I think that Steerpike's effort has superseded mine, so it is more likely to be a 2-way shoot-out. It is possible that in the future I might use some of the lessons learnt from Steerpike's circuit to implement more functionality as per my original intention. For now, I'm a bit overextended and just grateful that Steerpike is running along with it.
I can see no reason why it won't; though the application notes show all motor drive circuits as non-inverting.
Most op-amps work somewhat better as inverting amps, though since it's being used as an amp with a gain of only around 1-2x, with a bandwidth of 10Hz, I never thought there was much in the way of 'performance' being asked of it.
I thought I might omit all/any preceedig buffer stages at some time in the future (to reduce complexity & component count) and then it would be nice to have the very high input impedance of the (+) input.
My original plan was a very boring push-pull stage made with TIP31/32 discretes, but the L165 just takes up less space, and makes for easier PCB design - laziness prevailed here!
I also rather liked an excuse to buy a handful of L165's - they make rather Ok audio amps too I have read - something to play with on a rainy day.
There are a few dedicated audio chips like the TDA2040 that would be drop-in substitutes for the L165. Some people may want to experiment with those.
Mark: is there a write-up or design theory of your progress so far, anywhere on the www?
Steerpike
Details of what I'm doing are not available for publication yet, I have to lodge some patent papers first. I'm still working through some of the implementations so I know what to include.
Re the inverting stage, because the op amp is seeing a very inductive load and you are pulling it down near to unity gain you are actually asking a hell of a lot. I've found that the inverting configuration gives better distortion performance, but that was when I was trying to find out how distortion affected motor performance so I was looking for THDs of -90 dB or so.
BTW I might have asked this before, is your 'nik a reference to Gormenghast?
Shaun
The three way shoot out was you guys, my effort and the original. I thought you were both in on this, sorry if that was a rash conclusion.
Details of what I'm doing are not available for publication yet, I have to lodge some patent papers first. I'm still working through some of the implementations so I know what to include.
Re the inverting stage, because the op amp is seeing a very inductive load and you are pulling it down near to unity gain you are actually asking a hell of a lot. I've found that the inverting configuration gives better distortion performance, but that was when I was trying to find out how distortion affected motor performance so I was looking for THDs of -90 dB or so.
BTW I might have asked this before, is your 'nik a reference to Gormenghast?
Shaun
The three way shoot out was you guys, my effort and the original. I thought you were both in on this, sorry if that was a rash conclusion.
I have no way of measuring something that small! I don't contest it though.
That may be barely audible if it were in the actual signal path, let alone just powering the motor.
Can we 'guess' that your SP10 drive is closely related to the electronically commutated motor article on your web page? Phase shift oscillators, etc.
Steerpike is indeed lifted from Gormenghast... and I want my throne!
Steerpike.
Good guess but no cigar.
I've gone away from the phase shift oscillators, too hard to get good precision and adjustability out of them at the same time (the tempco of the resistances changes with potentiometer setting).
I've gone over to the digital dark side, using OCXOs to get frequencies so precise that I have to use the ratio function in my eight digit counter to be able to see the errors (using a GPS disciplined VCXO as reference).
The distortion measurement were done by running the signal through the notch filter in my AWA distortion analyser then to the input of an HP spectrum analyser. I can reliably achieve a floor of -120dB so even -90 dB shows up pretty clearly.
I found that ultra low distortion was not the answer I thought it might be. The influence of wave shape on motor performance turns out to be very interesting indeed.
Good guess but no cigar.
I've gone away from the phase shift oscillators, too hard to get good precision and adjustability out of them at the same time (the tempco of the resistances changes with potentiometer setting).
I've gone over to the digital dark side, using OCXOs to get frequencies so precise that I have to use the ratio function in my eight digit counter to be able to see the errors (using a GPS disciplined VCXO as reference).
The distortion measurement were done by running the signal through the notch filter in my AWA distortion analyser then to the input of an HP spectrum analyser. I can reliably achieve a floor of -120dB so even -90 dB shows up pretty clearly.
I found that ultra low distortion was not the answer I thought it might be. The influence of wave shape on motor performance turns out to be very interesting indeed.
There's a name you don't often see in this country. I bought a pair of AWA valve compressor/limiters pulled out a radio station (prob. early 60s). I had high hopes of putting them into use for home-live recordings, alas another of the numerous half-fixed up audio boxes on my shelves!
The build quality is better than anything I have ever seen in any other brand.
Their chief engineer was Fritz Langford Smith. I'm pretty sure both Thiele and Small worked there at some time as well.
A mate of mine just wrote his PhD on the role of Fisk Radiola / AWV / AWA in the communications industry in Australia, he's in the process of turning it into a book.
I have nearly finished the PSU and power stage circuit board layout (5.5"x5" excl. heatsink); the power op-amp stages are now selectable - inverting or non-inverting, selected by wire links, so the world is your oyster!
The "controller" will be a second board as mentioned before;
with my current plan, I'm hoping to make it possible to implement a digitally synthesized 3-phase drive just by changing the firmware (ROM code) and a few wire links.
So (hoping!) with the same circuit board: option-1 would be analogue waveforms derived from the motor's own generator coils, option-2 would be look-up-table sine waveforms.
The "controller" will be a second board as mentioned before;
with my current plan, I'm hoping to make it possible to implement a digitally synthesized 3-phase drive just by changing the firmware (ROM code) and a few wire links.
So (hoping!) with the same circuit board: option-1 would be analogue waveforms derived from the motor's own generator coils, option-2 would be look-up-table sine waveforms.
A Japanese friend told me that Kaneda san just published a new controller for the Technics SL1100 turntable in the September issue of MJ magazine...
Sorry I have never read the magazine nor have I ever seen the cover, but guess that's perhaps one of the best alternatives for your SP10 motors.
Sorry I have never read the magazine nor have I ever seen the cover, but guess that's perhaps one of the best alternatives for your SP10 motors.
I'm very curious as to your progress with the PSU and controller board? This project is so very interesting to me, I'm looking foreward to reading your next update.
Have a great weekend,
Rick
Have a great weekend,
Rick
Steerpike said:
Ahh.. i've been slightly diverted with a Marantz 6170 that I converted to 16 & 78 rpm since I had no other reasonably good TT to play those speeds.
The SP10 pcb artwork I am just slightly slow at turning into actual PC boards, but that will not be delayed for much longer.
I can prove it here! sp10psu.gif
I'll publish the actual track image once I've tested it.
Oh, and a requirement for me is SINGLE SIDE boards only! Double-sided is too difficult for most DIYers, and I'm trying to not create something that requires specialist equipmemt, or an expensive purchase.
I know there are some that will bleat at my putting the power supply and motor drive stages on the same board. My philosophy is that this thing is rather like an audio amplifier, so the output stages ough to be closely integrated with the power supply, and the interlinking wiring kept short.
The SP10 pcb artwork I am just slightly slow at turning into actual PC boards, but that will not be delayed for much longer.
I can prove it here! sp10psu.gif
I'll publish the actual track image once I've tested it.
Oh, and a requirement for me is SINGLE SIDE boards only! Double-sided is too difficult for most DIYers, and I'm trying to not create something that requires specialist equipmemt, or an expensive purchase.
I know there are some that will bleat at my putting the power supply and motor drive stages on the same board. My philosophy is that this thing is rather like an audio amplifier, so the output stages ough to be closely integrated with the power supply, and the interlinking wiring kept short.
Ah, that would be the Mk 2A you are referring to?
I just downloaded it to scrutinize.... seems like they have put all the functions in 3 ICs: AN640, AN660, DN860
I suppose these are now quite rare as spare parts?
For anyone trying to get their mind around how the control system works, this MK2A with ICs is much easier to follow.
I just downloaded it to scrutinize.... seems like they have put all the functions in 3 ICs: AN640, AN660, DN860
I suppose these are now quite rare as spare parts?
For anyone trying to get their mind around how the control system works, this MK2A with ICs is much easier to follow.
Read in numberous places to avoid the MIIA model...
I remember reading some negatives a few years ago about the MkIIA's controller/power supply... I can't remember the specifics, but I read multiple, independent postings and they said to avoid the MKIIA model
Maybe by a look at both the power supply and the controller of the MKIIA, whatever design/performance flaws can be avoided in the design of the new controller/power supply?
I believe one problem was something with the strobe light effecting the controller..either on.. or if it burned out and was no longer in the circuit..
Just something to think about...
Rick
I remember reading some negatives a few years ago about the MkIIA's controller/power supply... I can't remember the specifics, but I read multiple, independent postings and they said to avoid the MKIIA model
Maybe by a look at both the power supply and the controller of the MKIIA, whatever design/performance flaws can be avoided in the design of the new controller/power supply?
I believe one problem was something with the strobe light effecting the controller..either on.. or if it burned out and was no longer in the circuit..
Just something to think about...
Rick
Steerpike said:
What are the chances of this ps/controller being able to run a mk111? I've got an orphan motor unit in a box somewhere.
Colin
Colin
I don't have any Mk 3 circuits, - just collecting one in the backgroud now. After scrutinizing it, I can tell you the answer &/or what mods would be required.
innernerd said:
Chances are pretty slim, the feedback loop of a DD drive must be tuned to the inertia of the platter and the Mk111 platter was much heavier.
If you want to sell the mk111 motor I'm buying. Name your price.
Since I have no original SP10 platter, my design is not restricted to its unique characteristics.
However, since I have no Mk3 parts either, you'd have to measure the motor properties - I doubt they are published on the www anywhere.
One of the neat things about using a microprocessor controller is that (if one has the inclination to write the software appropriately) *it* can measure the mechanical propertiess of the motor/platter during operation, and 'design' or optimise the feedback system parameters itself on the fly. (Rather like tape decks that will auto-align themselves to any tape)
The downloads section is not giving me the MK3 file I want - will keep trying though.