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toppobrillo
Joined: Dec 10, 2005
Posts: 766
Location: oakland, ca
G2 patch files: 1
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 Posted: Fri Jul 27, 2007 2:59 pm Post subject:
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| Quote: | | Hmm, are you sure, the Aries 3080 based VCO track's very well! |
yeah, the aries uses a CA3080A and an E- the A is supposed to have better linearity. there are some of those on ebay right now i believe.
i have had fine luck with the Es in VCO circuits. this isn't rocket science, anyways (or communications)... 50-12,800 Hz (beyond my hearing  ) is only 8 octaves.
josh |
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frijitz
Joined: May 04, 2007
Posts: 1734
Location: NM USA
Audio files: 54
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Posted: Fri Jul 27, 2007 3:44 pm Post subject:
Re: Thru-Zero VCOs
Subject description: Thru-Zero VCO pro PCB in the works! |
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| fizmoo wrote: | >frijitz"]
> Oh, I now see that I forgot to mention that OTA's don't have
>linear Iabc responses, so it is quite difficult to get good tracking
>something I would think you might want for serious FM work.
Hmm, are you sure, the Aries 3080 based VCO track's very well! |
Hmmm ... well, I would need to know what you mean by "very well". Do you have any numbers, by any chance?
I'd be very surprised if my non-OTA tri core didn't do better. 
Ian |
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frijitz
Joined: May 04, 2007
Posts: 1734
Location: NM USA
Audio files: 54
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| Posted: Fri Jul 27, 2007 4:01 pm Post subject:
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| topp wrote: |
i have had fine luck with the Es in VCO circuits. this isn't rocket science, anyways (or communications)... 50-12,800 Hz (beyond my hearing ) is only 8 octaves. |
I've made detailed measurements on several dozen E's and AE's. I measure non-linearity as the the difference between the output at Iabc = .5 mA and 1 mA. Nonlinearity is always between 1% and 3%. IIRC the chip spec is 2%.
Also changes in offset with Iabc affect the tuning.
How accurate is your tuning? It would be easier to discuss with some numbers. My tri VCO is better than 0.1%/oct up to 40 kHz. And I can't measure better than that, so I don't even know how accurate it is.
Anyway, the question here is how well VCO's will work for FM applications, ie, keeping the same waveform over a range of pitches. This is very demanding application, and, I believe, is the main reason that serious FM is usually done digitally.
Ian |
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toppobrillo
Joined: Dec 10, 2005
Posts: 766
Location: oakland, ca
G2 patch files: 1
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| Posted: Fri Jul 27, 2007 8:03 pm Post subject:
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| Quote: | | i have had fine luck with the Es in VCO circuits. |
i should elaborate- they seem to work well enough for me..
have you performed the same tests with the 13700? it seems like i saw a comparison chart someone made someplace...
| Quote: | | It would be easier to discuss with some numbers. |
sure, i will try and take it to work with me to test with a decent freq. counter.
i have absolutely no doubt that your VCO is the bee's knees- and i can't testify at all to the tuning accuracy of the Aries VCO...
| Quote: | | ie, keeping the same waveform over a range of pitches |
i suppose waveform integrity would be an important consideration for more complex FM type synthesis. that would be one reason for using digital methods...another would be the enormous amount of sensitive (and repetitive) circuitry required to emulate what those things do!
anyways, i like discreet design! the transistor isn't goin' anywhere.
Josh |
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frijitz
Joined: May 04, 2007
Posts: 1734
Location: NM USA
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| Posted: Sun Jul 29, 2007 11:30 am Post subject:
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| topp wrote: | | Quote: | | i have had fine luck with the Es in VCO circuits. |
i should elaborate- they seem to work well enough for me.. |
Yes, I agree, that design approach works well enough in most circumstances. I have one in my system that runs at 10x audio frequencies followed by a ten-step waveform generator.
| Quote: | | have you performed the same tests with the 13700? it seems like i saw a comparison chart someone made someplace... |
Yes, I have. I found a fair amount of batch-to-batch variation, so it is hard to generalize, but linearity is much better than what I saw for the 3080's. The one batch I did the most measurements on had nonlinearities under 0.6%.
| Quote: | | sure, i will try and take it to work with me to test with a decent freq. counter. |
I would be very interested in seeing those results. There is very little available quantitative information on VCO performance.
| Quote: | | i suppose waveform integrity would be an important consideration for more complex FM type synthesis. that would be one reason for using digital methods...another would be the enormous amount of sensitive (and repetitive) circuitry required to emulate what those things do! |
Yes, I'm not really certain how critical this is overall, but I gave up on doing any FM synthesis because I couldn't get it to work over any significant frequency range. I was trying to make waveforms with the VCO frequencies at an integer ratio.
OTOH, Rene has some nice demos done with his thru-zero VCO which is based on an OTA core.
| Quote: | | anyways, i like discreet design! the transistor isn't goin' anywhere. |
Yep, I'm all set for when all the OTA's disappear.
Ian |
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Coriolis
Joined: Apr 11, 2005
Posts: 616
Location: Stilling, Denmark
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| Posted: Sun Jul 29, 2007 11:32 am Post subject:
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To come back to the original question, I have to be a noob and ask?
WHY would I want one of these? What does a TZ-VCO do, that a regular vco doesn't?
Listening to demo's of the Zeroscillator right now, and it is impressive stuff, but the diy circuit we're talking about here is not quite as sophisticated, is it?
c |
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frijitz
Joined: May 04, 2007
Posts: 1734
Location: NM USA
Audio files: 54
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| Posted: Sun Jul 29, 2007 11:44 am Post subject:
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| Coriolis wrote: | | Listening to demo's of the Zeroscillator right now, and it is impressive stuff, but the diy circuit we're talking about here is not quite as sophisticated, is it? |
Ah, that's the big question. If we redo our diy designs to add TZFM will they work as well as the ZO? The ZO has lots of nice frills, but just looking at the core design, can we do as well? If so, then we can go on to add the bells and whistles, as desired.
This is a good challenge! I have worked very hard to develop accurate and stable VCOs. It's very tempting to put several identical high-performance and carefully compensated VCOs in a box and see what their limits are.
Oh well, add it to the list, anyway. |
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Nosferatu
Joined: Jul 27, 2007
Posts: 234
Location: Planet Rock.
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Posted: Sun Jul 29, 2007 3:30 pm Post subject:
Re: Thru-Zero VCOs
Subject description: Thru-Zero VCO pro PCB in the works! |
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>Hmmm ... well, I would need to know what you mean by "very well".
>Do you have any numbers, by any chance?
Unfortunatelyn no, but compared by ear to my SY77 it sounded that it
tracked quite well. What i meant with that are *well enough* not to
cause any sudden phasing when ratio switching.
However i might just had been lucky when picking the OTA's for the core!
>I'd be very surprised if my non-OTA tri core didn't do better.
Off course its better, the Buchla core are also better, what i was more
referring to was that you said :so it is quite difficult to get good tracking:
off course that is relative, it sounded worse then it probably was?!
>The one batch I did the most measurements on had nonlinearities
>under 0.6%.
For the frequency range of 0-20khz, more?
Back to the EN zero osc, wouldn't the non ideal full wave rectifier cause
non symmetrical zero modulation? Also if doing the EN zero one could remove plenty of components without losing initial functionality.
For instance OA9 and 10, R26, R27 can be removed. |
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frijitz
Joined: May 04, 2007
Posts: 1734
Location: NM USA
Audio files: 54
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Posted: Sun Jul 29, 2007 4:37 pm Post subject:
Re: Thru-Zero VCOs
Subject description: Thru-Zero VCO pro PCB in the works! |
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| fizmoo wrote: | what i was more
referring to was that you said :so it is quite difficult to get good tracking:
off course that is relative, it sounded worse then it probably was?! |
Agreed! I'm thinking in terms of how you would make an FM waveform -- say with an integer frequency ratio -- that didn't change significantly as you went up a scale. I believe that's a more stringent requirement than whether the tuning is good enough for a more ordinary (non-FM) patch.
| Quote: |
>The one batch I did the most measurements on had nonlinearities
>under 0.6%.
For the frequency range of 0-20khz, more? |
This characterization just looked at the OTA output at Iabc levels of 0.5 mA and 1.0 mA, so it wasn't a detailed look at the whole curve.
| Quote: |
Back to the EN zero osc, wouldn't the non ideal full wave rectifier cause
non symmetrical zero modulation? |
Interesting question. Definitely something to look at closely.
| Quote: |
Also if doing the EN zero one could remove plenty of components without losing initial functionality.
For instance OA9 and 10, R26, R27 can be removed. |
Perhaps. I think the Schmitt trigger is to prevent chattering due to noise near the reversal point.
Interesting discussion!  |
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Nosferatu
Joined: Jul 27, 2007
Posts: 234
Location: Planet Rock.
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| Posted: Sun Jul 29, 2007 5:12 pm Post subject:
Re: Thru-Zero VCOs |
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del
Last edited by Nosferatu on Mon Nov 26, 2007 3:30 pm; edited 1 time in total |
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Randaleem
Joined: May 17, 2007
Posts: 456
Location: Northern CA, USA
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| Posted: Sun Jul 29, 2007 7:33 pm Post subject:
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| Coriolis wrote: | To come back to the original question, I have to be a noob and ask?
WHY would I want one of these? What does a TZ-VCO do, that a regular vco doesn't? |
Hi Coriolis,
First part of the answer is simple: What it DOES (that a regular VCO doesn't) is go into reverse. What that MEANS is: It gives you access to sounds you can't get with a regular VCO. Period.
| Quote: |
Listening to demo's of the Zeroscillator right now, and it is impressive stuff, but the diy circuit we're talking about here is not quite as sophisticated, is it? |
It's not a s far removed as (perhaps) some would have you believe...
In my efforts to offer this as a commercial PCB and module; I have of course been looking closely at the ZO. And while I do NOT have access to the ZO's schematic or details beyond those online; Bernie did tell me that Cynthia also asked for the rights/info to use this same EN129 core.
Using the published ZO docs against the EN docs and making comparisons; I think it's a fairly safe bet to say that the ZO simply (or not so simply!) adds quadrature outputs and some waveshapers to the EN circuit. The rest appears to be clever naming of controls already in existence in the EN core circuit. A good product, and some very good marketing.
To me, sophistication is not just adding bells and whistles, but rather something of the core elements. While the "basic black dress" looks pretty good with a diamond necklace and bracelet; it's still capable of being pretty sophisticated by itself. Under that definition; l'd say that the EN circuit has plenty of "sophistication" to be a worthwhile addition to your synth.
(FWIW, I AM looking at what sort of "accessories" might enhance that inherent sophistication.)
Going back to the simple answer from above. TZ gives you access to more sounds than a normal VCO. Period. And that's really what we're after, isn't it?
Randal |
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Randaleem
Joined: May 17, 2007
Posts: 456
Location: Northern CA, USA
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| Posted: Sun Jul 29, 2007 7:56 pm Post subject:
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| frijitz wrote: | | This is a good challenge! I have worked very hard to develop accurate and stable VCOs. It's very tempting to put several identical high-performance and carefully compensated VCOs in a box and see what their limits are. |
Hi,
I'm glad I've not gotten caught up in the mathematic-ization (is that a word?!?  ) of synths that seems to be ever more rampant these days.
I find it interesting that everybody wants the "analog" sound, even as the modern designers Of that analog sound try to get their designs to have "digital" characteristics and performance.
Begging the question: Is this for music or test equipment?
Now I'm not saying I disagree that certain results from FM really does require more in the way of stability and accuracy. I'll not be arguing the superiority of analog OR digital ANY time soon... (Each has its place; and each is important to what I believe is the MOST important element of what we're here about.)
MUSIC.
We have come full circle when an MOTM 300 VCO is considered by some to be a bit "sterile". Even as it's wonderful stability and accuracy are widely known and espoused. There's a reason piano's have three strings per key...
Let's not lose that in the discussion of "test results" that might be more apropriately reserved for the test equipment we use to design and build our synths!.
So while I TOO would like to see a VCO "shootout". I'd want it to be based on SOUNDS, not tables of achieved numbers! The only "limits" I'm interested in are those which affect my musical results.
Has anybody really paid recent attention to the simplicity and "TERRIBLE" specs of parts used in the "vintage" synths? Those "babies" still look (sound) pretty good sitting in their dirty "bathwater"...
IMO It's about the music (and sounds).
Comments invited,
Randal
BTW, I miss NOT having instant access to EVERY stat during a sportscast or event TOO! Be. Here. Now. Patch some modules. Twist some knobs. Let your EARS decide if the "specs" are good enough! 
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Randaleem
Joined: May 17, 2007
Posts: 456
Location: Northern CA, USA
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Posted: Sun Jul 29, 2007 8:20 pm Post subject:
Re: Thru-Zero VCOs
Subject description: Thru-Zero VCO pro PCB in the works! |
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| fizmoo wrote: | | Back to the EN zero osc, wouldn't the non ideal full wave rectifier cause non symmetrical zero modulation? |
If one wants a digital FM synth; one should build one. If a person wants analog; he or she should enjoy its limitations(strengths).
Is there any good reason today to HAVE TO use one versus the other?
It's not like the old days when either was in an infancy... Nowadays, Each can be applied where it most makes sense.
I believe we will see in coming months and years the same re-evolution of the DIGITAL aspects of synths that we have seen in ANALOG since the late 90's. It's already happening. And IMO it will only gather steam and increase dramatically over the next few years. It's like the early 80's are back...
First we'll see the Prophet5 type things, then we'll get the 00's version of the DX7 stuff. (Hmm, we're already seeing that too!)
| Quote: |
Also if doing the EN zero one could remove plenty of components without losing initial functionality. For instance OA9 and 10, R26, R27 can be removed. |
Can you? Have you breadboarded this?
Quoting from the EN129 document, page 7: "It was found experimentally that neither the single comparator (OA-10) nor the weak Schmitt trigger comparator (0A-9) would give reliable triggering over a wide frequency range. The combination works well however."
If you've found otherwise; I'm interested in hearing your results; PC board space is a always at a premium!
What other components do you feel can be eliminated?
Randal
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andrewF
Joined: Dec 29, 2006
Posts: 1176
Location: australia
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| Posted: Sun Jul 29, 2007 8:39 pm Post subject:
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Hi Randal
not essential stuff but
i left out nearly all the waveshaping circuitry (EN#129 (5) Fig 2B) except for OA17 and its associates.
leaving me with just Square and triangle outs. but as I had 2 sections of an 074 free (yes i used TL074s for all op-amp requirements) , i added a CGS simple wave folder to give a pulse out and a ... 'folded' tri out. It was a worthy mod, i seem to use pulse out more than any of the others. |
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Randaleem
Joined: May 17, 2007
Posts: 456
Location: Northern CA, USA
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| Posted: Sun Jul 29, 2007 10:27 pm Post subject:
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| andrewF wrote: | Hi Randal
...i left out nearly all the waveshaping circuitry (EN#129 (5) Fig 2B) except for OA17 and its associates.
leaving me with just Square and triangle outs / / i added a CGS simple wave folder to give a pulse out and a ... 'folded' tri out. It was a worthy mod, i seem to use pulse out more than any of the others. |
Thank you Andrew,
Yes, it seems the output waveshaping is a key area which distinguishes a given TZ implementation. I appreciate your comments.
Randal |
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Coriolis
Joined: Apr 11, 2005
Posts: 616
Location: Stilling, Denmark
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| Posted: Mon Jul 30, 2007 12:52 am Post subject:
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Thanks for the answers.
From what I gather, it is possible to achieve DX-type fm-sounds from a TZVCO. But I suppose there's more to it.
For FM, I have a DX7 in the closet, but of course it doesn't easily integrate with a modular setup... 
Anybody got other examples of a TZVCO doing neat things a standard vco cannot?
C |
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frijitz
Joined: May 04, 2007
Posts: 1734
Location: NM USA
Audio files: 54
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| Posted: Mon Jul 30, 2007 8:34 am Post subject:
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| Randaleem wrote: | | And while I do NOT have access to the ZO's schematic or details beyond those online; Bernie did tell me that Cynthia also asked for the rights/info to use this same EN129 core. |
Oh-ho Now that's worth the price of admission.
Thanks  |
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frijitz
Joined: May 04, 2007
Posts: 1734
Location: NM USA
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| Posted: Mon Jul 30, 2007 8:59 am Post subject:
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| Randaleem wrote: | Now I'm not saying I disagree that certain results from FM really does require more in the way of stability and accuracy. I'll not be arguing the superiority of analog OR digital ANY time soon... (Each has its place; and each is important to what I believe is the MOST important element of what we're here about.)
MUSIC. |
I agree that the bottom line is the music. I do not agree that any one person can be the arbitrator of what is musical or musically useful.
I worked on stability and accuracy in VCO design because I was doing classical music, which requires good intonation. I was tired of having to retune all the time, and in fact I ruined a couple of recording sessions because I failed to do so.
You may hear a couple of short clips of some of my music here.
http://home.comcast.net/~ijfritz/demos.htm
(Feel free to reciprocate -- I'd love to hear what you do musically.)
| Quote: | | We have come full circle when an MOTM 300 VCO is considered by some to be a bit "sterile". Even as it's wonderful stability and accuracy are widely known and espoused. There's a reason piano's have three strings per key... |
Perhaps some do consider it sterile, but the fact is that it is based on a very old design. The idea of analog warmth is pretty slipery. Myself, I think most of the time you can't hear it in a mix. Warmth mainly comes from how you play.
My position is that if you start with accurate VCOs, then you can add whatever degree of detuning and modulation that you want, but if you use inaccurate ones, then you are pretty much stuck with their particular characteristics.
| Quote: | | So while I TOO would like to see a VCO "shootout". I'd want it to be based on SOUNDS, not tables of achieved numbers! The only "limits" I'm interested in are those which affect my musical results. |
Fine, but please don't confuse your musical needs and results with others'.
| Quote: | | Be. Here. Now. Patch some modules. Twist some knobs. Let your EARS decide if the "specs" are good enough! |
Amen. |
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v-un-v
Janitor
Joined: May 16, 2005
Posts: 8932
Location: Birmingham, England, UK
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| Posted: Mon Jul 30, 2007 9:08 am Post subject:
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| frijitz wrote: | Warmth mainly comes from how you play.
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Does it?! Are you referring to emotional warmth or just plain warmth as a whole?
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frijitz
Joined: May 04, 2007
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| Posted: Mon Jul 30, 2007 11:34 am Post subject:
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| v-un-v wrote: | | frijitz wrote: | Warmth mainly comes from how you play.
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Does it?! Are you referring to emotional warmth or just plain warmth as a whole? |
A shocking statement?
Anyway, I don't understand the distinction you are making and I don't care to get into a semantic argument. All I will say is that nobody has ever been able to convince me that one sawtooth sounds more warm than another. You have to do something with them, dynamically, to get them to sound warm to my ear. |
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v-un-v
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| Posted: Mon Jul 30, 2007 11:49 am Post subject:
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| frijitz wrote: | | v-un-v wrote: | | frijitz wrote: | Warmth mainly comes from how you play.
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Does it?! Are you referring to emotional warmth or just plain warmth as a whole? |
A shocking statement?
Anyway, I don't understand the distinction you are making and I don't care to get into a semantic argument. All I will say is that nobody has ever been able to convince me that one sawtooth sounds more warm than another. You have to do something with them, dynamically, to get them to sound warm to my ear. |
I too, likewise, didn't understand the distinction you were making either!
The saws on my MS20 sound thin and nasal, and when the thing is played 'dynamically' it still doesn't sound 'warm'.
Perhaps you perception of 'warm' is different to mine? 
_________________
ACHTUNG!
ALLES TURISTEN UND NONTEKNISCHEN LOOKENPEEPERS!
DAS KOMPUTERMASCHINE IST NICHT FÜR DER GEFINGERPOKEN UND MITTENGRABEN! ODERWISE IST EASY TO SCHNAPPEN DER SPRINGENWERK, BLOWENFUSEN UND POPPENCORKEN MIT SPITZENSPARKSEN.
IST NICHT FÜR GEWERKEN BEI DUMMKOPFEN. DER RUBBERNECKEN SIGHTSEEREN KEEPEN DAS COTTONPICKEN HÄNDER IN DAS POCKETS MUSS.
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elektro80
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| Posted: Mon Jul 30, 2007 12:02 pm Post subject:
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frijitz does a have a point or three here.
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elektro80
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| Posted: Mon Jul 30, 2007 12:06 pm Post subject:
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| v-un-v wrote: |
The saws on my MS20 sound thin and nasal, and when the thing is played 'dynamically' it still doesn't sound 'warm'. |
Well, the MS series was a low end product line. I know what you mean.
The MS20 can be percieved as rich and warm based on the context and how it is used. That being said, is it OK if I drag the term "analougue warmth" out into the parking lot and semtex it to death and beyond?
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ian-s
Joined: Apr 01, 2004
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| Posted: Mon Jul 30, 2007 12:47 pm Post subject:
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I totaly agree with Ian regarding starting with stable oscillators.
It's been a few decades but I do remember getting some warmth out of a MS20. I think what is mostly responsible for it's cold sound, is the reputation of it's cold sound. |
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frijitz
Joined: May 04, 2007
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Location: NM USA
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| Posted: Mon Jul 30, 2007 1:17 pm Post subject:
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| v-un-v wrote: | The saws on my MS20 sound thin and nasal, and when the thing is played 'dynamically' it still doesn't sound 'warm'.
Perhaps you perception of 'warm' is different to mine? |
I've never even come near a MS20, so I won't disagree with what you hear. But I have never noticed one saw sounding much different from another. I would suspect what you hear is more a function of the downstream electronics than the osc itself.
Why can't you warm it up by filtering it a tad to boost the bass, adding some dynamic vibrato, adding some chiff or chirp on the attack envelope, adding a second detuned osc etc? |
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