Dual Phase SDS power supply

Dual Phase SDS power supply

Postby Ducky » Sat Feb 18, 2017 1:12 pm

I finally decided to build one of these DIY motor controllers that have been floating around on DIYAudio.com for awhile. I like the digital control and accuracy of the SDS, but since it is no longer available, this seemed like the next best thing. The best part is that the DIY kit can be configured for dual phase output so I can minimize the motor vibration by adjusting the phase of the second output. This has really helped reduce background noise and seems to improve imaging and dynamics as well.

The SG4 (purple PCB) is the heart of the design and is a 4 phase sinewave generator that is crystal controlled and digitally adjustable in 0.01Hz steps. It has 4 outputs, but I only needed to use 2 of them (zero and 90 deg). The output of the SG4 is 5VPP, so it requires an amplifier and step up transformers to get the voltages up to 120VAC and it has a reduced output voltage after 5 seconds that is programmable in 1V steps. Luckily, there are lots of cheap amp modules available on e-Bay. The one I used is a stereo amp (one channel for each phase) with LM3886 chip amps and built-in power supply; the amp was only $15! All that was needed to build a complete controller was to add a power transformer to power the amp, 2 output transformers (one for each phase) and a case. The case was the most expensive part of the project (also because I used lighted buttons that were $15 each), but I was able to construct a fairly decent looking supply for $250 plus it has dual phase outputs!

The SG4 comes as a bare PCB ($15) and a shared shopping cart from Mouser ($32). The PCB was easy to build as it uses all through-hole parts and the micro-P is socketed for easy installation. It took approx 1 hr to solder the parts and it fired right up, first time. I think the most difficult part was all of the drilling and machining of the aluminum case, which took the better part of a day. The front panel is fairly thick and I needed to cut 2 square holes (one for the on/off switch, the other for the display). I drilled out as much of the material as I could, then removed the rest with the help of several files and lots of elbow grease.

There are wiring diagrams available on the DIYAudio website which made interconnection of the various modules easy. I used a standard 3 prong AC outlet for the output, putting one phase on the 'hot' wire, one phase on 'neutral' and the common on the ground lead. I also needed to rewire the motor to remove the phase cap (no longer needed) as shown in one of the pics below.

Overall, it was a great improvement over powering the motor from the wall socket. Speed stability is really noticeable on voices, woodwinds and piano notes, especially on single notes with long sustains. Switching between 33 and 45 RPM is now just a matter of flipping a toggle switch. The 3 buttons on the front panel are for increasing frequency (Green), decreasing frequency (Red) and standby mode (Blue). The buttons are also used to access the reduced voltage mode and for adjusting the phase of the 2 signals.

Dual Phase SDS.jpg
Dual Phase SDS.jpg (268.27 KiB) Viewed 1823 times


Motor Connection.jpg
Motor Connection.jpg (253.28 KiB) Viewed 1823 times


Inside View.jpg
Inside View.jpg (310.43 KiB) Viewed 1823 times


Standby.jpg
Standby.jpg (266.91 KiB) Viewed 1823 times
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Re: Dual Phase SDS power supply

Postby luckydog » Sat Feb 18, 2017 2:04 pm

Wow, nice job!

I built one back in high-school for an electronics class project, but unfortunately I never got it working (I think I fried an output transistor while soldering.) I still somehow got a decent mark on it, but then I put the project on the back burner and sadly never completed it.

I recently bought a Phoenix Falcon, but in hindsight it would have been fun to try a DIY project again. When I built mine, there was no internet to answer questions, and getting the parts meant riding the bus all over town to electronics shops and hoping they had what I needed in stock.
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Re: Dual Phase SDS power supply

Postby Analog Aecad » Sat Feb 18, 2017 3:52 pm

+1 :)
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Re: Dual Phase SDS power supply

Postby Packgrog » Sat Feb 18, 2017 11:37 pm

That is very sweet! Pity I lack any electrical skill.
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Re: Dual Phase SDS power supply

Postby mreeter » Sun Feb 19, 2017 9:13 am

I envy you folks with this kind of talent, a project like this is way above my skill set.

Looks great, very nice work indeed!
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Re: Dual Phase SDS power supply

Postby MMMC » Wed Feb 22, 2017 7:08 am

Ducky,

Very Nice!

It's something I need to build,...... if I can.

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Re: Dual Phase SDS power supply

Postby Brf » Wed Feb 22, 2017 9:15 am

Very nicely done! It does NOT look like a DIY job, very professional looking!
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Re: Dual Phase SDS power supply

Postby DeeCee » Wed Feb 22, 2017 12:07 pm

Cool! All you need is a nice custom vanity plate with your name on the front:

https://www.crownawards.com/Dance.Engra ... oCMTTw_wcB

(no affiliation with this company, just happened to see it on the web)
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Re: Dual Phase SDS power supply

Postby Ducky » Wed Feb 22, 2017 1:48 pm

Thanks for the kind words everyone.

It was actually a lot easier to build than I would have thought. The instructions on the SG4 are simple and easy to follow, as are the interconnection diagrams. The amp comes fully assembled with just one modification needed (swap out 2 resistors). There are also connectors on the SG4 and amp PCBs so they are easy to connect/disconnect while working on the case.

The case I used comes disassembled in 6 pcs (top, bottom and 4 sides) so it is easy to put individual pieces in a vise and work on, or to drill on a drill press. The switches, although expensive, give it a real finished look, and they mount easily in a 5/8" round hole. As with anything, it's the set up and detail work that matter. :mrgreen:

If anyone else is interested in building their own, there are 2 links for the instructions; One for the SG4 and another for the amplifier(s):

http://www.diyaudio.com/forums/analogue-source/298018-diy-4-phase-sinewave-generator-turntable-motor-drive.html

http://www.diyaudio.com/forums/analogue-source/300371-60-wpc-amplifier-diy-turntable-motor-drive.html
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Re: Dual Phase SDS power supply

Postby Brf » Wed Feb 22, 2017 2:11 pm

Ducky, what would you ball park the price of the parts for your dual phase motor drive? Thx
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