RME Filter tuning

[soulstar108]

Hello, I've got a brand new Voyager RME and just want to know if it's normal that the filter is unable to be tuned to the keyboard ? I want to play eg a major scale, or have the filter oscillate and track the oscillators. At the moment with the KB Cont Amnt maxed I'm only getting a Major 7th interval instead of an octave.
Thanks

[Voltor07]

Even though the filter self-oscillates, it is not tuned to the keyboard, nor is there a way to tune it to the keyboard.

[c7sus]

ten characters

[thealien666]

Hello, I've got a brand new Voyager RME and just want to know if it's normal that the filter is unable to be tuned to the keyboard ? I want to play eg a major scale, or have the filter oscillate and track the oscillators. At the moment with the KB Cont Amnt maxed I'm only getting a Major 7th interval instead of an octave.
Thanks

I'm sorry to say that it looks like you've got a miscalibrated Voyager RME. All the Voyagers (including Old School) have filters that should track the keyboard over at least 2 octaves before going off scale a bit.

If that's not the case, the filter keyboard tracking needs to be re-calibrated.

Note: I've seen Voyagers that could only track accurately over 1.5 octaves and not much more right out of the box (it was the case on mine) but after having been repaired and fixed for something else entirely, the techs that did the repairs had also re-calibrated the whole analog board (brand new replacement board), and after that the filters tracked the keyboard correctly over almost 2.5 octaves.

[c7sus]

Maybe I'm misunderstanding the op.

Can you give an example of what you are describing? I was able to track the pitch with the filter but not at intervals, and was under the impression that the only way to do this is with the pitch CV output patched through something like a CP-251 to adjust offset and then back into the filter CV input.

Or are we talking about a function of the Pedal/On buss?

Thanks.

Is there a preset that demonstrates this effect better than most?

[thealien666]

Close all outputs in the mixer, flip the filter "Mode" switch to "Dual lowpass" then set the filter resonance to self oscillation (maximum), set the spacing knob so that both filters are in sync, place the "Cutoff" knob at 11 o'clock, finally turn the "KB Cont Amount" knob close to maximum (it varies a bit from unit to unit), the filters cutoff should track the keys 100% properly, and play scaled notes over at least 2 octaves (or even more) before going off scale a bit, if the Voyager has been correctly calibrated.

Of course, you'll need to tweak the cutoff knob to tune the filter to a reference (i.e. playing an A key and try getting a 440 Hz), but the intervals between the notes should be correct.

[c7sus]

Thank you for clarifying that. I learn something new every day hanging around here.

[thealien666]

Thank you for clarifying that. I learn something new every day hanging around here.

You're welcome. And me too, I'm still learning new things almost every day coming here !

[Portamental]

the filters cutoff should track the keys 100% properly

Nope. Not to me. the relationship between Cut Off frequency, the note played, and the keyboard tracking is more complex than that. The resonance happens at the cut-off point of the 24 db slope, which is different than the frequency of the note played. The keyboard tracking is a factor that will help in modifying the way the filter sounds but not in total relationship with the key played. Upon reaching full resonance, all bets are off.

Turn the keyboard tracking all the way up, Cut off at noon, play a note. From there, turn cut-off knob either way. The frequency a which the filter oscillates changes.

FWIW, and in my opinion, Voltor said it best.

[thealien666]

the filters cutoff should track the keys 100% properly

Nope. Not to me. the relationship between Cut Off frequency, the note played, and the keyboard tracking is more complex than that. The resonance happens at the cut-off point of the 24 db slope, which is different than the frequency of the note played. The keyboard tracking is a factor that will help in modifying the way the filter sounds but not in total relationship with the key played.

Turn the keyboard tracking all the way up, Cut off at noon, play a note. From there, turn cut-off knob either way. The frequency a which the filter oscillates changes.

FWIW, and in my opionion, Voltor said it best.

Reminder: we're talking about a self-oscillating filter that acts as a stand alone sound source. Not the relationship between a resonant filter and a signal passed thru it...

Of course, it's understood that the cutoff knob will offset the filters frequency in relation to the keys played (or if you will, transpose the whole keyboard). But it should do so equally for all the keys. And most importantly, the voltage control coming from the keyboard when the "KB Control Amount" knob is set to maximum should in turn offset the cutoff frequency to increase it by a factor of the twelfth root of two (approximately 1.05946309435929) for each successive key pressed, resulting in a playable pure sine wave. Provided, as I've said before, that you "tune" the filter to a reference with the cutoff knob (i.e. playing an A note on the keyboard and adjusting the cutoff to obtain 440 Hz (A4)).

As a concrete example: let's say you have a filter that is self-oscillating at 987.77 Hz (B5 on a piano) with the cutoff knob at a certain position. When you turn the KB tracking knob to maximum, and play the lowest key (F), nothing should change in the frequency. But with each higher note played, that frequency should increase by a factor of the twelfth root of two, so 987.77 Hz x 1.05946309435929 = 1046.50 Hz, resulting in one semitone increase (C6 on a piano). And so on for each successive higher note played.

It has often been mentioned in Moog literatures, as way back as I can remember, that the filter can act as an additional playable sound source when the keyboard tracking is set to 100%, resulting in a playable pure sine wave oscillator.

[Portamental]

Well... I don't want make this a long point by point discussion...

Let's just say, as a DSP software engineer, I know a thing or two about frequencies, waveforms and the Voyager. Pictures shown don't display as well as they did on the older version of the forum software. VU-Synth and VU-Enligne are derivatives of my own software, licensed to paper mills and mining companies to monitor vibration levels of heavy machinery.

[thealien666]

Well... I don't want make this a long point by point discussion...

Let's just say, as a DSP software engineer, I know a thing or two about frequencies, waveforms and the Voyager. Pictures shown don't display as well as they did on the older version of the forum software. VU-Synth and VU-Enligne are derivatives of my own software, licensed to paper mills and mining companies to monitor vibration levels of heavy machinery.

You're right, let's keep it to the point.

And the point is this;

the initial post by soulstar108 stated: " I want to play eg a major scale, or have the filter oscillate and track the oscillators. At the moment with the KB Cont Amnt maxed I'm only getting a Major 7th interval instead of an octave."

Which in my humble opinion, is an indication that the KB tracking scaling trimpot isn't properly adjusted inside his Voyager. Since on any synth, hardware or DSP software driven, when "keyboard tracking" switches, or a variable pot, are set to 100% it should track the keyboard scaling at 100%. Be it a filter, an oscillator, an LFO, or anything else.

[c7sus]

<backing slowly out of this thread...>

[Voltor07]

Well... I don't want make this a long point by point discussion...

Let's just say, as a DSP software engineer, I know a thing or two about frequencies, waveforms and the Voyager. Pictures shown don't display as well as they did on the older version of the forum software. VU-Synth and VU-Enligne are derivatives of my own software, licensed to paper mills and mining companies to monitor vibration levels of heavy machinery.

You're right, let's keep it to the point.

And the point is this;

the initial post by soulstar108 stated: " I want to play eg a major scale, or have the filter oscillate and track the oscillators. At the moment with the KB Cont Amnt maxed I'm only getting a Major 7th interval instead of an octave."

Which in my humble opinion, is an indication that the KB tracking scaling trimpot isn't properly adjusted inside his Voyager. Since on any synth, hardware or DSP software driven, when "keyboard tracking" switches, or a variable pot, are set to 100% it should track the keyboard scaling at 100%. Be it a filter, an oscillator, an LFO, or anything else.

The 2nd and 3rd oscs only track to a major 7th...it says so under the specs page for the RME. I'm thinking the filter is probably tracking to the same interval as the 2nd and 3rd oscs. It makes perfect sense to me, unless I'm missing something.

[thealien666]

Voltor07, I think you might have misunderstood that we are talking about Keyboard Tracking and not semitones offsets.

This is what you're probably referring to from the manual ?: "The Frequency control can change the pitch of Oscillator 2 or 3 a total of +/- 7
semitones relative to Oscillator 1. This allows more than one frequency to be played when a key is pressed."

But this is about the "frequency control" knob range of each of OSC2 and OSC3. Not keyboard tracking.

Keyboard tracking is defined as the ability to track individual scaled notes on a keyboard. And as such, the "KB Control Amount" knob in the filter section should do exactly that when set to maximum. The "cutoff" knob would be equivalent to the "frequency control" knobs of the oscillators in this case, if the filter is being used as a sound source in self-oscillation.

But from what I understand, soulstar108 cannot get a full octave interval out of the self-oscillating filter when he plays two keys one octave appart with the "KB Control Amount" knob in the maximum position.

Or did I misunderstand him ?