Delay modulation changed from subtle to ridiculous phaser/flanger sound

    Title says it all. Modulation was behaving as normal for the analog delay, all of the sudden it's now a ridiculous phaser/flanger type of sound that's overpowering. Can't seem to make it go back to what it was. Any ideas?

    I know what it is now. I had set my output for the Main output to Mono. When I do that, I hear the problem. I am running the left main output into the return of a tube amp.


    Does the same thing if I run the monitor output into the return because the monitor output is mono by design.


    Now why would it do that? Is there some kind of incorrect summing of the left and right channels when setting to mono?

    I had the same problem. If I remember correctly, the reason for this is that the modulation is in different phase in L and R, and when you mono it, it will result a chorus-kind of effect. I wish that the modulation would be in the same phase so it would stay a vibrato regardless of whether it's mono or stereo.

    sambrox wrote:
    "Well, the modulation parameter is there to create movement across the stereo field, so it would actually be redundant in mono anyway."


    No you are misinformed modulation is produced by using an LFO table of coefficients to either shift pitch or delay line times in relationship to the desired LFO waveform used to create the offset lookup table .
    This may be used in such a manor as to yield a stereo panning effect.


    That point aside.


    When the Output = L+R there should not be any phase cancellation if proper input signal phase has been maintained.


    A chorus in stereo is a chorus in mono...


    If it's anything else something has affected the Input signals phase proceeding the application of the Chorus algorithm.


    Let me clarify ... Ofcoarse now if the code were written to use a sinewave positive going on the Right and negative going on the left to make a dramatic stereo image. There would be a problem when summed .... Still that would be flawed logic by the programmer.


    Instead for this example Sample_Blocksize=256 then use a
    2×(Sample_Blocksize) that constitutes
    (Input_Blocksize_R)(Input_Blocksize_L) applying the modulation waveform over the entire 512 word buffer which creates stereo modulation.


    If a user decides to switch the output to mono a programming Mono_Stereo_Flag should have been used to reflect the desired output mode chosen throught the entire effects routing chain so when applicable the code uses
    a different processing approach as in this case using (Single Blocksize Dry buffer) +( Single Blocksize Modulated buffer) instead of dual to produce a mono chorus with the identical characteristics of its stereo counter part.
    You can produce a single blocksize modulated buffer easily by taking every other sample across the double sized buffer this technique is called Downsampling.


    If the stereo buffer was 512 words take every other sample to produced a 256 word buffer.
    Accumulate [ (Dry Buffer ) + (256 downsampled modulated buffer)] = Mono 256 word buffer output which is copied to both Right and Left Blocksize output buffers respectively.


    Based on this example using a Sample_Blocksize =256


    Simply put you copy the same 256 word final effects mix output buffer to both left and right output streams. Maintains phase in Mono

    Yes, I've noticed this too. I'm running the KPA at home primarily mono through a DXR10, and as soon as I go over 0.1 on the modulation settings on the delay it all sounds like I have a deep chorus switched on the delay trails.
    But this is not noticeable when running in stereo through my studio speakers...
    So all my delays have 0.1 modulation. :whistling:

    No idea what you just wrote, but Christoph Kemper has stated that the delay modulation is actually a vibrato effect with one side microshifting in one direction whilst the other side is shifting in the other, if I recall correctly. This is what generates the perceived movement in the stereo field. Summed to mono, they would sound like a chorus/flanger/phaser (ie modulation) effect, no...?

    Quote from sambrox


    No idea what you just wrote, but Christoph Kemper has stated that the delay modulation is actually a vibrato effect with one side microshifting in one direction whilst the other side is shifting in the other, if I recall correctly. This is what generates the perceived movement in the stereo field. Summed to mono, they would sound like a chorus/flanger/phaser (ie modulation) effect, no...?


    Support answered my ticket and said that the effect I'm hearing is normal behavior and it's been that way from the beginning. I beg to differ that it's normal.


    It should sound like a mono chorus. Not a phasey-flangey mess. In the Axe-Fx, Helix, POD HD, M13, Strymon Timeline, El Capistan, GT-100....whatever, when you sum a modulated delay into mono, the modulation portion sounds like a mono chorus type effect.


    I'm going to have to record a short clip and post for example because this is definitely not what it's supposed to sound like.

    Quote from Karl_Houseknecht

    Support answered my ticket and said that the effect I'm hearing is normal behavior and it's been that way from the beginning. I beg to differ that it's normal.


    It should sound like a mono chorus. Not a phasey-flangey mess. In the Axe-Fx, Helix, POD HD, M13, Strymon Timeline, El Capistan, GT-100....whatever, when you sum a modulated delay into mono, the modulation portion sounds like a mono chorus type effect.


    I'm going to have to record a short clip and post for example because this is definitely not what it's supposed to sound like.


    Yes, please, that would be very helpful.

    Sambrox,


    You are correct in assuming that indeed there should be no perceived difference between a mono chorus and stereo.
    What you have described that Mr. Kemper said
    Tells me that there are two modulators involved. Instead of one modulation wave table applied spanning the Left and Right ouputs.


    In the case of Mr. Kemper modulation approach when summed together you will have phase combing artifacts occuring.
    The comb effect happens in reverb but not quite as pronounced and with reverb is a natural occurence in the wild.
    I
    agree with you that code compensation should be made for those who expect what has been the industry norm for guitar effects for ages
    Mr.Kempers first claim to fame before this wonderful stroke of genius was
    The ACCESS VIRUS as in Keyboard synthesis...


    So although the algorithm for profiling has been aimed at the Guitar Amplifier Market
    The operating system has been developed essentially from a Keyboard Players prospective. That's why the things you and every other guitar player expect such as allowing this mono phasing issue to even exist and call it normal or the inability to assign any parameter to the external expression port are behind the Guitar effects industry norm.


    We can only hope when 4.0 appears the operating system starts to approach par in many respects.


    It wasn't too long ago they expected us to use NRPN messages for external Midi Control in most of not all Guitar Players said WTF !


    Thank goodness they at least offered a spackling of MCC to work with.


    So the good is the KPA delivers great amplification!


    The rest is still way behind in the basic professional external controls and effects implementation that guitarist consider a given.


    Ofcoarse the in some of the KPA " Enlightened " types on this blog would never admit that this wonderful thing has some drawbacks that from its conception should have had implemented from day one instead of still doing catch up 5+ years later.


    And before you say it YesTrue Cab is a step forward.
    Great nice innovative... It would even be more awesome if everything else was caught up.


    And then we have "Morphing"(tm)


    I'll say this much .... and this goes out for all the players reading this.


    Think about this....


    If the KPA could recall presets without any dropouts instamtly most of us would never need morphing.


    Here's one more ...
    How fast do you think you can move a pedal with your foot from heal to tow in milliseconds.


    If your very nimble possibly 100ms ?


    That buys a lot of preset changing time does it not.


    But it's seamless?


    This is one of the greatest feats of marketing magic I have ever witness.
    The Marketing people at Kemper have brilliantly created a way to divert the users attention away from the preset recall latency issue while promoting this as some great new feature.


    How about fixing all the basic issues like instant preset recall then perhaps this morphing diversion ( although some may have a use for it) wouldn't have been needed in the first place.


    While your at it how about improving the power on time to play annoyance too.


    Ok I'm done ragging... I'll put on my bullet proof vest and helmet for the incoming onslot.


    I love the KPA and do not want to consider any other preamp ...


    I like every one else await the anticipated release of 4.0 which hopefully addresses 95% of what myself and other users with respect to Midi Control , External Control Port assignments and Effect upgrades/fixes along with industry standard routing options as well as User Interface improvements.


    I beg you.... Please
    I'd like to eat my last meal before you kill me.
    Peace to all Kemperanians!

    IMHO this has probably to do with the modulation control itself, ideally rate and modulation depth should be controlled separately but as it stands what's probably happening us that the rate rises to a more or less fixed frequency from very low values, making the effect too pronounced even at low modulation depths, which are the actual principle of phasers and then flangers. Crank it up a notch and you'll get into chorus territory, but then the effect is a bit over the top for my taste since there's no separate rate control as I've mentioned.