Conference napalm::commusic_v1

1320.0. "Homemade sampler completed" by EKLV00::COLLINS (STEVE) Tue Apr 19 1988 12:58

  Hi,

   I thought  some of you guys might  be interested in a project  that I 
   recently completed . It's a homemade Echo/sampler .
   
   First a little background ...
   I work as a Technician here in the Clonmel  plant in Ireland . I like
   to design and build things in my spare time ,to keep the brain alive.
   I've always had an interest in electronic  music and synthesisers and 
   about a year and a half ago I started work on an idea I'd had ,to put 
   together an A/D a D/A  and some memory . This was to see what kind of
   quality  I could  get out of such a system because I had no practical
   feel for what it would sound like  or what capabilities I may be able
   to  stretch it to . I  was reading  anything I  could get my hands on
   about analogue to digital conversion ,echo chambers etc.
 
        A year and a half later I have a working machine which  I'm very 
   proud of . It's taken a lot of perseverence and a  lot of painstaking 
   constuction  and developement work . But  I now know alot more than I
   did  when I  started and am using that knowledge on the MK2 version .
   Which I've just started and am very excited about .

   Anyway here's the spec for the mark one version ...

   Linear A/D 12 bit conversion .(switchable to 8bits to hear how it sounded)
   Sampling rate switchable @ 95,48,32,24 khz .
   Memory 64k x 12
   Four modes of operation ( Echo , Sample , Play , Refresh )
   Sample start and end point editing .
   continuous or one shot mode .
   Usual mix and delay controls in echo mode .
   External trigger input .
   Built in monitor amp .
   Mic and line level inputs .

   Here's some of the limitations ...

   Monophonic only .
   No midi .
   Input and output filters fixed @20khz ,not variable .
   Sample rate not continuously variable .

   Probably one of the best features of this unit is the sample editing.
   There  are just two  continously  variable knobs . One sets the start
   point  another  sets the  end point . I  did this  by  converting the 
   voltages on the  pots with  A/D's and using these to preset and limit 
   the memory address counters .It works very well and enables you to do 
   things  like splicing  two  samples together  ( even  two samples  at 
   different speeds) .

   Before anyone asks this is not something everyone can  put together .
   This is because I used parts I had myself which would not necessarily 
   be  the most readily  available or cheapest . For example I  used six 
   A/D's @40 pounds each .

   The  MK2 version will feature 4 independent memory banks . It will be
   more  of  a sampling drum machine and will allow continuusly variable
   sample rate on each bank . It will allow the same sample to be loaded 
   into each  bank and then each played back at slightly different rates 
   all from  a single trigger . I'm hoping  this can be used  for 4 note 
   tuned bass samples . In echo mode it will give  4 copies of the input 
   signal summed together ,with independent variable delay between each.
   I'm hoping this will give a  more or less realistic reverb . Sampling 
   rate will be variable between 30khz and 100khz and resolution will be 
   8 bit with compansion ,memory will be 256k x 8 .

   I'll keep you posted 
   Steve ..

    Well, congratulations. YOu finished it.
    In 83,84 I was preparing to build a simple 2 second echo, but the
    movers that brought me to Massachusetts lost the box with all my
    electronic parts, tools, and some instruemnts, so I took the money
    and bought a DOD digitech RDS 1900, which turned out to be almost
    identical in parts and connection to my design.
    I am interested in music on general purpose computers, and would
    not now build a specialized device, but I understand why you did
    and find it fascinating.
    Good luck!
    Tom

    How was the signal to noise ratio?
    
    I built a digital delay last year with 8-bit converters and 8K bytes
    memory.
    
    It was ridiculously noisy.  Since I had fancy test equipment at
    my disposal at the time, I actually measured the s/n.  Gee, Virginia,
    is 22 dB good?
    
    I didn't have my analog components well shielded, nor was the power
    well conditioned.
    
    Steph
    
    

    
    	Steve,
    
    A friend of mine did much the same thing! His was 12 bit also, and
    I thought he was *crazy* to wire wrapp all those connections. His
    archetecture was a little different, I recall being able to set
    3 different time delays for the monophonic echo processing - that
    was so the echo could be composed of reflections inharmonically
    related. Setting the time delays was a pain, because you had to
    throw this switch and wait for it to count up to the value you wanted.
    Of course, once the power was removed = settings gone!
    
    Advice for future project considerable factors? Memory - saves your
    past settings through power on/off cycles...
    
    His next project is also similar to yours (Too bad this guy works
    for Raytheon now! :') ) - he wants to build a drum sampler. He wants
    to be able to write and recall his samples from a disk memory. Sounds
    super, but all_those_wire_wrapps! (guess *I* never did an 11/70
    backplane...)
    
    You might try finding a computer with a parallel output port, to
    do the data transfer necessary to store and retrieve samples captured
    by your device.
    
    Good Luck and remember, your not alone in the hardware hacker realm!
    (How do you think it "all" started, anyway!?!?)
    
    	Joe Jas
    

    
    Re: 2
    
    I measured the signal to noise by feeding in a 1khz sinewave and
    using a spectrum analyser at the output .There is a difference of
    70db between the signals @1khz and 10khz .(This was taken @96khz
    sampling frequency)
    
    The unit sounds good .If you make sure the input signal is always
    just clipping then you only hear "noise" in the output if you listen
    for it . 

    Steve..