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  • PI Audio output

    PI Audio output.

    Hi all, just wondering what people here prefer with regards to type of audio output.



    1 Pitch change on a center frequency

    or

    2 Threshold with level change.


    All replies welcome.

  • #2
    Interesting type is in Tracker/Koschej PI. It gives an encreasing tone, but encreasing by steps. On every its tone an LED would be lighted. Step change VCO -?

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    • #3
      HI Mick,

      How about both frequency and amplitude(volume).

      Cheers Mick

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      • #4
        Thanks for the replies.

        ATM I'm testing a 4046 but the problem with this idea is the constant volume, it gets annoying after a while. So I think the threshold method might be better suited.

        Time to do some more testing.


        Cheers
        Mick

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        • #5
          Most of the VLFs have threshold set too high, I guess to boost the indication of weak target responses, almost binary-like, however, this approach makes noise chatter unbearable. I made some mods in my IGSL to keep the low response quiet, and large response loud, and in a logarithmically compressed way. It works for me.

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          • #6
            Pitch change on a centre frequency with Threshold
            That could be interesting, I have a Excal and the buzzing is annoying
            I think Tinkerer said something about his setup is a low tone for ferrous
            and a high for other metal.

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            • #7
              Hearing is more sensitive to slight changes in pitch than slight changes in volume, so a VCO response is usually best. Most detectors combine changes in both pitch and volume. While you can do this either with a running threshold or as silent search, having a running threshold gives greater depth. The trick is to come up with a comfortable threshold tone/volume, which can vary person-to-person.
              Last edited by Carl-NC; 08-21-2012, 05:11 PM.

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              • #8
                Thanks for the replies everyone.


                Earlier today I added a basic log amp between the final integrator stage and the 4046 output, this made a noticeable difference I'm now able to clearly hear a small test nugget at far greater distances. The only downside I can see at the moment is any large targets will over load the range of the 4046.


                The detector is running what I would call low gain.

                The first amp is 100 times.

                The diff integrators are 68 times and final integrator is 68 then into the log amp.



                Maybe i need to increase the gains in the earlier stages then I might not need a log amp ?





                Mick

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                • #9
                  I agree with carl, threshold a must for the deep stuff VCO for depth/location, ferrious/non ferrious high/low, easer on the ears.

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                  • #10
                    Originally posted by mickstv View Post
                    Thanks for the replies everyone.


                    Earlier today I added a basic log amp between the final integrator stage and the 4046 output, this made a noticeable difference I'm now able to clearly hear a small test nugget at far greater distances. The only downside I can see at the moment is any large targets will over load the range of the 4046.


                    The detector is running what I would call low gain.

                    The first amp is 100 times.

                    The diff integrators are 68 times and final integrator is 68 then into the log amp.



                    Maybe i need to increase the gains in the earlier stages then I might not need a log amp ?





                    Mick
                    Hi Mick,

                    I would increase the gain(the front end is fine) until you can just hear the audio starting to change from the cct noise. Ground the input of your preamp to the coil ground.

                    Cheers Mick

                    Comment


                    • #11
                      Originally posted by Mechanic View Post
                      Hi Mick,

                      I would increase the gain(the front end is fine) until you can just hear the audio starting to change from the cct noise. Ground the input of your preamp to the coil ground.

                      Cheers Mick

                      Hi Mick, thanks for the info will do.

                      Just sending you a pm.


                      Cheers
                      Mick

                      Comment


                      • #12
                        would you be so kind and post the circuit you are talking about?
                        Thanks
                        Monolith

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                        • #13
                          Originally posted by Monolith View Post
                          would you be so kind and post the circuit you are talking about?
                          Thanks
                          Monolith


                          It's not drawn at the moment, but will do it and post up in the next couple of days. It's all a work in progress on breadboard at the moment.



                          Cheers
                          Mick

                          Comment


                          • #14
                            If you are referring to a Tinkerer's solution, you could do with a little high pass at the final stage prior to the VCO. Point is that log amps are not happy with offset, so when you block DC they are much happier.
                            I made such change in my IGSL mods and audio is superb. OK, it is a volume thing, not frequency shift, but the log compression does that nicely.

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                            • #15
                              Originally posted by Davor View Post
                              If you are referring to a Tinkerer's solution, you could do with a little high pass at the final stage prior to the VCO. Point is that log amps are not happy with offset, so when you block DC they are much happier.
                              I made such change in my IGSL mods and audio is superb. OK, it is a volume thing, not frequency shift, but the log compression does that nicely.


                              No it's actually one of my bipolar TX circuits. As soon as I get time I'll draw and post the schematic.



                              Cheers
                              Mick

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