Strange preset behavior

  • kostia

    kostia - 2010-02-26

    I use v0.4.2, but it started before, first was Naranja One, and now even more - Metal Tone, True Heavy-3 and others.
    When I use one of those presets, it feels like hard noise gate is allways on. I turn off all effects, but hard gate is still working. What's wrong with them?
    How can I controll it? My guitar is a bit noisy, and I would like to use it… WHEN I NEED it :) in my bank pressets.
    Thank you for this great amp :)

  • Josep Andreu

    Josep Andreu - 2010-02-26


    You right, in 0.4.2 we put an (invisible) Limiter at the end of the chain,  unfortunatelly we release 0.4.2 with a bug on this limiter parameters, the limiter is necessary in order to safe your speakers, because most of the effects can amplify or deamplify  a lot the signal, in 0.3.0 if you turn off some effects in some presets you can have bad surprises.  That is is fixed with this limiter in 0.4.2 but  we mistake on some parameters.

    If you know to compile please get our git version that has a lot of new features, of course is a development version, but they have a lot of bug fixes too, in fact this end Limiter needs even more revision, but some things are fixed.

    In order to compile the git version, please read the instructions on the Donload page in our website.



  • Transmogrifox

    Transmogrifox - 2010-02-26

    With high gain settings like Naranja One and Metal Tone (really high gain) the problem has nothing to do with rakarrack.  Here is how I convinced myself this is true:
    1) Use soft synth like Zynaddsubfx that does not interface w/ sound card -> no problems.
    2) I tried my recorded *clean* guitar from the same jam session when I had the troubles.  Using a media player (audacious), I played the clean guitar through rakarrack --> No problems….other than some of the noise you would expect from high gain distortion.

    Thanks for your input.  I also have been noticing this problem with a few presets.  Acoustic Sparkle also has this problem to a certain degree.

    Here's the problem:  Most sound cards have a certain amount of crosstalk between input and output.  If you have two guitar cables (in/out) in close proximity, this makes it even worse.  I have a theory the problem is legitimate feedback from input to output.  What I mean is, the cross-talk on the sound card along with the incredibly high gain within rakarrack is enough to make the sound card self-oscillate.

    Second, the noise gate must always be placed on the INPUT of distortion.  The distortion effect does not generate noise.  It amplifies the noise that is already there.  For example, on Metal Tone, the amplification factor is over 10,000.  So any noise from your guitar is 10,000 times as loud. 

    Since there is always a lag between our work and releases, and distro packaging, here are some easy work-arounds to help you modify your presets while we are working on improving them.
    You can make the preset useful by reducing the "Drive" level on the distortions until there is a good balance between "enough drive" and "I can tolerate the noise".  Then put a Noise Gate in  FRONT of the distortion.  Adjust the threshold and range until you hear the noise, then raise the threshold just until the noise is gone.  Save the preset and send us a copy so we can incorporate it into the default bank of the next release :)

    You said something about "hard noise gate".  I'm not sure exactly what you mean, but there is a hard limiter on the output that keeps the output level from getting too high.  Limiting starts at -3dB (about 70%).  Upon more reflection, it should probably be at -1dB.  In either case, you can prevent it from having any effect by reducing the "level" controls on the last distortion in line to bring the output to within range.

    Finally, "preset bugs" are not hard coded bugs, so you can fix them easily for your self like this:
    Move sliders around on the FX until the preset behaves properly.
    Right click on the preset name in the bank and a message will pop up asking if you want to overwrite the preset.  Click Yes, and your preset is fixed :).

  • kostia

    kostia - 2010-02-26

    Oh! so many words… :)

    If my output (or input) level is to high, then why this limiter keeps working when ALL effects turned off?
    Do you plan to add controlls to it? I like it, but I want to controll it :)

    As I see your latest release on SourceForge is 0.4.2 But I will try your latest, from git.
    Hope it won't break ;)

  • kostia

    kostia - 2010-02-26

    And more about presets: I don't use insane drive, I reduce it ewerywhere. But some clean "accoustic" presets gives more noise then "super-duper-black-metall-horror" presets :)
    Well maybe my guitar is to… to?

  • Transmogrifox

    Transmogrifox - 2010-02-27

    "If my output (or input) level is to high, then why this limiter keeps working when ALL effects turned off?
    Do you plan to add controlls to it? I like it, but I want to controll it :)"

    I suppose we could disable it with all FX bypassed, but then why?  Then you just use master bypass for Rakarrack and then Rakarrack just gives jack back what it gets.  The output limiter uses the exact same code as Compressor.  If you want to control it, then put a Compressor in the chain of FX.  When we have perfected this hard-coded limiter, it will be out of your way entirely unless the output level exceeds industry standard limits.

    I think you may misunderstand the reason for the hard-coded limiter.  The standard audio data format is 32-bit floating point bounded between -1.0 and 1.0.  If the signal gets outside of that range, something further down the line will clip - it may be the next jack effect, may be the sound card, but it is likely that unless that device does what Rakarrack does, it will do so in a very ugly way.  Currently, if the volume bars on the output are all green, the limiter is inactive…it doesn't kick in until somewhere in the orange.  If you are driving it that hard, you need to turn it down.

    The hard coded limiter is meant to catch signals at levels where they are distorting in an ugly way in your sound card and clamping them to within the +/-1.0 range (and this is a standard).

    The fact that it catches the signal too soon before this level is a bug, but this will be fixed, and I don't think it should be any more user adjustable than the power supply voltage on your sound card.

    "Acoustic Sparkle" is the preset that comes to mind about getting more noise than high gain distortion FX.  I added a lot of gain at high frequencies to use the distortion effect as a harmonic exciter.  Now in git repository, we have added a proper exciter for this purpose, and it does not require so much gain to get a nice acoustic sparkle…so this preset will change when I get around to it :).  Some other clean presets have a certain amount of distortion added as harmonic exciters, or to increase "presence".  Just reduce drive on the distortion if the noise is too much.

    Please submit presets if you fix some or make some nice ones you like.

    About git, and "Hope it won't break" :-)  Well…we try really hard not to push anything that is broken, and even more we don't push anything that breaks the whole program.  If we find any bad bugs, we fix them fast.

    It sounds like you have a really noisey guitar, sound card, or something…  If you plug directly into a sound card without either a preamp or guitar with active electronics, there will be a lot of noise.  A quiet preamp will take the high impedance guitar input, and offer power to drive the low impedance sound card.  This will improve noise drastically.

    I hope that is helpful.  I expect you will enjoy what is current in git.   We have added a lot of new FX since releasing 0.4.2…but we have not done any work on the presets, so it's the same there :)  Just today I stabilized an IR convolver (basically uses measured amp cabinet impulse responses to emulate an amp stack).  What I mean by "stable" is it is useable, but still a little quirky :)

  • Transmogrifox

    Transmogrifox - 2010-02-27

    By the way, thanks for feedback. This helps us make design decisions.

    I should not say we won't let the user control the output limiter, but more that I personally am not in favor of it at the moment.  It is a hard design decision…just because it's purpose is to stay out of your way, not like an effect….and since the compressor is the same block of code, you can configure it as a limiter

    Would you be interested in having a "limiter" module added to the effects line-up?  This would basically be like having two compressors available.  One for regular compression, one for hard limiting.

  • Transmogrifox

    Transmogrifox - 2010-02-27

    …and one more.  I thought I would announce I have fixed this problem in git and thoroughly tested the results using Audacity to generate test tones, and observing the limit threshold and reaction.

    I ended up using -1dB as the threshold (+/-0.9).  This will keep it from ever clipping a program like Ardour or Audacity…unless you set the output gain up enough to do this…I better look into that more.

    Anyway, I found a bad bug, and maybe what you were experiencing?  When the input level was really really high, like at 50dB, the limiter "latches up".  Basically the number gets so huge, that it takes several minutes of silence to fully release.  I set some code to prevent it from latching up like this.

    As it is now, you can really drive it hard before you get much distortion on the output.  Now it is out of your way.  If it limits, you have some levels set too high and you need to back off.  If the level never gets hotter than -1dB, the limiter never even kicks in.  After -1 db, it has a ratio of 15:1, and after that it just hard clips the signal…so you can feed it about 15dB before it hard clips. In reality, this is closer to 14dB…but all the same…


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