Filtering adc and dac for live-gigs. help me.


    Feb 09 2006 | 2:53 am
    guys, i have a gig coming up, and I do not want the dac to go above 1. I am planning to filter any hz that does not need to be there. have a mic and some synth-like stuff connected to the interface. Should I cut below 10hz and above ?khz. Low=10hz High=?khz ??? I do not have a clue.
    Any advice would greatly appriciated.
    snif

    • Feb 09 2006 | 11:06 am
      Highcut won't help you much, since high frequencies have little energy compared to low ones. 10hz is really low, and not even perceived as a tone but LFO (good for modulation but not something you want as a frequency in a music signal). You can easily cut below 40 or maybe even 60. After your lowcut filter you should insert a limiter at the end stage. Synths typically don't have a very dynamic output, but for your mic source, an additional compressor is probably useful.
      T_
    • Feb 09 2006 | 1:16 pm
      It's difficult to say how you should treat the sound from the microphone without knowing what kind if sound you are trying to capture and what you want to do with that sound in Max. Some people would say filter out any frequencies that are not present in the source material others would filter off the very low end with a hi-pass filter. A notch filter might be useful to reduce feedback if this is an issue. With out a doubt you should test your entire setup before the gig.
      to keep the sound from going over 1 (or under -1 this is called clipping) you can use a limiter. You can make a very basic hard limiter by using the clip~ object or a better solution may be to use the new omx.PeakLim~ object that comes with Max. Check out the OMX Tutorials folder!
      good luck,
      john.
    • Feb 11 2006 | 3:39 am
      Quote: thijskoerselman@gmail wrote on Thu, 09 February 2006 20:06 ----------------------------------------------------
      > compressor is probably useful.
      thx, mate. I have used the limiter at the end and it is working like a charm. Will you please recommend me any cpu-freindly compresser, or highpass filters ?
    • Feb 11 2006 | 3:45 am
      Quote: Leafcutter John wrote on Thu, 09 February 2006 22:16 ---------------------------------------------------- > It's difficult to say how you should treat the sound from the microphone without knowing what kind if sound you are trying to capture and what you want to do with that sound in Max.
      Exactly. You really know your stuff.
      >others would filter off the very low end with a hi-pass filter. A notch filter might be useful to reduce feedback if this is an issue.
      Will you please tell me where I could find the notch filter is ?? As mate above said, I am planning to cutoff around 10-60HZ. I checked the tutorials and msp externals, but could not find any notch filter or highpass filter. If you know any cpu-friendly highpass filter, please inform me. I really appriciate for your great advice.
      > to keep the sound from going over 1 (or under -1 this is called clipping) you can use a limiter. You can make a very basic hard limiter by using the clip~ object or a better solution may be to use the new omx.PeakLim~ object that comes with Max. Check out the OMX Tutorials folder!
      Thank you so much with the omx.PeakLim. I would not have come up with this if it wasn't for you. And it is working like a charm. Thank you so much with your big help, john. It's always nice to see you in the forum+mailing list. > > good luck, >
      thx ----------------------------------------------------
    • Feb 11 2006 | 6:36 am
      I'd try using either biquad~ or cascade~, with a filtergraph feeding it the desired parameters. If you look at the help files and/or the tutorials for those two filter objects (sorry, not on the right computer now to double check for you,) there should be a sample patch with a menu object connected that feeds sets up filter object for a variety of different responses: high pass, low pass band pass, band reject (notch), etc.
      Cheers,
      *V*I*R*G*O*
    • Feb 11 2006 | 1:51 pm
      You could use the cascade~ like this....