Friday, 27 September 2019

Model 155 - Dual Integrator

Some pics of a build I'm doing for a friend.
This is the LA 67 version.

I am in no way affiliated with the manufacturer.
These are just my personal notes to help trouble shoot any problems I might encounter during the build.

A vintage Buchla 155 is super super rare. I have never seen a real one and can only imagine how it would function. My hope is that Buchla USA will reissue this module soon. (please Eric).
Or if you have one and wish to part with it, don't hesitate to contact me.

The module is described in some old 1992 docs as such:

"(The 155) produces continuous control voltage functions when used in conjunction with sources of discrete control voltages (e.g. keyboards, sequencers). Positive and negatives slopes may be individually varied from 15 volts in .0025 seconds to 15 volts in 10 seconds; either or both slopes may be voltage controlled. Particularly useful for generating complex voltage controlled envelopes, frequency glides, and repetitive control functions."

(from a catelog for the 1992 Ars Electronica exhibit Eigenwelt der Apparatewelt. Pioneers of Electronic Art, edited by David Dunn)

So it looks like it's an early form of function generator.

 The integrator is a very important electronic circuit. You will see this type of op-amp circuit again and again.

This is a common RC or resistor capacitor circuit.
It's also commonly known as a Op amp integrator circuit.

This module however doesn't use op-amps. 
Instead it uses transistors.
Google Miller integrator.

Wednesday, 18 September 2019

Synth Surfers - Bega Valley Synth Festival

Looking forward to the Bega Valley Synth Festival.
Just 1 month to go.

Workshops, demonstrations and displays in the day and OSCILLATIONS with live performances from local and interstate synth artists at night

There will be demonstrations/displays during the day and performances at night.
This is an inaugural event

The day is full of workshops to learn everything from DIY synth coding to Ableton Live to learning VCV Rack a free modular software synthesiser. There are displays of a variety of instruments and synthesiser formats all set up ready for you to try and play on.

10am - 12pm: Synthesis and sound design in Ableton Live
This workshop will give you a basic introduction into subtractive synthesis using the Ableton Live and the Simpler instrument.

12.30pm - 1.30pm & 1.30-pm - 2.30pm: Lunetta Synthesis
Join Adam Buckley as he gives you an introduction to the basics of creating your own synthesiser using the Lunetta Synth Cookbook.

3pm - 4pm & 4pm - 5pm: Intro to VCV Rack
VCV Rack is a free open-source virtual modular synthesiser:

10am - 5pm  - demo of the AE Modular from tangible waves.
See the latest modules from the newest modular format with demonstrations from tangible waves representative Carsten Eckelmann/The5thVoltScott Baker/Abre Ojos.

7.30 till late - OSCILLATIONS - Live electronia performances.
Local artists playing alongside artists from further afield. Featuring The 5th Volt . Myst Mach . Abre Ojos . DJ Jon Dent . Virus Installer . Vitals . DJ Hedge Zeppelin & more to be added!

When : Sat, October 19th.
Time: 10am till late.
Location: Murrah Hall 2989 Tathra - Bermagui Road

+ Murraha Hall
+ ACT Synthesizer Group
+ Facebook

Tuesday, 17 September 2019

211 power supply

Some pics of the Buchla Format 211 PSU

Perfect for a small system.
These are personal pics to help trouble shooting the build.
They are not official build notes.

The build however looks pretty straight forward except for one surface mount component (IC3).

Get those ICs on first.
There are 3 ICs
LM2575 IC1 1 926-LM2575SX-5.0NOPB
LM27313 IC2 1 926-LM27313XMF/NOPB
LM25575 IC3 1 926-LM25575MHX/NOPB

Some closeups:

IC 1: LM2575
 The LM 2575 is a switching, step down voltage regulator
The LM2575 and L3  inductor are used for the +5V supply.


IC2 (LM27313) and the inductor L2 are used for the +15V supply.


IC 3 

This IC is a voltage regulator. LM25575
It supplies -15V (along with the L4 inductor)


Quite tricky to solder by hand.

Those inductors


+ All about inductors

Jantar Mantar, Jaipur, India

These astronomical instruments were built in 1734 by Sawai Jai Singh II, the founder of Jaipur.

Quite incredible structures.
There are 5 such monuments scattered throughout India: Jaipur, Mathura, Delhi, Ujjain, and Varanasi. 
This is the largest one.

This is very much like visiting a modern sculpture park

 There are a pair of these facing north and south.
They represent the Earth's two Hemispheres.

It's a UNESCO World Heritage site.
There are 19 instruments in total.

These super sized monuments allow observation of astronomical positions with the naked eye.

 Brihat Samrat.-- possibly the largest sundial ever built. Its 23m high. Apparently, it has an accuracy of 2 seconds.

The ramp of this sundial points towards the North Pole, hence Jaipur time can be easily calculated from the position of ramp’s shadow on the fine divisions of the carved scale. It calculates time up to the accuracy of twenty seconds.


Jaya Prakash Yantra

 These two marble hemispheres detect elevation, azimuth and hour angles.

Ram Yantra

It measures the elevation and azimuth of the Sun and planets

Noise, LC Filters, Inductors, etc

noise, Noise, and MORE NOISE.

Filtering noise is really important when building your synth.
Lots of ways to do this and the method may vary depending on the scale ... does the noise effect the whole synth (the PSU) or a small part of a circuit.
Decoupling capacitors, Ferrite beads, Inductors, LC Filters ??

I guess before you do this, you need to ask the questions;
  1. Are you better off filtering the noise, or preventing noise in the first place?
  2. Is there actually much noise to begin with?
  3. Is any LC filter you might install making more noise than it is removing?

On the macro level, a common method is to use something like a LC filter.  This often is found in the psu (the main power supply). An LC filter consists of inductors ( represented by the letter L) connected in series with the power flow and capacitors (represented by the letter C) from the filtered voltage to ground.

Ferrite Beads
A ferrite bead and capacitor is another form of LC Filter. It is often used to filter power for specific power pins on an IC.  They are frequently used on sensitive parts of a circuit like PLL’s & analog sections.

 LC filters are used to keep noise in one section of the circuit from getting to another section.

Decouplig Caps.
A decoupling capacitor is a capacitor used to decouple one part of an electrical network (circuit) from another. Noise caused by other circuit elements is shunted through the capacitor, reducing the effect it has on the rest of the circuit. (Wikipedia)

Also known as bypass capacitors.
They act as energy reservoirs ... you will often see them close to ICs ... they help to smooth out any voltage fluctuations.

You can also use decoupling caps on your main power distrobution board.
Here is an example for eurorack:
NLC power distro board

Below is a LM7805 voltage regulator.
Notice the two decoupling capacitors:
The capacitors are placed between the power line & ground.
The 0.33uF helps to smooth out any low-frequency changes in an input voltage. 
The 0.1uF helps to smooth out any of the high-frequency noise at the output.
Combining these two caps helps to deliver a smooth uninterrupted voltage to your circuits.

As mentioned earlier, decoupling are often used with ICs. Logic circuits tend to do lots of sudden switching ... between on & off with not much in between..So decoupling caps help to smooth  and stabilize the input voltage..... absorbing excess voltage if the voltage spikes suddenly, and providing more power to the IC should the voltage suddenly drop.   

The decoupling capacitors are connected between your power source, whether that’s 5V or 3.3V, and ground. (Generally it's recommend to use a 100nF ceramic capacitor and a larger 0.1-10uF electrolytic capacitor for each integrated circuit).

These are also called coils or chokes.
They are passive two terminal components.
Like capacitors, they store energy.

 However, in this case, energy is stored as a magnetic field.
They are usually made up of a insulated wire, wound round a core (magnetic ... iron or ferrite).

We measure inductance in units of Henry (H).
1Henry = 1 volt of EMF across the inductor with 1 Amp of current.
The larger the number, the higher the inductance.
The higher the inductance, the more energy we can store and provide.
It will also take longer for the magnetic field to build.

Ferrite Beads.
Also called Ferrite chokes, cores, rings, blocks, EMI filters.
These are passive components that suppress high frequency noise.
They are often wrapped around cables to  prevent the cable from acting like an antenna and receiving interference from other devices.

These are snap on ferrite beads. The upper pic shows one used at the end of a USB cable.

Ferrite beads convert Radio Frequency (RF) energy to heat. They are like a filter.
(Contrast this with inductors, which by design do not convert RF energy to heat, but rather offer a high impedance to RF.) 

 On the left is an inductor. To the right is a PCB ferrite bead.
You will probably have seen many of the PCB ferrite beads in DIY synth modules.


Splitting ground planes.

I recently read a great article from Texas Instruments re splitting ground planes as a way to reduce digital noise.
A ground plane is an electrically conductive surface, usually connected to electrical ground.
On a PCB this is a large area of conductive material which is connected to the power supply ground terminal and serves as a return path for current from different components on the board.

 Hoikka1 [CC BY-SA 3.0 (]

Placing the ground planes below the relevant components and signal traces is also helpful. ...
maybe on a seperate layer of a multi-layer PCB .
This should help reduce electromagnetic interference, cross talk & ground loops.

I often see single ground planes on pcbs (with just analog components).
But if there are both analog and digital circuits on a single PCB, best practice seems to be to:
"separate the ground plane on the back layer into a digital section and an analog section, but leave the two planes connected near the return to the power supply. This ensures that digital signals do not follow a return path beneath sensitive analog components....

It is a bad idea to completely split a ground plane and try to bring the sections to the same potential using something like a ferrite bead, as this creates more EMI and noise problems ." (Altium resources)

I've always wondered why Don Buchla used two grounds on his power distro busses.

This may be the reason.
Two separate grounds for analog and digital.???
He never used this on the earlier 200 series.
This type of distro was first used in the 200e which of course uses digital components.

Other ways to reduce noise:
+ Use two separate supplies .. one for the analog & the other for digital
+ keep the analog & digital components separate & don't let their grounds touch.

But I think splitting your ground planes is a really neat idea.

+ Altium
+ Texas Instruments