Thursday, 23 March 2023

ARP 2600 - Ring Modulator

The basic principle of ring modulation involves taking two input signals and multiplying them together. The resulting output signal contains a series of harmonics that are the sum and difference frequencies of the two input signals. 


We are basically combining two frequencies to create sidebands.
This technique is commonly used in electronic music synthesis and sound design to create complex, dissonant, metallic or bell-like sounds and timbres.

The ring modulator on the ARP 2600 is particularly interesting because it can also be used as a frequency multiplier. By sending a single frequency into one input of the ring modulator and adjusting the frequency of the other input, you can create complex and evolving harmonic patterns and evolving sounds.

The left and right inputs are normalised to VCO 1 & VCO 2
though these signals can be over-ridden by patching into the jacks.

You can also use it as a very unusual CV mixer.

Notice the Audio/DC switch.



The Ring-Mod module is normalised to both the VCF and VCA.
This means you can have both a filtered and a non-filtered ring-modulated signal


Patch 1
Since VCO1 & 2 are already hard-wired to the ring-mod its 
good to start experiments just by tweaking the frequencies of the two VCOs.

You don't have to do any patching.
Just open up the connection to the VCA and listen.
Results can be pretty wild and unpredictable.
It's a sound designers dream. ;-)

Patch 2
Adding different wave-forms into input 2


Play around with the Audio/DC switch.
You can also change one of  the inputs to a LFO, and keep the other as audio.

Patch 3
Using the ring modulator to create CVs
Set both inputs to Low frequencies.
Thus the Ring Mod won't produce sound ... instead  it will produce control voltages.

So the ring modulator is now converted into an unusual CV mixer.
It's output can now be plugged into anywhere that accepts CVs.

In this example the inputs to the RM are LFOs.
The output of the RM is modulating the Fc of the filter.



Patch 4
Ring Mod as a VCA
The ARP's ring mod is kind of "super" vca because it is a "4 quadrant" multiplier vs the normal VCA which is a 2 quadrant multiplier .


Set the control switch to DC.
I'm using noise as a sound source.
Plug this into the left input
The right input are various waveforms ... all LFOs 
The output of the ring mod is plugged straight into the mixer.






Wednesday, 22 March 2023

Greece - rhodes 1

 Some pics of Rhodes.

Rhodes is a Greek island located in the eastern Aegean Sea.
It is the largest of the Dodecanese islands and has a rich history dating back to ancient times.

The island was an important center of the Minoan civilization, and later became part of the Roman Empire. It was also a stronghold of the Byzantine Empire and was conquered by the Knights Hospitaller in the 14th century. The Knights constructed the famous Palace of the Grand Master of the Knights of Rhodes, which still stands in the island's main town.


This is the entrance to Rhodes Harbour.
According to legend,  it was on this spot that was erected a statue of the Greek sun-god Helios,
by Chares of Lindos in 280 BC. One of the Seven Wonders of the Ancient World, it was constructed to celebrate the successful defence of Rhodes city against an attack by Demetrius Poliorcetes, who had besieged it for a year with a large army and navy.


The walled city of Rhodes, also known as the Old Town of Rhodes, is a UNESCO World Heritage site and one of the best-preserved medieval towns in Europe. The city is located on the northern tip of the island of Rhodes and is surrounded by a massive defensive wall, which was constructed by the Knights of St. John in the 14th century.

..
The walled city covers an area of approximately 200 acres and is home to many historic 
buildings and landmarks. One of the most famous landmarks in the city is the Palace of the Grand Master of the Knights of Rhodes, which was built in the 14th century and served as the headquarters of the Knights Hospitaller.
D' Ambrose Gate, City Wall entrance, Rhodes, Greece





St. Anthony’s Gate, or the Gate of St. Athanasios, is a popular historic entrance to the walled city of Rhodes. The locals also habitually refer to it as Saint Francis' Gate due to the church of Saint Francis of Assisi, built by the Italians in the first part of the 20th century, located just outside.

The coat of arms displayed above the entrance, dates back to the times of Grand Master Jean de Lastic (1437-1454), 




The Street of the Knights, which is lined with medieval buildings and served as the main street of the Knights' quarter.




The walled city of Rhodes is also home to many shops, restaurants, and cafes, as well as several hotels and guesthouses. It is a popular destination for tourists who come to explore its rich history, admire its architecture, and soak up its vibrant atmosphere.









Lawrence Durrell House (villa Kleobolus).
Durrell set up house with his partner, Eve in the little gatekeeper's lodge of an old Turkish cemetery.











The Goverors Palace.
This is modern.
The palace, which overlooks the Porto del Mandraccio on one side and the Foro Italico on the other, was built in 1926 - 1927 to a design by the architect Florestano Di Fausto , taking up the Gothic style of the Doge's Palace in Venice .






.






Saturday, 18 March 2023

ARP 2600 - Sample and hold (& electronic switch)

This is a brief rundown of the ARP 2600 Sample and hold section.
It's a very useful module often used for creating random or stepped sequences of notes, as well as for adding subtle variations to existing signals. It can be triggered by an internal clock, an external signal, or manually. 

The stepped levels produced in this manner are useful for controlling things like oscillator and 
filter frequencies and VCA gain.


Firstly, what is a sample and hold circuit?

It's a circuit that samples an incoming voltage signal and holds it at a constant level until the next sample is taken. It consists of two main parts: the sample circuit and the hold circuit.

The sample circuit takes an incoming signal and converts it to a voltage that is stored in a capacitor. The rate at which the capacitor is charged determines how quickly the circuit responds to changes in the input signal. The faster the charging rate, the more responsive the circuit will be to changes in the input signal.

The hold circuit is responsible for holding the voltage level once it has been sampled. It uses a switch to disconnect the capacitor from the sample circuit, allowing the voltage level to remain constant until the next sample is taken.

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

There are 2 sliders:
Rate & Level

Rate: It controls the speed of the internal clock.
The automatic triggering of the envelopes is controlled from here.

When it is disconnected from the S/H circuit (by plugging a cable into 
the external clock in), the rate control will have no effect on the operation of the S/H circuit

Level : The level control attenuates the input signal before it is fed to the S/H circuit. 


This connection labelled S/H gate is rather confusing.

There is a small switch above the jack.
In the switch's upper position, the ARP's keyboard trigger & gate signals are connected to the EG and will fire them when a key is pressed.


In the lower position the connection to the keyboard will be broken and instead, the EG will be connected to the ARP's internal clock (a square wave), not the sample & hold.
So the Envelopes are triggered by the internal clock.
You can also trigger these envelopes with an external sequencer. 
They respond to +10V triggers & gates (pulse waves are nice).

The Sample and hold has 2 inputs and 1 output.


Inputs: a trigger input - Clock in
            Sample in (the waveform to be              sampled), 
Output: S/H out

The trigger input (ext clock in) is defaulted from the internal clock, 
but any square or pulse wave, or the keyboard gate or trigger signals, will work.




The default Sample input is from the Noise Generator.
Thus, as the default signal being sampled is random noise, the output voltages are correspondingly unpredictable.
So an infinite variety of cyclical output patterns may be obtained, 
You can of course sample periodic waveforms rather than random noise. 
The alternative sample input is rather confusing labelled: Noise Gen/Sample & Hold
Here you can plug something like a LFO or a VCO to be sampled instead of noise.


The electronic switch is Bi-directional and consists of 3 jacks
labelled A, B & C.

Ie it can switch switch between two inputs (A/B) & one output (C)
OR
1 input (C) & 2 outputs (A/B).

The electronic switch can be made to alternate between  A & B.
The switching speed is controlled by the internal clock & the rate slider.





----------------
Some patch examples

The S/H is normalled to VCO 1.
It's sending random CVs to VCO1 -- thus the random notes.
Its similar to a Buchla Source of Uncertainity.

Audio from VCO1 is passed through to the filter.
The filter is modulated by the ADSR which in turn is triggered by the internal clock.

By playing with the two Noise siders & two S/H sliders you can create lots of variation.
(all audio is from the 2600's speakers)


--------------
Patch 2
A single patch cable from the ramp waveform output of VCO2.
Its behaving like a LFO
This is the voltage which will be sampled instead of random noise.


The audio is from VCO 1 only





Remember that the three VCOs have a LF (low frequency)
setting so can be used as LFOs

In the video above I'm using the VCO in the audio setting.
It sounds very random as you increase the frequency.
But if you use the VCO in the LF setting, the voltage is sampled
more slowly and you'll get arpeggios.








--------------
Using the Lag processor.


Its kind of like portamento

----------------
Analog bit-crushing (down sampling)
We need to give the S/H a really fast clock

We can swap out the internal clock with an external clock.

Setup:
I'll use VCO 1 as the clock. (square wave output)
VCO 2 is the sampled audio source
Plug the output of the S/H into the VCO 2 input of the filter


----------------------
Use the clock out as a extra LFO
the Clock out is a square wave.

So this 1st photo is of a square wave LFO

This second photo takes the same idea but uses the lag processor to smooth out the square wave
and shape the LFO.


-------------------------------
PWM 
Of the ARP 2600 three VCOs, only VCO 2 has a pulse width modulation input.

This patch is a neat way to add some PWM without loosing another VCO


As in the patch above, I'm using the lag processor to convert the square pulse to a triangle LFO



----------------------
panning effect






Links
ARP Index
17. Sample & Hold  ... build notes for the TTSH
+ 18. Electronic Switch .... build notes for the TTSH
16. Internal Clock ...build notes for the TTSH

Friday, 17 March 2023

Digitakt & Korg Volca FM - patch notes

Current Live Rig

I'm using a Volca FM 1 with Unofficial Firmware 1.09
The new firmware is excellent
I'm sending CC values from the digitakt to the FM

Possible CCs

TRANSPOSE 40*_Val 1
VELOCITY 41*_Val 2
ALGORITHM 48*_Val 3
CC 88: Load patch, value 0-4: patch 1, 5-8: patch 2 etc up to 127_Val 4
MODULATOR ATTACK 42*_Val 5
MODULATOR DECAY 43*_Val 6
CARRIER ATTACK 44*_Val 7
CARRIER DECAY 45*_Val 8
ARP TYPE 49
ARP DIV 50

CC 1 : (Mod wheel) assignable via CC 91, defaults to Pitch Mod Depth
CC 85: Chorus on/off. value < 64 off, value >= 64 on_Val 1.
CC 86: Chorus stereo width, 64 is default_Val 2
CC 87: Chorus speed, 64 is default_Val 3
LFO PITCH DEPTH 47*_Val 5
LFO RATE 46_Val 6
CC 89: Load pattern, value 0-8: pattern 1, 9-16: pattern 2 etc up to 127
CC 90: Tempo divisor, value 0-31: 1/1, 32-63: 1/2, 64-95: 1/4, 96-127: 1/8 (!)
CC 91: Mod wheel mapping: decides what MIDI CC mod wheel should map to. Example: value 42 sent on CC 91 -> Mod wheel now controls Modulator Attack


Remember that the Digitakt has 8 MIDI channels (A-H)
Of course you can have multiple channels running at the same time sequencing
the one Volca.
These different channels can have different CC sends.

The CCs I picked for MIDI channel A are labeled with Val 1-8
The CCs I picked for MIDI Channel B are labeled with Val 1-8



You will notice that once you have mapped a CC
to the Volca it's LED will light up everytime it receives a CC from the digitakt
(apart from transpose & velocity)

Once you have done this you can also map it to the Digtakt's LFO



This CC is useful:
CC 88: Load patch, value 0-4: patch 1, 5-8: patch 2 etc up to 127_Val 4

You can load a different patch / preset with each pattern.
Or you can control this with a LFO / randomse to change patches on the fly