Richard Brewster's Synthesizer

Old Fashioned Drone

Richard — Sat, 15 Jun 2013 22:12:11 +0000

Just an old fashioned drone, made with modular Tetrazzi, Zeroscillator, an LFO, a sample and hold, and some envelope generators.… —Read more

Two of twelve sample and holds

Richard — Sun, 19 May 2013 19:18:13 +0000

Here is a CGS SSG board, assembled as a dual S&H with a one-shot circuit. It’s the first of six identical boards.

A while back I posted about a ‘quartussy‘ project I wanted to do. Since then I have extended the design to six sections and enhanced the block diagram to include a VCA between the first sample & hold output and the CV input to the VCO. I’ve tentatively decided to call this project the Quantasise, indicating six quantized things. There will be more about this project as it develops. Each section will have a VCO, a VCA, and two sample & holds (S&H). That’s 12 sample & holds total. This post is about the sample & hold circuits, which are made from CGS SSG boards.

The SSG (Smooth & Stepped Generator) has two virtually identical sections that can each function as a VC slew, VCO, or Sample & Hold. The S&H function is implemented by pulsing the track and hold function. A pulse releases the hold for a moment, allowing the output to slew towards the input and then hold again. The minimum acquisition time obtainable with the selected capacitor (about 0.28 milliseconds) is relatively long for a S&H, but it works just fine for my purpose. No external rate pot is needed, because the trimmer is capable of setting the rate for the shortest acquisition time. I selected a 47 nf polypropylene capacitor for the integrator. This capacitor is Mouser part number 505-MKP20.047/100/5 (WIMA MKP2D024701C00JSSD). I have not tried to measure the droop rate of this S&H, but for this use I’m sure it will be acceptable.

In addition to the two S&H circuits, each SSG includes two one-shot pulse generators. One of these is used to drive two S&H circuits, as shown in the block diagram. More about this in a future post.

Stand Alone Power Supply

Richard — Sun, 05 May 2013 15:19:57 +0000

I built a stand-alone power supply that delivers +/-15 volts @ 800 ma to use as a bench supply for testing modules under development, and also to use as the external supply for a new stand-alone synthesizer I’m building. The supply is Power One HAA15-0.8-AG. Two jumper wires near the output posts must be cut to change the output levels from +/-12 to +/-15 volts. These are labelled VW1 and VW2.

The enclosure is Hammond 1458VD3 (Mouser 546-1458VD3). The top and bottom are vinyl-coated steel, with ventilation slots, and the front and back have painted aluminum panels, easy to machine. I mounted all parts on the front panel, with the Power One supply fitting nicely in the rear of the box.

I used the same Schurter AC Power Entry as on my portable cabinets. It’s very convenient, having the AC inlet, dual fuse, and power switch all in one unit, Mouser 693-4304.6090.

The red and yellow LED power indicators are in chrome bezels I had lying around. I put a 2K resistor in series with each.

Red and yellow banana jacks output +15 and -15 volts, with two black banana jacks for ground. The outlet that will supply the stand-alone synthesizer uses a high quality 4-conductor locking connector that includes earth ground as well as plus, minus, and supply ground. The connector shown is a female panel mount. The corresponding connector on the synthesizer will be a male panel mount and the cable will have mating male and female connectors. These connector Mouser part numbers are:

Panel mount female 523-C01620G00310012
Panel mount male 523-C01620C00310012
Cable end female 523-C01620D00310012
Cable end male 523-C01620H00310012

Asheville Butoh Festival 2013

Richard — Mon, 29 Apr 2013 20:03:53 +0000

I was in Asheville, North Carolina, last week, visiting my friends David Linton and Claire Barratt, and was invited to join in an improvisational piece to be shown at intermission at the BeBe Theatre, during a performance for the Butoh Festival. David and I had practiced with a setup that included his zither and my Tetrazzi and Cocoquantus. The piece, designed by Claire Elizabeth Barratt, involved the use of a number of instruments set out in a space to be played by wandering musicians. This video captured a part of it. Because of the complexity of the overall resulting sound, I decided to omit the Cocoquantus and just use Tetrazzi. We all wandered about slowly, playing instruments at will. I wasn’t the only one playing Tetrazzi.

http://www.youtube.com/watch?v=LCueQTKRCT0

The Other Studio

Richard — Thu, 18 Apr 2013 23:14:05 +0000

The dining room table has been taken over by Ciat-Lonbarde stuff. I also set up the RCF powered monitors in the room. Combined with the Macbook Pro and the firewire interface, it makes a complete recording studio. Tetrazzi and Roland Mobile Cube are in the background of first picture.

Shown below, clockwise from lower left: touchpad, gong, origami, gong, Cocoquantus, Plumbutter, Tetrazzi, Shbobo Shnth.

Shbobo Shnth

Richard — Thu, 18 Apr 2013 22:58:25 +0000

I was lucky to snag a first-run Shbobo Shnth, Peter Blasser’s just released computer music device. It is tiny at 4.25 x 4.25 x 1.25 inches. It features:

4 touch-sensitive wood barres
8 control buttons
2 touch-sensitive antennae (on the back side)
8 LED indicators
A microphone input

The output is through a stereo mini-jack.

Shnth is programmed in a language called shlisp. The programs load from a computer via a USB cable, which also serves to charge the internal battery. Shnth can be disconnected from the computer and played with the currently loaded program. Programs can contain a group of separate ‘situations’, which represent different patches.

Here’s a quick demo, using one of the supplied programs, called ‘vancouver’, which has several different situations that I stepped through to demonstrate.

Cross Mutterings

Richard — Wed, 17 Apr 2013 20:43:53 +0000

This was made by Plumbutter with the AVDog FM inputs modulated by two of the castle outs on the Cocoquantus. Plumbutter also goes through Cocoquantus and receives AM on the inputs from two of the Quantussy oscillators. Coco delays were not used.

Planet 0130

Richard — Sun, 10 Mar 2013 20:36:17 +0000

I patched up a conventional drone, which I recorded while improvising. The featured oscillators: Synthesis Technology Cloud Generator (E340) and Modcan VCDO. Each passes through a Mattson VCA with an envelope (Blacet EG2070 looping) and modulation from a MOTM-300 VCO. No digital effects were used; only a pair of Blacet Time Machines patched through the effects loop of my studio mixer.

Drone with PB BB and Serge

Richard — Sat, 02 Feb 2013 21:45:10 +0000

Plumbutter, BugBrand, and CGS Serge all use banana jacks. I did some serious cross-patching among the three for this little drone that uses two BugBrand VCOs, each processed with a Serge Wave Multiplier and then fed to the external inputs of the Gongue modules in Plumbutter, which act as low pass filters. Gongues then pass through the Ultrasounds. One of the VCOs is modulated by the Man with the Red Steam, slewed through a Serge Smooth module. The BugBrand Noise Crusher S&H modulates the rate of one of the 3-rollz, and a Negative Slew and a USG are used to modulate the Gongue frequencies. The Plumbutter outputs were directly recorded. It’s self-running.

Bananas

Richard — Sat, 19 Jan 2013 22:16:58 +0000

My banana cabinet is finished! It combines 5U modules, a rack of BugBrand, and my custom CGS Serge panel into one cabinet. Note the vertical alignment between the CGS Serge and the BugBrand. It’s no accident, because I used BugBrand dimensions for the CGS panel.

The functional combination is excellent, with the BugBrand supplying VCOs and killer modulators (Low Pass Gates, Frequency Shifter, Digital Delay, Bit Crusher) and the CGS Serge supplying controllers for modulation and the unique Serge Wave Multipliers. With 10U width of MOTM-size modules in the top section, I can swap in just about any 5U height module that I need. At the moment the 5U section contains, left to right:

CGS Super Psycho LFO
CGS Dual Slope Detector
Buchla Dual 281 Function Gate
CGS Twin CMOS (Wasp) Filter
Dual Flight of Harmony Plague Bearer
Ciat-Lonbarde Tetrazzi
Multiples

It’s a lot stuffed into one luggable cabinet. But current draw is reasonable. Measured on the +15V side:

CGS Serge draws 130 ma
BugBrand draws 280 ma
5U modules draw 180 ma (100 ma of that for the Tetrazzi)

That’s 590 ma total on a power supply rated at 800 ma, less than 74% of load.