"CNC" Moving Magnet Cartridge Phono Stage Part 2

Written by Darren Myers

In a previous issue, Jim Langley shared his famous DIY CNC phonostage with us, recommending various component modifications and upgrades.  We will soon have CNC PCBs available for purchase directly from PS Audio; this is a non-profit effort from Leebs and me to encourage and support the DIY community.

You will need a soldering iron, solder, and an inexpensive multimeter for checking resistor values or battery voltage (optional but recommended).

We’re awaiting final details, but it looks as though the PCBs will cost approximately $15.00, subject to variance. We hope to have the boards available soon, and will provide details in the next issue of Copper. The component values are written on the PCB, making it easy for anyone to populate and know where each component belongs.

The link below will send you to a cart at Digikey.com with all the parts that you’ll need (be patient—it may take a few seconds  for the cart to populate). I’ve included various different capacitive loading resistors for you to experiment with (47pF, 100pF, and 180pF). If you are using long RCA cables out of your turntable, you may want to experiment with leaving these capacitors unpopulated. For shorter, low capacitive cables, try 100pF or 180pF.


The cart also includes two different OP amps (2 each) so that you can experiment with different amplifiers and see what sound you prefer.  Jim recommends an OPA2134 in position 1 and a LM4562 in position 2.

For indication, I’ve added a red LED and 8.2K bias resistor to the cart. You may choose to go with a different color such as blue or green. Refer to Jim’s previous article for more information on how to wire this.

9V battery contacts and mechanical clips are included in the cart so that you’ll have to do is decide on an enclosure and add some 9V batteries.

Special thanks to muffsy.com for the PCB design and my close friends Jim Langley and Bill Ennis for making this DIY project possible for so many.



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