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Guy's Turntable http://www.dcaudiodiy.com/phpBB3/viewtopic.php?f=4&t=90 |
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Author: | Guy [ August 1st, 2013, 11:42 am ] |
Post subject: | Re: Guy's Turntable |
Drive System and Motor Enclosure, Part 2 Online forums also had a lot of suggestions for motor power supplies. Mark Kelly from Australia wrote a great article in an on-line publication from BasAudio.Net called DIYMAG. (Go to http://basaudio.net/blog/diymag/ and look for “early 2006.”) In the back of the publication was 10-page article about AC and DC turntable motors and how to drive them. Mark’s article impressed me, and he certainly understood more about platter drive than I, so I used his design for a DC motor driver with error correction. There used to be a kit marketed by diyAudio.com for the controller, but it was no longer listed. Instead I laid out a PC board using Kelly’s circuit (see Figure 23). I still have a couple PC boards left from my first run. Attachment:
File comment: Figure 23: Kelly Controller Printed Circuit Board Kelly Controller Printed Circuit Board.jpg [ 233.35 KiB | Viewed 21888 times ] Figure 24 shows the controller board mostly loaded with components. The op amps (U3, U4) and voltage reference (U2) have not been plugged in, and the resistors that set platter speed as also missing. The pots (R7, R27) that adjust platter speed were actually mounted on a piece of perforated board and suspended below the top of the motor enclosure so platter speed could be adjusted while the enclosure was assembled (see Figure 22). Attachment:
File comment: Figure 24: Kelly Controller PCB With Components Kelly Controller PCB With Components.jpg [ 209.62 KiB | Viewed 21888 times ] John Parker of Choir Audio indicated that I needed a belt material that addressed two major points:
2. Low-Noise Operation: Surface area causes friction, and friction causes noise and unwanted energy (vibration). John preferred round belts because they addressed both points. He also suggested that I try 3/16”- and 1/8”-diameter belts, which he was able to provide once I used a piece of string to determine the length of belt I needed, which turned out to be 45”. Now for a pulley: There is nothing like friends. One of mine made a bronze ¾ ” diameter pulley with a ½”-diameter groove for the pulley (see Figure 25). The groove had a 1/8” radius (so my round belts would fit nicely and maximize contact) that was located 3/8” from the bottom of the pulley, and the edges were flared at 45° so the belt wouldn’t get pinched. The pulley had a 3mm hole drilled ¼“ into the bottom, and was glued to the Maxon motor shaft to drive the platter using a round-cross-section rubber belt. Attachment:
File comment: Figure 25: Drawing of Drive Pulley Drawing of Drive Pulley.png [ 34.32 KiB | Viewed 21888 times ] Copyright 2012 Guy W. Riffle. All rights reserved. |
Author: | tomp [ August 1st, 2013, 12:51 pm ] |
Post subject: | Re: Guy's Turntable |
Guy: This is very well designed and implemented project. Kudos for the effort. It truly must have been a labor of love. If you have not already published it, you should consider submitting it to "AudioXpress" magazine. They would love it. I can provide you with contact info if you need it. Tom |
Author: | TubeDriver [ August 1st, 2013, 12:56 pm ] |
Post subject: | Re: Guy's Turntable |
Impressive work! |
Author: | craigh [ August 1st, 2013, 1:40 pm ] |
Post subject: | Re: Guy's Turntable |
This is great Craig |
Author: | Guy [ August 1st, 2013, 4:19 pm ] |
Post subject: | Re: Guy's Turntable |
Tom, I tried to submit this to AudioXpress, but they considered it more of a product review than a construction project because I bought the platter and tonearm. At that point club members started trying to decide if amplifiers are construction projects because we buy resistors, capacitors, transistors, and tubes. Well, the magazine rules, and has changed after being consumed by Elektor. |
Author: | Guy [ August 1st, 2013, 4:20 pm ] |
Post subject: | Re: Guy's Turntable |
Thanks, Everyone! See, even a person of limited experience can build something interesting! |
Author: | Jim G [ August 2nd, 2013, 4:17 pm ] |
Post subject: | Re: Guy's Turntable |
Guy, Great article about your turntable. I'm interested in following your plans and building one. Save me one of those controller boards. Jim |
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