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Saturday, 20 July 2013

Adjustable Mains Hum Notch Filter Stripboard Veroboard Layout


I built this for those of you who have guitars with single coil pickups or indeed anything that picks up mains interference up (that annoying set of speakers in my bed room for example) anyway this little device reduces the mains hum by several orders of magnitude

it is adjustable between 45Hz and 90Hz so just put it before your amp or whatever and adjust the trim pot till the hum goes away.

it uses the same Texas Instruments TLC071 OP-AMP as I used in the last project for pretty much the same reason



13 comments:

  1. This will help me out a lot! But, what does Vin mean? I'm still sort of new to this, please forgive me..

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    1. it means "voltage in" in this case it's 9 volts.

      don't be ashamed - we all had to start somewhere

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  2. A bit confused...
    There's no DC path for the non-inverting input. Is this right?
    Since this is a fet input opamp and has a very high input impedance, what does C3 do?
    Brian Grimshaw

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    Replies

    1. it is part of the filter - this is for audio (AC signals)
      and I assure you it does what it should do.

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  3. Where does it goes to the board? i don´t see a Vout... (assuming out is the audio signal).
    Does tlC071 = tl071?

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  4. did you forget a 620 k resistor from in to the non-inverting input of the op amp?

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  5. Hi dear Paul, may is possible use this circuit as filter to remove 60Hz from single coils pickups like music man do with their buffer/filter. Thanks

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    1. in theory yes, it will certainly make it quieter if nothing else - most noiseless single coils use a dummy coil to cancel out the hum
      I was thinking about trying to design a proper noiseless circuit at some point for my Brian May guitar but so far I haven't gotten around to it

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    2. Paul, I will try, maybe adding a JFet preamp to calibrate the gain in dB, I've studied some about dummy coil and active pickups, and some active pickups they are a noiseless, with output buffer to give their low impedance. Thanks, if I have good response i will keep you informed.

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  6. Sorry Paul for this dummy question, I'm searching TLC071 and I found in some website TL071C, isn't the same integrated circuit?

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    Replies
    1. you can use the TL071C - the other one is just a lower power version

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