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  • Originally posted by demassive View Post
    its the dtxplorer...its the head is just not sensitive enough....you know how you said the piezo output (tip) is the right hand end of the second strip down. Well isnt the black end of d3 connected to r3...so the other end of d3 which is on the top of the board is the output for main piezo...
    No, the other end of D3 (the non-black end) is the input. Your diode connections seem correct.

    A couple of suggestions:

    1. try swapping the piezo wires over - piezos are polarised

    2. try shorting out D3 (that is an option I provided on my board with a jumper).

    Keith.
    Keith Raper
    http://www.dtxpander.co.uk
    http://www.kdel.co.uk

    Comment


    • do i just swap the main piezo or do i have to swap the aux piezo wires aswell so they still remain offset?

      Comment


      • Originally posted by demassive View Post
        do i just swap the main piezo or do i have to swap the aux piezo wires aswell so they still remain offset?
        If you are only having problems with the main piezo, just swap those wires over. While piezos are polarised, most manufacturers don't identify the polarisation. If you have two "identical" piezos, there is no guarantee they will be polarised the same way round!

        Keith.
        Keith Raper
        http://www.dtxpander.co.uk
        http://www.kdel.co.uk

        Comment


        • and for the jumper would i just run some insulated wire like the link on tr1
          going from the top 8 across to 2nd from the top 8 across

          Comment


          • Originally posted by demassive View Post
            and for the jumper would i just run some insulated wire like the link on tr1
            going from the top 8 across to 2nd from the top 8 across
            Yes, just effectively shorting out D3 using the two free holes at the top right hand corner of your drawing. You could even use a jumper if you had one.

            Keith.
            Keith Raper
            http://www.dtxpander.co.uk
            http://www.kdel.co.uk

            Comment


            • gots it working keith beautiful head response now...so is that jumper effectively just skipping d3 completely...so it almost need not be there if i was to do it again for the dtxplorer?
              and if i want to get a stronger rim response what suggestions would you give, extra piezos less isolation etc, any different mounting suggestions

              Comment


              • Originally posted by demassive View Post
                gots it working keith beautiful head response now...so is that jumper effectively just skipping d3 completely...so it almost need not be there if i was to do it again for the dtxplorer?
                and if i want to get a stronger rim response what suggestions would you give, extra piezos less isolation etc, any different mounting suggestions
                I'm glad it's working.

                D3 was put there for "symmetry". For the intended purpose of the circuit when I designed it (two identical pads being fed into one input) that made sense. However, when you make your own pads and the signals are different sizes, the signal lost across the diode can be an issue. Also, the polarisation of the piezo is important. The DTXpress (and therefore the DTXplorer) responds to positive pulses. If the piezo is wired the wrong way round the initial pulse will be negative and not seen. Then the only thing that will trigger the module is the "ringing" which goes positive. For some pads, such as the KP65 kick pedal, the ringing is well damped so the wrong polarity can be a real problem. With a home-made pad, I don't know.

                Anyway, if you are making more of the same pad then you can leave off the diode.

                I cannot help with the construction side - I have never made my own pads - but hopefully someone here can help.

                Keith.
                Keith Raper
                http://www.dtxpander.co.uk
                http://www.kdel.co.uk

                Comment


                • all your help has been greatly appreciated keith....now that i can complete it relatively confidently ill construct a fairly easy to follow step by step (w. pics) for noobs like myself with no electronics experience
                  regards demassive

                  Comment


                  • Originally posted by demassive View Post
                    all your help has been greatly appreciated keith....now that i can complete it relatively confidently ill construct a fairly easy to follow step by step (w. pics) for noobs like myself with no electronics experience
                    regards demassive
                    I am sure that will be useful, although I think this thread started out as being just that. It is difficult for me to appreciate how difficult it is for people to understand because I design electronics every day for a living.

                    Keith.
                    Keith Raper
                    http://www.dtxpander.co.uk
                    http://www.kdel.co.uk

                    Comment


                    • hi Keith.

                      im helping a friend with a diy snare for this dtxpress kit, and i was wondering with version of your circuir would work more accurately for the 3 zone pad.

                      ive seen the DKDI-31 and the DTXpander 3zone - 2 piezo designs.

                      as far as i can understand the, the main difference seems to be that the first uses 3 piezos where 2 of them go trough the tip, one as a piezo and one as a swith but can be triggered separately, while the third piezo goes alone through the ring. all piezos with common ground to the sleeve.

                      and the 2 piezo design sends a "mixed" signal piezo and switch throught the tip.

                      im i understanding the difference correctly?

                      can I asume that the DKDI-31 is more accurate as far as replicating the input created by the TP65S (or other 3 zone P/S/S pad) and should be a better choise?


                      thx in advance.

                      greetings, Ignacio
                      Dual td-8 setup. all diy pads. (drop pan)

                      Comment


                      • Ignacio,

                        You are correct that you need the DKDI-31 for three zones, assuming you are using 3 piezos. I am not sure which other circuit you are referring to - there are a lot of variants out there, some drawn by other people. There was one I drew for someone specifically for a Roland to put the cymbal edge on input 10 of a TD12 and the rim and main piezo on input 9.

                        Anyway, if you are using 3 piezos & 1 input on the DTXpress you need the DKDI-31 circuit. All three piezos supply the signal to the tip and the two rim switches come from the other piezos, with a 10k resistor for the third zone.

                        Keith.
                        Keith Raper
                        http://www.dtxpander.co.uk
                        http://www.kdel.co.uk

                        Comment


                        • hey Keith, thx for the fast responce.

                          i will be using 3 piezos so ill go for the DKDI-31 rev:E diagram.

                          a couple of cuestions about it. do the two switch piezos need to be isolated from each other?

                          do the switch piezos need to be isolated from the head piezo?

                          im gonna see if I can manage to make a perf/stripboard diagram to add to the post.

                          thx again

                          best regards, Ignacio
                          Dual td-8 setup. all diy pads. (drop pan)

                          Comment


                          • That's the correct diagram (it is on DTXpander.com).

                            I have never built my own pads, but I would expect the piezos need to be acoustically isolated otherwise if you hit any one you will get the same sound! Electrically they are isolated as well, although they share the same ground connection.

                            Keith.
                            Keith Raper
                            http://www.dtxpander.co.uk
                            http://www.kdel.co.uk

                            Comment


                            • great. i think i have an idea to isolate the piezos. but first i need to build the circuit.

                              starting with the part list

                              R6 Resistor , 10k
                              R5 Resistor , 1M
                              R4 Resistor , 10k
                              R3 Resistor , 1M
                              R2 Resistor , 1M
                              R1 Resistor , 10k
                              vr1 Trimmer, 100k
                              vr2 Trimmer, 100k
                              TR2 transistor, BC337
                              TR1 transistor, BC337
                              D5 1N4148 Diode, 1N4148
                              D4 Schotky-diode, BAT46
                              D3 Schotky-diode, BAT46
                              D2 Schotky-diode, BAT46
                              D1 1N4148 Diode, 1N4148
                              J1
                              piezos

                              ill post the stripboard diagram when im able to figure it out, hehe

                              i guess it would be wise to use a protoboard first.... gonna focus on that

                              greetings, Ignacio
                              Last edited by nachosavage; 07-06-09, 01:43 PM. Reason: new info
                              Dual td-8 setup. all diy pads. (drop pan)

                              Comment


                              • Ignacio,

                                For the diodes, you could use 1N4148 or 1N914 for all of them. The BAT46 is not really essential (and harder to find & more expensive).

                                Similarly, the BC337 isn't critical - any small signal NPN will do, but preferably one with a reasonably high current gain (>100).

                                Keith.
                                Keith Raper
                                http://www.dtxpander.co.uk
                                http://www.kdel.co.uk

                                Comment

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