Doepfer A-100 Review *** Part Two

From analogueman@delphi.com
Sent Wed, Apr 17th 1996, 06:30

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                                                                    17 April 1996
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>From the great responce that I received for my review of the first batch of 
Doepfer modules that I bought, it seems that a further instalment for the latest 
batch would seem in order. For all those who have been waiting, apologies for the 
delay. So here goes...............

N.B. Whereas the first batch could be classed as the basic bread and butter 
configeration modules, this second batch are more utilitarian, and vary
somewhat in their usefulness. 


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                       A-114  Dual Ring Modulator
                       --------------------------


Mmmmmmm........ I'm not quite sure what I can really say about this module, apart 
from the fact that it is two self contained ring modulators. Each ring mod has an 
X and a Y input socket and an X*Y output. Internally, each has an MC1496N, and a 
TL062CN ic a piece. It's a simple module that sounds fine.


                          A-115  Audio Divider
                          --------------------


This was a module that I was looking forward to using. It only has two sockets on 
the front panel, one signal input and a mixed signal output. There are five pots 
to play with, which mix the divided input signals. The divider gives you the 
original signal out, along with one, two, three and four octaves below. The 
resulting waveform outputs are squarewaves. Now, I've never owned any of Roland's 
SH series of synthesisers, and so the usefulness of this kind of modifier has 
always passed me by, until now. Talk about rattle the windows! Wow! This really 
is a most usefull module to add to the system. And yet the pcb is very sparse. 
One transister, five capasitors, eight resistors, one TL061CN, and a CD4024BE ic.
Quite how this stands up against Roland's hardwired versions, I don't know, but 
it is very good.


                      A-116  VC Waveform Processor
                      ----------------------------


The waveform processor has, in the past, been described as voltage controlled 
distortion. I wouldn't go as far as that. In the time that I've had with this 
module, I've found it to be a modifier of subtlety, rather than harshness, and 
although I don't posses an oscilliscope, the inputed waveform is definitely 
changed somewhat. The module has four sockets, one audio in, one audio out, and 
two cv inputs. The audio input is complemented with a level pot, and a manual 
clipping level knob. The change of waveform symmitry can be done manually, with a 
dedicated pot, or with a control voltage, whose amount can be varied with it's 
own knob, as can the waveform clipping, which has one too. It's obviously a shame 
that more of the modules don't have this degree of voltage control. The pcb has 
two ics on it. One TL064CN, and a CA3080E. I find it quite difficult to describe 
how the processor effects the waveform input in sound terms, other than that the 
results are quite pleasing, and laid back, rather than in your face, which I 
think most people were expecting.


                            A-132  Dual VCA
                            ---------------


This is a cheap simple dual VCA module, which the manual recommends to be used 
for control voltage purposes ie. non-critical amplification. Each VCA has two CV 
inputs, a signal in and a signal output socket. Internally, each uses a TL061CP, 
and a CA3080E ic.


                        A-151  Sequential Switch
                        ------------------------

The sequential switch is very much self explanitory. It has a trigger in, a reset 
in, and a commonm in/out socket. It also has four seperate in/out sockets that 
are stepped through as a result of a received trigger in. Each of these four 
sockts have an individual LED indicator to show which of them is active. I can't 
say that I've found a use for this module in my system as of yet, but it's use as 
an electrical rotary switch for use in automatic switching of oscillator 
waveforms etc could be useful in the future. It uses two ics....a CD4024BE, and 
an HCF4052BE.


                          A-160  Clock Divider
                          --------------------


Now this is one module I have used a few times. I suppose you could say that this 
thing is the equivelant for triggers, as the A-115 is for audio. You put a 
trigger, or clock source into the trig.in socket, and that trigger is then 
outputted in a divided down form, from six seperate output sockets, each one 
exactly twice as slow as the previous one. So if a clock rate of 32 hertz were 
inputted, the first output would be 16 hertz, the one below it would be 8 hertz, 
and so on etc. This on it's own may seem fairly boring, until, when creating a 
percussive type line, you put the trigger in, and start to take some of the 
divided down outputs (using the A-162 delay) to seperate sound sources, and 
suddenly, you have a slightly unpredictable, but never the less, worthwhile drum 
track (or whatever other sounds you may be using). Make no mistake, this is 
brilliant fun, and what synthesis, at least for me, is all about. Each of the six 
output sockets have an LED, and there is a reset input socket as well. It only 
uses one ic.......a CD4024BCN, and nine BC549 transistors.


                         A-161  Clock Sequencer
                         ----------------------


The Clock Sequencer is a module that must be used with the A-160 Clock Divider. 
It only has outputs, and receives it's clock/trigger from an internal connection 
via ribbon cable with the A-160. This panel expands what the A-160 does, by 
outputting a sequential trigger starting at output socket one, and running 
through to output socket eight. Each output has it's own LED, and the pcb has a 
CD4017BCN ic on it. In connection with the above module, these two modules are 
useful and great fun, especially when used to trigger multiple EGs etc.


                        A-162  Dual Trigger Delay
                        -------------------------


A very useful utility module, in which each of the delays have an input, and an 
output socket, an LED for the output, and two pots. One for controlling the delay 
time, and the other for adjusting the width of the gate pulse at the output. The 
delay time has a maximum delay of about ten seconds. It's uses are almost 
infinite- wherever there is a trigger to be used basically. Each of the delays 
uses a B556D ic.


                       A-165  Dual Trigger Modifier
                       ----------------------------


Each trigger modifier has four sockets: two connected inputs, an inverted signal 
output, and a short trigger pulse output. This last output gives you a full 
trigger for each rising and falling edge of the original input signal. Both of 
the outputs have an LED indicator. Each modifier uses an HFC4077BE ic. This 
module works just fine as a trigger inverter.


                         A-170  Dual Slew Limiter
                         ------------------------


The first slew limiter is a fairly standard portmento controller. It has a signal 
input, and a signal output socket, two LED indicators (- and +), and a pot for 
controlling the slew time. The second one has the same arrangement of sockets and 
LEDs as the first, but has a three position toggle switch for changing the time 
range. This switch still retains Doepfer's oddball labelling (ie. high to the 
left, low in the middle, and med to the right). It also has two control pots. The 
first adjusts the portmento rise time, and the second one, the fall time. The 
interesting point about this second slew unit, is that it can also be used as a 
simple AR generator, when a trigger/gate is applied to the input socket. The 
module itself uses two TL062CN ics.


                       A-175  Dual Voltage Inverter
                       ----------------------------


Each of these voltage inverters are exactly the same. They have two connected 
input sockets, and one inverted output socket. There is also two LEDs (-/+) 
indicators. Each inverter uses a TL062CN ic.


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This second batch of modules aren't perhaps quite as interesting as the first, as 
this batch consists of modules that are perhaps described as occasionally 
usefull, rather than the all the time blow your socks off type! The next batch of 
modules, which I should be ordering soon, will consist of some of the other CEM 
VCFs and stuff, which, judging from the feedback that I've had, are generating a 
lot more interest.

One of the changes that I've noticed, is that the LEDs that Doepfer are now 
using, are of a different type to those on the earlier modules. The older LEDs on 
the LFOs, and the EGs, are of the deep red variety, and are the rounded toppped 
type (Roland used them on most of their gear- see the LFO on the Jp8 etc), but 
these have been changed on the more recent modules, to ones with a flat top, so 
they are absolutely flush with the surface of the faceplate, and are of a more 
bright orange colour than before. I think that it's an improvement.

I have, over the last few months, been at great pains to point out to people 
enquiring, that this system is in no way competing with Serge, rather it is 
complementing the current range of available analogue equipment. I don't know how 
well the system is selling in the States, but I do know that orders here in 
Europe seem to have taken Doepfer by suprise, leading to slight delays in 
delivery, but something that they are coping with quite well. An off shoot of 
this, is that Dieter Doepfer has been given the confidence to release a further 
range of modules, which seem to be addressing the main gripe from current users, 
that being a request for more voltage control of the modules. The information 
that I have at the moment, is for a further dozen or so new modules, and these 
are listed below, with a short description. They should be available as you read 
this.

Hopefully, this posting has proved helpfull and interesting, and if feedback 
proves to be as positive as it was for the last one, I will continue to do the 
same, for the next batch of modules that I'll receive later this year. Please let 
me know what you think :)

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  A-117 Digital Noise Generator
  
        Digital noise, variable from white noise to slow Geiger counter
        like effects. Also simulates TR808 cowbell, cymbal and hi-hats.


  A-129 Analogue Vocoder:

          A-129/1 Analyser Unit
          A-129/2 Synthesis Unit
          A-129/3 5-Way Voltage Controlled Slew Limiter
          A-129/4 5-Way Attenuator/Offset Generator
          A-129/5 Voiced/Unvoiced Sibilant Detector


  A-141 Voltage Controlled ADSR Envelope Generator

        Each ADSR parameter has a voltage control input, with an 
        attenuator.


  A-146 LFO 2

        Variable sawtooth/triangle and square wave outputs, variable 
        range from several minutes to 5 kHz.


  A-147 Voltage Controlled LFO

        Frequency controllable from two CV inputs, as well as manually.


  A-171 Voltage Controlled Slew Limiter

        Single channel, voltage controllable portmento.


  A-176 Control Volt/Gate Source

        Accesses internal CV and Gate signals, and a button for clock signals.


  A-177 External Controller Module

        To connect footswitches, volume controllers etc.


  A-191 Shepard Generator

        Sixteen phase shifted control voltage outs, creating infinite rising
        effects, when used to control phasers, VCFs etc., or translate pitch,
        modulation, volume, pitchbend, velocity etc., from a single midi 
        channel input.


These newly announced modules mean that Doepfer are now offering a selection of 
44 modules altogether, with possibly more to come, depending upon feedback, and 
sales levels.

I have to say, that I'm slightly perplexed at the moment, as I've yet to see 
anything of the supposed deal that Doepfer struck with CEM, for a range of their 
chips. Apart from the filters and amps, most modules seem to use fairly standard 
ics, so where the rest of the curtis chips have dissapeared to, I don't know. 
Perhaps in future modules..............

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