Doepfer A-139-2 Headphone Amplifier Announced

A-139-2 Headphone
Amplifier

Doepfer also announced a re-design of their (discontinued) A-139 headphone amplifier (find the original version HERE)

Main features:

- Two-channel headphone amplifier
- Two audio inputs with level controls

- Input 1 is normalled to Input 2
- Common loudness/master level control
- Headphone output (stereo 1/4" jack socket)
- Max. output power ~ 2 W per channel (@ 8 Ohm load)

- DC coupled inputs and outputs (i.e. also useful for other applications like small loudspeakers, lamps, LEDs, magnets, motors - provided that the power is sufficient)

6 HP wide - 40mm deep
Price: ~ Euro 50.00
Release date: spring 2015
All features, specifications, prices, date of delivery are still without obligation !

Source: Doepfer website http://www.doepfer.de/a1392.htm

Doepfer A-135-1 Quad VCA/ VC Mixer Tutorial Videos by Raul Pena

Time for another new tutorial series by Raul Pena.
The subject this time is the Doepfer A-135-1 Quad VCA /Voltage Controlled Mixer (version 2)

Video 1: Doepfer A135-1 QVCA/VCMIX basics

" A short description of the beasic features and functions of the Doepfer A135-1 Quad Linear VCA, Voltage Controlled Mixer. Sound and Video by Raul Pena."

Video 2: Doepfer A135 Quad Linear VCA/ Voltage Controlled Mixer Audio Demonstration One
" A short demonstration of A135 Quad Linear VCA with oscilloscope views to show how external cv effects amplitude of an audio signal. Sound and Video by Raul Pena."

Video 3: Doepfer A135 Quad Linear VCA/ Voltage Controlled Mixer Audio Demonstration Two

The second of two Audio Demonstrations of A135 Quad Linear VCA with oscilloscope views to show how external cv effects amplitude of an audio signal. Sound and Video by Raul Pena.

New videos in this series will be added to this post weekly on Thursdays.

Check out Raul's latest survey at http://www.surveymonkey.com/s/K3Z9PVF

Other places to find Raul's World of Synths on the Web:

raulsworldofsynths on YouTube

raulsworldofsynths on Vimeo

raulsworldofsynths on SoundCloud

raulsworldofsynths at iTunes

raulsworldofsynths at CDBABY

Doepfer A-131 Demos by Raul Pena

Raul Pena (from http://raulsworldofsynths.com/) has released four more new demo-videos, this time involving the A-130/A-131 Voltage Controlled Amplifiers.

Video 1: Doepfer A-131 VCA Intro
http://www.youtube.com/watch?v=MivzVdpz5Dg

" Introduction to the features of the Doepfer A131 EXP VCA.Short demonstration of Tremolo.Sound and Video by Raul Pena. "

Video 2: Processing CV with Doepfer A131 EXP VCA Part One

http://www.youtube.com/watch?v=DIdWbrbkSD8

" Demonstration of Doepfer A131 EXP VCA for processing CV. From the manual "For audio signals, you would normally use the exponential VCA (A-131), and for control voltages, the linear VCA (A-130). It doesn't always have to be that way, though." "The old versions of A-130/131 (those with CEM3381/CEM3382) are not able to process slowly varying control voltages (AC coupled in/outputs). Sound and Video by Raul Pena. "

A-132 Dual VCA

Module A-132-1 Dual Low Cost VCA contains two simple voltage controlled amplifiers, each with a linear response.
They are most suitable for controlling the level of all kinds of control voltages like LFO or ADSR amount,  Joystick or Wheels voltage etc.

In non-critical situations though, these VCAs can also be used to control audio signals, and i have to say it still sounds pretty good; audio controlled by an ADSR or Ribbon voltage through this module.
Amplification is controlled by the sum of the voltages patched into the two CV inputs.

Although these 'Dual' modules are small and don't have many other controls (like knobs or switches), they are very useful low-cost solutions for your amplification needs...

They are cheaper (two-for-the-price-of-one) than the A-130/131 VCA's so you could consider using one of these in your next setup if you are on a budget or want to spare valuable rack-space...

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