Kick Drum Sound Module Project

Discussion in 'The Projects Forum' started by Joster, Oct 15, 2013.

  1. Joster

    Thread Starter Member

    Jun 12, 2013
    95
    0
    Hi Folks!


    I'm planning on building my own drum trigger as there is nothing on the market currently that can do what I want. I play heavy metal and only require that the kick drum be triggered because the rest of the kit is mic'd. Every drum trigger interface out there has inputs for all the elements of a drum kit when all I need is the kick. Also, I want to be able to you load my own samples, at industry standard bit depth and sample rate. There are some units that will do it but the price point is too high for what I need it to do as I would be paying for everything else it does too. What I am looking to build is a black box that has trigger in, analogue line level out and a few pots for sensitivity control etc. I am very surprised there is not something like this on the market already but there isn't. I have searched hi and low. If there was I would just buy it haha!


    Ok enough of the complaining....


    I have a Roland kick trigger that outputs about a volt when I hit the drum. This signal needs to initiate whatever process required to output a 24bit 48kHz sample of a kick drum stored on an SD card (or other R/W storage media) in less than 9ms.


    I am an intermediate electronics technician and stronger in analogue than digital. I am familiar with digital audio, and am very experienced in building circuits for practical use. (Soldering, PCB layout and manufacturing). My main problem is figuring out how the SD card will be triggered to send the digital data and how the DAC chip will handle the incoming data.


    I have already implemented a comparator type circuit to deal with all the sensitivity parameters. That way, the digital part is only dealing with a high or low.


    High = trigger


    Low = do nothing


    Furthermore, I only require to trigger one sample over and over again. There will be only one sample on the card so that should make things easier.


    If there is anyone out there that can give me some pointers that would be just great.

    Thanks!

    JM
     
  2. cornishlad

    Member

    Jul 31, 2013
    196
    25
    Hi..There may be electronically able folk reading you query who are not familiar with drum sound triggering and so may not understand the question.

    Is this the scenario ? You have a recorded sample of a bass drum sound (bummmph) in some audio format - possible .wav - on an SD card.

    You have a triggering device on your bass drum that gives a strong pulse that you want to initiate playback of that sound when the bass drum is played ? And that is what you want to build..

    If not ...explain !
     
  3. rogs

    Active Member

    Aug 28, 2009
    279
    37
    If you can understand that 24 bit sampling is massive overkill for a kick drum sample - (and as you're experienced in analogue, I'm sure you can:) ) then you can make this project a lot simpler by using analogue processing to realise the full potential of companded 8 bit sampling.

    By using compressed (and all kick drum samples are compressed!) 8 bit samples, recorded at, say, 48KHz sampling (or even higher - not really necessary though!) you can store those on normal 8 bit EPROM ics, and use a simple CMOS counter arrangement to address the data, together with an 8 bit DAC , (like the TLC7524) and an SA571 expander, to make a simple kick drum generator with an output quality that might surprise you.

    Would allow the whole project to be made from simple logic, using through hole components, and not needing any microprocessor control.

    You would need to find a way to convert your wav samples to a .bin file, to be able to get your data into the EPROM, and you would need a way to program the EPROM.

    This is the method employed by the great drum machines of the 80s (LinnDrum, Simmons etc..) and they can sound pretty good.

    It's an old fashioned way of doing it of course, but it's much simpler -especially for a 'one off' unit.

    All depends whether you believe that 8 bit kick drum sampling can be made to sound good enough?.....:)
     
    Last edited: Oct 16, 2013
  4. Joster

    Thread Starter Member

    Jun 12, 2013
    95
    0
    Thanks for the replies!

    This is very informative for me and gives me alot to ponder. I really appreciate your insight and will be trying this out for sure. Didn't think of compressing the sample down.

    Can this all be done in under 9ms?
     
  5. rogs

    Active Member

    Aug 28, 2009
    279
    37
    Well, not the whole thing, obviously (the sample is going to be a lot longer than that!), but can it be triggered in under 9ms, then yes, easily.

    (You simply need to start a counter with your trigger pulse).
     
  6. Joster

    Thread Starter Member

    Jun 12, 2013
    95
    0
    Hello again!


    I want to thank you for giving me the information I needed to move this project forward. I have since given much though and research into the details and have reached some new road blocks, just gaps in my knowledge.


    It's easiest for me to layout the process as I see it and then insert the questions accordingly


    • - Trigger signal is generated from drummer hitting drum (about 1V)

    1. - Comparator IC (LT1016) http://www.linear.com/product/LT1016 is used for both sensitivity control (external ajustable voltage divider) and to deliver a logic 1 to a latch (MC14043B) (the supply to the LT1016 will be about 7 - 8V to be sure when triggered the output is a logic 1 or 5V)

    1. - The MC14043B http://pdf.datasheetcatalog.com/datasheet/motorola/MC14044BCP.pdf latch will deliver a clock signal to the 13 bit counter
    Clock Signal and Frequency:


    555 timer setup https://sites.google.com/site/derekmolloyee223/experiments/clock-generator-circuits or crystal oscillator?
    What normally generates the clock signal in most audio ADC's and DAC's?
    I suppose the counter must run at the same sample rate as my sample, correct?
    Is it ok to control the counter simply by stopping and starting the clock signal?


    Counter:


    I can't seem to find a “13 bit EPROM Address Counter” maybe I'm missing something. You would think there would be some kind of IC that would handle this?
    Failing that, it looks like I will need to build my own by cascading two 74HC590's http://www.nxp.com/documents/data_sheet/74HC590.pdf together



    • - When the counter reaches 1111111111111 it will reset itself via a 13 input NAND gate and also reset the latch thus disconnecting the clock signal from the counter.

    • - Therefore the counter is back at zero and the comparator is ready for the next pulse.

      - Provided my thinking is correct about the frequency of the counter, as the data is being addressed it can be delivered to an R2R DAC, fed tru a voltage buffer, and finally to some kind of line level amp.


    I do not yet understand the need for the TLC7524C or the SA571 Expander chip. I'm sure I'm missing something here.


    Anyway, this is where I'm at with it and hopefully I'm going in the right direction.


    Thanks again!


    Joe
     
  7. Joster

    Thread Starter Member

    Jun 12, 2013
    95
    0
    Also, I suppose it would be better to design the counter with an enable input and control it with that rather than connecting and disconnecting the clock signal, correct?

    Cheers
     
  8. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    Why not buy a cheap drum sensor with MIDI output, and plug that into a cheap MIDI drum sound module?
     
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