Hi Folks,
Various people have asked about this so here is something I wrote for the maxon AU web site. It is by no means an exhaustive list, although the suggested model families are a good choice there are many variations within those families, primarily nominal voltage, which as explained below can prove critical in the selection process. Also $AUD one off prices are given in the pdf..they are for comparison only. Call maxon for an exact quote as the exchange rate varies. I do not claim to be the foremost expert on this topic, I respect others, such as Mark Kelly for one, have done much work on this.
Maxon Brushed motors for Hi-Fi turntables
Much has been written about this subject and I appreciate that others have gone into considerable detail. The purpose of this document is to put together suggested motor choices available from maxon in one place, and give an idea of the relative pricing. Note these are guide prices only as for example, the exchange rate fluctuates. Also note, we have ‘cherry picked’ some likely motors here, but this list is in no way exclusive. Other motors in these series and other series may be suitable. If you are not sure please call maxon.
Before we start we should outline the basic requirements
1) Sufficient power, ie speed x torque
2) Low noise, electrical and mechanical
3) Minimal torque ripple
4) Reasonable cost
For most people, particularly novices, a brushed motor is a good choice. The control electronics are comparatively simple and as they can be linear, low noise and the cost is lower. The wiring is also simpler, just two wires to the motor. The drive system is inherently smooth and quiet as long as we are aware of some basic points.
Motor Selection
For a retrofit situation we often have little control over the mechanics, the motor speed is much as determined by the original design. In the case of TT’s employing synchronous type motors this may be quite low, much less than 1000 rpm.
This requirement is usually at odds with the brushed motors available, which tend to be high revving when run at their design voltage, typically 4000 to 6000rpm.
Fortunately the solution is at hand. By using a large diameter motor (which provides good torque, and more power than is ever likely to be required) we can under run it from a lower voltage than its nominal design voltage. This will reduce the speed whilst torque remains purely proportional to the supply current. From a datasheet perspective this means selecting motors with a low rpm/volt speed constant, line 13 in the maxon data sheet tables.
Taking the A-max 26 110191 as an example, a nominal 48V motor, this has a speed constant of 127 rpm/V. So we can see that in a typical turntable application (~600rpm) the supply voltage will be only approximately 4-5V. This is perfectly fine as long as the motor has sufficient torque. From the datasheet the motor makes 15mNm torque at max current.
As the turntable belt drive multiplies the torque by 20X approximately this is quite substantial. We could go into more details as regards start up times if we know the moments of inertia, frictions etc etc, but unless we are designing for broadcasting applications this is probably not required here. In most real world situations belt slip will limit the torque in any case.
So we need to look at some large diameter brushed motors, large in this context is ~>25mm diameter, with low volt/rpm..
What else is important? We want the lowest noise, mechanical and electrical. This means minimal brush noise and low torque ripple. So the choice is now towards precious metal brushes (PMBs), for minimal drag, noise and best efficiency, a long life capacitor (CLL) module to prevent brush sparking and as many poles as possible for smooth torque delivery.
Some suggestions, in order of cost, lowest first.
A-max 26 series
A-max 26 7W 13 pole 110191 an old favourite and still a good choice
RE-max 29 series
RE-max 29 9W 13 pole 226779 (bit more power has extended shaft)
RE-max 29 15W 13 pole 226761 (more power for heavier platters, faster start etc)
The RE-max 29 and A-max 26 support both DC tacho (as a special) and encoder options.
RE 25 series
RE 25 10W 11 pole 118748 (with extended shaft, more power smaller size, tacho option)
Can have DC Tacho 118909 factory fitted for closed loop control
The RE 25 comes with the option of a factory fitted DC Tacho 118909, and so if required a true ‘closed loop’ control can be closed around the motor and the speed controller. It is also the most powerful motor for its diameter, which may help in some conversions, although it is also the longest. See table for approximate dimensions.
Speed control.
The LSC 30/2 4Q linear controller 250521 could be used for TTs. It supports I x R mode. This technique provides motor speed control by a form of feed forward. A brushed motor can be modelled as a source of voltage (the back EMF) in series with a resistance (the winding and brush resistance) . The voltage is proportion to the motor speed and opposes the supply voltage. The current is proportional to the motor torque. As motor torque and current increases, and the motor slows, the current increase is measured and used to estimate an increase in motor supply voltage in an attempt to stabilise the speed.
As there is no true feedback control, the accuracy of this arrangement is limited. The advantage is that no feedback device is required, so simple, low cost, and there is no NFB loop to stabilise.
The more accurate option is to use a motor with the Tacho option. Coupled with the LSC30/2 or other DC servo amplifier this would give absolute control of the motor speed. However be warned the combination of a high mass turntable, compliant drive belt system and low motor inertia will make the loop more difficult or impossible to compensate.
Further hints and tips
Check the drawing of the motors carefully in the datasheet to get the exact dimensions; those above are a guide only.
Be careful not to damage the motor when fitting the drive pulley. In particular the shaft of the motor must not be subject to excessive axial loads which might damage the bearings. If press fitting chose a motor with an extended ‘through’ shaft, then the press can be applied carefully directly to the shaft.
Never press on the motor body to press fit a pulley.
Details of all motors are on our web site:
www.maxonmotor.com.au
Various people have asked about this so here is something I wrote for the maxon AU web site. It is by no means an exhaustive list, although the suggested model families are a good choice there are many variations within those families, primarily nominal voltage, which as explained below can prove critical in the selection process. Also $AUD one off prices are given in the pdf..they are for comparison only. Call maxon for an exact quote as the exchange rate varies. I do not claim to be the foremost expert on this topic, I respect others, such as Mark Kelly for one, have done much work on this.
Maxon Brushed motors for Hi-Fi turntables
Much has been written about this subject and I appreciate that others have gone into considerable detail. The purpose of this document is to put together suggested motor choices available from maxon in one place, and give an idea of the relative pricing. Note these are guide prices only as for example, the exchange rate fluctuates. Also note, we have ‘cherry picked’ some likely motors here, but this list is in no way exclusive. Other motors in these series and other series may be suitable. If you are not sure please call maxon.
Before we start we should outline the basic requirements
1) Sufficient power, ie speed x torque
2) Low noise, electrical and mechanical
3) Minimal torque ripple
4) Reasonable cost
For most people, particularly novices, a brushed motor is a good choice. The control electronics are comparatively simple and as they can be linear, low noise and the cost is lower. The wiring is also simpler, just two wires to the motor. The drive system is inherently smooth and quiet as long as we are aware of some basic points.
Motor Selection
For a retrofit situation we often have little control over the mechanics, the motor speed is much as determined by the original design. In the case of TT’s employing synchronous type motors this may be quite low, much less than 1000 rpm.
This requirement is usually at odds with the brushed motors available, which tend to be high revving when run at their design voltage, typically 4000 to 6000rpm.
Fortunately the solution is at hand. By using a large diameter motor (which provides good torque, and more power than is ever likely to be required) we can under run it from a lower voltage than its nominal design voltage. This will reduce the speed whilst torque remains purely proportional to the supply current. From a datasheet perspective this means selecting motors with a low rpm/volt speed constant, line 13 in the maxon data sheet tables.
Taking the A-max 26 110191 as an example, a nominal 48V motor, this has a speed constant of 127 rpm/V. So we can see that in a typical turntable application (~600rpm) the supply voltage will be only approximately 4-5V. This is perfectly fine as long as the motor has sufficient torque. From the datasheet the motor makes 15mNm torque at max current.
As the turntable belt drive multiplies the torque by 20X approximately this is quite substantial. We could go into more details as regards start up times if we know the moments of inertia, frictions etc etc, but unless we are designing for broadcasting applications this is probably not required here. In most real world situations belt slip will limit the torque in any case.
So we need to look at some large diameter brushed motors, large in this context is ~>25mm diameter, with low volt/rpm..
What else is important? We want the lowest noise, mechanical and electrical. This means minimal brush noise and low torque ripple. So the choice is now towards precious metal brushes (PMBs), for minimal drag, noise and best efficiency, a long life capacitor (CLL) module to prevent brush sparking and as many poles as possible for smooth torque delivery.
Some suggestions, in order of cost, lowest first.
A-max 26 series
A-max 26 7W 13 pole 110191 an old favourite and still a good choice
RE-max 29 series
RE-max 29 9W 13 pole 226779 (bit more power has extended shaft)
RE-max 29 15W 13 pole 226761 (more power for heavier platters, faster start etc)
The RE-max 29 and A-max 26 support both DC tacho (as a special) and encoder options.
RE 25 series
RE 25 10W 11 pole 118748 (with extended shaft, more power smaller size, tacho option)
Can have DC Tacho 118909 factory fitted for closed loop control
The RE 25 comes with the option of a factory fitted DC Tacho 118909, and so if required a true ‘closed loop’ control can be closed around the motor and the speed controller. It is also the most powerful motor for its diameter, which may help in some conversions, although it is also the longest. See table for approximate dimensions.
Speed control.
The LSC 30/2 4Q linear controller 250521 could be used for TTs. It supports I x R mode. This technique provides motor speed control by a form of feed forward. A brushed motor can be modelled as a source of voltage (the back EMF) in series with a resistance (the winding and brush resistance) . The voltage is proportion to the motor speed and opposes the supply voltage. The current is proportional to the motor torque. As motor torque and current increases, and the motor slows, the current increase is measured and used to estimate an increase in motor supply voltage in an attempt to stabilise the speed.
As there is no true feedback control, the accuracy of this arrangement is limited. The advantage is that no feedback device is required, so simple, low cost, and there is no NFB loop to stabilise.
The more accurate option is to use a motor with the Tacho option. Coupled with the LSC30/2 or other DC servo amplifier this would give absolute control of the motor speed. However be warned the combination of a high mass turntable, compliant drive belt system and low motor inertia will make the loop more difficult or impossible to compensate.
Further hints and tips
Check the drawing of the motors carefully in the datasheet to get the exact dimensions; those above are a guide only.
Be careful not to damage the motor when fitting the drive pulley. In particular the shaft of the motor must not be subject to excessive axial loads which might damage the bearings. If press fitting chose a motor with an extended ‘through’ shaft, then the press can be applied carefully directly to the shaft.
Never press on the motor body to press fit a pulley.
Details of all motors are on our web site:
www.maxonmotor.com.au
Hi, thanks 3GGG
Since I wrote this I have received some feedback regarding the 110191 motor in this application.
Because the motor is mounted vertically, has sleeve bearings...and is run at low speed I understand the top bearing can get worn after about 12 months of continuous use.
The sleeve bearing is chosen for low noise (and low cost), but hydrodynamically the lubrication will not be optimal at low rpm and there is no proper bearing to support the motor shaft in the vertical axis. Therefore I would recommend that the top bearing is a ball bearing. This adds around $30AUD to the cost. The bearing will be slightly more noisy, but the life will be much extended. This is a factory option, as is two ball bearings.
Another alternative would be to use a sintered iron sleeve bearing, which has better wear chacteristics but provide an end cap where the motor shaft rests on a single ball (as in a traditional platter bearing). This now becomes a custom, so incurring some engineering cost, time etc. It is really the sort of mod that might be offered to a volume manufacturer, but should provide the lowest noise. A brushed motor will always be more noisy than an EC motor, so it may not be worth the trouble.
Since I wrote this I have received some feedback regarding the 110191 motor in this application.
Because the motor is mounted vertically, has sleeve bearings...and is run at low speed I understand the top bearing can get worn after about 12 months of continuous use.
The sleeve bearing is chosen for low noise (and low cost), but hydrodynamically the lubrication will not be optimal at low rpm and there is no proper bearing to support the motor shaft in the vertical axis. Therefore I would recommend that the top bearing is a ball bearing. This adds around $30AUD to the cost. The bearing will be slightly more noisy, but the life will be much extended. This is a factory option, as is two ball bearings.
Another alternative would be to use a sintered iron sleeve bearing, which has better wear chacteristics but provide an end cap where the motor shaft rests on a single ball (as in a traditional platter bearing). This now becomes a custom, so incurring some engineering cost, time etc. It is really the sort of mod that might be offered to a volume manufacturer, but should provide the lowest noise. A brushed motor will always be more noisy than an EC motor, so it may not be worth the trouble.
Hi 3GGG,
The 226761 has sleeve bearings as standard, so my recommendation would be to go for a ball bearing, at least on the output shaft side. However I personally have no idea how this will effect the mechanical noise level. There will be a different mechanical signature.
Perhaps order a sleeve bearing motor for lowest cost/shorter leadtime prototype use and see how you go. You will get at least 12 months use out of this and probably much much longer.
BTW just so you know maxon do not support sale or return unless the product is obviously faulty and these motors are not able to be retrofitted with a ball bearing as the end caps are different. Thats the official position on bearings anyway!! A keen machinist might not share that view...
The 226761 has sleeve bearings as standard, so my recommendation would be to go for a ball bearing, at least on the output shaft side. However I personally have no idea how this will effect the mechanical noise level. There will be a different mechanical signature.
Perhaps order a sleeve bearing motor for lowest cost/shorter leadtime prototype use and see how you go. You will get at least 12 months use out of this and probably much much longer.
BTW just so you know maxon do not support sale or return unless the product is obviously faulty and these motors are not able to be retrofitted with a ball bearing as the end caps are different. Thats the official position on bearings anyway!! A keen machinist might not share that view...
The bearing noise dominates in an EC brushless DC motor, as it is the only mechanical noise I guess this makes sense. In a brushed motor you obviously have some brush noise, but using the PMBs this should be very low.
So its a bit of a moot point if ball bearings are more noisy than the brushgear.
Unfortunately how the motor is suspended/decoupled will have an effect as will the drive belt and a myriad of other mechanical nasties.
So I would take the low cost option
and go for the sleeve bearings, as discussed.
Cheers!
So its a bit of a moot point if ball bearings are more noisy than the brushgear.
Unfortunately how the motor is suspended/decoupled will have an effect as will the drive belt and a myriad of other mechanical nasties.
So I would take the low cost option
and go for the sleeve bearings, as discussed.Cheers!
Hi Jev,
The LSC30/2 can be configured to output a motor control voltage which is proportional to a DC input. By adjusting the DC input you can change the speed. So a simple resistive divider chain, from the LSC30/2 reference to ground, with a switch to switch an additional resistor in or out across the bottom resistor, is in theory all that it required. This can all be low powered circuitry. In reality you would make the bottom two reistors trim pots so you can set up the speeds exactly.
However, I personally think the LSC30/2 is probably an overkill for TT use, it has a much larger current capability than required, it is also 4 quadrant, for forward reverse speed/braking control. For a TT you can get similar results using an adjustable 3T regulator, or one of the specialist TT controllers, such as those designed by Mark Kelly.
Unfortunatley I speak only from theory, I do have a TT at the moment, but it is not mine to experiement with!
Best regards
Jon Pippard
The LSC30/2 can be configured to output a motor control voltage which is proportional to a DC input. By adjusting the DC input you can change the speed. So a simple resistive divider chain, from the LSC30/2 reference to ground, with a switch to switch an additional resistor in or out across the bottom resistor, is in theory all that it required. This can all be low powered circuitry. In reality you would make the bottom two reistors trim pots so you can set up the speeds exactly.
However, I personally think the LSC30/2 is probably an overkill for TT use, it has a much larger current capability than required, it is also 4 quadrant, for forward reverse speed/braking control. For a TT you can get similar results using an adjustable 3T regulator, or one of the specialist TT controllers, such as those designed by Mark Kelly.
Unfortunatley I speak only from theory, I do have a TT at the moment, but it is not mine to experiement with!
Best regards
Jon Pippard
Hi Jon, thanks for your answers! I am not sure what 4 quadrant means (four controllers?) but anyway I think I will build my own supply. There is a very good thread in the pinkfishmedia dot net DIY section about a simple dc motor controller. I think I will build that one in combination with a 226761 motor. I will not choose the ball bearing option, I wil see how it goes...
Jev, I have a spare board from the PFM motor group buy, it has all the surface mount capacitors on and one or two of the other components. If you'd like it I can stick that and a selection of the spare components I have left over in the post for you.
I just bought an SME10 and sold my previous deck so it's excess to requirements.
Simon
I just bought an SME10 and sold my previous deck so it's excess to requirements.
Simon
Hi Jev,
4Q (quadrant) basically means the controller is able to supply and absorb power from the motor, so typically a traction application (accelerate and brake) would require a 4Q type controller. 1Q control only supplies power.
Most domestic TT apps would be 1Q, although broadcast/DJ type TT might use 4Q for quick start/stop.
Cheers
Maxon LSC 30/2
Hi All
This is a very interesting thread.
I recently posted a WTB in the swap meet section looking for a new or second hand motor for my Oracle TT, which has unfortunately bit the dust.
I too have come to the conclusion that a Maxon motor and the LSC 30/2 controller is a viable option.
The LSC 30/2 controllers are quite expensive, but fortunately they do come up quite regulary on the second hand market quite cheaply.
My question is, has anyone actually tried and tested the LSC 30/2 conroller?
Thanks
Regards
George
VK5ZG
Hi All
This is a very interesting thread.
I recently posted a WTB in the swap meet section looking for a new or second hand motor for my Oracle TT, which has unfortunately bit the dust.
I too have come to the conclusion that a Maxon motor and the LSC 30/2 controller is a viable option.
The LSC 30/2 controllers are quite expensive, but fortunately they do come up quite regulary on the second hand market quite cheaply.
My question is, has anyone actually tried and tested the LSC 30/2 conroller?
Thanks
Regards
George
VK5ZG
LSC controllers
Hi Gee Vee,
I no longer work for maxon but happy to add my 2 pennyworth.
I have not personally tried the LSC in a turntable application, but I suspect it will perform in a similar fashion to most analogue turntable motor controllers, in as much as it will provide adequate control, but may 'drift' with time and temperature.
The LSC is designed for small power industrial servo control and in that market it is quite low end, so first class stability is not something that may have been in the design brief for reasons of cost and complexity.
That said, the maxon electronic components are competently engineered and quality built, so it is certainly not rubbish. A second hand unit from ebay would be a great way to suck it and see. Ideally you need a motor with tacho feedback so you can run closed loop. I suspect RI mode may not be so suitable, although easier to implement.
I would be interested to know how you get on. Keep us posted.
Hi Gee Vee,
I no longer work for maxon but happy to add my 2 pennyworth.
I have not personally tried the LSC in a turntable application, but I suspect it will perform in a similar fashion to most analogue turntable motor controllers, in as much as it will provide adequate control, but may 'drift' with time and temperature.
The LSC is designed for small power industrial servo control and in that market it is quite low end, so first class stability is not something that may have been in the design brief for reasons of cost and complexity.
That said, the maxon electronic components are competently engineered and quality built, so it is certainly not rubbish. A second hand unit from ebay would be a great way to suck it and see. Ideally you need a motor with tacho feedback so you can run closed loop. I suspect RI mode may not be so suitable, although easier to implement.
I would be interested to know how you get on. Keep us posted.
Hi Jon
Thanks for the response.
I agree, for what you can by them for on the second hand market, it is definately worth trying out.
I also agree with your comment that it is a lower end controller that was meant for a particular application (servo control), but to my way of thinking, its still probably overkill when you look at what is provided with most turntables.
OK, the Oracle may have had a better motor and controller than the average unit, but I still reckon that this will be worth trying.
I will post my results once I get the various bits.
Regards
George.
Thanks for the response.
I agree, for what you can by them for on the second hand market, it is definately worth trying out.
I also agree with your comment that it is a lower end controller that was meant for a particular application (servo control), but to my way of thinking, its still probably overkill when you look at what is provided with most turntables.
OK, the Oracle may have had a better motor and controller than the average unit, but I still reckon that this will be worth trying.
I will post my results once I get the various bits.
Regards
George.
ESCON controller
Hi Guys,
UPDATE A new maxon controller the ESCON 36/2 403112 offers a digital versatile solution. I have not tried this unit personally. It is a switching solution so will need some expertise to minimize any RFI, but it meets the relevant legislation.
The controller is capable of closed loop or open loop control with motor parameters software programmable via USB.
The LSC unit is 'not recommended for new design'.
Cheers
Hi Guys,
UPDATE A new maxon controller the ESCON 36/2 403112 offers a digital versatile solution. I have not tried this unit personally. It is a switching solution so will need some expertise to minimize any RFI, but it meets the relevant legislation.
The controller is capable of closed loop or open loop control with motor parameters software programmable via USB.
The LSC unit is 'not recommended for new design'.
Cheers
Hi,
the Maxxon RE-29 226761 was used in the tuntables of at least one german highend manufacturer.
It runs very lownoise, and when fitted into its housing it was very close to noisefree.
Electronic were simple.
Just have a look at BBs AN-0433, "DC-Motor Speed Controller: Control a DC-Motor without Tachometer Feedback, SBOA043"
Speed control is done via monitoring and controlling the current flowing through the Motor (EMF).
It dosen´t compensate for temperature effects though, similar as old servo driven Dual EDS DD-motors that also relies on a servo without tacho feedback.
I was asked to design a fully automatic lead-akku powersupply for it.
This method and motors require heavy platters with loads of inertia.
One could hear small differences -mainly in bass performance- between 40mm, 60mm and 80mm high platters, improving with increasing height/mass.
Though the sonic results were very pleasing, I think that a drive, where one notices such differences in performance even when only rather minor important parameters are changed, must be off of optimal.
It opens up a whole playground for tweaking and tuning, which certainly alot of highenders and non-technicians may like, as even the blindest rooster eventually finds the piece of corn that tunes and turns the duckling into his white swan.
I myself prefer a drive system that´s less dependent on accidental try-and-fail, but behaves stable under all conditions.
So I returned to DDs.
jauu
Calvin
the Maxxon RE-29 226761 was used in the tuntables of at least one german highend manufacturer.
It runs very lownoise, and when fitted into its housing it was very close to noisefree.
Electronic were simple.
Just have a look at BBs AN-0433, "DC-Motor Speed Controller: Control a DC-Motor without Tachometer Feedback, SBOA043"
Speed control is done via monitoring and controlling the current flowing through the Motor (EMF).
It dosen´t compensate for temperature effects though, similar as old servo driven Dual EDS DD-motors that also relies on a servo without tacho feedback.
I was asked to design a fully automatic lead-akku powersupply for it.
This method and motors require heavy platters with loads of inertia.
One could hear small differences -mainly in bass performance- between 40mm, 60mm and 80mm high platters, improving with increasing height/mass.
Though the sonic results were very pleasing, I think that a drive, where one notices such differences in performance even when only rather minor important parameters are changed, must be off of optimal.
It opens up a whole playground for tweaking and tuning, which certainly alot of highenders and non-technicians may like, as even the blindest rooster eventually finds the piece of corn that tunes and turns the duckling into his white swan.
I myself prefer a drive system that´s less dependent on accidental try-and-fail, but behaves stable under all conditions.
So I returned to DDs.
jauu
Calvin