266e notes

This page is mostly about the buchla 266e SOU or source of incertainity.
It's part of the 200e system that came out in about 2004/5.
It's based on the earlier 266 & 265. These are certainity among Don's iconic modules.
Along with the 281 & 292. I think all buchla systems need at least these 3 modules. 
On the surface the 266e looks simple. Just some noise and 3 flavors or random.
However, if you explore you will be amply rewarded.

There are 4 sections:

1. Noise

2. Fluctuating Random Voltages

3. Quantized Random Voltages 

4. Stored Random Voltages

1. Noise:

 We have 3 flavours: Normal, high pass and low pass filtered.

 

-3 db/octave (brown)

Flat (pink)

+3 db/octave (white)

2. Fluctuating Random Voltages.

This section provides two (channel A & B) continuously changing, unquantized,low speed random voltages.

 

We have 2 inputs and 2 outputs

The black banana inputs are for voltage control of bandwidth (ie: speed at which these voltages change).

These changes range between 0.05Hz to 50Hz.

The range of random available is huge : "barely perceptible movement to rapid fluctuation.".

3. Quantized Random Voltages (QRV).

Here we have two independent quantized random voltages (channels C & D) that share some parameters (no. of states & their distribution). 

The random voltages change upon receiving pulses so you can trigger them on time

and control their distribution over a curve.

In the 200e series, trigger pulses are +10V. 

The knob sets the number of random states: between 2 to 24.

There is also a CV input for this parameter. It can be found in the Stored Random Voltages section

Their distribution (curve) is set with the grey switch. This is a statistical distribution of randomness.

A flat distribution means that all states are equally likely, so extreme voltages are just as likely as small ones. The 'bell' curve concentrates voltages in the centre, resulting in a 'tighter' sounding range. 

4. Stored Random Voltages (SRV).

In this section, voltages are not quantized.

The module must be triggered with a +10V pulse. The random voltages will change upon receiving more pulses. The orange bananas are for pulse inputs

The black bananas are CV inputs.

Skew biases the randomness toward one extreme or the other.

Number  sets the number of random states: between 2 to 24.

This is linked to the above  "Quantized Random Voltages" section.

Degree varies the amount of randomness.

Chaos alters the distribution from just a little uncertain (narrow band) to total chaos (wide band). 

If all controls are in their zero position, you can realize classic S/H with a signal patched into the Skew CV input & trigger pulses into the orange bananas.

A very detailed description of the functions of the random voltages and their application can be found in Allen Strange's excellent book "Electronic music - systems, techniques and controls" from page 82

It's interesting to see how the source of uncertainity developed and evolved.
From the humble 165 to the mighty 266e.