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Author Topic: Strange resonance behaviour  (Read 270 times)

MarctheDarc

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Strange resonance behaviour
« on: November 10, 2014, 04:05:00 am »
I've been through a rather unproductive period, but tonight i switched my MiniBrute back on after a few months.
It has worked perfectly for just short of 2 years, but suddenly the filter/resonance is acting strangely.

In BandPass mode i have almost no resonance at all, you can barely hear the difference between off and full reso.
If i turn down the oscillator, there's no sound what so ever, so not even the slightest touch of self-oscillation, even at full crank resonance.

In LowPass, HighPass and Notch modes i do get resonance, however only while cutoff frequency is above roughly 250Hz - once i drop it below that, the resonance just vanishes. No peaking, no self-oscillation, nothing. Above 250Hz it seems fine.

But, tweaking resonance amount also changes the cutoff point. Even small tweaks in the self-oscillation band, will change the frequency of said self-oscillation by over an octave.
The same also happens when tweaking the BruteFactor.

All the above strike me as very odd, and is a very different experience to how it last behaved.
It has been stored safely, under dust-cover and without any connections. So i can't see how anything external could've somehow influenced or damaged it.

Does any1 recognise above described behaviour from their units? Is it perhaps a change to be somehow expected within the parameters of the design? Or is this perhaps a known fault?

Thank you in advance for any info you can provide.
« Last Edit: November 18, 2014, 04:17:18 am by MarctheDarc »

MarctheDarc

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Re: Strange resonance behavior
« Reply #1 on: November 15, 2014, 01:35:09 am »
I could really use some feedback on this, if some1 could test theirs and let me know if there's any similarity to the results.
I still have a few months of store-warranty, if it has somehow suffered, i still have a chance to have it fixed.

MarctheDarc

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Re: Strange resonance behaviour
« Reply #2 on: November 18, 2014, 03:31:18 pm »
Seriously, not a single person could be bothered to switch theirs on and take 2 mins testing the frequency response of the resonance?
Or some of the guys here in the know on the design, could say if it's the proper behaviour?

Thunderroad75

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Re: Strange resonance behaviour
« Reply #3 on: November 20, 2014, 09:01:28 am »
Sorry i sent  my minibrute back last year because of fluctuating pitch issues. The only thing i can recomend is try looking at a few youtube videos. Hopefully you can get an idea of the scale of your minibrute problem or hopefully thats its ok and maybe your missing something really easy. The old saying you cant see the wood for the trees! Hope you get it sorted..
« Last Edit: November 20, 2014, 09:03:42 am by Thunderroad75 »

MarctheDarc

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Re: Strange resonance behaviour
« Reply #4 on: January 17, 2015, 04:46:26 am »
A final update: In november i took it to the store where it was bought. The store clerk agreed that it would be prudent to have it tested. In fact he believed that their demo-model had undergone a similar change, to what i described, within the past couple of months. But he had previously disregarded it as just his "imagination"/remembering wrong. Not unlike myself, as it was a subtle difference.
But it was sent in for repairs, just to be safe and know for sure.

A couple of days ago it finally came back, after near as makes no difference, 2 months with no information what so ever in the mean time. The final report said that something had been soldered, and it was now repaired. But no specifics about what had been faulty. Logic dictates that something must've been wrong, either measurably or visible on the circuitboard. Otherwise i guess they wouldn't try to fix it, but instead sent it back with a "nothing wrong, quit wasting our time" note attached (as would be reasonable had it been the case, i might add).

I'm happy that my beloved synth have come back. That is, untill i switch it on...
Within minutes the filter start emitting a strange scratchy noise at note on, which rapidly escalates in strength while the intended sound of the synth become erratic and diminishing. Next thing i know, there's no sound what so ever - nothing i can do to get any sound.
I switch it off and back on, which restores it to normal behaviour. Or so i thought...
When i turn the BruteFactor past roughly the 1 o'clock position, something in the circuits start emitting a low pitched, out of tune, (60-65Hz ish) sawtooth-like drone. It's unaffected by the gate, and note information. But the filter cutoff does remove frequency information. Tweaking the BruteFactor reveal it disappears once below 1 o'clock setting, and reappears above.
The droning is so powerful that it completely drowns out the oscillator waveforms - even all of them at full tilt at the same time, and the noise source, is a distant whisper behind the droning. The drone's frequency have no correlation to any of the oscillators parameters or function, as far as i can tell.
And before americans think that roughly 60Hz noise = electrical noise from the wall socket. I'm from Europe, our sockets supply 50Hz, which is a noticably lower freq, and any such noise would sound VERY different.
Soon after the filter starts scratching again, and shortly after all sound (incl. the droning) disappear.

The behaviour is repeated 3 times within 30mins, each time the same faults.

Today i took it to the store, disappointed, and explained that whatever they had done, they had just made it worse. I would've liked an explanation as to what the original problem was, as well as whether or not the escalation was caused by the "repair" or was just the original problems "natural" evolution. They offered to attempt again to repair it, but with a heavy heart i asked for my money back.

This total outcome, as well as the many issues people describe in this very forum (and many others), have led me to believe that Arturias components are of sub-par quality. No doubt they made the best sounding and most inspired synth of the new batch of cheap analogue mono synths. And they were 1st (disregarding DSI and Moog doing their kinda seperate thing). But somewhere along the line they must've cut some corners to keep costs low or something.

 

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