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I built Mark's kit and have been running it in for several days with a 7.5W 300RPM motor on a VPI TNT with flywheel and various modifications including thread drive. The AC-1 uses both analog and digital circuits to derive separate phases of an AC sine wave from a 12V battery. This requires removal of the stock AC motor's phasing capacitor.
I will post more after full break-in, but I am initially impressed by an improvement in speed stability that easily surpasses my previous VPI PLC II or an AC outlet conditioned by an isolation transformer. (I have not tried the VPI SDS.) Everything gets better: treble detail and refinement, dimensionality, punchiness, relaxation, top-to-bottom continuousness, shapely & extended LF.
The kit is straight-forward, but requires shop skills to drill a DIY enclosure. To the standard fitment I added an integrated Ibex 1.5A frame charger, a DC panel voltmeter, an array of parallel capacitors to decouple from a 100AH Enersys Odyssey battery, and ebony fascia. This battery has probably twice the reserve necessary for the AC-1.
Follow Ups:
Could someone be so kind to tell me which power amp IC was used to drive output transformers? Mark sent me months ago schematics but there's no parts list. Thanks.
Found it, sorry!
Some years ago I bought this but never got around to assembling it. I have lost the documentation and is left with a lot of stuff that I do not know how to put together. Would any of you people be willing to send me a copy of the build instructions? I have tried Mark, but he is not answering his e-mails.
all the best from Scotland.
Is this some kind of top secret project? I saw a few people asking how and where and how much to obtain this kit, and I see no response from anywhere, even Mark Kelly himself. All I see is "yeah, yeah this is great, here's my version, how's yours? yeah, yeah... huh huh...
Hi there, where can I get the board or kit / parts list to build this raving drive controller???
Help?
Thanks
T
DaveI am glad it's worked out so well and you are happy with the kit.
In turn I must thank you, Bob, Al and Brian who have been invaluable in helping me through the start-up wobbles and in giving me advice on re-drafting the support materials. They are (hopefully) comprehensible now, it seems I'm much better at creating the design than I am at explaining to others how to make it go.
Mark Kelly
Hi, I'm a newby and a little late to this thread, but is the Synchrotron AC-1 available anymore as a built-up unit? Can it handle 24W?
I'm running 3 hurst ACs on a rimdrive setup and before I shell out on overseas kit I thought I would see if something was available locally.
Would the better option be to Power regen like a Purepower and just make sure the pulleys were machined to correct the speed? This would seem more of a set and forget option. Hope someone may be able to steer me in the right direction.
Not to step on Mark Kelly's reply, but, in a nutshell, no (it was always a kit) and no (7W specified maximum, though 5W in reality); I believe it could have been adapted for multi-motor (or multi-phase) use. The AC-1 is way beyond a simple sine wave regenerator.
-Richard
Thanks Richard for the prompt response. I hope Mark has further developments in store for us speed control freaks. Shame some of the commercial Micro VFDs dont go down to the tens of watts as there are a proliferation of these small and inexpensive units on the market.
-Pico
.
So, where can we get a Kit or board or info on building this???
Thanks!
ending with 'tron' is halfway home.
BTW, still waiting....(-:
The Mark Kelly Synchrotron AC-1 is the ultimate upgrade for anyone using a turntable powered by an AC synchronous motor.
I have a beta version of the Synchrotron AC-1, and I have to say that without qualification this is the best PSU you will find for driving a synchronous motor powered turntable on the affordable side of $1000.
For those who are not familiar with the Mark Kelly turntable PSU, it is available in kit form directly from Mark himself. The PSU comprises three PCBs which together provide a split phase sine wave generator for driving a 110V AC synchronous motor.
Now, one could be forgiven for wondering why there is a need for another such power supply; there are, after all, several such products already on the market: Heed Orbit, Hercules, Linn Valhalla and Lingo, Project Speed Box etc; but the Mark Kelly Synchrotron AC-1 includes a number of vital additions over other commercially available turntable power supplies such as the Heed Orbit PSU etc.
First up, there is the fact that the power supply produces the two phases to drive the motor directly. Many of the currently available turntable power supplies, such as the Project Speed Box, provide a single phase output and leave the phase splitting to a passive network located at the motor. This arrangement doesn't work very well, because a typical passive phase splitting network branches the input into a pair of outputs: one which connects the input directly to the first motor terminal, and another which connects the input to the second motor terminal via a series capacitor. The series capacitor does provide a phase shift, but a series capacitor cannot provide the correct phase shift (90 degrees is the required value). Moreover, the series capacitor reduces the amplitude of the voltage applied to the second motor terminal. The result of the different voltage amplitudes on the motor terminals and the incorrect phase difference is to add a significant amount of 100Hz vibration to the motor.
The second benefit of the Mark Kelly Synchrotron AC-1 is that the frequency is adjustable; this may not seem like such an important adjustment, after all isn't the pulley on a synchronous motor machined to give the right rotational speed for a 50 Hz or 60 Hz input? But actually, speed adjustment is a vital feature of a turntable power supplies particularly if you are using a turntable which has seen changes to production over the years. My measurements carried out on several Pink Triangle PT TOO turntables and a number of Thorens TD 160 turntables let me to the conclusion that many synchronous motor driven turntables are running at the wrong speed. For example, the effect of belt tension on the platter speed should not be underestimated: it is easy to produce a deviation in the order of 1% by changing the tension and width of the drive belt. Even changing the oil in the bearing housing can have some effect on the speed of rotation of the platter, so the lack of frequency adjustment on most power supplies for driving synchronous motors is a major omission in my opinion.
To verify the above, I tried running one PT TOO below the correct speed and above the correct speed, and the effect on the music was very apparent. Incidentally, I was not born with so called ‘perfect pitch’, but I found it quite easy to observe that a speed deviation of 1% too slow imbued the music a ponderous and deliberate mood, whereas a deviation of 1% too fast made the music sound pacey yet artificial (did someone say PRaT?). With the Synchrotron AC-1, the speed is adjustable to a precision of less than 0.02 %, so concerns about the turntable running at the wrong speed can be banished forever.
Next there is the fact that the phase between the motor windings can be adjusted about the theoretically optimum 90 degrees. In principle, this is not needed either, except that for may synchronous motors the alignment of the metallic teeth which produce the rotating magnetic field in the stator is not perfect, and an adjustment of the relative phase of the voltages applied to the two terminals can correct this problem.
Finally, there is the method by which the sine wave is produced. In private correspondence Mark Kelly comment that producing a signal by analogue methods (such as using a Wien bridge oscillator) has the benefit that a pure sine wave without unwanted harmonics can be produced but that creating a second signal with a 90 degree relative phase is difficult to achieve, and that accurate frequency control is difficult to maintain; on the other hand, producing a signal by digital methods enables the precise control of frequency and phase, but requires very high order filters to produce a pure sine wave output. So the solution was a hybrid, the signal is produced digitally, but by sampling the sine wave at a higher frequency (400 Hz instead of 100Hz), the result is the best of both worlds, accurate control of frequency and phase, and a relatively benign residue of harmonics which are suppressed using a relatively simple low pass filter circuit.
I have been using the Synchrotron AC-1 PSU to drive a Pink Triangle PT TOO which is partnered with a Grado Signature tonearm and a Denon DL103R for the past 3 months. The speed is exactly right at both 33RPM and at 45RPM, and the motor is absolutely silent. It’s so quiet that even if I touch the motor with my hand, I can only tell if it is running or not by observing whether the platter is spinning. I have never had a synchronous motor run so silently in any turntable that I have owned over the years. I put in some time and effort to restoring this innovative turntable to its former glory throughout 2007 and can now say with confidence that the turntable sounds better then it did when it came off the production line about 20 years ago!
The picture below shows the PT TOO turntable; the Mark Kelly Synchrotron AC-1 is housed inside the original metal housing for the PT TOO PSU, there’s nothing much to see, it’s just a black metal box, so I have hidden it at the base my rack.
BK
Nice review.
The one thing, though, that you omitted to mention is how the sound of the PT with Mark's PSU compares with the sound with the original PSU.
I am interested as a former owner of a standard PT TOO. Mine is now upgraded to full Vector status with a DC motor, so the Synchrotron wouldn't be appropriate (though Mark has interesting things to say about DC motor controllers too).
Alex
Do you happen to know how AK's DC controller works? He describes it as a new circuit and has apparently applied for patents but I can find no technical details anywhere. I'm guessing this is because he doesn't want anyone copying his work. I'm interested because I'd like to know how different the path he's going down is from mine.
Mark Kelly
I was very interested in the Synchrotron AC-1 when Mark first announced the product. But after looking at the price of an assembled unit the I have decided to look for a used VPI SDS. A used SDS usually sells for around $700 on audiogon. (about $50 dollars more than a new assembled Synchrotron AC-1 when you include shipping.
The VPI SDS offers adjustment of both the voltage and frequency fed to the turntable motor and has been appreciated by a lot of inmates who run VPI's.
For a small difference in cost, I would much rather have a product that's UL tested for safety (no small concern if you have ever had a house fire as I have), is made by a company with a good track record for service and longevity, doesn't have to be shipped to Australia for repair, and has proven resell value should I ever decide to sell it.
Please don't interprete this post as an attack on Mark's fine effort. I just think that the SDS (even new at about $900) is a better value.
Where do get the impression that VPIs SDS is UL listed?
Your points are all reasonable but I'd like the opportunity to answer them.Of course I cannot match the reputation of a company with thirty years' track record when I am just starting out. Similarly there is no history to establish resale value.
What I can offer is a product which significantly outperforms the available alternatives where it really counts and personal service from the bloke who designed the equipment.
Your comment about safety concerns me. I have designed the circuit to be inherently safe: the components used are UL rated, the output power is limited by the configuration of the chip amps and they are isolated from the turntable by the output transformers. I have complied with all relevant safety regulations and certification requirements.
I use my designs myself and I live in a wooden house in a hot dry climate.
Mark Kelly
I was cured, alright
I am still troubleshooting mine when I have the time and inclination to do so.I went for industrial ugly and have a nice, '50s bakelite knob for the speed selector switch now.
I hope to have time to mess with it again soon.
--
Al G.
Yeah, the troubleshooting was a tiresome and detailed and long process. The flubs causing the problems were mine, for sure. Other than that the final issue was one bad trace on a board. Funny how a single resistor can cause a whole design to not operate properly :-)
I have to publicly thank Mark Kelly for his great design, and his infinite patience with my stupid questions and e-mails along the way. It was certainly a worthwhile project and I learned a lot along the way.
Enjoy,
Bob
A gentleman is best defined as someone who knows how to play the accordion ... and doesn't.
Hi Dave. I was waiting for a post from you before I jumped in.
I also built one in conjunction with Dave's construction (we commisserated on several things along the way). I would say that it is not a kit for a beginner, and some knowledge of what you are doing besides being ablt to handle a soldering iron would be beneficial. In my implementation I am not using a 12V DC battery, but rather an AC to DV 12V laptop power supply. My costs came in at about $400, about half of a used SDS, but the time it took to build was not insignificant.
I agree with Dave's assessment of the level of improvement. Fundamentally I noticed that the image and soundstage are very stable now (they were pretty good before, but this is rock solid now). The 10W VPI motor that I have, in its housing, didn't seem to vibrate very much. However, when removed from the housing and held in the hand you can feel the vibrations clearly. This is due to phase problems with the AC coming in.
Mark's controller, aside from maintaining a stable frequency for speed control, does a wonderful job of synchronizing and stabilizing the 2 phases of AC power to the motor thereby making it very quiet. There is a truly noticeable improvement of how quiet the motor rund when in the hand, and a quiet motor will not transmit vibrations through the belt to the platter.
Enjoy,
Bob
A gentleman is best defined as someone who knows how to play the accordion ... and doesn't.
Just curious, what size metal box are you using for the unit in the photo?
this is probably the minimum size that you could use to fit the boards into a box. I would recommend going a bit larger for anyone else building from scratch - it was a tight fit.
Enjoy,
Bob
A gentleman is best defined as someone who knows how to play the accordion ... and doesn't.
Yes, the new set-up is running smoother and quieter than before & the addition of the drive controller has taught me something about AC motors. In my custom thread drive, the level of vibration & instability in the drive system can be assessed by placing a finger on top of four pressure rollers that guide the thread through points on either side of the flywheel. Mechanical vibration at these points has gone from moderate to almost nill. Previously, I had assumed that vibration at these points was generated by friction from the sleeve bearings in the guide rollers, or by torquing effects in the aluminum structure that supports the guide rollers. But undoubtedly this vibration originated at the motor. It's even more surprising that a large intermediate flywheel had failed to buffer any meaningful amount of vibration from passing through the motor-to-flywheel thread segment and into the flywheel-to-platter thread segment-- and from there, of course, into the platter. An inelastic thread is very revealing of such vibration as compared to a rubber belt.
Looks nice.
How much did the whole project cost? did you buy the whole kit from Mark Kelly or PCB only(and sourced the parts yourself?)
The kit is sold as preassembled & tested boards, or a "half-kit" (as I bought it.) For US$95 the half-kit includes three PCBs, several hard-to-find parts, instructions, and a BOM for about $140 in piece parts referenced to Digikey p/n's. Add DIY enclosure, charger, good cabling, and a decent 55AH battery like an Optima Yellow Top, and total costs are $450-$700 & well worth it.
Instead of lead plates and an acid bath, the material is wound into cylinders. We used these alot for award winning auto stereo systems where a normal battery would have just gone dead after an hour of competition. These Optimas just sailed on through.
I also like that they are dry....Better for an in home environment.
Thanks for posting. I am very eager to try this device later in the year.
So "instead of lead plates and an acid bath" it has (unspecified) "material wound into cylinders" which makes it "actually function(s) a lot like a capacitor".
If this is so, how come the manufacturer says that it is actually a lead acid battery?
Mark Kelly
I have seen one cut apart and they are very intriguing batteries.
In an automobile it can be exposed to nearly any angle where a standard battery needs to be kept upright and level. This makes it ideal for off-road racing. The manufacturer claims high resistance to vibration as well. I sincerely doubt there is any liquid free flowing acid anywhere in the case.
Gel perhaps?
I should not have stated it is dry...
Mark, your controller looks luscious. It certainly goes beyond anything I have seen in the current market place and it is ultra affordable for anyone wanting a world class turntable. Awesome work Mark. I hope the product is a huge success.
Sorry my descriptions are so poor. I am trying to work on this as my new years resolution.
Kudos Mark!
sense that it stores electrical energy. But, we're here to learn....apparently, from car stereo shoot-outs. Who knew?
I currently use & have compared 55AH Optima Yellow Top and 100AH Enersys Odyssey, powering a Sony SCD-1, a Merlin BBAM, and now the AC-1. To my knowledge both are SLA batteries. Both are deep-cycle types with very thin, dense plate structures. The YT uses spiral plates. Both have low impedance in the 2-3 millohm range-- orders of magnitude less internal resistance than small SLA batteries & standard automotive types. But even so, in high-end audio applications both batteries audibly benefit from adding lots of additional capacitance between the terminals and near the load.
Dave, Do you have a model number for the Enersys battery rated at 100Ah? A quick google search reveals one model rated at 67Ah, tops.
Enersys Oddyssey PC2150, also marketed in car audio as the Stinger PC2150. About $250 from batterymart.com.
In car audio applications it was very common to see higher quality ofc wires. Almost every competition system would utilize anywhere between 0.5 to 1 farad capacitance at the battery. I have seen systems with multiple batteries and multiple capacitors for competition.I have been told that having the appropriate capacitance allows the battery to function with less distress since instantaneous demand would be covered by the capacitor and the deep cycle battery would have a "buffer" in a mannor of speaking.
One category in the auto stereo world is called the iron man competition. They basically run the system at 110 to 130 db with a bass sweep cd and the last car playing music wins. Optima owned this category!
I liked the Red top batteries for my high compression racing motors. They had the best cold cranking amperage.
I would think the more capacitance you put at the battery the better!
Nice work on your project Dave! It is one great looking item. The digital read out is very nice.
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