Friday, 5 June 2020

Top 40 synth blogs

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This site has reached #21


Metro Modular Eurorack Power system 101 - MM1527A

Metro Modular Eurorack Power system 101
Some pics of my build.
The model number: MM1527A
This is a combined Eurorack PSU with bus board.


It will supply +12V (1A), -12V (600mA) & +5V (1A)




You will need 3 of these 12V DC/DC converters
490-VXO7812-1000




When soldering these components, I found that some needed more heat than I usually use on my soldering iron. My standard temperature is 300 degrees celsius.
My guess was that the ground was acting like a heat sink.
I consulted Justin about this and he confirmed that he used planes on all the rails except the 5V .
In addition, he used 2 oz copper which doubles the thermal conductivity.

So when building one of these boards, it's probably a good idea to use temperature controlled irons.
Keep the temp around 350 to 400 degrees, but drop the temp when soldering temperature sensitive components like capacitors.


The PSU is designed to use a DC brick 17V to 20V DC
These are commonly used in laptop PSUs



Inductors



This is the 5V DC/DC converter.
Just one is needed
Mouser : 490-VXO7805-1000







For more information see their sites:

+ Metromodular Facebook
+ Metromodular Youtube
+ Metromodular website  
+ mODULAR Grid

mAKEnOISE - 0 cONTROL - bASIC pATCHES

Some very basic beginner patches ... just got the 0-control

Basic pATCH          1


to trigger the 0-coast you have to plug a gate/ envelope into either the gate or dynamic inputs of the 0-coast.
The picture above has a gate from the o-control  keyboard triggering the gate of the 0-coast
Use the gates/envelopes coming from the "keyboard" or "strength" of the 0-control.


.....
The interrupt function is interesting.
When Interrupt is ON :you can force the 0-CTRL to any step by touching the corresponding touchplate. 
When Interrupt is OFF, you can generate touch CV and touch gates without interrupting the 
clocked sequence.


The Clock
The Clock Input obviously is how you sync the 0-CTRL to another device.
Standard Euro pulses work fine.
The Clock Output is more complex as
it contains both internal and external clocks. Its affected by the Time parameter.
Using both internal and external clocks at the same time will create unique rhythms 
 

Direction
Apart from the touch plate,
Direction is voltaged controlled.
It has its own jack

pATCH 2



Below is a gate from the keyboard triggering the dynamics input




Last video:
Showing the different types of effects from the 4 types of Gate/envelopes

1. Pressure CV Output.
    Outputs CV according to amount of pressure applied to Step Touchplate(s). 0-5V.
2.Touch Gate Output.
   Outputs Gate signal when one or more Step Touchplate is being touched. 0V or 8V.
3.Dynamic Gate Output.
   Outputs Dynamic Gate Signal based on Strength and Time of current Step. 0-8V.
4.Dynamic Envelope Output. Outputs Dynamic Envelope based on Strength
   and Time of current Step. 0-8V.

Thursday, 4 June 2020

mOOG 907 Fixed Filter Bank.

Fixed Filter banks have been around from the earliest days.
But they are often misunderstood.
They look like simple graphic equalizers. This is not the case.
In the case of a EQ, each band has a boost & cutoff. If all the sliders were in the centre position
the input will be the same as the output.
In the case of the 907, the output is definitely not the same as the input. The frequency changes as it passes through each stage.
The knobs for each stage are attenuators. They do not have gain.


The 907 is a beautiful module to behold. It seems so simple, yet it's classic design is an example of why Moog modulars are still revered around the world.
We have just 2 jacks --- input & output.
In between there are 10 filters. 8 bandpass & a low & high pass at either end (shelf filters).
(The later Moog 914 provided 12 instead of 8 filters).

The 907 has 8 bandpass fixed-frequency filters spaced at approximately half-octave intervals:
They have centre frequencies of 250Hz, 350Hz, 500Hz, 700Hz, 1Khz, 1.4KHz, 2KHz, and 2.8KHz.
Each of the BPFs has a single knob for boosting or cutting frequencies within it's range.

There is no voltage control.

The special sound of the 907 is I think due to the the sharp sonic notches produced between the adjacent filter bands. Some people say it's because of the inductors used in their manufacture.

+ Inductors, ferric beads, noise reduction methods, etc
Inductors are basically coils of wire.
Each band uses a LC-filter ... which is a capacitor/inductor combo.
The filter has a total of 10 overlapping LC networks.
The claim is that they introduce nonlinear irregularities.
I don't know -)

"The fixed filter bank is often referred to as a Formant Filter

907 filter Specs:
Signal Input impedance: 10k ohm
Signal Output impedance: 680 ohm
Signal Gain: unity
Output Noise:  -65 dB
Output Polarity : No Shift
LP attenuation at Fc : 24dB
HP attenuation at Fc : 24db
Attenuation of Passbands : 24dB/octave

Pin assignments:

1. +12V (+/-10% at 20mA)
2. Gnd
3. -6V at 10mA
8. Signal input
9. Signal Ground
21. Signal output
22. Signal ground

"The Fixed Filter Bank is often referred to as formant filter because it can be set
 to emphasize or attenuate midrange frequencies, which fall within a particular band,
 no matter how the frequencies of the signal are moved.
Like many acoustic instruments, a characteristic set of formants, are always a part of the
resultant output (given a particular complex waveform). Emphasized bands of this sort are
particularly evident with double reed instruments.
Thus, this filter is part of the patch for these simulations.
In addition, completely different timbres can be set up for different ranges of the same tone,
if the output of the filter is recombined with unfiltered frequencies at different levels. "
                                                                                                                 (Moog Manual)



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

There are quite a few fixed filter banks in the modular world.
Eurorack: The Doepfer A128, Analogue Systems RS215, Behringer 914, AJH Fixed Filter Bank 914,
Aion 907A FFB.


Serge: Serge Kitchen 1 panel, Serge EQ Shifter, Serge M-Class Audio Interface. Serge Resonant EQ.

Buchla : 296 - spectral processor, 296e & 295 .

Don described the 296 thus:
"It has 16 channels of filtering, but they cover the same frequency range of a 24 channel 3rd octave filter because they are constant BARK FILTERS  and the channels are wider


Moog also introduced a series of filterbanks into one of their pedals:
The MuRF. : Multiple Resonance Filter Array
The MF 105 came out around 2004. It's a classic pedal.

It contains 8 resonant BPFs, with their own level sliders, a sine LFO, and a sequencing envelope generator. You can control the tempo with a pedal or knob. Its really cool to sequence the different filter settings.
There are 24 preset patterns
Rhythmic variations can be created by adjusting the levels of the filters.


Wednesday, 3 June 2020

Moog, Korg & Yamaha trigger CABLE V-trig to S-trig


Some pics for making a S-trig to V-trig cable.
Useful is you don't have a Moog 961 conversion module
 + 961 INTERFACE 


tHIS  first cable uses two 1/4 inch jacks.
To convert V-trigs from a 960 sequencer to S-Trigs.

It will also work well to convert a V-trigger from a Eurorack clock (for example) to a S-trig.

This cable is also compatible with old Korg (eg MS 20) & Yamaha synths


 Just 3 components:
10K resistor
1N4148 diode
2N3904 transistor


 Bluetack is a easy way to hold the components together while soldering.

Prevent shorts. Insulate !

 



If you are triggering a KORG SQ-10 sequencer, the sequence mode switch
 must be in either of these two settings for the s-trigger to work.






Links


Tuesday, 2 June 2020

Triggers & the mOOG 961 INTERFACE

.... iT'S  interesting that old Moog Modulars use both S-trigs & V trigs.
 Triggers might be produced by sequencers, the key on a keyboard, drum controllers & foot pedals.
They are useful for starting an envelope generator or advancing a sequencer.

A S-trig is just a passive switch closure to ground.The voltage starts high, and when the trigger occurs the voltage shorts to ground. It's also known as a switch trigger or shorting trigger.
Moog Keyboards produce S-trigs. 
Moog 911 Envelope Generators need S-triggers to start their cycle.
In comparison,  V-triggers start at zero volts and rise to a standard level .. usually 3V.


The 911 plugs into the Moog modular using a 22 pin PCB/edge card connector.
It's a ADSR envelope generator.
The pin out is as follows:
1. +12V
2. GND
3. -6V
14. Trigger out
21. to Trigger switch (Jones S-302)

The Moog manual suggests a regulated AC supply, such as a Moog Model 901 or dry batteries.
Max current is 50 milliamperes.

Range of T1: 10 ms to 10 secs (attack)
Range of T2: 10 ms to 10 secs (delay)
Range of T3: 10 ms to 10 secs (Release)
Range of  Esus:  0 to Emax

Esus = sustain.
Emax = voltage at which T2 begins. = 5.5V +/- 10% 

You trigger the 911 by closing a switch. So unlike most EG's you will encounter today, no voltage is supplied to trigger the module ... its quite the opposite.

The 960 sequencer produces V-triggers.
V-triggers start at zero volts and rise to a standard level .. usually 3V.



In the Moog Modular world, the S-trigger uses a special  2 blade Cinch Jones connector.
The V-trig uses the standard 1/4 inch jack. 
 So how do you get a trigger from the 960 sequencer to start a envelope cycle of a 911 EG.

To convert triggers from one to another, you can use a special conversion cable or the 961 interface


There are 2 types of this module..... the P (portable) and the C (console).
The above module is the P-type ... used for portable systems.




This is a audio to V-trig converter.
Plug in any audio source (like an old drum machine) into the jack on the left.
It will be transformed into a voltage trigger.

The control is a sensitivity knob.
The console version has this section right at the top of the module.






This is the V-trig to S-trig converter.
My module, has been modified somewhat, so may look a bit confusing. However, the V-trigs (from your 960 sequencer) enter into the jacks on the left, and S-trigs exit via the dual blade Cinch J plug.

There are 2 input sections: A & B
Any inputs into column A will have the same duration as the outputs
The Column B in jacks are connected to a Switch-On Time knob.

This allows you to control how short or long the “ON” duration is for S-Trig signals. (40ms to 4 seconds). You can use this to trigger the 911 envelope generator. 


                                                                                                                                                                                                                                             
                                                                                                                                                                                                                                
  Links        
+ Modular Synthesis                 
     
+ Here are the Mouser links for the Moog connector hardware:
https://www.mouser.com/ProductDetail/571-5-530501-5
https://www.mouser.com/ProductDetail/571-582388-9
 

Moog models using the S-Trigger system
  • Moog Modular System 15
  • Moog Modular System 35
  • Moog Modular System 55
  • Moog Modular System 3C
  • Minimoog Model D
  • Moog Sonic 6
  • MicroMoog
  • Moog Liberation
  • Moog Source
  • Moog Taurus
  • Moog Prodigy
  • Moog Rogue
  • Moog Sattelite
  • MinitMoog
  • Moog Ribbon Controller
  • Moog Sample & Hold Controller
  • Moog Drum
  • Moog 1130 Drum Controller
  • Moog Modular Keyboards 
  • Moog Mother 32 ??
I've got two Synthesizer.com Q961 modules
SynthMania: Q961 & 963

Behringer also produce a variation of the 961