Most of the xtals are rated for 18-22pfd loading; I used 10pfd loading caps because I needed the xtal frequency to be +1966Hz high to be 100% accurate with the numbers used in the DDS algorithm. At 18.432MHz, the frequency at 60HZ will be 0.0064Hz low (59.9936Hz). This is not noticable and most likely unmearsurable.
With a xtal frequency of 18.433966 MHz, the output frequency will be 60.0000 Hz.
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
Thx Ralph and others for comment...
Sure I believe that our little Chinese friends offer the biggest bang for the bucks but I was wondering if I can hear a difference between this cheap class-D against a more dedicated class-AB like a Peter Daniels chip amp for example.
A friend of mine (we call him the man with the golden ears)made his own sine generator drive years ago and did a lot of tweaking with the power supply capacitors. The panasonic FC series and Elna Simic2 gave the best results for his situation. This proves we are talking about a very sensitive circuit like a real audio amp. He also suggested that the output of the step-up transformer should use a double winding like 2x110v with the middlepoint to GND to get a real balanced output with all it's profits so not something floating.
To keep a long story short...I have to try it myself and see what happens.
Except it's not an audio circuit, is it, unless you listen to a lot of 50Hz sine waves?
The motor drive signal is a fixed frequency at a fixed voltage, and the load on the amplifier is light and quite consistent. If the load is complex and has demanding changes in current, then your turntable is broken and probably needs a new motor. Now I don't doubt that your friend heard what he claiimed, but it sounds to me like a severe case of audio nervosa. He swapped parts and, mirabili dictu, heard a change in the sound. This happens all the time, and the results generally track the cost or "reputation" of the part, and is never backed up with measurements. However, this is a hobby and is meant to be fun, so if you want to swap parts or use a 100W Class A tube amp, enjoy!
That's actually an interesting idea worth testing. I can see his point, especially when using two phase drive. OTOH you would then be referring the drive signal to ground, which might have spurious noise currents on it. Again, some rigorous measurements might tell us whether that makes any difference at all, and if so whether it is an improvement or the opposite.
To keep a long story short...I have to try it myself and see what happens.
Yup!
You probably won't be satisfied if you don't try these options, so you might as well scratch that itch now as later.I understand your doubts but this guy is really serious and the process of tuning took a very long time. Maybe over a year. Sometimes capacitors at certain positions did change after weeks and were removed so it was a very longterm proces. I wish we could prove everything by measurements but there are so many parameters and the human ear is a wonderful thing.
Maybe you have followed this thread...
Linn Lingo vs. Dr. Fuß or Square-Wave vs. Sine Wave Oscillator for Motor Control
There is a guy who adds 3th harmonics to his controller...amazing
Don't forget please - through output transformers, can not pass high frequency ""switched mode distortion"" ,
or they will be too low, especially through kind of transformers where primary and secondary have this kind of winding:
Isolation transformer - Wikipedia .
---
Of course too many "things" can be heard , but everyone must decide for himself where and what to change for better listening
.
I never suggested he wasn't.
Ears are great, I have two of them, though they are a bit old and worn. Everything an ear can detect is easily measured, and conversely even rather crude instruments can discriminate differences in level, frequency, and distortion that no ear can. So yes, ears are great, but the the wetware between them is where all the msgic happens.
The job of a sine wave generator is to generate clean sine waves. If I wanted 3rd harmonic I would just plug into the mains. I assume this gentleman has produced evidence, other than sighted listening tests, that show an improvement in the stability of the rotational velocity of his turntable caused by the introduction of harmonic distortion to the drive signal. I'll have to take a look at that thread.
I don't mean to be argumentative and this thread is probably the wrong place for this discussion, so I will drop it. You should do whatever you need to do to satisfy your curiosity, and I will be interested to hear about your results.
Hello guys,
Thanks Nezbleu for highlighting the output center tap to ground matter.
I live in Malaysia where our mains voltage conform to British Electrical standard and regulations which is 220-240VAC/50hz nationwide.
Without doubt, any electrical appliance must conform to local mains supply and the use of a step down for 100-120V equipement without any voltage selector is a last resort to have it working.
As for my SG-4, its fortunate that I've installed a 12V to 115/230 (twin 115 primary winding now as secondary) as the output transformer for the SG-4. All the while its series connected to output socket to produce 230VAC. This means the output is floating and no polarity. In practice so far, there's no ill consequences and the turntable run like normal, My VPI turntable is a Asia Pacific export model with fixed 230V/50hz motor with custom pulley for this region. The mains cable is the usual IEC type but terminated with a 13amp fused plug (most common, a regulatory requirement for most electrical products to be used here). Hubble type plugs are a rarity here unless people self import and install them by themselves for whatever they see fit. Our mains supply conform to British standards, all mains sockets are polarized and designated as Live, Neutral and Ground. 2 pin sockets are also not common or used here unless using an adapter plug.
I paid more attention how I initially terminated the output and thought about it. After reading the most recent responses, I decided to ground the output center tap and done it. With this done, I now believe my output is now polarized to Live, Neutral and ground and the appliance is fused at the plug at the live line. So far my tt works well with no issues. I'm now thinking this is what I should have done all along and permanent. Its perhaps that its apparent that any equipment used here shouldn't be supplied or connected to some floating 230VAC supply.
I've never been to USA nor familiar with USA electrical wiring practice or anything that require 110V/60hz, including Japanese 100VAC gear. I'm reckoning at 100-120VAC, non polarity supply or appliance isn't of any issue in practice and always been like that in USA or Japan. Its apparent to me its different for me over here and no harm done adapting and conforming to the local electrical practice.
Comments welcome.
Lee
Thanks Nezbleu for highlighting the output center tap to ground matter.
I live in Malaysia where our mains voltage conform to British Electrical standard and regulations which is 220-240VAC/50hz nationwide.
Without doubt, any electrical appliance must conform to local mains supply and the use of a step down for 100-120V equipement without any voltage selector is a last resort to have it working.
As for my SG-4, its fortunate that I've installed a 12V to 115/230 (twin 115 primary winding now as secondary) as the output transformer for the SG-4. All the while its series connected to output socket to produce 230VAC. This means the output is floating and no polarity. In practice so far, there's no ill consequences and the turntable run like normal, My VPI turntable is a Asia Pacific export model with fixed 230V/50hz motor with custom pulley for this region. The mains cable is the usual IEC type but terminated with a 13amp fused plug (most common, a regulatory requirement for most electrical products to be used here). Hubble type plugs are a rarity here unless people self import and install them by themselves for whatever they see fit. Our mains supply conform to British standards, all mains sockets are polarized and designated as Live, Neutral and Ground. 2 pin sockets are also not common or used here unless using an adapter plug.
I paid more attention how I initially terminated the output and thought about it. After reading the most recent responses, I decided to ground the output center tap and done it. With this done, I now believe my output is now polarized to Live, Neutral and ground and the appliance is fused at the plug at the live line. So far my tt works well with no issues. I'm now thinking this is what I should have done all along and permanent. Its perhaps that its apparent that any equipment used here shouldn't be supplied or connected to some floating 230VAC supply.
I've never been to USA nor familiar with USA electrical wiring practice or anything that require 110V/60hz, including Japanese 100VAC gear. I'm reckoning at 100-120VAC, non polarity supply or appliance isn't of any issue in practice and always been like that in USA or Japan. Its apparent to me its different for me over here and no harm done adapting and conforming to the local electrical practice.
Comments welcome.
Lee
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Hi, it'll be interesting to know if there's any sonic quality or picture (for better or worse) differences, when swapping between different amplifiers.
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I wanted to add that this is purely for knowledge or experience, no purpose to endorse or highly suggest any particular make or type for best sound. Anyone is free to make own choice.
Hi joho: You have my admiration! Many of us talk the talk, but you are actually going to perform the experiment.
Do you have a test record? I would be interesting to correlate listening tests with measurements.
I've also been interested in the question of whether or not one will notice differences between chips amps and switching amps for the motor drive and linear vs. switching power supplies. The current conversation seems focused on the effect of these changes on the turntable but I think a more likely source of audible differences is the way these devices interact with the power systems of other components.
I haven't done the experiment with the motor drive but I have compared switching to linear power supplies in computer audio playback and found that most of the changes seem to come from noise getting into the AC power grid and degrading the sound of preamps and power amps. When I used aggressive power line filtering between the AC line and the switching power supply, most of these effects went away and then I often preferred the switching power supply.
---Gary
I haven't done the experiment with the motor drive but I have compared switching to linear power supplies in computer audio playback and found that most of the changes seem to come from noise getting into the AC power grid and degrading the sound of preamps and power amps. When I used aggressive power line filtering between the AC line and the switching power supply, most of these effects went away and then I often preferred the switching power supply.
---Gary
Sure. I use the same (actually 6 Amp) or similar filtered IEC power entry module on my phono pre and line stage preamp as well, and those are plugged into a "surge protector / power bar" which also contains some filtering. The turntable is currently plugged directly into the mains outlet, and I intend to use the same outlet for the SG4. That should put 3 stages of filtering between the SG4 and it's SMPS, and other components (except my powered speakers, I should probably add filtered power entry to those as well someday).
Papst motors
I may have the Papst motor you refer to but was told it was probably a two phase by another member...here is the original post... I purchased two green flywheel papst motors from ebay for possible use in a diy turntable project. I know nothing of them and got little info from the seller but the price was right...highest bidder at 16.50 cdn...I am looking to get a power supply/speed control for them...I will try to attach pics for these (original from ebay)...Motor numbers are as follows: KLO 14.50-2-420D followed by a triangle symbol...second line reads as follows: 7cha Nr 7882-064...what type of motor is this AC or DC?..could these possibly be 3 phase?...no indicaton of voltage, frequency etc...any info or help would be appreciated.
Attached Thumbnails http://www.diyaudio.com/forums/atta...urntable-drive-system-motor-thread-papst2-jpg
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.
I may have the Papst motor you refer to but was told it was probably a two phase by another member...here is the original post... I purchased two green flywheel papst motors from ebay for possible use in a diy turntable project. I know nothing of them and got little info from the seller but the price was right...highest bidder at 16.50 cdn...I am looking to get a power supply/speed control for them...I will try to attach pics for these (original from ebay)...Motor numbers are as follows: KLO 14.50-2-420D followed by a triangle symbol...second line reads as follows: 7cha Nr 7882-064...what type of motor is this AC or DC?..could these possibly be 3 phase?...no indicaton of voltage, frequency etc...any info or help would be appreciated.
Attached Thumbnails http://www.diyaudio.com/forums/atta...urntable-drive-system-motor-thread-papst2-jpg