krabbencutter
Well-known member
Hey everyone,
I've successfully built a W295b inspired EQ in the spirit of Ian's "Poor Man's" circuits and you can find the schematic (KiCad & PDF) as well as a BoM on GitHub.
My goals were as following: continously variable gain, gryator circuits instead of real inductors, only readily available parts, bipolar supply voltages and of course ICs instead of discrete amps.
I already have a +/-12V PSU from my modular synthesizer so I didn't bother designing one myself. Parts cost without a dedicated PSU should be around $20-$25.
The original W295b did pose a couple of challenges. First of all the high frequency control needs a center tap. To work around this the high frequency control in my design only works one way, but you can use a switch to toggle between boost/cut. Next up I had to figure out the inductance values on the mid band. I couldn't find much on the internet but fortunately it's a German EQ and if we write 700Hz on the front panel you can bet the center frequency is dead on 700Hz. Since I had the resistance and capacitance values I could just calculate the inductance values and arrived at 235mH / 170mH /110mH / 80mH/ 50mH & 30mH. Last but not least the W295b mid band is kind of a proportional Q design, but the bandwidth gets much wider than usual at lower gain values. This is where my design is only "inspired by" the W295b. It's a proportional Q design as well and closely matches the W295b at +/- 8dB but will not be as wide at +/- 2dB and +/- 4dB.
Since I don't have an original W295b at home I could only compare my circuit to Arturia's Sitral-295 plugin and it was pretty spot on.
Let me know if you have any questions or suggestions for improvements
I've successfully built a W295b inspired EQ in the spirit of Ian's "Poor Man's" circuits and you can find the schematic (KiCad & PDF) as well as a BoM on GitHub.
My goals were as following: continously variable gain, gryator circuits instead of real inductors, only readily available parts, bipolar supply voltages and of course ICs instead of discrete amps.
I already have a +/-12V PSU from my modular synthesizer so I didn't bother designing one myself. Parts cost without a dedicated PSU should be around $20-$25.
The original W295b did pose a couple of challenges. First of all the high frequency control needs a center tap. To work around this the high frequency control in my design only works one way, but you can use a switch to toggle between boost/cut. Next up I had to figure out the inductance values on the mid band. I couldn't find much on the internet but fortunately it's a German EQ and if we write 700Hz on the front panel you can bet the center frequency is dead on 700Hz. Since I had the resistance and capacitance values I could just calculate the inductance values and arrived at 235mH / 170mH /110mH / 80mH/ 50mH & 30mH. Last but not least the W295b mid band is kind of a proportional Q design, but the bandwidth gets much wider than usual at lower gain values. This is where my design is only "inspired by" the W295b. It's a proportional Q design as well and closely matches the W295b at +/- 8dB but will not be as wide at +/- 2dB and +/- 4dB.
Since I don't have an original W295b at home I could only compare my circuit to Arturia's Sitral-295 plugin and it was pretty spot on.
Let me know if you have any questions or suggestions for improvements
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