Oh yes I see it now. 322.4 divided by 2 = 161.2 divided by 1.414 =114.0 . Can I ask you what amplifier you are using? Like I said before the waveform looks very good. Cheers, Rob.
The waveform, are clear from the source - SG4 ( Thanks for , Pyramid )
The amplifier is : TDA7498 Dual-Channel Class D Audio :
TDA7498 Dual-Channel Class D Audio Stereo Amplifier Board Component Power 2X100W | eBay
The transformers: 115+115 : 12+12 V , 30VA two pcs :
Low Profile Transformers for Printed Boards
Power transformer: 115+115 : 26 V , 60VA.
( have no link about )
Reagrds.
I have just received my order of SG4 and THP encoder boards.
I have sent out all the orders for just SG4 chips to date.
Please note I only have a limited supply of boards, because of this I will only supply boards singly, if you require more than 1 the you should order directly from Oshpark (see first post).
For those who have been waiting patiently, please PM me again with your requirements and I will do my best to get them out to you asap.
I have sent out all the orders for just SG4 chips to date.
Please note I only have a limited supply of boards, because of this I will only supply boards singly, if you require more than 1 the you should order directly from Oshpark (see first post).
For those who have been waiting patiently, please PM me again with your requirements and I will do my best to get them out to you asap.
Origin Live DC motors
Hi,
Maybe is not the correct forum to ask this and I am not pretending to derail the thread. Please moderators, if you or the thread starter consider that way, please delete this post.
I am trying to know how the SG4 plus an AC motor compares to the Origin Live DC range of motors....or am I comparing pears to apples?
Does anyone have experience with those kits?
Regards and thanks in advance.
Jorge
Hi,
Maybe is not the correct forum to ask this and I am not pretending to derail the thread. Please moderators, if you or the thread starter consider that way, please delete this post.
I am trying to know how the SG4 plus an AC motor compares to the Origin Live DC range of motors....or am I comparing pears to apples?
Does anyone have experience with those kits?
Regards and thanks in advance.
Jorge
Mark Kelly did a very good expose on DC (and AC) motors at his website: [url]http://web.archive.org/web/20080803214151/http://www.members.iinet.net.au:80/~quiddity/audio/DCbrushed.html[/URL]
The early Origin Live DC controllers had an option for current compensation, but it was fairly simplistic (compared to the Mark Kelly controller for instance), and it lacked temperature compensation. I believe the OL motors were made by Maxon and were fairly decent, but expensive.
It is easier to control speed in AC synch motors as it is related to frequency of the drive only. The downside is vibration related to the construction of the motors (Hurst), the windings and AC hum from the drive frequency. They are fairly limited on the range of speeds they are capable of, losing torque at high speeds and cogging excessively at low speeds.
DC motors are also prone to noise both electrical (brush) and mechanical (cogging), but in general are quieter than AC synch motors. They have a higher range of speed than AC synch motors.
From all of the measurements and testing I've done, the right combination of BLDC motor and 3 phase sinewave controller provides the optimum solution: Ease of speed control, determined solely by frequency (although drive level is important), and very smooth operation (little of no cogging) with better bearings (precision ball bearings vs friction bearings that cannot support high loads and wear over time) and 100:1 speed range.
The early Origin Live DC controllers had an option for current compensation, but it was fairly simplistic (compared to the Mark Kelly controller for instance), and it lacked temperature compensation. I believe the OL motors were made by Maxon and were fairly decent, but expensive.
It is easier to control speed in AC synch motors as it is related to frequency of the drive only. The downside is vibration related to the construction of the motors (Hurst), the windings and AC hum from the drive frequency. They are fairly limited on the range of speeds they are capable of, losing torque at high speeds and cogging excessively at low speeds.
DC motors are also prone to noise both electrical (brush) and mechanical (cogging), but in general are quieter than AC synch motors. They have a higher range of speed than AC synch motors.
From all of the measurements and testing I've done, the right combination of BLDC motor and 3 phase sinewave controller provides the optimum solution: Ease of speed control, determined solely by frequency (although drive level is important), and very smooth operation (little of no cogging) with better bearings (precision ball bearings vs friction bearings that cannot support high loads and wear over time) and 100:1 speed range.
Sorry Bill, I started this before I saw your reply, and I've put too much in to just delete it 
The DC motors I have come across all need a feedback loop of some sort in order to maintain a consistant speed, whether this is an optical sensor on the motor, a hall effect sensor monitoring the speed of the platter, or a method of using the back emf of the motor. In addition brushed DC motors can also be prone to a small amount of cogging, but this is generally insignificant with the better motors having more poles. This type of motor is often driven at very low speed and low power compared with its rated value, this also keeps any noise at a low level.
There are 3 different types of 'AC' motors used with the SG4, the simplest being a sqirrel cage induction motor as used in the Thorens td124 (E50), the Garrard 301 and 401, and the Lenco GL75. In all these cases only one phase of the SG4 is used, in order to generate a higher quality sine wave than can be obtained from the mains. It is possible to use the variable frequency of the SG4 to obviate the need for the eddy current speed control for the 301/401 or td124, but as the motor is not synchronous there may be some drift as the motor warms up
The SG4 can be used to generate 2 phases 90 degrees apart, which would allow it to be used with many belt drive turntables that use the Premotec, Hurst, or other similar 2 phase motors. The ability to adjust the output phase and voltage allows these motors to be optimised in a way thar cannot be done with the simple capacitor phase shift usually employed. In addition these motors will normally allow the SG4 to generate 2 different frequencies that will remove the need to swap the belt to another pulley.
Unfortunately these motors rarely allow the vibration to be reduced to a near zero levels, but the motors are such low power devices that any remaining vibration is at a low level
Another type of motor that is used is a Brushless DC motor, usually referred to as a BLDC. These are similar to stepper motors, but are designed for electronic commutation with a sine wave signal, thereby making them a type of 3 phase synchronous motors. They are quite efficient, and with good bearings, can provide good torque characteristics
They also have the advantage that they are generally low voltage motors and do not need high voltage amplifiers or transformers to operate.
The last type of motor I am aware of that is used in turntables, at least in belt drive ones, is the Papst external rotor 3 phase Hysteresis Synchronous motor. This motor is the least efficient of the AC motors, and needs 115 or 230V to operate. It does have 2 significant advantages over any other of the AC motors that I am aware of:-
1. There are no permanent magnets in the motor, so there is zero cogging, in addition, being a 3 phase motor there is an absolutely constant torque, a feature that is not possible with any of the other motors (AFAIK). This, inconjunction with high quality sleeve bearings produces the lowest amount of noise/vibration.
2. Being an external rotor design the motor has a high polar moment of inertia, which means that the belt is the limiting factor in achieving ideal drive characteristics.
The only downside of the Papst motor is the fact that it is only available secondhand, having not been made for many years.
The DC motors I have come across all need a feedback loop of some sort in order to maintain a consistant speed, whether this is an optical sensor on the motor, a hall effect sensor monitoring the speed of the platter, or a method of using the back emf of the motor. In addition brushed DC motors can also be prone to a small amount of cogging, but this is generally insignificant with the better motors having more poles. This type of motor is often driven at very low speed and low power compared with its rated value, this also keeps any noise at a low level.
There are 3 different types of 'AC' motors used with the SG4, the simplest being a sqirrel cage induction motor as used in the Thorens td124 (E50), the Garrard 301 and 401, and the Lenco GL75. In all these cases only one phase of the SG4 is used, in order to generate a higher quality sine wave than can be obtained from the mains. It is possible to use the variable frequency of the SG4 to obviate the need for the eddy current speed control for the 301/401 or td124, but as the motor is not synchronous there may be some drift as the motor warms up
The SG4 can be used to generate 2 phases 90 degrees apart, which would allow it to be used with many belt drive turntables that use the Premotec, Hurst, or other similar 2 phase motors. The ability to adjust the output phase and voltage allows these motors to be optimised in a way thar cannot be done with the simple capacitor phase shift usually employed. In addition these motors will normally allow the SG4 to generate 2 different frequencies that will remove the need to swap the belt to another pulley.
Unfortunately these motors rarely allow the vibration to be reduced to a near zero levels, but the motors are such low power devices that any remaining vibration is at a low level
Another type of motor that is used is a Brushless DC motor, usually referred to as a BLDC. These are similar to stepper motors, but are designed for electronic commutation with a sine wave signal, thereby making them a type of 3 phase synchronous motors. They are quite efficient, and with good bearings, can provide good torque characteristics
They also have the advantage that they are generally low voltage motors and do not need high voltage amplifiers or transformers to operate.
The last type of motor I am aware of that is used in turntables, at least in belt drive ones, is the Papst external rotor 3 phase Hysteresis Synchronous motor. This motor is the least efficient of the AC motors, and needs 115 or 230V to operate. It does have 2 significant advantages over any other of the AC motors that I am aware of:-
1. There are no permanent magnets in the motor, so there is zero cogging, in addition, being a 3 phase motor there is an absolutely constant torque, a feature that is not possible with any of the other motors (AFAIK). This, inconjunction with high quality sleeve bearings produces the lowest amount of noise/vibration.
2. Being an external rotor design the motor has a high polar moment of inertia, which means that the belt is the limiting factor in achieving ideal drive characteristics.
The only downside of the Papst motor is the fact that it is only available secondhand, having not been made for many years.
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I have just received what is likely to be my last purchase of SG4 chips. I also have a few SG4 boards, along with the rotary encoder boards. As I have indicated before, I will supply any sensible number of chips, but the boards only singly as it's cheaper if you buy multiple boards direct from Oshpark (see first post).
If you are thinking of purchasing these items please order soon as I don't anticipate ordering any more for the forseeable future.
If you are thinking of purchasing these items please order soon as I don't anticipate ordering any more for the forseeable future.
Class D versus AB amp
Very interesting motor story btw...
I've build 3 SG-4's without any problems. Many thanks for this design.
Now I'm arrived at adding an amplifier... It looks like that many members use that extreme cheap 50w class-d amp from China. I'm wondering this is the right way to go? Yes price good, efficiency ok but what about all that switched mode distortion and harmonics of such a low cost design used in a very sensitive circuit? I have bad feelings about that. Maybe I'm completely wrong but I prefer to start with a small class-AB amp using a regulated power supply. My motor is a 1.7w Premotec two phase which is used in all "affordable" Nottingham Analogue decks like Space, Ace Space and Hyper Space decks.
Any comment please?
What is a common used BLDC motor example which is currently available?
Cheers,
Johan.
Very interesting motor story btw...
I've build 3 SG-4's without any problems. Many thanks for this design.
Now I'm arrived at adding an amplifier... It looks like that many members use that extreme cheap 50w class-d amp from China. I'm wondering this is the right way to go? Yes price good, efficiency ok but what about all that switched mode distortion and harmonics of such a low cost design used in a very sensitive circuit? I have bad feelings about that. Maybe I'm completely wrong but I prefer to start with a small class-AB amp using a regulated power supply. My motor is a 1.7w Premotec two phase which is used in all "affordable" Nottingham Analogue decks like Space, Ace Space and Hyper Space decks.
Any comment please?
What is a common used BLDC motor example which is currently available?
Cheers,
Johan.
I implemented an affordable TDA8950 Class-D amp which have built in conventional rectifier and capacitor filter PSU for the amplifier. I power it with 18-0-18V toroidal. I prefer this arrangement. My SG4 works well at this time. Its the cheaper smaller power amps that need external DC supply and probably the easiest solution is a SMPS for purpose.
Very recently I had the opportunity to do an A-B comparison with another DIY controller I built up with XR2206 frequency generator and Class AB TDA7293 amplifier. I experienced 2 different animals contributing a different sonic presentation. Its possible while maintaining the SG4 generator in this case and swapping to different amp modules could affect or change sonic quality and satisfaction for better or worse, you be the judge of that. If the opportunity and time allow, I may swap the amp module just for experience sake and some fun with it.
Since I live in a tropical country where room can be quite warm, I hot glued a slim 80mm 12V PC chassis fan (2000rpm silent type) over the amp module and it run so cool, not even warm to touch. During some tests, I stressed the controller with a 40W solder iron, its still good. The fan will stay and be part of it all. I also installed a 25VA 12V transformer to a LM317 regulator to power both fan and SG4. These are from spares I have on hand to use. I know this sounds like more parts count but its my preference.
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Do you have evidence that these little amps produce a lot of noise or distortion? Don't forget that in this application they are not handling audio signals, just a very clean low frequency sine wave. Specs indicate that distortion should be at ppm levels.
And is this really a sensitive application? Your motor is not going to notice high frequencies, and cannot respond to them. These cheap class D amps will provide a sine wave that is much, much cleaner than your mains supplies. These amplifier circuits may be "low cost" but that is because very complex circuits are in an integrated package. Minimal external parts, no soldering or assembly for the amp circuit itself, it's all done at the fab plant! The switch mode PSU rightly costs more than the amplifier, and this is a perfect application for these amps, just driving a couple of transformers.
Speaking for myself I have absolutely no concerns about the amplifier part affecting the rotational velocity of my turntable, and frankly the cheap as chips chipamp is what makes this project appealing!
I've tried a selection of amplifiers to drive my Papst 3 phase motors, but nothing I've tried works noticeably better than the cheap little class D amps I used at the beginning of my experimenting.
I'm not suggesting that better amps don't exist, but like Nezbleu above, I've observed that these little amps do seem to punch well above their weight.
Have a look at post #64 here, which shows the scope signal output from one of the transformers
Optimally driving a (VPI) synchronous turntable motor
I'm not suggesting that better amps don't exist, but like Nezbleu above, I've observed that these little amps do seem to punch well above their weight.
Have a look at post #64 here, which shows the scope signal output from one of the transformers
Optimally driving a (VPI) synchronous turntable motor
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For the moment, I'm quite happy with the Class D amp module that I've implemented including the kind of power supply I'm comfortable installing as described earlier. Its possible at a later date I will want to expand the controller for a 2 phase output. This could mean an extra amp module and transformer. Meanwhile, I noticed something earlier on the SG4 which prompted me to mod it slightly. Maybe its of little consequence but since I've got the parts and simple for me to do, might as well.
I was reading about the quartz crystal loading capacitors and whats required or ideal. I'm sure the specified 10pf load caps work fine and noticing that I had installed a 10ppm/18pf cap load spec quartz crystal, I swapped each to 22pf ceramic. It works fine with no ill consequences. I'm becoming more careful with the parts I chose to use on the SG4. I can't buy from Mouser or Digikey and get my parts from Element 14 or RS Components who are represented here with extreme ease of online purchase to door. I've also swapped the cheap Arduino rotary encoder with a high quality one from those online vendors. This is working very nicely with assurance its of high quality build. I noticed Arduino encoder is a 20 step/indents type, I swapped it for a 24 step. I reckon any model 12, 18, 24steps work just as well. The more steps, more frequency steps per revolution.
I was reading about the quartz crystal loading capacitors and whats required or ideal. I'm sure the specified 10pf load caps work fine and noticing that I had installed a 10ppm/18pf cap load spec quartz crystal, I swapped each to 22pf ceramic. It works fine with no ill consequences. I'm becoming more careful with the parts I chose to use on the SG4. I can't buy from Mouser or Digikey and get my parts from Element 14 or RS Components who are represented here with extreme ease of online purchase to door. I've also swapped the cheap Arduino rotary encoder with a high quality one from those online vendors. This is working very nicely with assurance its of high quality build. I noticed Arduino encoder is a 20 step/indents type, I swapped it for a 24 step. I reckon any model 12, 18, 24steps work just as well. The more steps, more frequency steps per revolution.
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Hi Folks,
I've just found that one of the parts on the SG4 parts list in Mouser UK seems no longer available -
DS1833-10+ Maxim Integrated | Mouser United Kingdom
I'm not very knowledgeable in electronics so I wonder if someone might point me in the direction of a suitable alternative component that is available on mouser - if there is one?
Thanks!
I've just found that one of the parts on the SG4 parts list in Mouser UK seems no longer available -
DS1833-10+ Maxim Integrated | Mouser United Kingdom
I'm not very knowledgeable in electronics so I wonder if someone might point me in the direction of a suitable alternative component that is available on mouser - if there is one?
Thanks!