Overview

This project is based off of the Sontec MEP250A 5 band parametric EQ. I've provided all the resources needed to build one yourself below. I also sell fully hand built ones over at https://operationalaudio.com/.











I've adapted it to use Blore-Edwards PZ style 23 step rotary switches but other switches or regular pots could be used as well.

Resources

I used the following references and resources when designing and tweaking this project:

• Original Sontec MEP250A schematic courtesy of Gyraf
• The Don Classics 250EQ 500 series module (I've built 4 f these and they are really really great - you should get one, or two!)
• Glass-Ware audio bipolar power supply I used this power supply in my build rather than design my own. You can substitute for any decent bipolar power supply that provides +/- rails around 15V - or whatever you want to use for your opamps.
• Igor's calculator for rotary switch resistor values: Igor's Calcs GSheet Link. I had the opportunity to customize the 'taper' on the Frequency switch so I added my own calculations here: My GSheet Link

Files

• Schematic: Schematic_StereoParametricEQ.pdf
• Gerber Files: Gerber_StereoParametricEQ.zip - A note on the board: I chose to go with a 4 layer PCB design for this project, mainly because I just wanted to try it out. I'm not a PCB design expert or an electrical engineer but I think having the power rails, audio ground, and power grounds on their own layers might be a positive thing? I don't know. I do know that making it 4 layers means it costs more and is harder to repair (read, impossible if an inner layer gets damaged). So there's that...
• Front Panel: Faceplate_StereoParametricEQ.fpd
• BoM: Stereo Paramatric Equalizer BOM & Costs - this is my BoM and includes my parts choices, you might want to make your own selections. Like, you might not want to spend $200 on knobs...
• PCB render for reference: PCB_StereoParametricEQ.png
• Wiring Diagram: TBD but should be fairly obvious.