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okay let's face it - resonance isn't what it should be
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okay let's face it - resonance isn't what it should be

by kokoon on Thu May 25, 2006 9:51 am

in this thread on watmm forum
http://forum.watmm.com/index.php?showtopic=8385

we made a comparison. i have a x0xb0x with the cruical transistors of beta over 340. what do you guys think? what can be done?
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by uvacom on Thu May 25, 2006 2:40 pm

Eh? The difference seemed pretty subtle to me, the only thing I noticed is that x0xb0x's resonance seemed a little less harsh in pattern 2, which I actually preferred. Which aspects of the resonance did you feel were lacking? Could you point out spots in the demos where you feel the TB-303 comes out ahead?
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by kokoon on Thu May 25, 2006 7:43 pm

yeah i'm talking mostly about the second sequence. for me that's the most important characteristic of the tb-303. full resonance, full cutoff. it has to squelch so it hurts! do you think boosting the resonance with one of the known mods would bring the x0xb0x closer to this?
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by uvacom on Thu May 25, 2006 9:07 pm

Maybe? I don't even think it's that there's less resonance, I think the 303's envelope mod just has a higher peak while it decays at the same rate, thus giving it a sharper sounding resonant character and a more piercing sound. See if you can increase the modulation range/peak of the filter envelope, that might do the trick.
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by pr0dis on Thu May 25, 2006 11:16 pm

Honestly, the biggest thing I notice is the differences in level, it sounds like the 303 track was recorded "hotter" than the x0x track, so I guess my main suggestion is to try pushing the x0x levels higher when recording, and anyway I've never heard a 303 track I didn't like more with a little overdrive.
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by moogah on Thu May 25, 2006 11:53 pm

The only clip I feel like there is a significant difference in is #2. And even then there is only small difference in the quality of the rezonance, the real difference between the two is a higher cutoff setting and possibly a little higher rez. Possibly there is something going on that further boosts the high end as well. Considering that I still don't feel like there is anything "inauthentic" about the your x0x.
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by kokoon on Fri May 26, 2006 3:18 am

well come on guys it's obvious that (at least mine) x0xb0x doesn't have as high resonance as the tb... that ear-piercing shrieking when all the five knobs are to the max... it's not exactly the same.
and it's not cutoff frequency - in order to get the filter as low as the original tb-303 samples i had to readjust the cutoff trimpot - almost to the minimum. but still i've lost nothing on the high end - before readjusting the filter at max cutoff & rez was just buzzing - almost no filter oscillation was heard. try it with your b0x. i'd say you mustn't go too high with the cutoff.
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by moogah on Fri May 26, 2006 1:35 pm

Well, I can't say that I don't hear a difference, I knew right away listening to the second clip that my x0x couldn't sound quite like that. I still must insist we aviod getting bent out of shape about these kind of differences tho, becuase what we are dealing with is likely to be caused be individual component tolerances, not an oversight in the design. Now, I'm with you on trying to find a way to get that extra 5% out of the x0x. For the record my x0x would sound nearly the same as yours with those patterns/settings. I have always felt that I needed to re-adjust the trims for the rez and cutoff as it seems that I'm missing the last 5% of each with the knobs all the way turned up, but you say that you adjusted yours when making those samples and couldn't "crank it up" so to speak. This would leave us with the 733's as suspect for causing the difference. Perhaps further expirimentation with replacements on the critical transistors is due. I don't have the bench space at the moment (808 project has it all) but I'm on the list for a second zocks and I'll make a point to try a bunch of different tranny's to see what effect it has.
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by kokoon on Fri May 26, 2006 2:25 pm

you're talking about a resonance trimpot? are you sure there's such thing in the x0xb0x?
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by uvacom on Fri May 26, 2006 4:02 pm

kokoon wrote:well come on guys it's obvious that (at least mine) x0xb0x doesn't have as high resonance as the tb... that ear-piercing shrieking when all the five knobs are to the max... it's not exactly the same.
and it's not cutoff frequency - in order to get the filter as low as the original tb-303 samples i had to readjust the cutoff trimpot - almost to the minimum. but still i've lost nothing on the high end - before readjusting the filter at max cutoff & rez was just buzzing - almost no filter oscillation was heard. try it with your b0x. i'd say you mustn't go too high with the cutoff.


Envelope range, dude. What I hear is that the TB-303's envelope peak is slightly higher, and it may also be a sharper transient as well.
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by kokoon on Sat May 27, 2006 5:15 am

does the envelope also affect resonance?
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by moogah on Sat May 27, 2006 1:12 pm

No, the envelope does not affect the rez, but TBH what I hear in those sound samples isn't a difference in the rezonant quailty as much as it is a higher cutoff and probably more movement from the envelope. Overall I think this is what give the "hotter" effect.
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by kokoon on Sat May 27, 2006 2:07 pm

okay - once more - i LOWERED the cutoff trimpot in order to get sound closer to the tb-303. the cutoff was too high, no squelching was left. take a random analogue monosynth out of your closet, set the low pass filter to like 50% (fairly below self-oscillation) resonance and slowly advance the cutoff from zero to max. you'll notice at one point the resonance shrieking (feedback oscillation) disappears. i've no idea technically why this happens but it does... the same thing is with the x0xb0x. i'm sure it's the resonance.
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by uvacom on Sat May 27, 2006 4:39 pm

kokoon wrote:okay - once more - i LOWERED the cutoff trimpot in order to get sound closer to the tb-303. the cutoff was too high, no squelching was left. take a random analogue monosynth out of your closet, set the low pass filter to like 50% (fairly below self-oscillation) resonance and slowly advance the cutoff from zero to max. you'll notice at one point the resonance shrieking (feedback oscillation) disappears. i've no idea technically why this happens but it does... the same thing is with the x0xb0x. i'm sure it's the resonance.


What you are describing is a combination of two factors:

1) The ear can't detect really high frequencies very well, so you will perceive them as being quieter
2) Most waveforms that a lowpass filter in a synthesizer typically processes contain less energy in the higher ranges of the frequency spectrum, thus a resonant peak will not boost those frequencies to the same level as lower frequencies

Combined, what you hear is a less pronounced resonance at higher cutoff frequencies.

However, just below that point what you get is a really sharp, piercing sound - not pleasant on it's own but it can add some bite if an envelope momentarily peaks right at that point.

What I hear is that the 303's envelope range is sufficient to peak right at that point where it sounds really sharp before resonant characteristics diminish. With your x0xb0x, you can't get that because the envelope range isn't quite as great - so to get the same peak, you have to increase cutoff which makes the sound lose it's squelch, but lowering the cutoff has the effect of lowering the peak, reducing that biting characteristic.

I hope all of that made sense. :) Anyway, there's no way to know for certain without trying it, but I think trying to boost the resonance further would probably just give the filter a kind of "whistly" sound you may not like.
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by subatomic on Sun May 28, 2006 3:52 am

kokoon wrote:you're talking about a resonance trimpot? are you sure there's such thing in the x0xb0x?


I think he's referring to the idea expresed (in the x0xb0x/make/vcf document ) that the trimpot affects the resonance pitch.
But... I think that pitch is affected only because the point of resonance is aligned at the tip of the filter falloff curve,
so adjusting the cutoff really does adjust the resonance pitch (as you can hear when you twist the cutoff knob)... :)

makes sense either way to me... but cutoff offset pot is probably an accurate way of describing it...



Also... wondering, did you first calibrate your 303 according to roland spec before comparing it to your x0x?
see the x0xb0x/Make/vcf page for calibration of the TM3 trimpot in your x0x, 303 may be similar, I wouldn't know...
Just making sure we're comparing apples to apples here. :wink:

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Please be positive and constructive with your questions and comments.