Noise & VC Tone Filter Module

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10 thoughts on “Noise & VC Tone Filter Module

  • Thanks for putting up your schematic, it answers a lot of questions I had looking through the datasheet. I like the idea of having different filter cap values on the left and right channels and using the balance control to mix them, I’m definitely stealing that!

    • Awesome! Let me know how it turns out. The balance is interesting, it acts like a choke. In the middle, both sides let sound pass, but if you go left or right, it amplified and attenuates or attenuates and amplifies the signal. The capacitor imbalance allows more of the signal to get through and it’s an interesting distortion effect. Good luck with the build!

  • ?

    One thing I picked up from the datasheet is that pin 17 should be connected to the upper value of the control voltage range if you’re not using the internal potentiometer supply (tables at the bottom of page 5/top of page 6 of the September 1987 Phillips datasheet in case there’s multiple versions around). It’s not made particularly explicit in the text (it’s not the greatest datasheet, but at least it exists). I’m unsure how much of a difference it would make to the sound but it might be worth considering…?

    • Oh, Interesting! I didn’t notice that. It might be worth shorting it to see what happens. I just assumed it was supposed to sit there unused. The other option would be to connect it to the input potentiometers instead of +5v. Then you could swap the noise chip out for a transistor-based noise circuit and get rid of the 5v regulator altogether. If you end up trying it out, let me know! ?

  • Hi Tyler,

    I have some ideas to expand in this circuit and I would love to get a pair of PCBs to experiment with. If you could sell it, or share the gerbers, or interchange for another parts that would be great

    Im the founder of Spherical Sound Society and I have all this in stock to pretty much interchange (at tindie or etsy)

    I adore this site to bits. Cheers!!

    • Hey JC,
      Thank you for your interest and the kind words! Definitely willing to exchange modules. I pinged you on FaceBook messenger.

  • Hi Tyler, Are you selling the panels for this module design? I am interested in building one to try out and learn more about how the circuits work. Please get in touch. Thanks.

    • Hey Thom, Thanks for your interest! I sent you an email reply.

  • Question: why do you use 5.1V zener diodes? If I’m not mistaken the datasheet of the TDA speaks of a max of 4.25V at the control inputs?

    • That’s a great catch, I think you are correct, that zener should probably be a 1n4730 or maybe a 1n4731. So far I haven’t had any issues with the signal being too hot, but I suppose it could damage the chip in the long run.

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