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This module produces random noise which has multiple uses is a modular system. This particular module can produce white or pink noise or a mix if you build it with a potentiometer instead of a switch to select white or pink.
From the Synthasystem manual:
This is a signal producing module which produces a randomly varying voltage which in theory is composed of all frequencies of the audio spectrum (range) and hence is called white noise because of its similarity to white light —being composed of all frequencies in the light spectrum. It has a sound similar to that of a waterfall.
If we filter out the higher frequencies we call this sound a pink noise.
Both white and pink noise signals are available by the use of the switch marked White-Pink. The output voltage level can be set from nothing to greater than 0 dBm by use of the knob marked Level.
An example of the use of white noise is to create a windstorm effect by feeding the white noise through a sweeping resonant filter. See Example #1. The noise generator has no inputs.
Example #1: Wind
White noise into the filter with the filter in the low pass mode with high resonance. Modulate the filter with KBD voltage and turn the KBD portamento all the way up. Or, you can produce the same effect without the KBD by manually turning the Filter Frequency knob up and down.
This module has one output:
- Signal out – This is a continuous output of white or pink noise.
This module has 2 knobs:
- Output – This attenuates the output.
- White/Pink – This pot will change the output continuously from white to pink. You can also build the module and use a switch here instead.
There is one switch if you don’t use the White/Pink pot. This will simply select white noise or pink noise.
Hooking it up is pretty simple. Connect the output to the input of a Sample and Hold, filter, or other module which takes a voltage input.
This module was originally built with carbon core, 5% resistors with one or two 1% metal film resistors. So, you have a wide range of options here. I recommend using 1% tolerance, metal film resistors everywhere.
See here for more notes regarding R4 and R19. For most circumstances, do not install anything where R19 goes and install a jumper where R4 is listed.
R4 will affect the color of the pink noise. You can try different values here if you want a different harmonic content for the pink noise.
R19 is used depending on the beta of Q5. If you are clipping the noise due to a too high beta, add a resistor for R19 which centers the noise between ground and +12 volts.
There are probably a billion different ceramic capacitors at a place like Mouser. Pick a capacitor that can fit the hole easily, typically 0.1 inch on centers.
Pick good quality electrolytics where designated.
The original used 2N5172 NPN and 2N5138 PNP transistors. These are still available, but I could only find a “PN5138” which I think is the same transistor. In any event, you can use any standard NPN or PNP transistors and they should work.
Q6 should be noisy. Use an old transistor, or try several until you get a good spectrum of noise.
Nothing special, 1N4148s are fine.
Your choice for your panel. If you use the panel I laid out, the holes and spacing will work for the Alpha 12 and 16mm pots. You can probably use nicer BTI, Bourns, etc. 9mm pots with “pot chiclets”
For the panel I laid out, a good 3.5mm or 1/8 inch jack will work. I use the Switchcraft 42A Tini-Jax true 1/8 inch jack. These are switched jacks and they work with 1/8 inch plugs and 3.5 mm plugs.
Use a good quality SPDT switch.
I assume you know the basics of soldering. I like to insert the low lying parts first, like resistors, diodes, etc. After these, I install the IC sockets. Next capacitors, transistors, connectors. Use a good solder, either an organic flux, which you should wash regularly, or a no-wash flux.
Take a break every so often, wash off the flux if you are using a flux which required cleaning. Double and triple check orientations, pins, and solder joints.
Power Supply Regulation/Filtering:
Some additional comments here. These modules are tested to run on +/-12 VDC. The original power supply in the Synthasystem was +12/-10 VDC due to how Nyle designed the -10 volt section of the power supply, not for any magical requirement to have -10 volts.
The power/regulation section has 2 voltage regulators on it which can be set to +12/-10 (or +/-12 volts) depending on your needs. If you are coming from +/-15 volts, you need both regulators and you may as well set one to -10 volts.
If you are coming from +/-12 volts, technically you don’t need the regulators, but if you want, install the negative one and set it to -10 volts. The LEDs are not strictly needed. They are there to establish a base current draw so the regulators will work.
Important… if you don’t install the regulators, you have to install a jumper between pins 2 and 3 as shown on the Power/Regulation PCB or you won’t get power.
This PCB has four holes to allow flexible mounting configurations. The FPE Euro panel is setup to allow this PCB to be mounted parallel to the panel using some 3/4 to 1 inch (typical) standoffs. The mounting holes are connected to ground. The Power Regulation PCB will mount to this PCB using standoffs.
There is no calibration.