive hub (aka sub-platter), or dropping off the hub altogether on 45. Belt 'wander' isn't really as much of a performance problem with round belts as with flat; the latter, especially so, with spring suspended sub-chassis decks.

Let me know via PM if you want to have a play with yours and I'll forward on the official instructions.

* Second biggest mistake, because over-tightening of the intentionally plastic (i.e. sacrificial) motor mounting screws can cause cracking of the plinth laminate round the motor where the cutout exists below.