Glossary (wiki)

Let’s see if we can set up a glossary wiki page, as discussed here.

Feel free to edit this post to add new definitions.

Please try to keep the entries in alphabetical order for easier visual search.

If you need more than one brief paragraph, or find it unwieldy to add things to an existing post, you can just add a comment instead (if you’re looking for a definition, use control-F). You can of course also link to definitions posted elsewhere on the site.

You can search via the search bar at the top of the page. Just click the checkbox “Search this topic” to constrain to this thread.

ADSR: Attack, Decay, Sustain Release. This is a type of Envelope Generator with four stages.(detail)

Amplifier: A device that increases the voltage or power of a signal.

Attenuator: A device that reduces the level of a signal. (schematic)

BOM: Bill of materials. The list of components in a circuit.

BPF: Band Pass Filter. It filters frequencies that are not around the center of the cutoff frequency. The frequencies this covers is the difference between the lower cutoff frequency and the higher cutoff frequency. Think of it as a LPF and a HPF combined.

Breadboard: test board for making seamless electronic circuits.

Capacitor: It is an electronic component designed to be able to store an electrical charge. This measurement in farads (F). There are different kinds (polarized or non-polarized). (types and symbols)

Cutoff Frequency: The point where the filter begins filtering.

CV: Control Voltage.

Diode: It is an electronic component that lets current flow in only one direction. It is the passing sense, or direct (polatity and symbol)

EG: Envelope Generator.(detail)

Envelope: Used to shape the loudness, frequency content or timbre over time.

Filter: Removes certain frequencies and harmonics from a sound.

FM: Frequency Modulation is where the pitch of an oscillator is modulated (changed) very quickly by another oscillator.

GAS: Gear Acquisition Syndrome.

Gate: A signal in an amplifier circuit that generates voltage signals that correspond to binary 1’s (high) and 0’s (low). This signal can be maintained.

Gerber: a standard vector image file format that is used to store and transmit fabrication data for the automated construction of a printed circuit board. See (Wikipedia article) for more details.

HPF: High Pass Filter. It filters frequencies lower than the cutoff frequency “letting only the highs pass”.

Jack: A socket for an audio cable to plug into (detail).

Kosmo: Sam Battle’s modular synthesizer and by extension, its modular synthesizer format. 200mm high panels, with big (¼"- 6.35mm) jacks. (Kosmo specifications)

Kosmonut: A fan of the Kosmo modular synthesizer format. A member of this forum.

LDR: Light dependent resistor. AKA Photoresistor. (symbol)

LED: Light Emitting Diode. AKA the blinky lights. (polarity and symbol)

LFO: Low-Frequency Oscillator (or VCLFO : Voltage Control Low Frequency Oscillator (detail))

Line Level: A standard signal level reference -10bDV (decibel volts).

LMNC: Look Mum No Computer.

LPF: Low Pass Filter. It filters frequencies higher than the cutoff frequency “letting only the lows pass”.

LPG: Low Pass Gate

Mixer: A mixer combines signals together.

Multiple: Splits or copies a signal to send to more than one destination (detail)

Patch: How to connect the modules to each other using cables.

PCB: Printed Circuit Board

Potentiometer: variable resistor (pin order and symbol)

PWM: Pulse Width Modulation Detail

Resistor: conductive component which opposes (more or less depending on its value) the flow of current. Detail

Resonance: The output of the filter is fed back into its input. Results in boosting the harmonics around the cutoff frequency.

Sample and Hold: Electronic circuit memorizing a voltage taken by sampling a signal.

SI: International System of Units, defining units like ampere, volt, and ohm, and prefixes like kilo-, milli-, and micro-. Detail

Stripboard: Plate for the construction of electronic circuits formed of several copper strips on an insulating panel.

Tolerance: How close the actual value of a part is likely to be to the nominal value. Smaller is better, but larger is cheaper and often perfectly good, unless you’re told otherwise. (detail)

Trigger: A signal in an amplifier circuit that generates voltage signals that correspond to binary 1’s (high) and 0’s (low).

Trimmer: (or trimpots) small potentiometers (variable resistance) that are often found on circuits that require precise adjustments, rarely designed to be controlled by the user.

Vactrol: A light dependent resistor (LDR) placed near an LED to add voltage resistance. As the LED gets bright, the resistance goes lower.

VCA: Voltage Controlled Amplifier.(detail)

VCF: Voltage Controlled Filter.(detail)

VCO: Voltage Controlled Oscillator.(detail)

Veroboard: a brand of stripboard developed in the early sixties. Usually used as a generic term for any stripboard.

White noise: Is a randomly generated tone combining all sound frequencies simultaneously.


Led :



Passive Attenuator :


I moved this topic to the FAQ category.


now i can’t edit it, it’s a too old post

1 Like

Capacitor :

Ceramic, Tantalum, Film , Electrolytic and Film

Note by @analogoutput :

Link for capacitor conversion



Resistors are devices that obey Ohm’s law: if there is a voltage drop V across a resistor, then a current I flows from the higher voltage to the lower voltage, and I = V/R, where R is the resistance of the device. So a resistor converts a voltage to a current. A larger resistance produces a smaller current, so a resistor can be used to limit current. Two resistors connected together can form a voltage divider whose function is to take one voltage and produce another, proportionally smaller voltage from it. A resistor connected to a positive voltage (or to ground) can set a voltage at a point where otherwise the voltage would be indeterminate; this is called a pullup (or pulldown, respectively) resistor.

The unit of resistance is ohms, whose symbol is Ω. Since this is hard to type sometimes people use R instead, or SI prefixes such as k or M alone; “1000 Ω”, “1000R”, and “1k” all refer to the same resistance value.

Besides resistance, there are two important parameters for resistors: Power rating and tolerance. The former indicates how much power the resistor can dissipate (current through a resistor produces heat, and too much current will burn out the resistor). For most purposes in synthesizer circuits, 1/4 W is large enough. If not, the BOM should indicate what power to use. Tolerance indicates how close to the nominal resistance the actual resistance may be; 1% tolerance, for instance, means a nominally 100R resistor might be as low as 99R or as high as 101R. Usually 5% tolerance is adequate but sometimes higher precision (smaller tolerance) is needed, and 1% resistors are cheap enough that it makes sense to use them everywhere unless even higher precision is called for.

There are different materials used in making resistors including carbon, carbon film, and metal film. Most 1% resistors are metal film. There are different physical sizes, which generally have to do with the material and power rating, not the value of the resistance.

Here are some resistors:

The value of the resistance and the tolerance are indicated by the colored bands but you may find it easier to just measure the value with a multimeter.

Two different symbols are commonly used for resistors in schematic diagrams:


A potentiometer is a variable resistor.


SI units:

Units for electrical quantities are defined by the International System of Units, or SI. Common units are:

Quantity Unit Symbol
Current ampere A
Capacitance farad F
Inductance henry H
Resistance ohm Ω (or, non standard, R)
Voltage volt V
Power watt W

Strict usage is that units are not capitalized but the symbols are capital letters.

There are various prefixes used to denote power of 10 multiples or divisions of these units. For example, a milliwatt is 1/1000 of a watt. The prefixes commonly used in electronics are:

Name Multiplier Symbol
mega 1,000,000 M
kilo 1000 k
milli 1/1000 m
micro 1/1,000,000 µ (or, non standard, u)
nano 1/1,000,000,000 n
pico 1/1,000,000,000,000 p

Note the capitalization of the symbols: M and m mean very different things.

A farad is an extremely large capacitance so you usually see µF, nF, or pF. On the other hand an ohm is a small resistance so you often see kΩ or MΩ.


A jack is a socket for an audio cable to plug into. The corresponding part on the end of the cable is called a plug. In England the tern “jack socket” is often used and some use “jack” to refer to the plug, though this usage is historically incorrect.

Jacks and plugs vary by size, number of terminals, and construction.

Common jack sizes are 1/4 inch (or 6.35 mm) and 1/8 inch (3.5 mm).

There can be two, three, or four terminals to connect to wires and ground shielding in the cable. There can also be switch terminals that provide for a normalized connection when no cable is plugged in.

Jacks can be of open or closed construction, and can be panel mount or horizontal or vertical board mount.

Diagram of terminals for the 1/4" jacks commonly used in Kosmo modules:


I’ll add :

  • ring and ring normal are for stereo (R channel, with tip being L channel) and rarely used in synth modules, except for some input/output modules which interfaces with the outer-world…
  • the “normal” connection(s) are used in some cases to “chain” some jacks in a convenient way, so you don’t have to explicitly patch the most common use of a module.

Say you have a dual filter module. Normaling the OUT of the first to the IN of the second will put them in series, unless you plug something in the IN of the second filter, which will break the normaled connection.
This is achieved by connecting the output of the first filter to the tip of its OUT jack, AND to the tip normal of the IN jack of the second filter, and the tip of that IN jack to the input of the second filter.
When nothing is plugged in that 2nd IN, the normal pin is connected to the tip pin, and thus the output of the first filter goes to the input of the second.
When you plug something into the IN jack of the second filter, the connection inside the jack from tip normal to tip is broken, and the second filter will only see what comes from whatever is plugged in the IN jack…
Without the normalisation, you’ll have to put a patch cord between OUT1 and IN2.
I hope that was clear :slight_smile:


Passive parts such as resistors and capacitors have not only a value (in ohms or farads, etc.) but a tolerance which is an indication of how far off that value might be. For example, a nominally 100 Ω resistor with 5% tolerance will not be exactly 100 Ω but should be within 5% of that. In other words, you can expect it to be somewhere between 95 Ω and 105 Ω. If it were 1% it would be between 99 Ω and 101 Ω. Obviously the smaller the tolerance number the “better” in the sense that its value will probably be closer to the nominal value. On the other hand small tolerance parts can be expected to cost more and to be harder to get, and you might not need that precision. But if you have a higher precision (smaller tolerance) part than is specified or necessary, it’ll work fine.

As indicated above, for synth circuits usually 5% resistors are adequate but 1% resistors are only slightly less dirt cheap and can be used almost everywhere, unless the build instructions call for something even more precise (which is rare). In fact if you have a few dozen 1% resistors of the right value, with a multimeter you can probably find several within 0.1% of the nominal value, and using them will be cheaper than buying 0.1% precision resistors.

For obvious reasons, potentiometers don’t have tight tolerances. The value is variable anyway, so it doesn’t really matter much how close to an exact value it is.

Capacitors tend to be lower precision than resistors. ±20% is not uncommon, and you sometimes even find ones with -20%, +80% tolerance — meaning that if it’s nominally 10 nF, it won’t be less than 8 nF, but it might be as high as 18 nF. Correspondingly, circuits usually aren’t designed to require capacitors to be very precise. If the instructions don’t say otherwise, a 20% capacitor will probably work fine. (In fact if you don’t have the right value cap but you do have one that’s within a factor of 2, there’s a good chance you can substitute it with little or no ill effect.)

With semiconductors (diodes, transistors, and ICs) there usually isn’t a single value to quote a tolerance on. If you check the datasheet there might be tolerances given, or min/typical/max values, for several parameters, but there won’t often be higher/lower tolerance versions of the same part. If there are, the circuit diagram or BOM will usually specify which to use — if not, feel free to use whatever’s cheapest or most readily available.


They have, for the total resistance (usually ±20%). Example, from an ALPS RK09L datasheet:


Tnx, corrected. Tnx, corrected. Tnx, corrected. Tnx, corrected.