Hz/volts - synths and sequencers

Analog synthesizer manufacturers typically adopt one of several standards:

Hz per volt - used by Yamaha and Korg 

1V per octave - used by Moog, Roland, ARP and Doepfer

1.2V per octave - used by Buchla and EML 

0.32V per octave - used by EMS

0.26V per octave - used on oscillator 3 of the EMS VCS3 

I've been playing a lot recently with my old Korgs.

I keep coming back to them. They are real classics !!!

They use the hertz/volts CV standard, meaning they follow a linear characteristic

where each successive octave requires a doubling of the control voltage.

In practical terms this means that the number of instruments which you can 

successfully integrate with your vintage Korg synths is limited.

Here is a list .. 

I'll update as I go along. 

If I have missed any, please let me know so I can add it to the list.

Arturia

Beatstep - cheap & flexible.

Beatstep Pro

Key step

Keystep Pro

Microfreak - one of the few modern synths whose sequencer can be configured to output Hz/v

Arturia Minibrute 2s

The MiniBrute 2S works. I suspect the rest of the "brutes" also work with old Korgs.

The standard used on most Eurorack modules and on Arturia's Brute series 

of synthesizers is V/Oct (1Volt per octave),

however, it can be changed to Hz/V (Hertz per Volt) using Arturia's MIDI control center.

CVs in the range 0V-1V, 0V-2V, 0V-5V, and 0V-8V.

Five clock standards are supported, including  analog clock, 24ppqn and 48ppqn. 

Of special note, the Brutes, beatsteps, etc  can convert analog clock to MIDI Clock and  then

transmit this over MIDI and USB. 

Thus you can synchronise MIDI equipment to those analogue clocks.

Keystep

The default is 1V/Oct , though this can be changed to Herz/Oct.

(1.2V /Oct is not supported).

Keystep pro

By default, the transmitted pitch voltage is compatible with the 1.0 V per octave standard,

To use a 1.2 V per octave or a Hertz per Volt (Hz/V) standard you can change the corresponding setting in the MIDI Control Center.

Microfreak

By default, the transmitted Pitch voltage is compatible with the 1v per octave standard.

To use the 1.2 V per octave standard, you have to change the corresponding setting in Utility>CV/Gate>Pitch Format or in the MIDI Control Center.

Gate signals can also have different output ranges (S-Trig, V-Trig 5V, V-Trig 10V). These too can be changed in Utility>CV/Gate>Gate Format or in the MIDI Control Center.

Doepfer

A-190-1 MCVS 

This is a MIDI to CV/SYNC Interface in Eurorack

You can set the CV to Hz/V and the trigger to -ve polarity

Expert Sleepers

Disting Mk1/2 (Eurorack)

Disting Mk 3

Disting Mk4

Silent way - software

It runs as a plug-in for your DAW

Elby Electronics

ED102 - Octave-Volts-Hertz

This is a eurorack module

Elektron

A4 - Analog 4

The synth's sequencer has a very flexible CV/gate

config. I use it with Buchla & well as Korg.

The CVs are digitally controlled which makes for high precision.

Endorphin.es

Shuttle control

PITCH 1V/OCT, PITCH 1.2V/OCT AND HZ/V are

the control voltages available

SHUTTLE CONTROL outputs +5V at C4 note 

(the highest voltage SHUTTLE CONTROL can transmit). 

Then 1 octave lower C3 will return +2.5V, C2: 1.25V, C1: 0.625V, C0: 0,313V, C-1: 0.156V and the last one C-2: 0.078125V (with pretty bad resolution however). 

As you may see, the accuracy in the lower octaves is bad and on the edge of SHUTTLE CONTROL's CV resolution possibilities. 

That is why the useful range for controlling such type of synthesizers is roundabout 3 to 4 octaves.

Future Retro

Mobius sequencer

G-storm

This is a eurorack module

Electro KVP Pitch CV + Gate Voltage Processor for MS-20

Harvestman aka Industrial Music Electronics 

English Tear (eurorack)

Hexinverter 

Mutant brain - polyphonic CV/gate 

                        CV output resolution: 12bits (V/oct or V/Hz)

Keith McMillen

QuNexus - keyboard/sequencer

Use the editor to set this to 1 Volt per Octave, 1.2 Volts per Octave (Buchla) , or Hertz per Volt

Kenton

Pro-solo

Pro-2000

Modular Solo

Korg synths & sequencers

One thing to always remember is that although the MS-20 uses Hz/V, the

original Korg designers showed some forethought & added a TOTAL IN 

socket on the patch panel.

This can be used as a V/Oct CV Input (with some careful adjustment of the

frequency modulation MG/T.Ext knob) 

It's not a proper V/Oct CV in (I think its better suited to filter, than pitch) 

but certainly better than nothing.

MS10

MS 20

MS 20 mini

MS 50 

VC 10 (vocoder)

X-911 (guitar synth)

MS-01 - foot controller pedal

MS-02 - CV/trigger interface

MS-03 - signal processor

               (Pitch to Voltage circuit)

MS-04 - pedal (CV modulation)

SQ-10 sequencer

SQ-1 sequencer

SQ- 64

Tracks A,B and C are for melodic/chords tracks and all have GATE/CV and MOD control voltage outputs for modular gear 

CV out can be: Hz/V, 0.26V/oct, 0.32V/oct, 1V/oct, 1.2V/oct  - 

with voltage bias adjustment and 0V reference note adjustment (per track)

Gate out: 10V, 5V, V-Trig, S-Trig

Mod out: 0V-10V,  voltage bias adjustment

Track D - the drum track has 16 possible tracks, via MIDI with 8 drum trigger 

outputs for working with modular gear.

FK - 3 Korg Vol pedal (not really part of the MS range, but still works well with them)

FK - 5 korg pedal

Sigma - KP-30 analog monophonic synthesizer

Cool joysticks & 19 presets

It possesses Hz/V CV & gate 

inputs/outputs

SE-500 Stage Echo

This is a Tape Echo machine.

Its has trigger inputs for feedback and turning the effect on/off.

There is also a CV input for controlling the speed

Torso Electronics

T-1 algorithmic sequencer

Ladik

U-202 V/oct to Hz/V converter (4HP) eurorack

U-201 Hz/V to V/oct converter (4HP)

Metasonix

S1000 Wretch Machine

RK7 VCO (eurorack)

RK4 Bandpass Filter/Osc (eurorack)

RK6 Dual-triode 12dB LPF

R-60 MIDI/CV interface

TM-3 SN80 Tube VCO 

TM-2 filter

TM-1 Waveshaper/Ring Modulator

R54 Vacuum Tube Oscillator & Filter

R-55 Thyratron VCO

TS-23 DUAL THYRATRON VCO

+ Phillip Rees 

Little MCV - Midi to CV converter

These are out of production, but I do see them come up

occasionally second hand on Reverb and Ebay

 Can generate control voltages for the common one-volt-per-octave (logarithmic VCO, as used by Roland and Moog) system and the so-called volts-per-hertz (linear VCO, as used by Korg) system. CV type is selected by a slider.

+ Polyend

 

 Polyend 2 - eurorack MIDI to CV converter

   1-4 Gate (0-5V or 0-10V),

   1-4 Pitch (0-10V, V/Oct, Hz/V, Buchla standard 1.2v/oct).

   A really handy module that allows you to use the sequencer

   of your choice

Pioneer 

Toraiz Squid sequencer

2x CV OUT (V/Oct, Hz/V) 

CV output range: 1V, 2V, 5V, 10V, ±5V (V/Oct) / 8V (Hz/V) 

2 GATE OUT (V-Trigger, S-Trigger) 

GATE output range: 5V, 10V (V-Trigger)

Sequentix 

Cirklon sequencer

Its a MIDI sequencer but the 

CVIO option adds 16 CV and 8 gate outputs.

The CV outputs support V/octave and Hz/V modes plus portamento/glide and micro-tuning options. 

The gate outputs can be configured in 5V v-gate or S-trig modes.

Squarp 

Pyramid sequencer

CV V/oct or CV Hz/V, 

or exotic voltages like 1.2, 0.32 or 0.5 V/oct.

Synthstrom

Deluge - synth/sequencer

The Deluge has been designed to support the widest range of CV / gate standards possible. 

A number of settings are available in the settings menu.

Each CV output may be set, in 0.01V increments, to any value between 0.01V and 2.00V per octave, or to “Hz per volt”. 

TouellSkouarn 

Jedonian 1V/Oct-Hz/V bidirectional Converter (eurorack)

Moog

The original Taurus I

PAIA

4700/2700 modular

Fatman

XOR Electronics

Nerdseq - eurorack tracker sequencer

Yamaha Synths

CS-5

CS-10

CS-15

CS-20 / CS 20M

Cs-30 ... has a built in sequencer.

Cs-40 / CS40M

These old Yamahas are Hz/V but have a different range

than say the Korg MS-10 or 20. 

The CS is scaled I believe at half the voltage of the MS 

(Yamaha's probably 0.25 to 0.5 to 1v and so on instead of Korg's 1V to 2V to 4V)

It's still double each octave ....so they have the same scaling curve) but the range

is different.

In practical terms this means you can sequence it with something like a SQ-1 

but you will probably find it won’t go down to the lower 0.25V?? octave of the CS.  

(I don't think the SQ-1 goes below 1V in Hz/V mode).

It's interesting that Yamaha never made a independent CV/gate sequencer.

It's a shame, as this would have made things a whole

lot easier

So the question is why even bother to add these connections??

I think the answer was to aid with expansion.

ie joining more than one synth.... 

in order to make a multiple-system synthesizer

Zlob

Dual VCO

This is a DIY eurorack VCO

There is a control voltage input, and a switch for selecting exponential or linear cv in.
The exponential setting should be good for Korg & Yamaha keyboards & sequencers 

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Final thoughts & conclusions

As I compiled the list I found that there were actually quite a lot of sequencers

that use the Hz/V standard. 

It's a testament to the MS20 in particular. It's legendary status ensured that lots and lots

of manufacturers chose to add a Hz/V option.

(Some even down right copied the synths).

I think it would be great if more manufacturers added a Hz/v option to new synths to add to this legacy.

I'd love to expand my MS system with a new 3 oscillator Korg MS 30 

For the moment (as far as synths that can use this standard go),

I'll have to be satisfied with using old Korg, PAiA & Yamaha synths.

Clocking the Korg SQ 10 - S triggers

I've been trying to clock or sync the Korg sq10 sequencer over the years with mixed success.
It's one of the limitations of this piece of kit.

Back in 1978 when this was made, there was no real industry standard such as MIDI. The different manufacturers went their own ways. Korg did provide a input jack for single stepping the sequencer. This is the best way to syncronize the SQ-10.

The clock/step input is a +5V trigger to ground.
Normally, the voltage is "high" . When a note is played, the trigger is shorted to ground.
This is also called an S-trigger, "short circuit trigger", or "negative trigger".
S-triggers are used by Moog, Korg and Yamaha synthesizers

(As a side note, the other form of trigger is a V-trigger. It's the reverse of an S-trigger, as it's a positive trigger. That is, normally the voltage is low (around 0 v) and at trigger produces a fixed positive voltage)

If you are trying to sync it up to other gear such as a roland Drum machine which uses sync 24 (also referred to as DIN), you will need a good clock divider, and probably some logic gates for it to work correctly.

Old Korg Drums seem to be the traditional way to clock the SQ10
The Korg Rhythm 55B (KR 55) clocks the sq10 perfectly.

The 55B manual, says you can choose the type of trigger with the switch on the left.

It has just the right outputs which match the SQ10's inputs
It looks like this drum was made for the vintage MS series of Korg synths.

 For this to work, there are only 2 settings on the SQ 10 you should use:

Sadly, the KR 55 as no sync or clock input. I would love to add midi sync.
The KR-55 runs at 8ppqn so a clock divider is required if you want to sync it to midi or sync24. 
The clock output on most Kenton midi to cv converters is ideal for this (divide by 3).

Other Korg drums that should be useful (Though I haven't tested them)include:
Korg KPR-77
Korg DDM 110 (Super Drums)
Korg DDM 220
Korg DDD 1

+ Korg Drum Machine Timeline
--------------------------------
Roland Drums

*** A Roland TR 606 drum will also step the sequencer. 
    Use the LT & HT trigger outs. This is a really cool way to 
    trigger the SQ10. turning on and off the toms will
    stop/start the Sq10.

The Roland CR 78 also sends a suitable trigger pulse.

This is the setting I used.

However, if you wish to sync this drum to something like midi, use the Future Retro Swynx. You can also program new patterns and you have DIN Sync.

-----------------------------

As the step input is a S-trigger, I decided to try a Moog Mother.
And guess what, it works.

The Moog Mother is the perfect midi clock to S-trigger converter.
(and it does a few more things besides)

plug the gate out of the M32 into the step in of the Korg sq10 
---------------------------------------------------------------------------------

For the Korg SQ-1 to sync the SQ10,  you need to change the SQ-1's GATE OUT polarity from positive (factory preset) to “-” (negative).

"While holding down the SQ-1's START/STOP button, turn the power on (the unit starts up in global parameter setting mode).
• Press the SQ-1's MODE/CLEAR button to make the button go dark. (This alternates between un-lit and lit each time you press the button: “-” when un-lit, “+” when lit.)
• Press the SQ-1's power button to save the setting."    (Korg Manual)

Sadly, the S-trigger uses up one of the gate outputs, not the sync out.

  Links
+ Modular Clocks - Analog, MIDI , PPQN
+ V-trig to S-trig converter