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 Forum index » DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
MFOS VCO module question
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ericcoleridge



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PostPosted: Thu Oct 11, 2007 8:59 am    Post subject: MFOS VCO module question
Subject description: Is the sync suppossed to sound like this?
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The sync on my VCO sounds like it's stepping through different octaves or harmonics rather than the fluid phasing/flanging type sound that I normally think of as oscillator sync. Is this normal for the MFOS VCO?
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RF



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PostPosted: Thu Oct 11, 2007 11:31 am    Post subject: Reply with quote  Mark this post and the followings unread

I think that has to do with where you have the frequency pot set on the 'slave' VCO... IIRC it need to be set lower in frequency than the 'master'
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ian-s



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PostPosted: Thu Oct 11, 2007 12:29 pm    Post subject: Reply with quote  Mark this post and the followings unread

RF wrote:
I think that has to do with where you have the frequency pot set on the 'slave' VCO... IIRC it need to be set lower in frequency than the 'master'


You only hear the sync effect when the slave frequency is higher than the master. Can you post an example?
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RF



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PostPosted: Thu Oct 11, 2007 3:45 pm    Post subject: Reply with quote  Mark this post and the followings unread

yeah - what he said Smile my answer was inverted....
Thanks G2.
bruce
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ericcoleridge



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PostPosted: Fri Oct 12, 2007 1:30 pm    Post subject: Reply with quote  Mark this post and the followings unread

I think I had the master tuned lower, I mean, the MFOS VCO was definitely syncing... but it doesn't sound like oscillator sync on any synth I've ever heard.

It's almost like it's too strong, it's "stepping" through harmonics in a choppy way instead of sweeping. The oscillator sync sound that I know, and really like, is more of a vocally formant type sound... sort of like phasing.
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Broadwave



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PostPosted: Wed Oct 17, 2007 8:41 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Eric,

I know exactly what you mean... I've built 4 of them, and the sync wasn't what I expected either.

Change the value of the sync input cap to 0.01uf, and you'll get much closer to what you want. It's not perfect, but it's much closer to conventional hard sync. I've found that using a square or pulse wave for the sync input signal also helps Very Happy


Andy

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ericcoleridge



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PostPosted: Sat Oct 20, 2007 5:47 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thank you very much for the reply. It's funny, I got this same recommendation from someone else. I'm looking forward to trying it out.

I believe I have a 102 Ceramic cap in there right now. Maybe a box cap would be better also?
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Pehr



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PostPosted: Mon Oct 22, 2007 3:22 am    Post subject: Reply with quote  Mark this post and the followings unread

Shouldn't the slave VCO be at lower frequencies? I've always thought so Confused

If you tune the slave VCO to a higher frequency than the master, the slave actually manages to squeeze two wave cycles in one cycle of the master. Hence, the "stepping-through-octaves" effect can be heard.

If the slave vco is set to a very low frequency and then sweeps up, I believe you should hear the real syncing effect as the slave wave is gradually introduced inte the mix... I have't really managed to try this on my vco's, but I certainly will Very Happy

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Broadwave



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PostPosted: Mon Oct 22, 2007 6:06 am    Post subject: Reply with quote  Mark this post and the followings unread

Pehr wrote:
Shouldn't the slave VCO be at lower frequencies? I've always thought so


Yes, I agree definately!

The problem is that some VCO designs are Soft Sync and some are Hard... And there lays the problem - which is which?

Some people see Soft sync as harmonics latching in intervals (3rds, 5ths octaves etc.) where as Hard sync gives that typical agressive vowel sound, but I've also read that the opposite is true... Hard Sync latches and Soft is smooth!! Very confusing!

But I can assure you that the Ray Wilson VCO's sync is latching onto harmonics, and it's not until the input cap is changed that I get (amost) the typical sync sound I crave for.

I think it's all down to the reset pulse the sync input is working with... Is it Bi-polar or positive voltage only? Is the amplitude enough? etc.

Many sync input circuits I've seen also involve extra 1N4148 diodes, resistors and NPN/PNP transistors - probably to rectify (positive going pulse only) and sharpen up the incomming sync signal - but as yet, not a single VCO that I've built gives me that perfect ARP Oddy sync sound Crying or Very sad

Andy.

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Pehr



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PostPosted: Mon Oct 22, 2007 6:15 am    Post subject: Reply with quote  Mark this post and the followings unread

Yes, I've heard of the different types of sync but I'm not sure if I know the difference... Embarassed

However, here's what I recorded with my modular today.

Master is saw and its square goes to the sync input of another vco that is tapped from the square output. Cool

Pardon the noisy recording... Embarassed

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Blue Hell
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PostPosted: Mon Oct 22, 2007 9:35 am    Post subject: Reply with quote  Mark this post and the followings unread

This is based upon the Nord Modular G2 synth, but it might still be of interest as a general source of knowledge about synthesis. To experiment with it you could download the free G2 emulator software from the Clavia website (here), for Windows and for OSX.
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also .. could someone please turn down the thermostat a bit.
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Broadwave



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PostPosted: Tue Oct 23, 2007 7:30 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Jan, thanks for the link, very useful info..

I bought a G2 Engine about 3 months ago, but not had the time to really get into it since I started building my modular.

Anyway... back to that syncing feeling!

I did some digging around Ray's site and found all the info on his previous VCO designs, including some recommended mods.

His older designs (http://www.musicfromouterspace.com/analogsynth/August2003VCO.html) have a dedicated sync output taken directly from the integrator pulse (is that the correct technical term?), which is very similar to the ARP Odyssey, which seems the obvious way to go.

There is also another design (http://www.musicfromouterspace.com/analogsynth/VCO200503REV01/tomandianssuggestions.html) where Ray has some recommended mods suggested by Ian Fritz and Tom Arnold... including sync modifications - quote "the hardest sync you'll ever hear", although I don't understand why Ray didn't incorporate this mod in his current design.

As soon as I get home, I'll give it a go and report back.

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Broadwave



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PostPosted: Wed Oct 24, 2007 7:56 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi all,

Followed the instructions for the Fritz/Arnold mods... The sync is great!!! Exactly what I was looking for.

BUT, I now have problems with the pulse width side of things - all sorts of clicks and pops, and the oscillator stops if the initial frequency is taken too high!! GRRR!!!!!Evil or Very Mad

I'm hoping it's all down to the changes I made in the "ref section" of the integrator i.e. removing C8 and exchanging a resistor for a diode, changing the integrator cap from 1n etc.

Will put that section back to what it was, but keep the sync mod in, if I can.

Getting there, but very slowly.

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Pehr



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PostPosted: Tue Nov 06, 2007 2:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

AndyR1960 wrote:
Change the value of the sync input cap to 0.01uf, and you'll get much closer to what you want.


wow! What a difference! Very Happy Cool

I tried this mod on one of mine... and now I'm changing all of my sync caps salut

Thanks Andy for this tip! Very Happy

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funkyfarm



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PostPosted: Wed Nov 07, 2007 6:58 am    Post subject: Reply with quote  Mark this post and the followings unread

Can anyone tell me which is the best waveform to sync vco ?

I remember once using square but I was told (maybe by Tony Allgood, about his OAKLEY 1o3 VCO) that sawtooth were better for that...

So, you'd vote for falling ramp sawtooth, triangle, pulse or sinewave ?
I guess it has to have sharpen edges...
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Broadwave



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PostPosted: Thu Nov 08, 2007 4:27 am    Post subject: Reply with quote  Mark this post and the followings unread

Pehr, Glad I've been of some use - it's always nice to give back to the community Very Happy

Funkyfarm:
As far as the sync signal is concerned, I've always used Square/Pulse on the MFOS Oscillators - I've got a feeling that the sawtooth output on these oscs are actually ramp so not good as a sync source (I may be wrong, but I'm on vacation 7,000 miles away from home, and can't verify that for you at the moment).

Andy.

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Pehr



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PostPosted: Thu Nov 08, 2007 4:51 am    Post subject: Reply with quote  Mark this post and the followings unread

AndyR1960 wrote:
I've got a feeling that the sawtooth output on these oscs are actually ramp so not good as a sync source .


I just found out yesterday that they actually ramps (upwards)... Confused

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PostPosted: Fri Nov 09, 2007 7:59 am    Post subject: Reply with quote  Mark this post and the followings unread

One could perhaps connect R26 to U4 pin 1 to get the original saw |\|\|\|\
that is inverted by U4-B. Confused

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loss1234



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PostPosted: Wed Apr 02, 2008 5:20 am    Post subject: Reply with quote  Mark this post and the followings unread

i'm confused. i have one of the newer mfos vco's where it looks like the diode mod and a few others have been implemented. BUT the sync is still very weak. So i am wondering, which mods should I do? just the cap size or are there other mods that Ian recommends? there are so many mods listed on rays site that some of them cancel each other out and i dont want to mess up my vco which is almost fine except for the sync

thanks

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PostPosted: Wed Apr 02, 2008 8:59 am    Post subject: Reply with quote  Mark this post and the followings unread

replacing the cap worked for me Very Happy
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loss1234



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PostPosted: Wed Apr 02, 2008 10:12 am    Post subject: Reply with quote  Mark this post and the followings unread

replaced the cap
sync now seems to work pretty good at some tune knob settings...its not as thick as my ken stone vco and it seems to act weird if you dont get the knob setting JUST right but,,,better than what it was before. i also followed the advice of Ian and put in the opa2134 (Sp?) and to change the integrator cap to a 103 styrene...and to change the ref cap as well. i am now tracking the whole keyboard...awesome!!


thanks

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j.dilisio



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PostPosted: Thu Jun 11, 2009 8:07 am    Post subject: Reply with quote  Mark this post and the followings unread

it's a good thing I found this thread.
I was just getting ready to order 2 of these vco's.
I can hear from the sample on MFOS that the sync sounds a little rough and jumpy.

Is there any way someone could upload a sample that demonstrates the sync after changing the cap?
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PostPosted: Sun May 27, 2012 10:26 pm    Post subject: Reply with quote  Mark this post and the followings unread

Sorry to resurrect and old thread. I e-mailed Ray Wilson telling him that his sync audio demo was interesting, unlike hardsync... well this was his response:

"It's hard sync since the VCO is ramp core and the sync pulse resets the integrator. My VCO can't do soft sync. Soft sync is generally associated with tri-core VCOs. Actually the MFOS Wave Freaker gives more a of a soft sync effect (see that project). For both tri and sine waves it can completely reverse the direction of the wave at selectable points in the cycle. I have a link to a simple ramp to triangle convertor on the front page at MFOS"

What I hear in the audio demo isn't hard sync and this thread proves it.

BUT, PEOPLE!!!! SOFT SYNC HAS ONE BIG ADVANTAGE, AND NO ONE MENTIONED IT? My advice: Don't mod your MFOS VCO, don't buy MFOS VCO if you don't want soft-sync.

Advantage of soft-sync: Phase-aligned oscillators. Now I don't own MFOS VCO, I can only guess that it's capable of this. It's essential if you want to have two saw waves an octave apart playing a bassline. It's essential if you want two of any oscillator playing perfect 5ths 7ths, octaves apart and maintaining this cohesive sound. This audio demo is created with a digital synth... if it was created with an analog synth it would sound even better, trust me on this... this is pretty much how the MOTM soft sync sounds... Intellijel Dixie VCO is also capable of this.


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