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Zeroscillator : what the .... ?
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Author Zeroscillator : what the .... ?
worker8
Hi there,

I got a Zeroscillator and wonder if it works properly.

The dynamic fm in is ok and the knob just above behave as expected. But when I plug an Adsr into the fm index input, I got an ugly sound rather than the nice bellish sound I'd like to ear.

Here's a video to show it (Edit : first half is ok, without adsr modulation. Second half, starting around 0:48 is not what I expect from an Adsr plugged into the Fm Index input).



Did I miss something in my patch ? Actually, I think there's something wrong with the module itself.

Your comments and advices will be highly appreciated.

Cheers,

Pierre
korrupter
Sounds like a FM Synth to me..

Isnt that what its supposed to be?
phasebash
That sounds about right to me. If you're looking for a prettier sound, you're going to want to look at the frequency ratios between your carrier and modulator in addition to their phase offsets.
worker8
Well ... I'm not comfortable with the sound starting at 0:48. I guess this is not what an Adsr is supposed to do when plugged into the Fm Index input. I believe the pitch should stay put.

In the first part of the video, I change the Fm Index manually, and the pitch doesn't change. So why does the pitch goes weird when I change the Fm Index with an Adsr ?

I don't get it. And that's not what you can here in this video at 1:17.



seriously, i just don't get it
rydan
If the modulator is the same, and in the first example you just turn FM index manually, while in the second example you modulate FM index by an ADSR, then, yes, I agree it sounds a bit strange, like the ADSR adds exponential FM instead of linear or something.

Have you tested modulating the FM index with just a fixed DC voltage? That should give the exact same result as manually turning the FM index knob I would think.
giorgio
that sounds like through-zero might be off. have you tried flipping the TZ switch and seeing if it makes a difference?
Navs
Your ZO is fine. Your modulator and index aren't lol

Seriously, I spent a lot of time finding a good FM pal for the ZO and also select my envelopes carefully too.

For the modulator I use either the MMF-1 filter or A-143-9 QLFO. Two reasons: pure sine and negligible DC offset. The latter is the enemy of tonal linear FM. The A-143-9 has the additional benefit, ironically, of being quieter than other VCOs which means you can send the ZO a hotter envelope.

As with a classic subtractive patch, where you would use two envelopes (filter + VCA), try the same for lin FM patches. Part of what you're hearing is the fading of the index. Depending on the C:M pitch relationship, this can sound ugly. Set up your VCA envelope first, then apply a shorter amount of FM envelope. Pay attention to the sustain level as this can also imply pitch. AD envelopes like Maths etc. can be an easier starting point, but bear in mind that 5V sweeps the full index on the ZO!
dkcg
Play with your ratios. It looks and sounds like it's working fine. Thru zero was on during the video, you can tell since the green LED lights up upon modulation.

Do you have something plugged into the exp input? Kinda sounds like it to me.

Tuning the ZO is a fine balance between index amount (which will depend on what envelope is feeding into it), whether lo/hi bias is on or off, the ZO frequency, and the modulator frequency. This is why tuning one can be a bit tricky, because you have to juggle 3 parameters (which may have parameters of their own, such as pulse width) and the smallest change can have a drastic influence.

I would try an AR envelope instead of an ADSR for chimes since that's how they react to being struck in the natural world.
giorgio
cool info navs.

maybe it is also possible to remove DC offset with a module that has AC coupled output. or a capacitor? makes me think that there should be an AC/DC switch on the input of the ZO, in a perfect world
worker8
rydan wrote:
If the modulator is the same, and in the first example you just turn FM index manually, while in the second example you modulate FM index by an ADSR, then, yes, I agree it sounds a bit strange, like the ADSR adds exponential FM instead of linear or something.


That's exactly what I'm doing.

rydan wrote:
Have you tested modulating the FM index with just a fixed DC voltage? That should give the exact same result as manually turning the FM index knob I would think.


I've just tried with an A-178 Theremin instead of the adsr, and the pitch changes in a similar way. I don't get the same result as manually turning the FM index knob.

I do agree with you : it should be the same result. But it's not.

I'm gonna read the test and calibration procedure seriously.
bwhittington
I think it sounded awesome at 0:48. w00t
worker8
Oh !

Lots of feedback while I was answering Rydan.

I got much more tests to do now.

Thanks you all.
rydan
bwhittington wrote:
I think it sounded awesome at 0:48. w00t


Good for you, you can save a lot of money by just using oscillators with regular exponential FM then. ;o)
Navs
To save you some of the grief (and emails with Cynthia) I had, have a listen to the attached MP3 I just recorded.

First is the MMF-1 filter self-oscillating, then the M15 VCO. Same pitch, same settings, completely different result.

The frequency relationships are important, but even more so is the integrity of the modulator.

The ZO's dynamic input is AC-coupled. The one marked 'linear FM input' is DC-coupled.
worker8
I asked here before sending a mail to Cynthia. I didn't want to start an argument without motive.

I tested the A-143-9 and you're right : that's much better. I don't understand why because without modulation at the fm index input, results are similar. But with an envelope to modulate the fm index, there's a huge difference between those two modulators.

So thank you Navs and all others. I was puzzled and you sorted it all out in less than a couple hour.

Chugging Beers
Navs
Super - glad it's sorted!

Re-reading my post: I didn't mean to suggest I had grief with Cynthia oops Cynthia was helpful and wrote me a long mail when I asked her a similar question. She outlined the ZO's principals, but it took my own experimentation to get the best out of the ZO.

My own take on those pitch artifacts is this: when patched non-dynamically i.e. at a fixed level, the ZO's AC-coupling has the time to filter DC content. After all, the DC is not being increased in depth, just maybe the pitch of your modulator.

As soon as you vary the index dynamically, that unwanted DC offset is applied at varying levels and the filter can't cope. This results in a slewed pitching effect and kills your FM joy.

You could try hi-pass filtering your modulator or feeding it through an AC-coupled circuit like Fonitronik's mh-01 mixer. It was a surprise to realize that some VCOs have a DC offset!

So, why is the ZO particularly susceptible to DC offset? Because it's integral to the way it works ('Bias' setting). Read the manual for a full description, but you can do this test: set up a non-dynamic patch with the bias set to high. Now flick the bias to off (middle) and mix you modulator with 5V DC before patching to the ZO. The result should be the more or less the same. Can you now see why a modulator with an unspecified DC offset would be bad?

One thought - in fairness to Cynthia, maybe you'd like to remove or at least annotate your video so people don't get the wrong idea thumbs up
worker8
Navs wrote:
You could try hi-pass filtering your modulator or feeding it through an AC-coupled circuit like Fonitronik's mh-01 mixer. It was a surprise to realize that some VCOs have a DC offset!

Good trick. I'll try with a LPF as well. I guess they're also AC coupled.

Navs wrote:
So, why is the ZO particularly susceptible to DC offset? Because it's integral to the way it works ('Bias' setting). Read the manual for a full description, but you can do this test: set up a non-dynamic patch with the bias set to high. Now flick the bias to off (middle) and mix you modulator with 5V DC before patching to the ZO. The result should be the more or less the same. Can you now see why a modulator with an unspecified DC offset would be bad?

Well ... that makes sense. The DC offset is no longer DC because of the envelope modulation. So it passes AC coupling.

But there's a big difference between turning the dynamic fm knob manually and using a slow envelope at the fm index input. And I still don't understand why.

Navs wrote:
One thought - in fairness to Cynthia, maybe you'd like to remove or at least annotate your video so people don't get the wrong idea thumbs up

Actually, my video is "Unlisted" (you can't find it with youtube search engine). Perhaps I'll rename it someday and put another one to show the difference between modulators.
3vcos
Navs wrote:
....
Read the manual for a full description,...... thumbs up


Wait, there is a manual for the zero oscillator? I haven't been able to find one? Is it actually on the cyndustries web page?
petejm
You should've got one shipped with the module but there's an older version of it at the yahoo group page.
3vcos
petejm wrote:
You should've got one shipped with the module but there's an older version of it at the yahoo group page.


If anyone has a pdf or text or any type of manual for the Zero Oscillator please contact me.
giorgio
worker8 wrote:
Navs wrote:
You could try hi-pass filtering your modulator or feeding it through an AC-coupled circuit like Fonitronik's mh-01 mixer. It was a surprise to realize that some VCOs have a DC offset!

Good trick. I'll try with a LPF as well. I guess they're also AC coupled.


i don't think it is just that the HPF is AC coupled, it is that HPF will filter out any slow movement in the signal such as something (close to) DC. DC is a almost like a very low frequency AC signal, and with a HPF, you can adjust the amount of filtering. dunno if I'm making myself clear...
worker8
http://f1.grp.yahoofs.com/v1/sIaYTo3GTZyj_zYqX2VL8vcGejFVepR6_Q93lL6YD oRD7CWm-ZBbYJ0qPsM8ChnBnadROTDxIzdddRoDCos-zcsXp6n0sTk/Zeroscillator%2 0OPMAN7.pdf
worker8
Hi Giorgio,
Yes I understand. But now that the basic patch works I want to experiment !

The A-143-9 is a nice modulator. The A-105 sine too. And thanks to Volta, I can play something like 4 octaves...
Navs
Sean Costello (Valhalla DSP) described HP filtering the modulator as resulting in phase modulation. I found it works, but depending on the cut-off, yields slightly less rich tones.

Attached are the two manuals that I have.
petejm
Very interesting thread. I get similar results as the OP using my AFG sine out as modulator. I need to sit down one afternoon and do the math but this...

worker8 wrote:
But there's a big difference between turning the dynamic fm knob manually and using a slow envelope at the fm index input. And I still don't understand why.


I also don't understand. I thought that the fm index input is the cv corresponding to the linear/dynamic fm pot?

Since the modulator signal goes in via the dynamic fm input, which is supposed to be AC coupled, why would any DC offset present in this signal affect the result when we apply a signal to the fm index input? hmmm.....

How does one measure the DC offset of the modulator signal?
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