Wednesday, December 31, 2014

Doepfer A-110-2 Basic VCO Demo

Warning: This is a hardcore technical modular synth post! I recently got my hands on the first copy of a Doepfer A-110-2 Basic VCO Eurorack module that was ever sold worldwide. It showed up at Schneidersladen in Berlin and I was the lucky one, the first one!

Doepfer A-110-2 Basic VCO and friends

The A-110-2 is the follow-up to the A-110-1 which has been selling for many years now. The A-110-2's basic features: Three waveforms (saw, square and triangle), 3-way octave switch, exponential FM (with attenuator), linear FM (without attenuator), pulsewidth modulation (with attenuator), hard and soft sync. It is only 8 units wide which is really cool. I decided to make a demo showcasing the basic and raw oscillator sound as well as two more musical snippets demonstrating various features of the A-110-2. In all examples whenever all three waveforms are presented they appear with their original volume in relation to one another. Warning: The audio files are big! Format: 44.1kHz, 16 Bit mono.

Let's start with the basic waveforms. You are hearing saw, square (50% duty cycle) and triangle in a range of 7.5 octaves. For pitch I used a Doepfer A-145 LFO (triangle waveform) through a Doepfer A-156 quantizer, set to output only 5ths and octaves:


Now let's add some pulse width modulation to the square wave. PWM source is a slowly moving sine wave LFO:


The A-110-2 has a nice feature: Linear FM. In this patch a Doepfer A-171-2 VC Slew Processor serves as the source for the modulation with a frequency modulated sawish triangle waveform. The result is not as dramatic as with Exp FM. Again saw, square and triangle:


Now for exponential FM. Modulation source is the Doepfer A-171-2 with the same configuration as in the Linear FM patch above:


Let's take a look at hard sync. With each of the 3 waveforms (saw, square and triangle) you first hear the A-110-2 slaved to a steady-pitch master oscillator while being pitch-modulated by an EHX 8-step sequencer. After a few seconds I add some LFO modulation via the EXP FM input. You can hear the timbre of the slaved oscillator changing along with the LFO swings:


Now it's soft sync. I must admit that I haven't managed to fully wrap my head around the theoretical implications of soft vs. hard sync. All I can say is that soft sync does not reset the waveform to 0 when the master oscillator finishes a cycle (unlike hard sync) so you won't get any such dramatic changes in timbre as in hard sync. Interestingly modulating the slaved oscillator's frequency does change the perceived pitch as well (again unlike hard sync). Same modulation as in the previous clip:


Now let's go "all in". I have put together two patches that are more musical than the above examples to showcase what the A-110-2 can do if you combine all those nifty features. What you hear in clip 1 is all three waveforms cycled through a Doepfer A-152 quad sequential switch (accounting for some clicking audio glitches here and there) with some random resetting. I have added PWM, Lin FM and Exp FM from various sources as well as hard sync. No filtering, just some amplitude modulation via MFB Megazwerg VCA (AHDSR modulated):


The following patch circumvents the VCA completely. However, there is some amplitude modulation on the saw wave. Later in the clip I start tweaking some of the parameters. Again, no filtering:


I hope I have managed to give you a good overview of the Doepfer A-110-2 basic sound and its most important features. Enjoy the demos!

Arp Axxe & Roland CSQ-600 (Youtube video)

Celebrating my freshly repaired Arp Axxe's resurrection, I hereby present to you this little demo jam. A Roland CSQ-600 sequencer is driving the Axxe with CV and gate information (a 32 note loop). Watch me manipulate the Axxe's controls as the sequencer is rolling on. Just a bit of Korg SDD-1000 delay and Roland RSP-550 chorus added to spice up things.

When I was first offered my Axxe a year ago, upon first inspection it was in a somewhat pitiful state. A good friend of mine offered to repair it so I decided to buy it from its former owner for a good price and have it fixed later. All good. However, following last year's move, my Axxe started having trouble staying in tune; its pitch would fluctuate by +- 30 cents, even after hours of operation. So I handed it over to my buddy Tobi Tubbutec who repaired it by replacing its power transformer with a new one so it can now return in full splendor.

I don't want to repeat any of the Axxe's well-known specs as you can find them all over the internet. It is true that being a stripped-down 1-osc synth the Axxe cannot hold up to its older brother Odyssey's grandeur feature-wise. However, it does have THAT powerful Arp sound due to its massive oscillator and filter. Speaking of filter, this Axxe has the Timothy Smith filter mod that fixes a design flaw in the original filter circuit preventing the filter to open up completely. With this mod the filter works as intended and has improved response. Anyway, playing the Axxe is pure joy. It's so simply laid out that you can't get lost even if you try. You can build a new sound within a minute. Admittedly I am not a huge fan of the Axxe's PPC pitchbender as I have to press really hard in order to bend a semitone but it sure gets the job done. Another one of Axxe's quirks is its strange Sample and Hold feature. When turned on, pitch drops to the lowest C on the keyboard when you release the last key. Strange. Summing up, the Axxe excels at basslines and leads and actually quite a lot in between (effects, sequencer lines, percussive sounds, noise sweeps etc.). Sure I can imagine eyeballing its bigger brother, the Odyssey, but for its price I think the Axxe is a great alternative if you want that big ballsy Arp Sound.

Arp Axxe

The Roland CSQ-600 is a fun sequencer. It hails from the early 80s and has a strikingly familiar design. Sure enough it's from the same era as the TR-808 and has probably even been designed by the same person. For today's standards its 600 notes memory does not sound like much but I bet in 1980 it was a huge thing. And huge the CSQ-600 is, by all means (physically, I mean). It has great build quality, its buttons are a joy to push and it is ridiculously easy to operate, making sequencing other analog synthesizers a real breeze.

Roland CSQ-600

Sit back and enjoy this demo featuring two great vintage pieces of studio equipment and keep in mind: Never underestimate the Arp Axxe!

Saturday, December 6, 2014

Korg Mono/Poly vs. EHX 8-Step Sequencer & Doepfer Modular Skiff (Youtube video)

Today I wanted to try out how I could spice up a simple 3-note arpeggio on my Korg Mono/Poly by sending some CV modulation to its filter CV input. So what you are hearing here is the Mono/Poly with its lowpass filter cutoff frequency being externally modulated by a small modular rig. I just added some delay and reverb from the Korg SDD-1000 and Dynacord DRP-20.

Running on its internal arpeggiator the Mono/Poly sends out a gate signal for every note. I took this gate signal and used it as a clock source to synchronize an Electro Harmonix 8-Step Program analog sequencer and a Pittsburgh Modular Cell 48 case with 5 Doepfer Eurorack modules.

Korg Mono/Poly

Electro Harmonix 8-Step Program Sequencer

Doepfer A-143-9, A-151, A-138m, A-133 and A-140

My latest modular acquisition is the Doepfer A-138m 4x4 matrix mixer. It really doesn't look flashy at all nor does it have a fancy name. But looks can be deceiving. This IS a highly versatile and mighty tool. What does it do? Well, the principle is simple: It has 4 inputs and 4 outputs. You can route any input (arranged in horizontal rows) to any output (arranged in vertical columns) with whatever level you like. One really useful feature is that you can set each output column to "bipolar mode", meaning you can turn each level knob to the center position for no signal or clockwise for positive and counter-clockwise for negative (inverted) signal. That's a great thing for CV signals, but you can also use it for audio signals for example in order to change the characteristics of a filter or for M/S processing of a stereo audio signal.
So here you can see (and hear) the A-138m in action. The A-143-9 VC Quadrature LFO is providing the Mono/Poly's filter with some nice audio-rate FM while the A-140 ADSR Envelope Generator modulates the amount of LFO signal going through the A-133 Dual VC Polarizer. You can clearly spot the effect of the ADSR in the youtube clip as it creates those "a-u" and "u-a" vowel sounds. The A-151 Sequential Switch is a real funky tool, too. It can be used to cycle through 4 independent signals by routing 4 inputs to 1 output or 1 input to 4 outputs at a time, making for some very interesting rhythmical modulations. You can use it both on CV and audio signals. Hey, you can even build a sequencer with it but I will go into this another time.
This skiff really is a fun little toolbox with lots of functionality in such a small space. Enjoy the demo!