interesting audio design needs

Discussion in 'The Projects Forum' started by gzero, Dec 12, 2009.

  1. gzero

    Thread Starter New Member

    Dec 12, 2009
    3
    0
    Hi guys,
    Interesting problem for you.
    I wanted to know if anyone could point me in the right direction.
    I have a specialized computer audio application and need to be able to either double or triple the frequency of the output of the soundcard, which would range from 20hz to 192khz and then pump it out to headphones. This would give me an effective range of 40hz to 384khz or 60hz to 576khz. I wasn't able to find anything online that looked like it would work, hoping you guys could help.
    Thanks,
    gzero
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    I don't think you are actually going to hear much of that increased frequency range unless you have bat genes. Very few people can heat up to 20 KHz, which is the accepted upper limit of human hearing. Your headphones will stop doing much at about that point, too.

    One way to try to expand the range of frequencies might be to half wave rectify the sound output and use the DC pulsating voltage to drive the input of a VCO (voltage controlled oscillator). Most of those that work in the audio frequencies give up at 100 KHz, but you can always experiment.
     
  3. gzero

    Thread Starter New Member

    Dec 12, 2009
    3
    0
    Beenthere,
    Appreciate the response.
    I understand about the limits of human hearing being approximatly 20-20khz in most people. I am doing some experiments with the higher frequencies, even if they are not audibly heard with the ears. Because of the need for frequencies greater than 192khz, I assume the design will need to be open state, aka tube aka analog as the highest frequency DAC that I know of cuts off there. I have seen some digital designs for frequency mulipliers, but without a DAC that supports the corresponding high frequency it is worthless.

    Thanks,
    gzero
     
  4. ifixit

    Distinguished Member

    Nov 20, 2008
    638
    108
    Would this work for you?...
    1. Record your standard speed signal using a sound card. It can save the digitized signal in a ".wav" file.
    2. You'll then need to read the .wav file out to a high speed DAC at 2 or 3 times the usual rate.
    3. The output DAC sample rate needs to be at least 1.152Msps. There are lots of DACs faster than this.
    4. Google: dac high speed <or> dac high speed PCI
    Good Luck
     
  5. gzero

    Thread Starter New Member

    Dec 12, 2009
    3
    0
    Thanks ifixit,
    Its a brilliantly simple idea, much simpler than I thought it was going to have to be.
    I think that should work assuming I can specify the high speed dac as the audio output device, and I'm sure accerated playback is supported in some readily available software. I will do some more research, but that looks like the ticket, hopefully I can find one thats affordable.

    Thanks,
    Gzero
     
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