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Any advantages to Hz/Volt
MUFF WIGGLER Forum Index -> Modular Synth General Discussion  
Author Any advantages to Hz/Volt
raccoonboy
I know the advantages of volts/octave obviously. Handy for filter tracking etc (however I have great keyboard tracking of the filters on my MS20m now thanks to the ES-3).

But are there any advantages or inherent differences in sound because of this (I realise back in the day it was a cheaper)?

I remember reading that when they remade the MS20 mini, they said that they considered volts/oct but didn't as then it wouldnt be the same synth anymore which made me assume maybe it does affect the sound...?

I know yamaha used hz/volt too. Was the cs-80 this way? If so that's two of my fav sounding synths using hz/volt.


Hmmmm
Joe.
I don't think there's any benefit at all. I'd say it's completely redundant.

V/oct is linear, in Euro where you have a 10 volt (positive) CV range you can have control over 10 octaves. HZ/Volt is exponential, and you would only have control over 4 octaves.

The benefit with a linear relationship is that you can Offset V/oct easily, it's always +1 or -1 volt to change a sequence up or down one octave. you can also add two notes using a v/oct signal, and still get an actual note with the end result.
UltraViolet
Both systems work and should sound the same. Volts/octave makes working with control voltages much simpler (add a volt to raise any note one octave). Volts/Hz is cheaper to build for simpler all in one systems.
papz
Hz/V or V/oct is related to pitch control only and doesn't affect the sound.
An advantage to Hz/V is no exponential converter is needed, which makes the build easier and cheaper.

Regarding the MS20 :

http://www.korganalogue.net/korgms/mstt.html wrote:
The Hz./V MS-20 is compatible with V/Oct. synths after all! -

"I can hardly believe no one knows about this already. It is possible to control an MS-20 from a V/Octave keyboard or MIDI/CV converter without a special interface. If you don't believe it, try it . .

When I first got my MS-20, I noticed that the filters don't track the keyboard at all. I plugged the keyboard cv to the filter cv in, but then the filter tracked the keyboard slowly in the lower octave, then went screeching off in search of tweeters to kill! I soon realised that the filter was tracking exponentially. I looked at the schematics and sure enough, both the VCO's and the VCF's have exponential converters on the modulation inputs. (You can tell this is the case, because the synth also goes radically out of tune when you plug the kbd cv to the TOTAL input, and wind up the MG / T.EXT knob in the FM section.)So, if you stick a V/OCT input into the modulation inputs and adjust the MG level for correct scaling, it all works and the filters track too.

Here's how you do it:

1. Plug the performance wheel into the keyboard cv input (middle, right) to disconnect the keyboard.
2. Plug the V/OCT cv from your MIDI/cv converter or another synth into the Total jack (top left).
3. Plug the s-trig. from your MIDI/cv or synth into the MS-20 trigger input.
4. Play a note on your MIDI keyboard or the controlling synth, and adjust the MS-20 performance wheel until you get a sensible pitch.
5. Adjust the VCO mod. levels until playing an octave on your MIDI (or other synth) keyboard gives an octave out of the MS-20. Then adjust the MS-20 performance wheel to coarse tune the MS20 and use the tuning pot to fine tune it.
6. The filter mod level pots adjust filter tracking in the same way.

You lose use of the performance wheel on the MS-20, but that's not a big problem if your MIDI/cv converter or your other synth has pitch bend. You will need a v-to-s trigger converter (i.e. the MS-02 Interface) to control the MS-20 from synths without s-trig. outputs, but they're simple to make (two resistors and an NPN transistor, plenty of circuits posted elsewhere).

I don't have the MS-20 in front of me, so apologies if the names of pots and jacks are not exact. Believe me, it does work!"

(from Steve Ridley)

Somebody else added:

"Beware of one thing... the VCF's are twice as sensitive as VCO's so that you must bring the VCF's mod pots to about 5 where as you would have the VCO's mod pot to 10. I think this can confuse some people the first time they fool around... Actually, if one wants good VCF tracking one has to be careful in trimming..."
raccoonboy
Thought as much. No real advantages except price. Didn't think it'd affect the sound either. Was just checking it dint give it some secret low fi sauce due to maybe less precise tracking or something.

Thanks to the above poster but I have MS20m with volt/oct in and filter tracking via es3 works great for me so...
jkjelec
One cool thing is that when Hz/V VCOs are controlled with a linear controller like the CS-80 ribbon, when pitch-bended down the frequency can go so low that the VCOs sort of stop oscillating or just get a few clicks a second. It wouldn't be so easy to recreate this effect with a V/Oct VCO.
jkjelec
I've probably posted this before, but something that the late David Wilson of the New England Synthesizer Museum told me about Hz/V always got me thinking. He told me that:

In the V/Oct system, an Offset of the control voltage transposes the VCO and a change of the Scaling of the control voltage changes the scaling of the VCO. While in the Hz/V system, an Offset of the control voltage changes the scaling of the the VCO and a change of the Scaling of the control voltage transposes the VCO.

Maybe it's just me, but, mind = blown Dead Banana lol
raccoonboy
jkjelec wrote:
One cool thing is that when they are controlled with a linear controller like the CS-80 ribbon, when pitch-bended down the frequency can go so low that the VCOs sort of stop oscillating or just get a few clicks a second. It wouldn't be so easy to recreate this effect with a V/Oct VCO.


I have heard this on my ms20, not with a ribbon, can't remember what with. Will have to try on my volt/octave synths and see if they won't push as far.

As for the above thing.. Then yes, my mind is blown, but only because I don't understand it. hahah.

I kinda know what these things mean individually but for some reason in that sentence is confusing me. lol
jkjelec
raccoonboy wrote:
Quote:
I have heard this on my ms20, not with a ribbon, can't remember what with.


Maybe just patch the MS-20's pitchbend wheel to directly control one of the VCOs (NOT using the Modulation Input which is V/Oct). Then bend down.
cornutt
raccoonboy wrote:


I kinda know what these things mean individually but for some reason in that sentence is confusing me. lol


The "scaling" is a measure of how much a change in the control voltage causes a change in frequency of the oscillator. If we expect the VCO to play in tune, something somewhere has to do the scaling. In a V/Oct setup, the VCO does the scaling itself. In a V/Hz setup, something external to the VCO has to do it.

Consider an old-fashioned monophonic V/Hz synth from the '70s, like an early Korg or a PAiA modular. They used V/Hz VCOs. In order to play in tune, the keyboard had to be wired to produce a control voltage that increased exponentially as you went from lower to higher notes. So if, say, the lowest C on the keyboard produced 1 volt, the next higher C produced 2 volts, the one above that 4 volts, the one above that 8 volts, etc. If the keyboard had a switch that transposed it down one octave, then what the switch did electrically was insert a voltage divider into the keyboard circuit. So with the switch on, it divided down the lowest C to 0.5V, the next higher one to 1 V, the next higher one to 2 V, and so on. By changing the scaling, it transposed the VCO.

Now take this same keyboard and add 1 V to its control voltage output. Now the lowest C, instead of producing 1 V, produces 2V, so it makes the VCO play the C one octave higher. However, the next highest C on the keyboard now produces 3 V instead of 2 V -- which means it plays about a fifth higher than the lower C! The C above that will output 4 V, which will make the VCO play one octave higher than the lowest C, even thought it's a span of two octaves on the keyboard. By adding the 1 V, we changed the scaling.
raccoonboy
cornutt wrote:
raccoonboy wrote:


I kinda know what these things mean individually but for some reason in that sentence is confusing me. lol


The "scaling" is a measure of how much a change in the control voltage causes a change in frequency of the oscillator. If we expect the VCO to play in tune, something somewhere has to do the scaling. In a V/Oct setup, the VCO does the scaling itself. In a V/Hz setup, something external to the VCO has to do it.

Consider an old-fashioned monophonic V/Hz synth from the '70s, like an early Korg or a PAiA modular. They used V/Hz VCOs. In order to play in tune, the keyboard had to be wired to produce a control voltage that increased exponentially as you went from lower to higher notes. So if, say, the lowest C on the keyboard produced 1 volt, the next higher C produced 2 volts, the one above that 4 volts, the one above that 8 volts, etc. If the keyboard had a switch that transposed it down one octave, then what the switch did electrically was insert a voltage divider into the keyboard circuit. So with the switch on, it divided down the lowest C to 0.5V, the next higher one to 1 V, the next higher one to 2 V, and so on. By changing the scaling, it transposed the VCO.

Now take this same keyboard and add 1 V to its control voltage output. Now the lowest C, instead of producing 1 V, produces 2V, so it makes the VCO play the C one octave higher. However, the next highest C on the keyboard now produces 3 V instead of 2 V -- which means it plays about a fifth higher than the lower C! The C above that will output 4 V, which will make the VCO play one octave higher than the lowest C, even thought it's a span of two octaves on the keyboard. By adding the 1 V, we changed the scaling.


Very good explanation thanks. It all makes sense now. Yes. So it is funny that the hz/volt and volt/oct are kind of opposites from each other.
timdrage
easier to build, escape from archaic 'music' paradigms grin
nigel
papz wrote:
An advantage to Hz/V is no exponential converter is needed, which makes the build easier and cheaper.

Regarding the MS20 :

http://www.korganalogue.net/korgms/mstt.html wrote:
[...] I looked at the schematics and sure enough, both the VCO's and the VCF's have exponential converters on the modulation inputs. [...]

So it still has exponential converters, but they are placed in a different position in the circuit. I'm not sure how this could be easier or cheaper than a V/Oct system. I guess the modulation converters can be less precise, which might be some minor advantage.
MikeDB
raccoonboy wrote:
are there any advantages or inherent differences in sound because of this (I realise back in the day it was a cheaper)?



Probably not so relevant nowadays but 'back in my day' as you say (my first synth was late 60s/early 70s) the huge advantage of V/Hz was you could build absolutely pure sinewave oscillators with excellent tracking. You had to select different capacitors for the octaves but it definitely gave a different sound to Moogs and VCSs.
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