Showing posts with label DIY. Show all posts
Showing posts with label DIY. Show all posts

Friday, 24 May 2019

Transistor Families

Some very very basic info regarding transistors.
(I'm writing this for a friend who is just beginning electronics so skip through if needed).

You will find "trannies" everywhere when it comes to synthesizers.
They are a fundamental building block of electronics & are great for making switches and for amplification.

There are two main types:
1) BJT's or Bipolar Junction Transistors (Current controlled)
2) FETs or  Field Effect Transistors. (Voltage controlled)


1)The BJT's are the most common.
    They are made by joining pieces of P-type to N-type material.
     (P-type & N-type materials are found in diodes).
    You will probably recognise BJT's as either NPN or PNP.

The BJTs have 3 leads : the base, the collector, and the emitter.
 These are are current-controlled devices (not voltage). This means that a small current entering in the base region of the transistor causes a much larger current flow from the emitter to the collector region.
You can see why these are so useful as switches and as amplifiers.

NPN = The majority current carrier are electrons.
(Here, the base is made of P-type material)
Probably the most common general purpose NPN transistor I have in my store is the 2N3904.
Its great for driving LEDs, making noise & current sources, and for amplification

PNP = the majority current carrier are holes.
(Here, the base is made of N-type material)
 Probably the most common general purpose PNP transistor I have in my store is the 2N3906

In both these BJT's current flows from one terminal to another (under the influence of current at a third terminal).
A small current at the third terminal controls a much larger current.at the other 2 terminals.
The "Base" is the controlling terminal.
The arrow indicates which direction current is flowing through the transistor.


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2) FETs can be divided into two further groups:
     a) JFETs - Junction FETS.
     b) MOSFETs --- Metal Oxide Semiconductor FETS

The main thing to remember is that FETS are voltage controlled. (unlike BJT;s which are current controlled).
FETS are really good in switch applications, as amplifiers and as voltage controlled resistors
They have 3 regions: a gate, a source, and a drain.
There is a channel or path between the source and the drain terminals.
A voltage placed at the gate controls current flow from the source to the drain of the transistor.

FETs can have an n-type or p-type channel.

Field Effect transistors have very high input impedance..... meaning the FET's gate input draws very little current from a circuit's power source.

The disadvantage of FETs over BJTs is that they won't provide the same amplification that could be gotten from bipolar transistors. Also, their very high input impedance (making them very sensitive to input voltage signals) means that they can be easily damaged by static electricity.

JFETs

Out of these two subgroups the most common one I come across in the synth world is probably the JFET.
The MOSFET however has an even higher input impedance than the JFET.... thus even less loading in a circuit.
The problem with JFETs is that it is much harder to make consistent JFETs than to make consistent bipolar devices. Therefore matching them is important.
 Here is a good link all about matching JFETs
http://djjondent.blogspot.com/2016/10/all-about-jfets-matching-for.html


A JFET is usually ON when there is no voltage between its gate and source terminals.
A voltage at the gate increases the channel resistance and reduces the drain-draw source current.

MOSFETs

Metal-oxide semiconductor FETs are really important in computers.
Most memory ICs are arrays of thousands of MOSFETS.
They are cheap, really easy to make, consume negligible power and can be made extremely small.
They are either N or P type.
Unlike JFETs, the gate of a MOSFET has no electrical contact with the source and drain.
(there is a layer of silicon-dioxide separating the gate from the rest of the trannie)
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Transistor Package  types
Transistors come in many shapes and sizes.
TO = Transistor Outline
Sometimes the component you need can be purchased in more than 1 package type and the leads may have different positions and orientations.
Probably the two most common through hole transistor packages you will come across will be the TO-92, the TO-18 and the TO-220.

Terminal identification [BJT]; Pin 1 Emitter, Pin 2 Base, Pin 3 Collector.
It's got a flat face & 3 leads.Note that not all transistors use this ID.
Because of its small size, its not great for dissipating heat and therefore not recommended for devices with high power consumption.

Below is an example of a TO-18 package
The above example is an Z414 IC, but lots of transistors also use this package.
It's made of a metal case (or can).
The tab is located 45° from pin 1, which is typically the emitter.... in the case of a BJT
If this is a JFET, then pin 1 will be the source.
When looking at stuff on data sheets, always be aware of the perspective. If you are looking from the top through the package, the pins may be shown in reverse. Just remember the metal tab marks pin 1.
Next closest to pin 1, is pin 2. 
 -----------------------------------
 Next is the TO-220 package
This package is used in high power applications. TO = Transistor outline but you will find this used in lots of other types of components such as voltage regulators and integrated circuits
The metal tab at the top is a heat sink. This metal tab is usually electrically connected to the device's internal circuit. Therefore you must place some form of insulator between the pad and the rest of your circuit if they contact one another. 
..............................................................................................

This page will be constantly added to over time and hopefully grow with lots of useful synth info
....... ... I'll place a link to it in the DIY page.

Links
+ Transistor Matching
+ JFETS - matching for synthesizers 

Thursday, 16 May 2019

Twenty Years of Loten

A really hard to find book.
If you can find a copy, buy it.
It's a great summary of the history of Eurorack.

Don't buy Crap :-)
Loten is German for Soldering

The edition was printed for NAMM 2015

Quite a bit on the early modules from Doepfer on Munich and Analogue Systems of Cornwall in England

It's a small but beautiful book.

There is a bit of info re Vermona who had to re design their instruments post German Unification.
Vermona hailed from the East and were not accustomed to the business practices of the West.

Its very interesting to read how things develop.
Eurorack started in Germany, but almost at the same time a similar system was being developed by Bob Williams of Analogue Systems in Cornwall, England.


 Around 1995 , on both sides of the English Channel the idea of condensing 5U modules into a 3U space was taking root.... Both companies, unaware of one anothers designs adopted 3.5mm jacks instead of 1/4 inch.
Both companies also chose a 3U module height. However, their modules were not easy to swap into each others systems. They each had different power configurations and there was no standardization as to where the red stripe went.

Jomox

Jomox - X base 09





Since the early days the Eurorack scene has grown exponentially.


Monday, 13 May 2019

Metro-Modular - Dual Stereo Locator - Model 2102

The Metro-Modular - Dual Stereo Locator - Model 2102 also goes by the name of "Warriewood" 
Warriewood is a suburb of Sydney Australia. It's postcode is 2102.

This Panner is our first entry in the "Postcode series": reissues and reimaginings of classic circuits, with an aim to make them more accessible. 


This is inspired by a panner circuit from the late 1960s that is now extremely, extremely rare (as in less than ten originals known to exist!), but is in fact a simple circuit that is a fun DIY build.


It is an ingenious circuit that uses JFETs as VCAs, which is a circuit technique common in guitar pedals but pretty much unknown in the synth world, with the exception of the Gristleizer.

It does not give constant power panning, and it distorts when overloaded or near cutoff, but it is very musical. Because each channel is individually controllable, it has the bonus feature of working as voltage-controlled 2-input, 1 output mixer should that be desired

The mode switches allow you to tailor the response when a single function generator controls both CV inputs.

 ................................................................
Metro-Modular  are from Sydney Australia. 
The new modules being released for SuperBooth 19 are:

 1.  The Boethian Wheel - Model 660
 2.  Dual Stereo Locator - Model 2102
 3.  Roomic Cube - Model 680
 4.  Dual Balanced Modulator - Model 2315
 5.  Todliche Finger - Model 601


Some Links
+ Metromodular Facebook
+ Metromodular Youtube
+ Metromodular website  

Monday, 15 April 2019

Buchla 251e - my notes

These are my user notes for the Buchla 251e.

The top half of the module contains 4 independent 50 step sequencers and their programmable control voltage inputs and output jacks.
Each stage has it's own pulse output and control voltage output for each of 99 stages.
Each stage is truly independent from the others... they can have their own tempos, time scales, pulse durations, stage lengths, etc.

Incoming “start” and “stop” pulses control each sequencer’s progress.
A “stop” pulse stops the sequence at the current stage number.
A “start” pulse does one of two things:
1. if there is a value entered for the initial delay, it resets the sequence to stage 1, and starts the sequence after the delay time has expired.
2. If a sequencer has a blank in its initial delay field, then the start pulse merely starts the sequence at the current stage number.

 ----------------------------------

SEQ Edit & STAGE Edit
The middle section has a sequencer edit interface and the stage edit interface.
This editing section allows you to set each parameter for a selected sequence.
The sequence can be running while editing a particular stage.
Also, the edit section can track the sequencer, (displaying parameters in real time),
but disabling any editing.


Sequencer edit section:
This manages the general relationships between the 4 sequencers such as copying, syncing, and pasting.
It affects the entire sequence, and not individual stages. (exceptions – “end” & “cycle” are displayed only for the last stage of a sequence, and “sync next” causes the following sequencer to reset to stage 1 whenever it is encountered).
It also manages the settings of each specific sequencer.... things like length, tempo,  cycling,  and the reversing of each sequence.

Tempo 
The internal clock has a range from 10bpm to 300bpm is supported.
Other modes besides the internal clock may also be used to advance sequences or select their stage numbers. Push the tempo knob to advance through five alternative schemes, all of which assign
new and novel functions to the “stop” and “start” pulses:

d A - “stop” pulses decrement the stage number; “start” pulses Advance it.
J A - on receipt of a “stop” pulse, the stage number Jumps to the
         next stage number that contains a “loop begin”; otherwise it jumps
         to stage 00. “start” pulses Advance it.
S H - “start” pulses sample the control voltage applied to the “stop” pulse;
          The sampled control voltage is applied to stage selection.
d i r - a control voltage applied to the “stop” pulse is directly applied to stage
          selection. A ”start” pulse inhibits this activity.
c l o - “start” and “stop” pulses are ignored. MIDI clock is enabled.

 init delay
“init delay” delays the sequencer start whenever it receives a start pulse.
It does not affect the timing otherwise, being ignored when cycling or looping.
The delay is in hundredths of a second, yielding a range from .01 to .99 sec. (Imagine the decimal point).
If nothing is entered in the initial delay (display is dashes), then the start pulse advances the sequence without resetting it.

“reverse” plays the sequence in reverse order.

“copy” copies the displayed sequence. With the copy LED on, hit the display/edit button for the sequence that you would like to copy the current sequence to. The copy LED blinks, and the edit section displays the sequence being copied to. Hit the copy button again to complete the copy process.

"clear" .....With “clear” illuminated, hit the display/edit button for the sequence to be deleted. The “clear” LED blinks; hit it again to complete the transaction.

"end" ................To end a sequence set an “end” in the stage you’d like to be the last. If desired to repeat the sequence, set “cycle”. Remember that in the cycle mode, “init delay” is ignored.
----------------------------------------------------------------------

Stage Edit:
This manages each individual step.
To edit a particular sequencer's setting, press the blue "display/edit" button specific to the sequencer in question.
 The associated LED will ignite, and the stage number it is currently on
will appear in the “STAGE EDIT” section.

Solid blue light = edit mode.
Blinking light = run mode (no editing is available)

In edit mode you can select the stage number and its companion CV value.

The CV voltage (on the indicated blue knob) range is 0V to 9.9V.
You can press this knob the display will blink .... this tells you that you are in fine tuning mode.
pressing the knob again will return you to coarse tuning mode.
0.1V = 1 semitone in pitch.



The 1/interval knob selects the denominator for note sub divisions.
1/1 = a whole note
1/4 = a quarter note
etc etc

Turning this knob to the right increases the value from 1 to 64. (single digits only).
If you turn the knob to the left, the values jump (they double) 
between the whole digits :  1, 2, 4, 8, 16, 32, 64.
-----------------------------------------------------------------

There is a yellow & green button to the extreme left.

The lower left green button sets the pulse duration outputted for the selected stage 
(the length of the stage itself is set with the "interval" control). .
Pulse durations may be set to fractions of the intervals. 
Press "dur" to cycle thru the LEDs. "x1" gives a pulse out for the length of the stage. "x1/2" gives a pulse out for half the length of the stage. "trans." gives just a short transient pulse at the beginning of the stage. If no LED is lit, no pulse is generated for this stage.  

The upper left yellow button sets triplets and dotted notes. 

 
 

-----------------------------------------------------------------
 Loop beginning & ending points are programmed here.
The Master Clock.

When the bicolor LED is off, displaying neither red nor green, the master clock multiplier is exactly 1,
Turning the knob or applying a c.v. to this section will advance or retard this clock.
Max advance = tempo x 1.5
Max retarding = tempo x 0.5

-------------------------------------------------------
Additional features include:
Inter-sequencer triggering
Variable start delay
Retrograde capability
Multiple nested loops
Master voltage-controlled clock

With the 206e or 225e Preset Manager, the parameters of the 251e can
be stored and retrieved as part of a preset.
A 200e USB card is necessary to download new firmware for this module.

Tuesday, 26 March 2019

Buffered Multiple with LED indicator

Multiples aren't the sexiest thing to build but they are essential in any system.
Really easy to build.
The choice is between buffered and un-buffered.

Building a buffered one today.

Here is the breadboarded test circuit.

The basic schematic


The opamp can be a TL084 or TL074
The pinout is identical for both ICs


This particular circuit uses a 074


One change I decided to make was to add a LED to give some sort of indication as to the type of signal this multiple was carrying.
Inspired a bit by the makenoise CV bus

To quote the manual:
"The CV Bus was originally designed for Alessandro Cortini's personal Make Noise system. It provides visual indication of level, rate and polarity for up to 4 control signals that will be shared throughout a patch. ..."
The MN CV bus is I understand passive/unbuffered & those jacks have LEDs built into them.

Here is my 1st perfboard 2HP module.

And the rear
I used a 1K LED resistor. ... experiment a bit.
This LED is standard so will only indicate rate & level.
I'll need to use a bipolar LED to get an indication of polarity.


It works !

I'll build a few versions with different coloured LEDs and try some bipolar ones too.


Bipolar LEDs work well.
(cATHODE  to ground)
Use a 470R resistor for green-red LEDs



Sunday, 24 March 2019

Modular in the Lounge Room VI

Yah... Modular in the Lounge Room 6 is here.
MITLR VI
Sat 23rd March 2019.

Thanks to Terry for the great visuals.

Ilya with some lazers

More pics to come.


----------------------------------------------

aNDREW aka Virus Installer



Paul - aka Allinaire



Mitch- aka Vitals



Hunter



gARETH




Ilya





Past Modular on the Lounge gigs:
+ Modular in the Lounge V
+ Modular in the lounge IV
+ Modular in the lounge III
+ Modular in the lounge II
+ Modular in the lounge I
+ Modular in the Car Park