All things control voltage.
Old 28th March 2012
  #1
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Thread Starter
All things control voltage.

Hello. I am hopping that those of you with experience would be willing to enlighten the rest of us in regard to all things control voltage. Many of us were born after the heyday of CV and into the world of midi and all things digital. I for one understand what CV is used for, but not how it works or any other technical aspect. So here are a few questions.

1 How does CV work?

2 Why are the voltages different from one brand to another?

3 What is Gate, Trigger, pitch, etc?

4 What else can be controlled through CV?

5 Are CV jacks simply attached to a straight wire soldered to a trace on the circuit board or is there some sort of chip or conversion process in the line?

6 Can any old analog synth be tricked out with a CV jack for every function if space allows? If no, why not? If yes I hope the answer to number 5 is a yes

7 Why CV? What are the pros and cons vs midi and are there other options that never really gained in popularity?

8 When you have a synth that accepts both CV and midi is there any audible difference between the method of control that affects the character of the synth? An example would be the Oberheim Xpander. Will there be less stepping when controlled through CV?

Thank you,
Old 28th March 2012
  #2
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3 gate and trigger are used for triggering sounds. you probably know what pitch is.

4 anything on analogue synthesizers. every analogue synth uses CV, if it has MIDI it still gets converted to CV. have you heard an LFO? that is CV controlling that filter or pitch.

7 pros it's sample accurate.

8 it's sample accurate so if it's played form a sequencer it will sound tighter.
Old 28th March 2012
  #3
3 + infractions, forum membership suspended.
 

There is a ton of well written info on the Internet to answer your questions.

Try google.
Old 28th March 2012
  #5
Banned
 

Quote:
1 How does CV work?
voltage goes up..pitch becomes higher..voltage goes down.. pitch becomes lower...

you can exchange the word pitch with volume, timbre, attack time.. resonace amount... whatever your synth allows to be cv modulated..

Quote:
2 Why are the voltages different from one brand to another?
independent developments... midi was actually the first time the synth manufactors sit together to develop a standard every synth manufator uses.

Quote:
3 What is Gate, Trigger, pitch, etc?
RTFM

Quote:
4 What else can be controlled through CV?
everything that can be controled with an voltage...

you can for example overpatch the pots in an old faderboc and turn it into a cv > midi controler interface..

or with a relay turn your coffee machine on and off..thats not so easy with midi than with a cv signal...

Quote:
5 Are CV jacks simply attached to a straight wire soldered to a trace on the circuit board or is there some sort of chip or conversion process in the line?
its analog ..no chips.. just resistors

Quote:
6 Can any old analog synth be tricked out with a CV jack for every function if space allows? If no, why not? If yes I hope the answer to number 5 is a yes
sometimes not any function.. but depedend on the synth quiete a few..
My synths allways get a cv input for the filter wehn they dont come with one for example.. and on my 303 i ve outputs for the filter envelope and the accent envelope.. so i can run external modules more with the dynamic of the 303 sequences..

Quote:
7 Why CV? What are the pros and cons vs midi and are there other options that never really gained in popularity?
midi just came after cv.. just as digital synthezisers came after the analog ones..

The advantages of cv are free experimentation and ultrafine resolution..no stepping..smoooth and lightspeed fast... everything digital is primitiv in relation to this technical data.

the advantges of midi and digital.. polyphon keyboard data on 16 channels with 128 modulation controllers each, over One ! cable.
So a hell of an advantage.

but rather slow and stepped... and not accesible for patching really without writing software for it...

Quote:
8 When you have a synth that accepts both CV and midi is there any audible difference between the method of control that affects the character of the synth? An example would be the Oberheim Xpander. Will there be less stepping when controlled through CV?
Yes.. in most cases.
I not 100% sure on the expander because the filterchips are digitally controlled there.. but it should react at least faster than thru midi.
Old 28th March 2012
  #6
Old 28th March 2012
  #7
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Yoozer's Avatar
Quote:
Originally Posted by sctt_stone View Post
Great post! Thank you for taking the time to answer these questions in such as detailed fashion. This was highly informative.
Dude, please - don't quote the entire post when they're as big as this. Reptil will not suddenly delete it to see if you saved it on your harddisk.

edit; you could've left your reply, just remove the quote itself
Old 28th March 2012
  #8
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Thread Starter
Sorry, my forum etiquette sucks.
Quote:
Originally Posted by Yoozer View Post
Dude, please - don't quote the entire post when they're as big as this. Reptil will not suddenly delete it to see if you saved it on your harddisk.
Old 28th March 2012
  #9
no worriesss, I'm glad you got something out of it
the quick answer turned out to be slightly longer LOL

books: Some basic knowledge of electronics when dealing with modular synths is very handy. It's not necessary, as the components are laid out in a schematic way, you (or I) don't have to know how an Oscillator circuit is built up. But it's nice to make some small mods, or to understand what the relationship between audio and CV (both electricity inside an analogue synth) are. Moreover, everything electronic that we work with (mixers, compressors, etc..) is built up from the same basic principles.

for patching ideas look at the sticky above.

"The Art of Electronics" Paul Horowitz is very good
The art of electronics - Paul Horowitz, Winfield Hill - Google Boeken

"Teach yourself: Electricity and Electronics" Stan Gibilisco is a nice introduction
Amazon.com: Teach Yourself Electricity and Electronics (0639785330844): Stan Gibilisco: Books
Old 28th March 2012
  #10
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infradead's Avatar
 

CV is basically a poor man's MIDI


>_<
Old 28th March 2012
  #11
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BTByrd's Avatar
Quote:
Originally Posted by infradead View Post
CV is basically a poor man's MIDI


>_<
More like the rich man's MIDI these days...
Old 28th March 2012
  #12
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Quote:
Originally Posted by BTByrd View Post
More like the rich man's MIDI these days...
i agree
Old 28th March 2012
  #13
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CV has absolutely nothing to do with MIDI, in case anyone was under this impression

Bob Moog implemented CV and v/oct standard in the 60s. MIDI came along in the 80s. CV are continuous voltages, while MIDI is digital.
Old 28th March 2012
  #14
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On the subject of CV, does anyone have any MIDI->CV recommendations and if that would work well for sequencing? Or is it better to sequence directly from an analogue CV sequencer?
Old 28th March 2012
  #15
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@Reptil

Above and beyond the call of duty!! nice one!

Re midi to CV devices - Kenton. You get a lot for your money especially if you buy second hand and they really know what they are doing. Also the head honcho is a very helpful guy.
Old 28th March 2012
  #16
Anyone wanna write about filters and list different filter types?
that would be nice!
Old 29th March 2012
  #17
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to quote from the great and only dude: "filters are like girlfriends"
.comparing them objectively is nice, but when you have one in your arms...in the heat of the moment.... all objectivity can go out the window.

that said, any modular will benefit from at least 3 filters to choose from - one state-variable or dedicated high-pass, one dedicated lowpass, and one raunchy/dirty/weird filter for variations.

there are oodles of 'extras' to consider: bandpass, notch, fixed filterbanks, VC filterbanks....and the weird topologies such as switched-capacitor(harvestman), combo VCF/VCOs in one(metasonix), quadtrature(mankato/octature) and on and on

there are also 'families' of components used with different sound tendencies:
VACTROL - obsolete yet fun. slow to react to cv as if built-in slewing. used in lowpass gates(buchla, makenoise etc) for woody, plucky timbres
TUBE - harmonically richer than transistor, generally. but also generally narrower ranges and unpredictable behavior under cv.
DIODE - varies widely; from EMS synthi to tb-303 they tend to sound squirty and squidgy. 'wet' and like to be goosed into screaming feedback.
OP-AMP - not seen much anymore; correct me if i'm wrong? i have run across a few op-amp ladder filters but damned if i can remember what they were in.
TRANSISTOR-LADDER - moog's famous recipe that everybody clones now that the patent is run out. smooth and syrupy with a tendency to go quieter as resonance is increased.

hopefully someone that designs these things can comment, too.
i may have a lot of experience but conveying this stuff in words is like describing the taste of food
just grab a few and go i say!
Old 29th March 2012
  #18
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BTByrd's Avatar
I've been leaving MIDI behind and gravitating toward a system entirely based on control voltage, that's also sync'ed to MIDI clock so I can use plugins - it's nice having Maschine and Maschinedrum locked in sync to the modular.

My favorite CV sources:

Modcan Quad LFO
Modcan VCDO
Modcan Touch Sequencer
4MS PEG
Synthtech E350 / Dual Morphing LFO
Make Noise Maths
Make Noise Pressure Points
Make Noise Rene
Livewire Vulcan + Mind Meld
TipTop Z8000

Other fun CV generators:

Anything + a quantizer
Doepfer or Cwejman external input module (or other envelope generator / comparator)
4MS RCD / SCM + Breakouts
Bleep Labs Thingamagoop V2
Silent Way

Fun modules to modulate:

Any filter
Waveshapers
Modcan VCDO
Modcan Dual Frequency Shifter
Synthtech E350
Harvestman Piston Honda
Livewire AFG
Old 9th April 2012
  #19
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Thread Starter
I have an addictive personality. If I get into the modular thing I will be broke forever. Like a true Gearslut I think I am going to start by installing a CV kit on my ARP odyssey myself. I would love to add a Mod wheel, wonder if that is possible? I hope I do not screw it up.
Quote:
Originally Posted by BTByrd View Post
I've been leaving MIDI behind and gravitating toward a system entirely based on control voltage, that's also sync'ed to MIDI clock so I can use plugins - it's nice having Maschine and Maschinedrum locked in sync to the modular.

My favorite CV sources:

Modcan Quad LFO
Modcan VCDO
Modcan Touch Sequencer
4MS PEG
Synthtech E350 / Dual Morphing LFO
Make Noise Maths
Make Noise Pressure Points
Make Noise Rene
Livewire Vulcan + Mind Meld
TipTop Z8000

Other fun CV generators:

Anything + a quantizer
Doepfer or Cwejman external input module (or other envelope generator / comparator)
4MS RCD / SCM + Breakouts
Bleep Labs Thingamagoop V2
Silent Way

Fun modules to modulate:

Any filter
Waveshapers
Modcan VCDO
Modcan Dual Frequency Shifter
Synthtech E350
Harvestman Piston Honda
Livewire AFG
Old 9th April 2012
  #20
ark
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Two points about CV that I didn't see mentioned so far in a quick readthrough of this thread:

1) Because control voltages take effect immediately (at least compared with MIDI), you can modulate a CV at audio frequencies. Such rapid modulation makes possible audio effects that MIDI is nowhere near fast enough to handle.

2) Some audio devices that accept CV inputs, notably Moogerfoogers, have current-limited power supplies that take effect if you use a TRS plug instead of a TS plug. Such devices let you use an analog expression pedal in place of a CV source. Read the manual for your device to see if this applies to you.
Old 9th April 2012
  #21
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I have my first modular system coming in August(so I am told). Ive been studying like crazy trying to prepare myself and learn everything from different sizes(I'm going 5U), formats, cases, power supplies, adapters, and on and f**king on it goes! So much to wrap your brain around. So to see a thread like this with the response Reptil and others here gave is fantastic. I hope this thread keeps going.
Old 9th April 2012
  #22
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infradead's Avatar
 

Quote:
Originally Posted by Gringo Starr View Post
I have my first modular system coming in August(so I am told). Ive been studying like crazy trying to prepare myself and learn everything from different sizes(I'm going 5U), formats, cases, power supplies, adapters, and on and f**king on it goes! So much to wrap your brain around. So to see a thread like this with the response Reptil and others here gave is fantastic. I hope this thread keeps going.
the biggest thing is experiment and play around. always try running everything at audio rates. run audio through a clock divider and all of a sudden you have a sub harmonic generator.
Old 9th April 2012
  #23
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Quote:
Originally Posted by sctt_stone View Post
How does CV work?
about 60 hrs a week including nights and weekends, with occasional time off for parties in the woods.

- controlvoltage

Old 9th April 2012
  #24
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I don't have a clever retort like the one above, but v/oct is preferred for oscillator pitch and filter tracking because the modulation index remains consistent over the entire range IE an LFO producing a one volt waveform results in a one octave modulation anywhere in the pitch range. That's doesn't happen in a v/hz system - a one volt LFO waveform will result in different modulation index across the pitch range. One reason the original Taurus I pedals were v/hz was because there was no LFO or modulation of any kind, and the one octave pedal lended itself to a v/hz system.

Korg didn't invent the v/hz system, it has been around decades before them (the telecommunications and test industry had v/hz systems).

For every octave change, the frequencies double (exponential). V/hz calls for an exponential change of voltage (1V, 2V, 4V, 8V, etc) to result in a doubling of frequency (100hz, 200hz, 400hz, 800hz, etc) and is called a linear system (the scale ratio of numerator over denominator is linear). V/oct calls for a linear change of voltage (1V, 2V, 3V, 4V etc) to result in a doubling of frequency (100hz, 200hz, 400hz, 800hz, etc) and is called an exponential system (the scale ratio of numerator over denominator is exponential).

The key part of a v/oct oscillator is the exponential converter, which converts a linear voltage to an exponential current (current drives the charging operation of the capacitor that produces the oscillator waveform). Designing an exponential converter during the 1960s/70s was tricky engineering and wasn't as advanced as today's technology. It was also the primary source of tuning drift if not designed well.

A v/hz oscillator is identical to a v/oct oscillator with the omission of the linear to exponential converter. Although it is a simpler design that stays in tune better, it has a more limited range than v/oct. The power rails of circuits are usually +/-15VDC. If you drive a v/hz oscillator to 2V, 4V, 8V, then 16V you will find the circuit will not respond any higher than 15V, you cannot exceed the power rail. At the other extreme where the voltage divides by two for every descending octave, you reach a point where the voltage is in the millivolt range and if you thought tuning drifts were bad with v/oct it's even worse with millivolt v/hz. And with today's 5-3VDC low voltage designs it is not hard to reach that limit.
Old 2nd February 2013
  #25
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Stevism's Avatar
this is an ultra noob question...

but where do i buy patch cables? are they just mono 1/8" (or 1/4") ts cable? does stereo not work?

:(
Old 2nd February 2013
  #26
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Mono cables, stereo doesn't work. Most modular supply places sell them.
Old 2nd February 2013
  #27
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thank you! i could never really feel confident about it

what if i wanted to use cv out from a mono cable, but then used the exposed wires to control something else?

i have this little device from Bleep Labs that accepts CV input but doesn't have cv jacks, and now that i have a minibrute i'd love to experiment

would i just strip one end of a cable?

"The screw terminals can also act as CV inputs."

the three things on top (pot, photoreceptor, pot) all screw in on the back, i can post a picture if you want of that

Old 2nd February 2013
  #28
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Reptil ,

This is why a little knowledge is a dangerous thing.

Its the amps and not the volts that will kill you?

Is the single most dangerous fallacy about electricity abounding around the internet today.

Please learn some ohms law before you start saying dangerous statements like this.

Its a misunderstanding of volts/amps and resistance that for many was incorrectly taught in school when often discussing static electricity which a we all know is very high voltage and very low current yet appears totally safe.

You cannot compare static electricity with normal high voltage electricity.

Capacitance and resistance matter hugely.

12000 volts is not an untypical voltage for static

and as you SHOULD know energy stored is 0.5 x c x v

so lets assume 100 pf and 1.5kohm , thats an energy dissipation of 72uJ

a TINY amount,

The reason why you only feel a tingle is that the energy is dissipated EXTREMELY quickly , over say a micro second , its peak Amperage is actually close to 8 amps but it lasts such a short period of time it cause no damage.

Now 'real' electricity ohms law says V/R = I voltage divided by resistance is current.

300volts / 2kohms would be 150ma thats enough to cause your heart to go into spasm.

V/R=I is a linear relationship.

As volts go up so does amperage and in humans we are not normal resistors as voltage increases passing through a human resistance drops so current increases.

It is an extremely misleading and potentially lethal to suggest otherwise.

As a moderator you really should know better than to say things like this.

lurn2electricity.

Gareth
Old 2nd February 2013
  #29
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Stevism's Avatar
i wish i was a normal resistor




thank you for the important information, i actually did read all of it and it was pretty cool
Old 2nd February 2013
  #30
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Thank you.

I left the rest of the inaccuracies alone , lifes to short no pun intended... no really.

However when it comes to stuff that can kill..........

G
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