motor speed controllers
I built one of the early Teres turntable kits using the Maxon motors and found the strobe disk / motor controller difficult to get working. As an interim way of listening to music, I hauled out a nicely regulated lab DC supply and it seemed to work fine with speed reasonably stable. So it seems that the high mass of the Teres platter along with the stronger maxon motor makes a non-feedback DC supply acceptable if not the ultimate.
The long departed (and lamented) dice45 recommended use of a L200 chip as a simple motor controller. The datasheet / app note ( http://www.us.st.com/stonline/books/pdf/docs/1678.pdf ) shows a simple circuit for use as a motor controller. The current from the motor is included in the feedback circuitry which allow better control for varying loads on the motor. Take a look at page 11 and Fig 25.
Alternatively, the following application note for OPA548 motor controller looks pretty interesting and has a good explanation of how one can use the motor current to monitor motor load and maintain good speed regulation without a strobe disk for feedback.
http://focus.ti.com/lit/an/sboa043/sboa043.pdf
I've been meaning to build a motor controller along these lines but haven't gotten around to it.
---Gary
krishu said:
I built one of the early Teres turntable kits using the Maxon motors and found the strobe disk / motor controller difficult to get working. As an interim way of listening to music, I hauled out a nicely regulated lab DC supply and it seemed to work fine with speed reasonably stable. So it seems that the high mass of the Teres platter along with the stronger maxon motor makes a non-feedback DC supply acceptable if not the ultimate.
The long departed (and lamented) dice45 recommended use of a L200 chip as a simple motor controller. The datasheet / app note ( http://www.us.st.com/stonline/books/pdf/docs/1678.pdf ) shows a simple circuit for use as a motor controller. The current from the motor is included in the feedback circuitry which allow better control for varying loads on the motor. Take a look at page 11 and Fig 25.
Alternatively, the following application note for OPA548 motor controller looks pretty interesting and has a good explanation of how one can use the motor current to monitor motor load and maintain good speed regulation without a strobe disk for feedback.
http://focus.ti.com/lit/an/sboa043/sboa043.pdf
I've been meaning to build a motor controller along these lines but haven't gotten around to it.
---Gary
The dc motors are not from linn. And the method above is very close to what Linn do in all their PSs. Amazingly the Valhalla does not show any attempt to stop the digital hash getting back into the mains. No idea bout the Lingo, but everyone seems to think it really screws up the sound of other components on the same spur.
Anyway, my claim was only that Linn's PSs are not really 'controllers'.
Anyway, my claim was only that Linn's PSs are not really 'controllers'.
Hi all,
Well the guys at TL Acoustics in Greece, sell a motor-controller combination, both from Maxon. The motor is from the A-Max range (cannot see part number!!!) and the controller is a dedicated one for that range of motors which in my case works as current sence with great speed stability. They also have an add-on digital encoder for voltage feedback for ultimate stability that i will try very soon. The controller is battery powered and the motor rod is over 12Kg of solid stainless steel.
Cheers
Analogue still sounds ............. better
Well the guys at TL Acoustics in Greece, sell a motor-controller combination, both from Maxon. The motor is from the A-Max range (cannot see part number!!!) and the controller is a dedicated one for that range of motors which in my case works as current sence with great speed stability. They also have an add-on digital encoder for voltage feedback for ultimate stability that i will try very soon. The controller is battery powered and the motor rod is over 12Kg of solid stainless steel.
Cheers
Analogue still sounds ............. better
fdegrove said:Hi,
Brett,
I don't know of any Nottigham Analogue design that needs a hand start and I all know them inside out.
I'm very familiar with Tom who's as helpful as I can possibly imagine.
Could it be the belt needs replacing?
Cheers,
Nottingham does indeed need a hand start to get the platter going. That is their design, the motor is always on and is very low torque, hence the handstart to get it going.
Hi,
What model exactly?
I can only think of the Omega Point model that didn't even have an on/off switch.
It took maybe 15 seconds to get it up to speed (without user interference) and you just left it spinning while changing records.
That's just a midweight design....
This applies to all the 240 VAC models, it could very well be that the 115/110 VAC models have less torque.
The 80 lbs platter Mentor and Mentor Reference start up fast and are up to speed within 10 secs. It will take a firm hand to stop the platter from spinning due to its very high inertia, about 120 tons in fact.
If a TT needs a hand to get up to speed than there's something you can do; either something is wrong with the bearing, its oil or its belt, or you could try applying a small amount of PTFE charged oil.
The latter can make a huge difference on any TT model, from a humble Thorens to a top flight NA design.
Always make sure platter, belt and pulley are squeaky clean; no greasy deposit whatsoever should be present.
BTW, the bearing assembly and concept of the Mentor and its derivatives were designed and developped in the early Eighties already with the help of...yours truly.
A concept that seems to have have stood the test of time...
And in case you really want to splash big cash...yes it does beat the 20.000$ TTs hands down....just dn't take my word for it, always listen for yourself first.
Cheers,
What model exactly?
I can only think of the Omega Point model that didn't even have an on/off switch.
It took maybe 15 seconds to get it up to speed (without user interference) and you just left it spinning while changing records.
That's just a midweight design....
This applies to all the 240 VAC models, it could very well be that the 115/110 VAC models have less torque.
The 80 lbs platter Mentor and Mentor Reference start up fast and are up to speed within 10 secs. It will take a firm hand to stop the platter from spinning due to its very high inertia, about 120 tons in fact.
If a TT needs a hand to get up to speed than there's something you can do; either something is wrong with the bearing, its oil or its belt, or you could try applying a small amount of PTFE charged oil.
The latter can make a huge difference on any TT model, from a humble Thorens to a top flight NA design.
Always make sure platter, belt and pulley are squeaky clean; no greasy deposit whatsoever should be present.
BTW, the bearing assembly and concept of the Mentor and its derivatives were designed and developped in the early Eighties already with the help of...yours truly.
A concept that seems to have have stood the test of time...
And in case you really want to splash big cash...yes it does beat the 20.000$ TTs hands down....just dn't take my word for it, always listen for yourself first.
Cheers,
McLennan's full address is :-
Mclennan Servos
22 Doman Road
York Town Ind. Est.
Camberley
Surrey, GU15 3DF
They supply Rega,Linn,Audionote (Systemdek) and many others.
Now if Anyone has a Swiss Sonceboz with a 50Hz. pulley if possible please let me know.
PS Brett (Mr Grunty) that photo looks like down to Union Mills in the Isle o' Man ?
Mclennan Servos
22 Doman Road
York Town Ind. Est.
Camberley
Surrey, GU15 3DF
They supply Rega,Linn,Audionote (Systemdek) and many others.
Now if Anyone has a Swiss Sonceboz with a 50Hz. pulley if possible please let me know.
PS Brett (Mr Grunty) that photo looks like down to Union Mills in the Isle o' Man ?
Hi,
O.K., that just confirms my reasoning that Tom is exporting the TTs with the same motor to countries using lower mains supply voltage than the U.K.
If you feel that this "handjob" is a major hassle using the NA TTs I'll talk to Tom and see what can be done about it.
Just don't hold your breath yet, the man often needs more than just financial persuasion...
I can already hear his argumentation...yes, Frank, but that would degrade sonics, won't it? Etc,etc...
Thank you,
O.K., that just confirms my reasoning that Tom is exporting the TTs with the same motor to countries using lower mains supply voltage than the U.K.
If you feel that this "handjob" is a major hassle using the NA TTs I'll talk to Tom and see what can be done about it.
Just don't hold your breath yet, the man often needs more than just financial persuasion...
I can already hear his argumentation...yes, Frank, but that would degrade sonics, won't it? Etc,etc...
Thank you,
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