Hi, that is correct.
At the moment this motor seems very stable.
Problem if any, is improvised belt.
Smaller pulley = less surface contact for belt= more slipping =more speed variations on platter.
But let me continue with this play. In next few days new test record will arrive, than I can much more accurately capture 1khz groove and make better concludions
Finally test record is in house, so I can play 1kHz reference tone to see what the speed is really doing.
Not sure if I'm doing this right, but it seems consistent:
1- I measured frequency with Fluke 87 and captured peaks during 1kHz track max = 1003.9 Hz, Min =994.9 HZ. That gives 9 Hz of play, or 0.9%
2. Captured peak dancing around 1000Hz by RTA window , please look at video below. It gave me 8Hz dancing area, or 0.8 %.
At the moment stock plastic pulley from VCR is on motor and belt is too long o-ring. I think this will further improve with precision metal pulley and flat belt.
Question is what would be the goal to achieve ?
Also I have no tool to confirm the precision of the LP, so result is added LP and motor non linearity.
Not sure if I'm doing this right, but it seems consistent:
1- I measured frequency with Fluke 87 and captured peaks during 1kHz track max = 1003.9 Hz, Min =994.9 HZ. That gives 9 Hz of play, or 0.9%
2. Captured peak dancing around 1000Hz by RTA window , please look at video below. It gave me 8Hz dancing area, or 0.8 %.
At the moment stock plastic pulley from VCR is on motor and belt is too long o-ring. I think this will further improve with precision metal pulley and flat belt.
Question is what would be the goal to achieve ?
Also I have no tool to confirm the precision of the LP, so result is added LP and motor non linearity.
Finally came back to motor subject.
One very good thing to report is that Richards's tacho + my sensor make very precise average speed measurements (it measures time passed for 1 rotation of the platter).
I continuously checked signal from test LP on scope and display of Richards Supaspin, the speed always matches exactly. Also very nice is that Supaspin adjusts frequency for 0.01 Hz by one click of rotary encoder, utmost sufficient to fine tune TT speed with ease!
This is very simple diagram of sensor. CNY70 is brought to about 2 mm from platter and on platter I put just a piece of black electrical tape, it works aplomb. Reflection difference between white stone and black tape is good enough, for testing at least.
4k7 resistor should be replaced with 3k3 or similar to bring trigger TAC voltage to about 3.3 volt, but Supaspin doesn't seem to care, it registers change in V as it is.
Next I connected vintage Papst asynchronous outer rotor (picture in post #55 and elsewhere), also this one is now running with flat 5mm belt and much smaller pulley (18mm vs 40mm with previous motor).
Papst is very stable and vibration free when holding by hand. In order to make it completely silent I run it at 40V RMS 3 phase (it is made for 165V) and only 20 and some HZ. It is big enough to manage such huge reduction in power, after all it was made to fast rewind big tapes, that takes much more watt than TT.
However, even this looks like more advanced solution, measuring "dance" when playing 1kHz signal stays almost the same, about +-4%
Here is dancing video:
This makes me believe that this is actually tolerance level of Ortofon test LP, and not turntable. Hierfi in another forum mentioned that 6kg platter could not dance so much in such short time anyway.
Now when considering all, preliminary conclusion is:
While old Papst has slight improvement, still super cheap capstan motor from Philips VCR is better:
As next step I will continue with small VCR capstan motor, cut unnecessary parts off and machine pulley for flat belt.... Then we will see...
Regards to all,
Dražen
One very good thing to report is that Richards's tacho + my sensor make very precise average speed measurements (it measures time passed for 1 rotation of the platter).
I continuously checked signal from test LP on scope and display of Richards Supaspin, the speed always matches exactly. Also very nice is that Supaspin adjusts frequency for 0.01 Hz by one click of rotary encoder, utmost sufficient to fine tune TT speed with ease!
This is very simple diagram of sensor. CNY70 is brought to about 2 mm from platter and on platter I put just a piece of black electrical tape, it works aplomb. Reflection difference between white stone and black tape is good enough, for testing at least.
4k7 resistor should be replaced with 3k3 or similar to bring trigger TAC voltage to about 3.3 volt, but Supaspin doesn't seem to care, it registers change in V as it is.
Next I connected vintage Papst asynchronous outer rotor (picture in post #55 and elsewhere), also this one is now running with flat 5mm belt and much smaller pulley (18mm vs 40mm with previous motor).
Papst is very stable and vibration free when holding by hand. In order to make it completely silent I run it at 40V RMS 3 phase (it is made for 165V) and only 20 and some HZ. It is big enough to manage such huge reduction in power, after all it was made to fast rewind big tapes, that takes much more watt than TT.
However, even this looks like more advanced solution, measuring "dance" when playing 1kHz signal stays almost the same, about +-4%
Here is dancing video:
This makes me believe that this is actually tolerance level of Ortofon test LP, and not turntable. Hierfi in another forum mentioned that 6kg platter could not dance so much in such short time anyway.
Now when considering all, preliminary conclusion is:
While old Papst has slight improvement, still super cheap capstan motor from Philips VCR is better:
- Small improvement could be due to better belt too.
- Papst needs about 40VRMS, small Phillips I run on just 5VRMS which allows for cheap chip power amp for cars to run it. For paps I would, or need to invent high voltage amp, or add 3 transformers.
- With Papst being asynchronous, setting exact 33.33 RPM becomes a continuous hunt. Speed depends not only on frequency, but also supply voltage (which is admit-ably easy to make fixed). It could be solved with servo feedback, but it would open another can of worms (kind of worms that are not good for fishing).
As next step I will continue with small VCR capstan motor, cut unnecessary parts off and machine pulley for flat belt.... Then we will see...
Regards to all,
Dražen
Took rotor of small Philips motor to machinist, by next week it will be equipped with precision pulley for 5mm flat belt 🙂
Hi, just that you all know that I did not forgot and drop this project. It is now 7th week that I'm not getting my pulley and motor base machined.
Every week the guy is telling me "next week". Next week is now his middle name 😉.
Hope next week Ill get lucky, but even if it happens then we go off for holidays.... So new year is the best possible. Next week, or next year, whatever comes later 🙂
Every week the guy is telling me "next week". Next week is now his middle name 😉.
Hope next week Ill get lucky, but even if it happens then we go off for holidays.... So new year is the best possible. Next week, or next year, whatever comes later 🙂
Maybe try LM675T instead of TDA?? Limit is 4 Amp´s 😉
Also works as a charm as Audio Amp.
Hi, thanks.
For the moment I picked STA540 , building a small PCB for it.
Its 4 channel amp for cars = decent current and low voltages... Guess will do???
For the moment I picked STA540 , building a small PCB for it.
Its 4 channel amp for cars = decent current and low voltages... Guess will do???
All this is very impressive DIY! Kudos!!
I wonder if you considered the Lenco idler drive motor? It's powerful, pretty robust, can be made super stable/accurate with electronic drive control.
https://www.lencoheaven.net/forum/index.php?topic=68.0
It might be a challenge to use on a belt drive. But you might also consider Lenco-style idler drive for its superior torque & speed stability under high dynamic load (heavily modulated portion of groove which can cause high drag & dynamic variations in RPM, esp. in belt drives). The motor/idler wheel position...
If you haven't seen this, it's well worth a read -- https://korfaudio.com/blog94
I wonder if you considered the Lenco idler drive motor? It's powerful, pretty robust, can be made super stable/accurate with electronic drive control.
https://www.lencoheaven.net/forum/index.php?topic=68.0
It might be a challenge to use on a belt drive. But you might also consider Lenco-style idler drive for its superior torque & speed stability under high dynamic load (heavily modulated portion of groove which can cause high drag & dynamic variations in RPM, esp. in belt drives). The motor/idler wheel position...
If you haven't seen this, it's well worth a read -- https://korfaudio.com/blog94
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Guess what? I had to look all over for a lever that 'matched'. It is indeed an old radio lever of sorts, and not a Lenco. I just really don't like the 'modern' plastic ones. No thanks. Now the Lenco name plate I don't recall where I got it, but it too was a bit (understandably) pricey.
I also got pretty nervous drilling two large vent holes in the top panel. One slip and everybody knows it.
I also got pretty nervous drilling two large vent holes in the top panel. One slip and everybody knows it.
These high inertia hysteresis synchronous motors come up on ebay all the time. These bigger ones are more powerful and have more inertia. They work awesome with that 3 phase controller from Pyramid. I haven't tried the other one but I bet it's fine too.
That looks the motor that I use on the current iteration of my DIY TT, except mine is an 8 pole version. I use the SG4, along with 3x80VA transformers and 3x200w class D power amps.
Those motors are wonderful except for their inefficiency 😏
Those motors are wonderful except for their inefficiency 😏
First, Merry Xmass to all!
Last year I was repairing one Lenco for a friend, nice turntable.
However it will be rather difficult to machine stone plinth in order to arrive with idler from underneath. Once I tried with idler from the outside rim of the platter, but it was not very stable, probably because of improvised solution and not for principle:
As for Lenco motor as belt drive, it is too fast. Idler is driven directly from the shaft and has much greater transfer ratio. For belt we need some pulley contact, lower speed motors are preferable.
Indeed, I looked at eBay now and there are many, one guy is even selling Revox motors for some 30+ Eur. If you search tape capstan motor instead of hysteresis even more results will come. These are typically capstan motors from R2R tape recorders.
I also think they are excellent, as Ralph things too. Few months ago when I was searching there were only few pieces for over 400 Eur... But I'm glad as if I bought it I would never discover great capstan motors from VCR.
R2R hysteresis motors are normally running high voltage= one needs transformers after amps.
They also normally (@50hz) run on 1500 rpm, one needs lot of luck to find dual speed one that also has 750 rpm. In my opinion drive pulley for belt drive should not be smaller than 15mm, best 20 to 30mm diameter to ensure belt contact surface. With these motors or very small pulley, or very low frequency is required.
I previously run my Papst at 22Hz and 15mm pulley, both at edge of practicality. Instead of analog amps I used frequency inverter and solved chunk of transformers issues as inverter could be programmed for 165V RMS , but at expense of huge switcher in vicinity.
On the other hand, VCR motor is 10 times smaller and about that much more efficient.
Its free of charge, just need to pick old VCR from scrap, there are many in the bin.
With 24 poles 50 HZ speed is 375 rpm, absolutely spot on to use 25mm pulley and around 50Hz.
Required voltage is just 3 - 3.2 VRMS, allowing to use 9V wall-wart PS and car audio amps that are designed for squeezing last mV from PS, allowing for super small and efficient=cool drive. Another very good consequence of wall wart is that it eliminates need to connect TT to safety ground through PS cable, which is not small thing.
Now, I would never go back to those R2R motors.
One correction : In post #51 i wrongly calculated speed of the motor, mistakenly used 2phase supply instead of 3 phase.
Proper calculation is:
RPM = 60 (seconds) X Frequency (1/s) /No of pole pairs
No of pole pairs = No of poles / No of phases
So, 24 pole motor run by 3 phases has 8 pole pairs
@ 50 Hz x 60s (60 s in a minute) / 8 pole pairs = 375 RPM
In the meantime I run also capstan motor from rare Sony HD digital video recorder, No 4. from post #50.
While it is much more robustly built and more powerful than cheap VCR motor, it does suffer from vibrations and noise. It can be heard and felt in the hand. When pressed against work bench it rattles the bench. Not very much but it is obvious and not observed with VCR motor.
Is it because ball bearings it uses, or something else, I don't know, but it is discarded.
While it is much more robustly built and more powerful than cheap VCR motor, it does suffer from vibrations and noise. It can be heard and felt in the hand. When pressed against work bench it rattles the bench. Not very much but it is obvious and not observed with VCR motor.
Is it because ball bearings it uses, or something else, I don't know, but it is discarded.
Finally pulley and motor base arrived just before holidays. Mr "next week" did not become Mr "next year" 🙂 Ill play with this when back home.
For the record, this pulley and base cost me 50 Euro, I think complete motor, Supaspin with Rpi and OLED, amplifier.... altogether did not reach 30 Eur...
What I managed to do, and I was avoiding for long, is to slot my TT chassis to accommodate new parts.
I was so afraid that veneer will spline and I will have to do it all over again, but luckily it survived routing.
On front side I opened window to accommodate SupaSpin display and rotary encoder. The setup push button I will put on the backside near PS input as it is not used daily.
I will make new plastic window to fit slot perfectly, this is just trial. I'm choosing color 🙂
On the back side I opened bigger hole that will accommodate amplifier in drawer fashion, so I can pull it out and modify when needed:
This will carry large 10 X 21 cm PCB that will serve as base for preamp and 3 x XLR jacks, 2 for signal and one for external PS.
For the record, this pulley and base cost me 50 Euro, I think complete motor, Supaspin with Rpi and OLED, amplifier.... altogether did not reach 30 Eur...
What I managed to do, and I was avoiding for long, is to slot my TT chassis to accommodate new parts.
I was so afraid that veneer will spline and I will have to do it all over again, but luckily it survived routing.
On front side I opened window to accommodate SupaSpin display and rotary encoder. The setup push button I will put on the backside near PS input as it is not used daily.
I will make new plastic window to fit slot perfectly, this is just trial. I'm choosing color 🙂
On the back side I opened bigger hole that will accommodate amplifier in drawer fashion, so I can pull it out and modify when needed:
This will carry large 10 X 21 cm PCB that will serve as base for preamp and 3 x XLR jacks, 2 for signal and one for external PS.