Barry
27-05-2015, 13:15
This Bank Holiday, having installed my Summer Amps and changed the phono stage (http://theartofsound.net/forum/showthread.php?38771-Bank-Holiday-tinkering), I thought I would, out of curiosity, check to see how level my turntables are. I have four of them: three Thorens TD124/II and an EMT930.
The EMT turntable does not have any indication of level, but was levelled using a simple carpenter’s spirit level. The Thorens turntables have a bubble level built into the chassis and the past I have simply relied on this for levelling. Recently I read somewhere that the accuracy of the Thorens device is not considered to be that good.
So I thought I would check all four decks with a calibrated bubble level.
http://thumbs.ebaystatic.com/d/l200/pict/231266872464_1.jpg
The resolution of this device is 0.125° (though I have no idea of the accuracy), and I am pleased to say that all three Thorens turntables were within 0.125° of bubble centre, as was the EMT. So much for hearsay!
Incidentally, the level must be checked on the platter, not on the armboard. Also rotate the platter and check the level when the platter is different positions.
I have no idea of how much deviation from being perfectly level is permissable. The effect on VTF is negligable (and likely to be well within the accuracy of the stylus scales), but the effect on the bias could be greater (but difficult to assess).
The EMT turntable does not have any indication of level, but was levelled using a simple carpenter’s spirit level. The Thorens turntables have a bubble level built into the chassis and the past I have simply relied on this for levelling. Recently I read somewhere that the accuracy of the Thorens device is not considered to be that good.
So I thought I would check all four decks with a calibrated bubble level.
http://thumbs.ebaystatic.com/d/l200/pict/231266872464_1.jpg
The resolution of this device is 0.125° (though I have no idea of the accuracy), and I am pleased to say that all three Thorens turntables were within 0.125° of bubble centre, as was the EMT. So much for hearsay!
Incidentally, the level must be checked on the platter, not on the armboard. Also rotate the platter and check the level when the platter is different positions.
I have no idea of how much deviation from being perfectly level is permissable. The effect on VTF is negligable (and likely to be well within the accuracy of the stylus scales), but the effect on the bias could be greater (but difficult to assess).