Linn Axis vs Thorens TD166 mkII

[SPL db]

I have a chance to pick up a Thorens TD166 MKII locally in very nice condition.

I currently run a Linn Axis with the Basik arm.

Not knowing too much about the Thorens line of tables, where does this model Thorens rank compared to an Axis?

The Thorens is all stock as well.

 

[dr*audio]

As far as performance goes, they are the same, IMO. The Thorens is more reliable and less tweaky. Lube the motor bearings on the Linn periodically (you have to take the pc board and motor out to get to the bottom bearing, dumb design) and the Linn should be ok. The Thorens should be lubed periodically, too, but the Linn motor drive circuit stops driving the motor about every 4 revolutions and lets the platter coast (another dumb design) so if the platter and motor bearings aren't lubed, the platter will lose speed or not turn at all. That won't happen with the Thorens unless the bearings in the motor are severely dried out, or the platter bearing lube gets gummy.
Also, some of the Linn arm bearings are glued in place and are non adjustable. Not so with the Thorens. In short, if I had a Linn and it was running ok, I'd keep it, but if I had the choice of buying one or the other, I'd take the Thorens.

 

[sreten]

... ..but the Linn motor drive circuit stops driving the motor about every 4 revolutions and lets the platter coast (another dumb design) so if the platter and motor bearings aren't lubed, the platter will lose speed or not turn at all.

Hi,

Why on earth would they do that and how would you design a circuit
to do that to a synchronous motor ? A very dubious statement.
Any references ?

rgds, sreten.

 

[dr*audio]

Hi,

Why on earth would they do that and how would you design a circuit
to do that to a synchronous motor ? A very dubious statement.
Any references ?

rgds, sreten.

Sure, I've repaired 2 of them. I did some searching on the internet and I found the schematic and an explanation of how it works. I analyzed the schematic and confirmed, it drives for a period of time while a cap is charging. Once the voltage on the cap reaches a set threshold, it then stops the drive for a bit, then starts the drive again and senses the current draw ( more current draw means the platter has slowed down) and applies a correction voltage to the drive to compensate, then they cycle starts again.
Here is the page I found offering a partial explanation:
http://www.diyaudio.com/forums/analogue-source/103911-repairing-linn-axis-motor-drive-amplifier.html
I am sure they did it to prove that their precision platter bearing had so little friction it could coast, no other reason.

 

[DaveyW]

In short, if I had a Linn and it was running ok, I'd keep it, but if I had the choice of buying one or the other, I'd take the Thorens.

Not quite the same pairing, but hopefully partly relevant.
An Axis of the same spec. and a TD160 (both std.) have passed my way and I'd say the same between this pair too.

 

[goldwax]

Not quite the same pairing, but hopefully partly relevant.
An Axis of the same spec. and a TD160 (both std.) have passed my way and I'd say the same between this pair too.

Wow, Thorens coming in on top of a Linn? Thorens are a fraction of the price of Linns, no?

 

[DaveyW]

Wow, Thorens coming in on top of a Linn? Thorens are a fraction of the price of Linns, no?

Hi G'wax,

The Axis was a paired down Linn (no formal suspension as such and early ones with the Basik arm) but with the advantage of electronically controlled 33 & 45 RPM speed control.

I moved from an Axis after trialling a LP12 Sondek and the all round improvement was very noticable.
I subsequently acquired the TD-160 and personally don't believe there is as quite as big a gap when compared to the LP12.
Saying this the Axis is a very capable deck and superior to a couple of Aristons I had prior to this.

I believe that the floating 3 point suspension has a part to play in this and the TP-16 arm isn't too shabby a performer either.

 

[sreten]

Sure, I've repaired 2 of them. I did some searching on the internet and I found the schematic and an explanation of how it works. I analyzed the schematic and confirmed, it drives for a period of time while a cap is charging. Once the voltage on the cap reaches a set threshold, it then stops the drive for a bit, then starts the drive again and senses the current draw ( more current draw means the platter has slowed down) and applies a correction voltage to the drive to compensate, then they cycle starts again.
Here is the page I found offering a partial explanation:
http://www.diyaudio.com/forums/analogue-source/103911-repairing-linn-axis-motor-drive-amplifier.html
I am sure they did it to prove that their precision platter bearing had so little friction it could coast, no other reason.

Hi,

That makes no sense. A synchronous motor doesn't really care about
drive voltage too much and and draws current related to the drag
phase angle, applying a correction voltage is pure nonsense,
as is interrupting the required constant AC drive signal.

There may be a circuit that after it has started reduces drive voltage,
fair enough, but your contradicting the fundamentals of synchronous
AC motor drive operation and making no sense whatsoever.

Your making statements that indicate you don't know how it works,
and adding total conjectures based on your misunderstanding.

rgds, sreten.

 

[goldwax]

Hi G'wax,

The Axis was a paired down Linn (no formal suspension as such and early ones with the Basik arm) but with the advantage of electronically controlled 33 & 45 RPM speed control.

I moved from an Axis after trialling a LP12 Sondek and the all round improvement was very noticable.
I subsequently acquired the TD-160 and personally don't believe there is as quite as big a gap when compared to the LP12.
Saying this the Axis is a very capable deck and superior to a couple of Aristons I had prior to this.

I believe that the floating 3 point suspension has a part to play in this and the TP-16 arm isn't too shabby a performer either.

Ah, I see. Thanks for the detailed breakdown. I wasn't familiar with the difference between the LP12 and the Axis. My profile doesn't show it, but I've got TD 160 that I took out of action a few months ago due to its needing some work.

 

[jleon92f]

I bought my Thorens TD-166 MKii new in 1982. With basic up keep, belt and lube , it has served me well. I will never sell it.

Good Luck,

John.

 

[dr*audio]

Hi,

That makes no sense. A synchronous motor doesn't really care about
drive voltage too much and and draws current related to the drag
phase angle, applying a correction voltage is pure nonsense,
as is interrupting the required constant AC drive signal.

There may be a circuit that after it has started reduces drive voltage,
fair enough, but your contradicting the fundamentals of synchronous
AC motor drive operation and making no sense whatsoever.

Your making statements that indicate you don't know how it works,
and adding total conjectures based on your misunderstanding.

rgds, sreten.

Look,
That's the best I was able to figure out the schematic. It is not a simple circuit. Have a look at it and tell us your analysis of it.
I'll share it here for everyone.
https://docs.google.com/open?id=0ByEbTRs85t22a3hKOFlCUzZhOFE

 

[dr*audio]

Looking at the schematic you can see that the motor current creates a voltage across R14 and is applied through switch U7 to U5.

 

[jrtrent]

There may be a circuit that after it has started reduces drive voltage

I believe you're right. I've been packing for an impending move and don't want to try to dig it out, but I have an issue of the Linn Magazine that goes into some detail on the Axis design. If I recall correctly, the later LP12 power supplies borrowed from the work done on the Axis, and the Lingo has a circuit that "feeds the motor with a higher voltage for increased start-up torque. When the platter reaches the selected speed, this load-sensing circuitry reduces the output to where the motor just maintains the platter's own momentum to keep it going silently."

I bought a TD146 around 1983 (same as TD166 except mine had auto-lift and shutoff at the end of a record). It was a good turntable--my older brother still uses it today--but in terms of sound quality it was about on a par with the BIC 960 and Garrard GT55 models I had had previously. At least when new, the Axis was a much better player (however, I never owned one, having replaced my TD146 with an LP12). When looking at 'tables well over 20 years old, I would think that the amount of use/wear and possible abuse/neglect will have a greater impact on sound quality than any differences in original design and materials.

 

[sreten]

Looking at the schematic you can see that the motor current creates
a voltage across R14 and is applied through switch U7 to U5.

Valhalla
Description: The Valhalla is a synthesized AC source, the board rectifies
the AC line, then uses a cheep and cheerful crystal oscillator and other
circuitry that is used to create a single sine wave at 50Hz, then a simple
phase shift cap is used to provide the shift for the second winding.
Date of introduction: 1984

Axis
Description: The power supply from Linn's Axis turntable.
"Basically a Valhalla with a 45 rpm option and can be fitted to a LP12"

Hi,

A reasonable assumption is the start up torque is higher than the running
torque. There is no reason to interrupt the AC drive to the motor, the
motor does not coast at any point. Drive voltage does not affect the
speed (that is frequency based), it only affects maximum torque.

A synchronous motor, fed with the right AC, locks to the AC frequency.
What makes them so good is as motor load varies, the motor draws
more current from the supply to maintain the correct speed.

The variable that determines the current is the phase angle between
the windings rotating field and the position of the rotor. The phase
lag increases with increasing load until you hit the "slip angle".
Above this point the motor slips and can't maintain synchronicity.

Starting is obviously a region that is not synchronous.

rgds, sreten.

 

[dr*audio]

Hi,

A reasonable assumption is the start up torque is higher than the running
torque. There is no reason to interrupt the AC drive to the motor, the
motor does not coast at any point. Drive voltage does not affect the
speed (that is frequency based), it only affects maximum torque.

A synchronous motor, fed with the right AC, locks to the AC frequency.
What makes them so good is as motor load varies, the motor draws
more current from the supply to maintain the correct speed.

The variable that determines the current is the phase angle between
the windings rotating field and the position of the rotor. The phase
lag increases with increasing load until you hit the "slip angle".
Above this point the motor slips and can't maintain synchronicity.

Starting is obviously a region that is not synchronous.

rgds, sreten.

All this makes sense, but the circuit definitely interrupts the drive to the motor, you can see it on the scope. It looks like the output of the circuit that senses the motor current feeds the flip flops on the left side of the schematic, and shut the oscillator down. You took me to task for an incomplete understanding of the circuit. I have yet to see your analysis.
Please understand, I hold you in the highest regard, I have read your posts and I know you are knowledgeable. But if you are going to criticize my circuit analysis, you should take the time to do it yourself, instead of simply saying, "That can't be right." I went through the circuit with a scope and verified that it is shutting the oscillator down. Perhaps my understanding of it is flawed, but it is definitely turning off the drive. So have a look at the schematic and take a shot at it, if you will.

 

[Pio1980]

From Wiki;
"hysteresis synchronous motors typically are (essentially) two-phase motors with a phase-shifting capacitor for one phase. They start like induction motors, but when slip rate decreases sufficiently, the rotor (a smooth cylinder) becomes temporarily magnetized. Its distributed poles make it act like a permanent-magnet-rotor synchronous motor. The rotor material, like that of a common nail, will stay magnetized, but can also be demagnetized with little difficulty. Once running, the rotor poles stay in place; they do not drift."

 

[sreten]

All this makes sense, but the circuit definitely interrupts the drive to the motor, you can see it on the scope. It looks like the output of the circuit that senses the motor current feeds the flip flops on the left side of the schematic, and shut the oscillator down. You took me to task for an incomplete understanding of the circuit. I have yet to see your analysis.
Please understand, I hold you in the highest regard, I have read your posts and I know you are knowledgeable. But if you are going to criticize my circuit analysis, you should take the time to do it yourself, instead of simply saying, "That can't be right." I went through the circuit with a scope and verified that it is shutting the oscillator down. Perhaps my understanding of it is flawed, but it is definitely turning off the drive. So have a look at the schematic and take a shot at it, if you will.

Hi,

I don't have the supply to play with or a scope to look at whats going on.
If your correct its very odd, that is the gist of what I was saying, but I
can't really argue with a man and his scope and his interpretation.

FWIW I had a look at the schematic and its not easy to understand.

I'm sorry if "that can't be right" seems unfair compared to your
experience and apologise for coming across as self-opiniated.

rgds, sreten.