Snare Drum decay too long (v1.02) [SOLVED]

Discuss Nava construction and related issues
  • Hi there,

    Could you probe ENV1, ENV2, ENV3 and IC36 between pin7 and 14?
    It seems that ENV1 does not pitch bend the VCOs correctly.
    Best regards,
    e-licktronic
  • (HI KlangGenerator... making my thoughts public - instead of PM)

    My guess is, your problem is in any of the two OSC AmpEnvs - ENV2 / ENV3. They both should have a Decay time of about 100ms - but one of yours is way to long! So after 100ms you should hear just the Noise portion.

    I've attached some snapshots of the ENV's...
    also scope ENV2/3 at C79/C70 - those are the 'real' Envelopes - also pay attention to the curve below 0,5V thats where the coresponding AMP-Transistors Q50/Q51 should close (BE forward Bias?)


    ENV1-Pitch
    Image

    ENV2
    Image

    ENV2 - C79
    Image

    ENV3
    Image

    ENV3 - C70
    Image
  • btw. I would be very much interessed in following scoped curves - if you (or someone else) can get them:
    - BD-NoiseDecay / at C12
    - BD-PitchDecay / at IC12A Output
    - SD-PitchAmount / at IC35A non-inv-Input
    I'm currently preparing the enclosure design for my Expansion-Kit that shalls display original 909 values of the mods.
  • Ok, here are a few curves...

    SD env1

    Image

    SD env2

    Image

    SD env3

    Image

    SD env4

    Image
  • Finished a second v1.02 Nava a couple of days ago. Again all instruments fine except too long snare vco decay. Tried and checked out everything, no chance.
  • It seems that ENV3 is too long.
    You can replace C83 value by 82nF or 68nF.
    Try it and let me know ;)
    Best regards,
    e-licktronic
  • e-licktronic wrote:It seems that ENV3 is too long.
    You can replace C83 value by 82nF or 68nF.
    Try it and let me know ;)
    Thanks Vincent. I tried this, even with 56nf no change. And to be honest, I would prefer to find the reason for this bug without changing the original values. It's really strange that I am having the same problem with two Navas. All components definately have correct values, I checked a thousand times, replaced all transistors, ICs. Even checked all(!) traces with the help of the original schematics. I can't find the reason. I'm very interested to know if other builders experience the same with the new version...
  • My snare also has more of a tom sound with the snappy/noise turned down. KlangGenerator did you ever find a fix for this?
  • I knew that this must be a v1.02 bug. I have spent countless hours on my two Nava's so far, but up to now I am not able to find the reason for this. Still working on it. If I find something I'll let you know...