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Archive for the ‘Music’ Category

eChucK Spatializer Circuit

In eChucK, Music on July 25, 2011 at 6:33 am

An eChucK Lunetta Spatializer Circuit

We’ve all heard the sound effect of music wooshing from one side to the other, especially while listening with headphones.  Ever wonder how that’s done?  It’s easy:  just make the left channel signal amplitude reduce while the right increases.

Actually good spatialization as they call it requires a lot more fancy stuff that models the speed of sound in air as it travels from the sound source to your ears in two separate and unequal paths, but you can get pretty good results from just fading the signal amplitudes.  That’s what this circuit does.

I created this eChucK Spatializer circuit in software form first by programming it in ChucK, then imgineered it into hardware form using a 4000 series CMOS analog mux chip, the CD4052.  It provides four spatial positions:  left, left of center, right of center, and right.

What you do is you apply your music signal to the input buffer, then select the spatial position with the A and B input pins to control where the sound will appear to be.  It works by creating four voltages with a voltage divider made of three resistors, then multiplexing those voltages to the left and right channels.

The voltage divider provides voltages Vin, (2/3)*Vin, (1/3)*Vin, and 0*Vin.  We apply these four voltages to the four X channel inputs, then apply them in reverse to the Y channel inputs.  The result is output voltage pairs of (left, right) equal to (1, 0) or (2/3, 1/3) or (1/3, 2/3), or (0, 1) times Vin, thus crudely but effectively spatializing the monaural input signal on the stereo output channel.

If all those numbers just went wooshing over your head like a jet airplane, just think of it this way:  the digital control input selects the appropriate left and right channel signal levels to create the impression that the sound source exists at one of four places.  Changing the digital input value moves the perceived location of the sound to a new position each time.  So you connect time varying digital signals to the A and B inputs and you get sound bounding around inside your head (with headphones) or in front of you (with speakers).

To create that left-to-right motion effect, just put a two bit binary count into the inputs B and A, with B as the most significant bit and A as the least significant bit.  That way the left channel amplitude reduces while the right channel amplitude increases.  The sound will be stepped in four positions instead of smoothly changing, but hey what level of perfection do you expect from a humble logic chip?  Not a bad effort for the lowly mux, I’d say.  Well done little CMOS chip, you’ve earned soome well deserved electrons!   Now go forth and spatialize your audio.

 

Clear Breadboard Chosen

In eChucK, Music on February 1, 2011 at 7:54 am

On the advice of DIY hobbyist tjookum, I have decided to switch the protoboard selected forr eChucK to the one shown below.

This breadboard is a little bit larger, well a good bit larger, and has power supply rails for convenience and ti improve circuit wiring ease.  One thing that I really like about it is that the plastic is clear so beginners can see where the connections are made underneath.

To reiterate, it is essential to select one and only one breadboard for eChucK’s beginnings because at first it will be breadboard only, then later we will make PCBs in that exact breadboard pattern so that designs may be transferred from breadboard to PCB.  This way the DIY enthusiast can enjoy the convenience of breadboard construction, and also still have the benefits of PCB construction for a more permanent solution.  More details to follow, stay tuned.

Enjoy!

Bourns Thumbwheel Pots

In eChucK, Music on January 28, 2011 at 8:24 am

Thumbwheel Potentiometer

One of the keys to eChucK’s 0.1″ spacing miniaturization is potentiometers.  We must have a better way than huge alpha pots to krank up our wholesome goodness.  These thumbwheel pots from Bourns are just the trick.  Available in quantity one at $1.24 each from Digikey, they offer exceptional breadboard friendliness.

You can get these pots in horizontal or vertical arrangement, and a few flavors of each actually.  I recommend the above shown configuration.  These pots can be located at either the center of the breadboard or it’s edge.  They have a screwdriver molding for both flat and phillips screwdrivers.

These pots are available in many values including the popular 10k and especially 100k for eChucK, and 1Meg for Lunettas.  Other values are also available.  The pots are rated at 200 turns, but they last for a whole lot more in practice.

Enjoy!

eChucK Supplier: sparkfun electronics

In eChucK, Music on January 28, 2011 at 4:36 am

One company that really catches my attention espeically for eChucK supplies is sparkfun electronics.  I have yet to get my finger on the pulse of this innovative group of individuals.  They seem to be collecting the coolest miniature prototyping parts for electronic builds of all types and offering them for silly-cheap prices.  Here’s a look at a few of them.

170 tie point breadboard

Miniature Breadboards sparkfun offers the 170 tie-point breadboard for $3.95 in quantiy one, part number PRT-07916.  Looking at that number, we see that we have five tie points on each node, and two such nodes per row.  So 10 tie points per row means we get 17 0.1″ pin spacings.  That’s enough for two 16 pin DIP chips or three maybe four 8 pin DIP chips.  The board lacks power supply tie points, so you’ll use some real estate up for power but that’s OK.  The total size of the board is 1.8″ x 1.4″, so a litle bit bigger than an inch and a half square in size.  Just for fun, these miniature breadboards are offered in several colors as well.

Spring Terminals another eChucK enabling part from sparkfun is part number PRT09077, a spring-terminal header.  To miniaturize eChucK we need a tiny connector system.  Hardly anything is cheaper than wire itself, so our cables are quite inexpensive, but we need a low cost pcb connector to complete the picture.  These spring terminals appear to be quite the part for the task.  They do not require a screwdriver and seem to be well suited for the task (having not tried them myself yet).

Another sparkfun alternative for eChucK is the miniature screw terminals on 3.5 mm spacing (remember, 2.54 mm is 0.1 inches).  One part number is PRT-08235.  These require a small screwdriver, and may hold more wires more firmsly.  You’d be hard pressed to find a better connector than this one for a miniaturized system like eChucK.

In addition to the parts mentioned above, there are many other interesting miniature parts with 0.1″ hole spacing, breadboard-friendly designs available at sparkfun electronics.  Have a look at their excellent collection of breadboards and LEDs and breakout boards, plus sensors and interfaces… sparkfun offers a great price on everything they sell and a lot of it is idea-fodder for eChucK.

Enjoy!

eChucK Standards Document

In eChucK, Music on January 28, 2011 at 2:54 am

There’s a new type of music synthesizer on the horizon.  It’s simple, elegant, inexpensive, and can take many physical forms.  Born out of a desire to make electronic models of software music programs, the e in eChucK is for electronic.  The ChucK part refers to my particular favorite music programming language, but that is not important here.  What is important is the standard, linked below:

eChucK_Standard

The eChucK_Standard document is very informal.  It’s not some fancy standards document intended to be a legal definition between corporations, rather it conveys the general idea (and lots of specifics) of a novel modular synthesizer system.

In addition to having roots in music software, eChucK has branches in the sky of business.  eChucK is an attempt to define a standard so that the average hobbyist can produce a module or collection of modules and have a ready-made market of enthusiasts who may choose to purchase those modules.  Whether it’s kits or completed modules that you are offering, or both, the goal of eChucK is to provide a framework of standards and marketplace for you to participate as a community member.

At this point eChucK is just an idea.  I personally am really close to offering some modules in kit form, though that may be a little while from now.  Some people in the Lunetta community are thinking about offering kits.  Famous synth makers have offered mini-synth boards.  Not-so-famous synth makers have come up with some really cool designs.

All this is happening in the chaos of the free market with all it’s incompatibilities and one-off prototypes.  That’s just fine, but what’s needed is a standard that provides a framework for such development efforts.  eChucK aims to be that standard.

OK, OK, what IS it then?  Well, imagine a modular synthesizer with the case and front panels removed.  You’ve got a bunch of circuit boards with wires hanging off of them scattered about on a desktop.  Now make each board small and simple by reducing it’s design to minimal form.  Now the circuit boards are really small and the wires just changed into 22 ga. solid hookup wire.  You rearrange the boards onto a panel or in free space, supporting their light weight with the stiff wire, and make your own free-form synth sculpture.  Rewire to your heart’s content to make the music that you want.  That’s the idea behind eChucK.

To summarize, eChucK is a standard of tiny simplified synth boards wired freely with various miniaturization tricks like thumbwheel pots and micro switches, mini screw terminals for pcb i/o, and plain old wire for hookup.

So have a look at the standards doc and if you’d like to start making eChucK modules for your own fun and profit, drop me a line and I will help.  Enjoy!