Friday, September 19, 2008

Supplies and Parts

Here's a list of places go for parts, plus a few specific suggestions in case you want to stock up on some basics. I've been meaning to get around to this for a long time, sorry 'bout that.

Mouser ( this is one of the big dogs... their catalog weighs about 5 pounds, and they carry just about everything. Sometimes can be a little overwhelming number of options--3,255 choices for .01uf capacitors, for instance. But you can find almost everything in one place, quick shipping, very pro. Similar to Allied, Newark, DigiKey, but maybe a little more geared up for small orders.

Jameco ( more oriented to hobbyists rather than engineers, not quite the selection of Mouser but they're a good place for basics. If you want to build up your parts stockpile, they have a couple of assortment packages that are a pretty good value (they're mostly what I pull from when i'm passing out parts in class):

Futurlec ( Good things: they carry some chips (CA3080) which are out of production and hard to find/expensive elsewhere... plus some insanely great prices on a few specific items, like pots for $0.55@. Bad things: they ship from someplace in SE Asia, can take a few weeks or longer depending on how the boat traffic is... and some folks have had issues w/ quality or missing orders that got bolloxed up. I never had any problems with them.

Small Bear ( specializes in parts for building guitar pedals, including some hard-to-find "vintage" parts for folks looking to recreate specific collectible distortion pedals and the like. But also good for non-purists, things like stomp-box enclosures and switches.

Soldering Irons. I think some folks got off on a bad foot w/ soldering, and it's partly due to cheap tools. A decent iron will really reduce frustration and help you do a good job. Weller is a respectable brand name; I have used a WLC100 (shown above) for a bunch of years and it's been flawless; there's also a model WP35 at about the same price (around $40) which comes recommended. I also use a ST7 tip, which is smaller than the stock tip that comes with the iron and really helps doing ICs and smaller components. If you want to transfer your gizmos from the solderless breadboards to something sturdy enough to gig with, I'd really recommend getting a good soldering iron.

Tuesday, August 26, 2008

More Catch-up

Since folks have pretty much got the hang of schematics and how to breadboard, we spent a couple Saturdays just playing around... working from various schematics around the net, interconnecting some of our building-block modules, and trouble shooting. Handouts were pretty basic, but I'll work on reformatting and expanding a little and posting documentation as I get a chance. Here's some of what we played with:

  • More on the magical Starve Pot
  • VCFilter (extracted from MFOS's Weird Sound Generator)
  • "Punk Atari Console"--basic noizer based on 555/556 timers
  • Digital Ring Modulator, based on 4011 chip (similar to Korg M10):

Monday, July 28, 2008

Dividers, Uniters, Filters

Small but productive session this week. Most folks had both the 40106 and 4093 oscillators going, and interconnecting them so they cross-modulate seemed to be the happening thing. I got some recordings on the 4track, will post as soon as I can MP3ify them.

We vaguely went thru this week's posting on passive dividers, mixers, and filters. Not quite as flashy as some weeks, but pretty powerful basic stuff. Chris had his mixer already boxed up. If you missed the session, hit me up for some extra capacitors for the filter.

Ryan had the winner when he hooked up a variable divider across the battery powering his oscillators. It's just like the volume control, except it allows you to dial down the amount of power going into the circuit... as you choke off the volts, the oscillators get unstable and start to glitch out in some very nice ways. This "starve" pot arrangement is sort of universal spice for circuit bending in general--try it on just about anything. He put it to good use on Sunday nite at Grog Shop--the final Thursday Club performance, how sad.

No workshop this week. Drop me a line on how it's going for you, and what you'd like to be doing in upcoming sessions. See you on the 9th!

Saturday, July 26, 2008

More oscillators

Late recap from last week: we forged ahead with a second oscillator design based on the 4093 quad-NOR chip. Some folks are still working with the 40106, which is fine--there's a ton of options in there, and you could play with just that one chip for weeks and not exhaust it. The 2nd circuit adds some twists, and most people got something going. I think a couple folks even started connecting the two together... we're starting to get dangerous.
A couple more hints based on last week's troubleshooting:

  • On the solderless breadboards, make sure not to shove the wires in so far that the insulation gets into the breadboard hole... insulation = no connection = no love.

  • Likewise, don't strip an inch of insulation off and then shove the whole thing into the board... it'll curl over underneath and short out to something you don't want. Practice the Middle Way.

  • If you're starting to transfer your designs to those perfboards, think ahead: work out your layout before you start soldering (on the breadboard, or paper). Use a fine-tipped soldering iron and just enough solder--no big blobs. Try not to use any more heat than necessary, you will eventually cook either your components or board traces. For IC's, use sockets.

  • The 386 amplifier is apparently a little power-hungry, and can drain your battery pretty fast (6 hours or so). You might want to put it on it's own battery, and make sure it's off when you aren't using it

Very glad to see some "finished" projects evolving out of this whole process. Almost everything we've built so far can be interconnected, and we're starting to see some frankensynths emerging. Keep bringing in your projects-in-process to show, or troubleshoot. Ted sent this pic of his monster Victorian synth, can't wait to hear it:

Sunday, July 13, 2008

Week 4: Intro to Oscillators

Whole lotta beepin' goin' on at this week's Intro to Oscillators session. For folks that missed it, instructions are posted as a web page, since some of you were having trouble with Word docs... follow along at home and we'll do some more next week.

A few suggestions, based on troubleshooting we did yesterday:

  • Use the thin solid wire on the breadboard, not the thicker stranded stuff.
  • Build one oscillator at a time, and get it to work, before moving on to the next one.
  • If some oscillators work but one won't, it could be the chip. I have spare chips, try using one of the other inverters (like pins 9 and 8, on the other side of the chip) in the meantime.
  • Make sure your components are seated all they way down on the breadboard--the IC has pretty stubby legs, so sometimes it looks like it's plugged in when it ain't.
  • Trim your component leads... when they're all gangly and sticking up, they can short out or lean over into their neighbors. For the resistors going into adjacent holes, fold one lead over so they can stand up vertically:
  • You don't have to be neat, but it's harder to troubleshoot if you're not. I'm just sayin'. Anybody that's seen the lab knows I'm not a neat person... but something like this is likely to work, and if it doesn't it'll be easier to figure out why:

I'm working on pulling together some resource and reference links, for things like resistor codes and suppliers. Let me know if you have suggestions.

Thursday, July 10, 2008

Voltage Dividers

A few folks were having issues connecting their Freds to their amplifiers, so this seems like a good time to introduce Voltage Dividers--these will come in very handy for a lot of purposes as we continue.

The problem is, Fred puts out enough juice to power a speaker directly (approx 2 volts); your amp is expecting to see no more than line level (approx .2 volts at most--guitar or mic levels are even lower). So the signal is just too "hot" for the amp to handle, and it distorts or otherwise freaks out.

The answer is to attenuate the signal with a voltage divider, made from 2 resistors:

Basically, the signal from Fred gets soaked up by the 2 resistors in series; most of it gets soaked up by the 100k resistor, and about a tenth of it (uh... 10/110ths, actually, but who's counting) is left over for the 10k resistor... so if you put 2 volts in, you'd get about .2 out... which is much better as far as the amplifier is concerned. Changing the values of the resistors would change how much voltage comes out... if you used 2 50k resistors, it would divide the input voltage in half.

A Volume Control works about the same way:

The only difference is that as you turn the knob on the pot, you change the ratio between the two resistances (the resistance of the pot before the wiper, and after), so the amount of division changes from 0 to full on.

BTW, the schemo for the amp shows an optional volume control on the OUTPUT of the amp, which is a little unusual... it's not efficient, and it only works on a small amp. It's more normal is to put the volume control on the INPUT...

Monday, June 30, 2008

Week 3: amplifier

I'm getting a little behind, and playing catch-up. This week is/was an introduction to the solderless breadboard, using the Little Gem 1-chip amplifier as a project. I believe everyone got theirs working, which is really great. We also added some new schematic symbols to our arsenal, and I think got our contact mics working.

I've posted updated instructions [.doc now converted to html--7/14] to clarify some questions that came up during the build. I've also added some more details for folks that want to transfer their amp from the breadboard to perfboard. Let me know if we need to go over that in more detail and I'll work it in. It will really help to have a little stand-alone amp for our next meeting

Sam got his amp perfboarded and nicely housed in a cigar box:

And Ryan had his Fred mounted in tupperware. Hoping to see more examples of creative cases.