Intro to Eurorack Modular by @Flux302

Ken Flux Pierce (@Flux302) had been getting a lot of questions about getting into eurorack, so he did an article and a video on what he has found so far.

The full article can be found at http://fluxwithit.com/intro-to-eurorack-modular/

He will be updating the article and adding to it with both videos and written chapters.

Here is the first video:

Video : Intro to Eurorack Modular Synths from Fluxwithit.com

" This is just simply a primer to get people a little bit of info on what eurorack is. How to get started, and what some of the key elements are.Visit Http://Fluxwithit.com for more info! "

Uploaded by Flux302 of Fluxwithit.com

If there is anything in correct or you feel he should touch on,

feel free to let him know via http://fluxwithit.com/intro-to-eurorack-modular/

Modular Synth Basics Tutorial series by The Tuesday Night Machines

Felix, known for his earlier Eurorack videos and perhaps better known as 'The Tuesday Night Machines' has started a completely new video series.
The first videos in his "Modular Synth Basics" series, show what a Eurorack Modular Synthesizer is and tells all about the basic control signals.

Modular Synth Basics #01: What's a modular synth?

" What is a modular synthesizer? What is the Eurorack format? Subscribe for more videos

Modular Synth Basics #02: CV, Gate, Trigger & MIDI

" What are Control Voltages/CV, Gate Signals, Triggers and MIDI data? You'll need (almost) all of them to control your Eurorack modular synthesizer! Subscribe for more videos:

Modular Synth Basics #03: How to start?

" Some thoughts on how to start building a Eurorack modular synth system? Subscribe for more videos "

Doepfer Power Supplies

There are 2 types of transformers used in the existing standard Doepfer A-100 racks and cases.

The old Doepfer power supply with a
rectangular transformer

If you are buying a secondhand A-100 rack, it might be useful to know how to distinguish the old transformer from the new version.

The newer version is a better version, more reliable and provides a steadier voltage that is better for your system, although i personally never heard any complaints about the old transformer besides the longer warming-up time.

The old power supply has a black or blue rectangular transformer, where the new power supplies have a round silver transformer.

The new Doepfer power supply with a round transformer

For a period during the transition (about 2 years) the customers could order both versions.
In any case all A-100 cases manufactured later than early 2005 are equipped with the new power supply, and all cases manufactured until about of 2002 are equipped with the old version.
For cases manufactured in 2003 and 2004 it depends which version has been ordered by the customer.

In any case the new power supply can be identified by a small label outside the case near the mains inlet.
It says "Power Supply II" unless it was removed by the user.

Source: Dieter Doepfer

Locating the A-100 Fuse

The fuse-box is located between the
power inlet and the on/off switch

It's pretty basic, but every once in a while i receive the question: "Where can i find the fuse on my Doepfer rack?"
I must admit i had to search for it too the first time i blew up a fuse.

The answer is quite easy.
On the backside of the G6 rack (and G3 rack and most other cases and koffers) you'll find the power supply and the On/Off switch.
Between these two there is a small compartment where the fuse can be found.

Use a small screwdriver to
slide out the fuse-holder

Always remove the power-cord before you are opening the fuse-box!

With a small screwdriver you can gently pull this fuse-box out of it's place and replace your A-100 fuse.
Check out the Doepfer FAQ to see what fuse-value you should use in your rack, depending on rack-size and country.

Fuse-holder with A-100 fuse

A-130 + A-131 Voltage Controlled Amplifiers

A Voltage Controlled Amplifier ( VCA or variable-gain amplifier) is an electronic amplifier that varies its gain depending on an incoming control voltage (or CV).
It is one of the most basic building blocks for a modular synthesizer.
Find more on this on Wikipedia.
Modules A-130 and A-131 are very simple VCA's that can be found in most basic Doepfer systems.

For audio signals, you would normally use the exponential VCA (A-131), and for control voltages the linear VCA (A-130), but it doesn't always have to be that way, though.

The amount of amplification of the VCAs is determined by the voltage at the CV input and the position of the gain control, which sets the overall gain in the system.
The VCA has two audio inputs, each with an attenuator.
They are amplified by the combination of the gain and the two CV controls.

Remark:
The old versions of A-130/131 (those with CEM3381/CEM3382, which are actually 2 VCA's on one chip*) are not able to process slowly varying control voltages (AC coupled in/output).
The newer versions of A-130/131 (those with CA3080) are able to process even slowly varying control voltages (DC coupled in/outputs).

*it might be worth investigating these a bit more for a future DIY treatment

A-138 Linear/Exponential Mixer

Module A-138 is a simple four channel mixer that can be used for either control voltages or audio signals. (although i hardly ever use one for CV)
Each of the four inputs has an attenuator, and a master attenuator, so that the mixer can be used to interface directly with an external mixer, amplifier, etc.

There are two versions of this module:
A-138 a: potentiometers with linear response, especially suitable for control voltage mixing.
A-138 b: potentiometers with logarithmic/exponential response, especially suitable for audio signal mixing.

The latest version from April 2004 is an improved version of the module A-138b.
For the revised versions control In1 works as a DC offset generator (about 0...+5V) provided that no patch cord is plugged into socket In1.
If this feature is not required it can be deactivated by removing a jumper on the pc board.
In the summer 2004 the A-138a was introduced with this improvement.

In the summer of 2007 Doepfer also released a mix expander module A-138x, that increased the number of inputs of the A-138 by five.
That module was discontinued last year...