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Hardware Instruments => MiniBrute => MiniBrute Technical Questions - FAQ => Topic started by: The01Habiitat on September 13, 2012, 08:52:36 am

Title: LFO Amp Knob issue
Post by: The01Habiitat on September 13, 2012, 08:52:36 am
Maybe ive never seen this before, maybe im about to clue everyone in on my knowledge of analog synthesizers. either way ill learn from this. maybe.

All wave forms are set to minimum, all envelopes are at min as well, all knobs are counter clockwise unless noted with a -/+ in which case they are at "12 oclock", arp is off, mod wheel is at 0, and the pitch wheel is centered by physical default.

HOWEVER! my LFO amp knob can be at - or + and i get a popping sound. the closer i get to - or + the louder it gets. now say i bring my sub osc slider up or any of the other wave forms up it plays me the last note as it would be affected by holding a key down. but im not holding a key down. im not sure if that makes any sense to anyone but im not pressing any keys, my LFO amp knob is at - or + completly pegged, and i bring up the sub osc, saw tooth, square, tri, or noise and suddenly im hearing the last note affected by the lfo.
is this normal? my Mg doesn't do it, my ms2000 doesn't do it. whats happening? 
Title: Re: LFO Amp Knob issue
Post by: Bruno@arturia on September 13, 2012, 09:34:11 am
This is a "normal" MiniBrute behavior.
MiniBrute's VCA processes audio output as follow:
Audio signal, coming from the filter, is multiplied by the sum of Amp modulations (Envelope, LFO, ExtCV) such as:
VCAOutput = FilterOutput * (AmpEnvelope + LFOAmp + ExternalAmpCV).
So if any of these modulations are not zeroed, VCA will open according to the modulation amplitude.
It was a design choice, it has it's advantages and drawbacks...
So obviously your unit is not faulty, but this thing could be disappointing for sure.

Title: Re: LFO Amp Knob issue
Post by: biographers on April 01, 2013, 06:02:40 am
So the last note being triggered by the LFO amp knob is normal. Ok, kinda cool, it can function like a "hold" button but without the arpeggiation. Interesting.

however, is the "popping" normal? I'm noticing in particular when the LFO is set to square wave. there is a regular popping based on the LFO rate. I find that less cool. Is that supposed to be happening?
Title: Re: LFO Amp Knob issue
Post by: Bruno@arturia on April 04, 2013, 10:55:34 am
Yes it's normal, square and saw have very fast edges. Modulating a VCA with a square, is like switching on and off a power amplifier, you'll get loud pops
Title: Re: LFO Amp Knob issue
Post by: metadb on April 13, 2013, 09:41:53 am
This seems to me to be an extremely limiting disadvantage. The amp mod is less of an amp mode an more of an effect which can't be played with musical dynamics. I've never heard of an amp mod still being open when the envelope generator is down. This makes it only useful for that one sustained sound. It makes it impossible to create an entire range of sounds with shorter envelops that use the mod only while the envelope is up. I'm really shocked at this design decision. Why limit a huge range of possible sounds in order to make possible this one sustained amp mod effect? I would suggest that if at all possible a switch is added to change the routing of the pathway to the standard use of amp mod. This might be a deal breaker for me.
Title: Re: LFO Amp Knob issue
Post by: wackyvorlon on August 06, 2013, 01:43:39 am
There's a CV input for the VCA. You can grab a modular LFO and have it drive the VCA. Not ideal, but it should work.
Title: Re: LFO Amp Knob issue
Post by: svmcwd on October 30, 2013, 02:32:59 am
When you crank the "brute factor" more than half way up and adjust the filter cutoff/resonance properly with LFO on Amp as well as Filter you can get some pretty decent kick sounds, especially with the LFO on pulse whyever that is.
Then bring in the envelopes and waveforms to advance it...

For me that is a really nice feature at the moment!
Title: Re: LFO Amp Knob issue
Post by: 13thirteens on April 05, 2014, 09:17:22 pm
So can someone explain to me how to fix this? Everytime I turn my Minibrute on now it just starts making noise without me hitting a key, like its stuck on a note. Very frustrating. 
Title: Re: LFO Amp Knob issue
Post by: Multinoise on April 13, 2014, 06:41:41 am
The same happens to mine like 13thirteens says!!
if i turn th Lfo Amp know to 3 o´clock or around that it will stop but the sound isnt the same!!!
And now a couple of days ago de Pitch from the Lfo also go crazy chaing the octave by +2 on the keyboard ..  i have to turn all - or all + to be able to play c2 in c2 if i dint c2 will play c4 ...

Title: Re: LFO Amp Knob issue
Post by: matias_thinKing on July 28, 2014, 06:05:44 am
this is a long shot, but... I believe the clicking can be corrected if the LFO shapes were to be modified.

Specifically, I think the wave-form shapes should be edited to emulate oscillator slop or maybe a bit of LPF.  Since the LFOs are digital, these analog "shortcoming" don't exist, but the perfect wave-form actually makes the VCA "click" because the change in voltage is too drastic and fast.

If the LFO shapes can be modified somehow, then the issue could be resolved.
Title: Re: LFO Amp Knob issue
Post by: radray on October 17, 2014, 03:01:48 am
Unfortunately for your wishes the LFO waves are actually created using analog waveshapers processing a triangle wave that is synced from the processor.  So to add any slew to wave shapes would require hardware hacks.