Pulse vs Overtone

[spydabee]

Hi - I have a question regarding the Pulse waveform.

On my MicroBrute, with Pulse Width set to the lowest value, it doesn't sound as though it's at 50% - still too buzzy. The Overtone oscillator (at full Sub position) is much more hollow, like I would expect a 50% pulse wave to sound.

Is this a deliberate "character" thing, or is my MicroBrute mis-calibrated?

[JnC]

Have you looked at it with an oscilloscope app? Mine appeared to be square, and much improved compared to the MiniBrute.

http://vimeo.com/80223769
See above link.

[ChuckL]

My Minibrute did this, but not my microbrute. The sub was perfect and hollow, but the square at zero was not. I used a spectrum analyzer on my computer and tweaked the pulse width knob until I got all of the even harmonics in a line, then I put that spot on the knob to memory(it was only 1-2 ticks up from 0).

[spydabee]

Interesting. On mine, I don't need a spectral analyser or oscilloscope to know that there is no 50%, unfortunately. It definitely isn't passing through 50% to 48% or anything like that - in fact there is a dead zone between 0 and 2 where absolutely nothing happens to the wave at all.

[spydabee]

So, can I recalibrate this myself? When I compare it to the Virus pulse oscillator, it seems the lowest I can get is about 53%.

Another strange behaviour is that the highest settings fade to silence very quickly as I play up the keyboard (filter fully open), meaning that the "90%" pulse is only really usable in the bass octaves.

[Bruno@arturia]

to fine tune PW to 50%:
 * set PW to min position
 * open the machine (remove the 12 black screws on the bottom iron plate).
 * Gently open it by taking great care to the flat cable connecting the keybed.
 * locate T5 of the board, it a small hole in the board, with a trimmer on the other side.
 * using a small screwdriver, slightly turn it to have the square at 50%. You can do it by ear on with a spectrum analyzer.

[spydabee]

Thanks Bruno!

That did the trick!

It's made a *huge* difference to me - I liked this thing before, but now it's *LOVE*   

[Howard]

@Bruno: Is a list of all internal Trimmer functions available?
(please, please...)

[Bruno@arturia]

I can give you the list, but I will not provide help or procedure on how to calibrate them.
Some can be quiet difficult to trim. You should really not touch them unless you have serious troubles with the machine.

On rear board:
T1 Pitch CV gain
T2 pitch CV offset
T3 LFO CV offset
T5 Saw offset (PW range , and triangle shape depend on this one too)
T7 Saw amplitude (Sub/5th range, and triangle shape depend on this one too)
T6 VCO offset
T8 VCO slope

On top Board
T3 Filter cutoff range
T2 filter resonance range