LM358 Op-Amp Issues

Audio Mixer Schematic

Should be simple…here’s the test circuit. It’s derived from the multi-channel mixer below. I’m just testing the circuit. It should basically pass through the one input signal perhaps with some attenuation. Instead, it distorts it all to hell-and-gone. Any ideas?

So — back to hammering and less yammering. I’m trying to build a small, portable, DIY audio mixer. Thus far — I’ve found nothing off-the-shelf that meets my, you know..specifications. There are lots of inexpensive and rather expensive field mixers but those are honking things with gigantic XLR inputs for proper microphones. I want about two 1/8″ stereo inputs, and maybe two or three 1/8″ mono inputs. I want to mix a few things and I want the whole thing about the size of deck of cards or something small like that. The only thing I can think to do is to build it.

Plus..we like to build things.

It should be simple but I’m about a decade out of analog electronics. I used to be able to debug op-amp circuits but not any more. And back when I could they didn’t have the internet the way they have now, so I’m sorta putting it out there with as much evidence of the problem as I can muster.

I built the circuit you see above using an LM358 op-amp. Seems like a reasonable go-to unit to build around and many op-amps, as I recall, are generic enough that I feel like it should work in this circuit. (But, I’m prepared to be wrong.)

The problem is that the signal gets super distorted right from the get go.

I’m using my MBP to generate a signal using Max/MSP. It’s just a 1kHz pure tone — a sine wave. The output comes out of the computer, right? Max/MSP generates the signal to go out on one channel and that’s what I feed into my circuit.

Basically — it gets distorted, even at the input. Check out the signal at pin 2 (the + on the left-most op-amp) — it’s what comes after a resistor and capacitor from the input signal. Why’s it so clipped even before it gets processed except for a couple of discrete components? I think that’s the heart of the issue cause the signal doesn’t even touch the op-amp?

So — obviously screen shots from my scope. The top cyan trace is the audio signal I injected into the circuit. It’s a 1kHz sine wave generated from Max/MSP and output over my MacBook’s audio output. It’s about 280mV P-P.

Pin 2 – Basically the input signal after a resistor and capacitor. It’s like..totally clipped there. Why it’s clipped between the raw signal and the input on pin 2 is baffling me. I’ve been so far from analog circuits for so long..I’m just not even sure why putting it on pin 2 alone clips it this way.

The output from the first Op-Amp in the mixer circuit..looks kinda hinky..worse than the input on pin 2.

Things only get worse from there. The output of the first op-amp looks like worse crap. This is basically the op-amp processing one signal and mucking it all up.

Now we’re at pin 6 which is the input to the second op-amp which comes after pin 6 with a 10k resistor in between.

Pin 7 is the final output. This should be a clean signal basically like the input for this test.

Final-final output after a couple of resistors and a capacitor. Distorted crap.

Why do I blog this? Well..I can’t figure out what might be wrong and because the circuit is so simple, I figure the problem is something as simple as the circuit. But, I may be a bit out of my depth and I’m baffled especially because the signal as measured at pin 2 — effectively the input — is distorted already.

Any ideas?

Continue reading LM358 Op-Amp Issues

Janet Cardiff Sound Art

JCB_25072011_080845_9970

Just a quick note on some material in this hard-to-find catalogue resume of Janet Cardiff‘s work.

It’s called Janet Cardiff: A Survey of Works, with George Bures Miller

Cardiff is well-known for her early-days “sound walks” where participants were given a Walkman or similar device to listen to as they walked about. Stories were told or experiences recounted in the audio track. The idea is simple, but from what I understand (never had the pleasure..) it was the story that made the experience engaging.

I first came across Cardiff’s work while doing sort of informal background research for the PDPal project where we were trying to understand interaction in the wild — away from desks and keyboard and all that.

What I find curious about her work is the way it augments reality before people even really thought about all this augmented reality stuff — but, it does not fetishize little tiny screens and orientation sensing and GPS and all that. It uses our earballs rather than our eyeballs — and somehow that makes it all much less fiddly. Although — if you look carefully at the bottom image you’ll see an image from a project in which one does use a screen — from a small DV camera which is playing a movie for you as you go along.

Janet Cardiff

Parenthetically, I think Cardiff had one of the best augmented reality projects with her telescopes. I’ve only seen this as documentation when I saw Cardiff talk in Berlin at Transmediale 08. There should be more documentation of this somewhere, but the effect was to look through the telescope and see a scene in a back alley that was the back alley — only with a suspicious set of activities being committed — perhaps a crime. The illusion was in the registration but the story was in the sequence of events that one saw, effectively the story. So much augmented reality augments nothing except coupons and crap like that. There is no compelling story in much augmented reality, but I don’t follow it closely so maybe things have changed.

JCB_25072011_080858_9971
JCB_25072011_080945_9972

Continue reading Janet Cardiff Sound Art

Whittling Away at Audio

Audio Whittling

I’ve become almost over-interested in audio as a new, untapped frontier for IxD and UX. In contrast to what our quite busy, jealous, overburdened screens offer us audio has the opportunity to form a kind of interaction experience and engagement with “stuff” (sorry early days…not sure how to be more precise..) and other people seems woefully antique. Could be some good wheels-on-luggage insights and opportunities to do design that makes things better — and makes what we have now embarrassing.

This is an unfolding theme and there have been some “observations” of things that just seem like they were never really designed so much as bolted on without a care or a concern that could be done better.

Some considerations:

I need a category of aspects of audio and it’d also be nice to become a bit more expert at audio and sound and the variances, cultures and interstices of the terrain.

Screens are all well and good, and HD audio may possibly become *more HD and surround-y, but even the small, low-hanging simple stuff is super interesting, like..

* Kitchen appliances that beep like a yelping puppy what that just got its tail stepped on
* Car horns and their abusive honk when you just want a chime to summon a friend or lightly remind that sleeping wanker at the head of the red light queue to move on
* Cars and their noises in the era of purring-whirring barely noticeable electric engines — I know this is a terrain that’s being actively explored
* Audio processing to make sound more expressive — are there alternatives and extensions to volume and tone control as ways of manipulating sound without getting goofy?
* What’s the Instagram of sound?
* What would a proper sound designer do if given a brief to design the audio experience for an operating system? Or a microwave oven? Or an airplane cabin interior?
* Consider that the high water mark of sound design for devices and the like are start up tones, beeps on notifications, &c. That’s not much — there could be more.

What would the world be like if proper, thoughtful sound designers came into the UX/IxD mix?

What’s the Design Fiction for the world in which, in some future/historical moment humans have enormous ears and pin-hole eyeballs..and they needed design work done? In other words — if we were more reliant on our ears rather than our eyes what would “X” (computer/smart device/car/chair/bicycle) look & behave like?

* Software to learn more about audio:

* Max/MSP (I end up using this about once every year anyway — and now it seems like it can “talk” to Abelton Live..need to figure out why this is interesting)
* Reaktor
* Logic
* Abelton Live

These are audio making softwares, mostly tilted towards making music or composing sound into rhythmic melodic assemblages or something like that. While the idea of being a DJ with throbbing thumping crowds manipulated by my expert mixing and all that sounds like fun, I’m actually more interested in the ways these tools and playthings can help design audio experiences of other sorts — like even mundane moments of sound..a new car horn, for example — or an intriguing car alarm that brain paralyzes the would-be car-jacker into doing the polka. ((I don’t know why I’m fixated on car sounds – maybe it’s LA getting to me..))

World's Largest Max/MSP Patch
ScreenLive
ScreenReaktor

A curious side note to this world of audio software you’ll notice from those screen shots above: it’s entirely baroque in its UI design, which is both super intriguing and somewhat annoying, but actually more intriguing than annoying.

An experiment:

I’m *trying to make a DIY small, portable, audio mixer with a variety of stereo and mono inputs and some “effects sends” so that I can experiment with mixing multiple sound sources and sound sensors while on the go — walking and riding around.

Seems simple enough but I’m having a bear of a time with it. More about that in a subsequent post.

That’s it. Rough early days. I can say that its super exciting. And nice to be tagging along with Russell as he experiments with some similar questions. (cf. Secondary Attention and Little Boxes of Sound, Secondary Attention and The Background Noises. I especially like the idea in the latter post about the “Ghost Box” concept of a thing that inserted sound effects, effectively into the environment.

Why do I blog this? Because if I didn’t, I’d forget what I was doing in the past when I’m in the future. Also it’s good to share things that are going on because then you hear from other people who are working on similar threads and friends should know what friends are thinking about even when separated by the Internet.

Continue reading Whittling Away at Audio

PDPal in Talk To Me

 

Well, I have a fondness for this old project — PDPal. PDPal is now enshrined on the Talk To Me exhibit’s little online catalog of thing-ies. Without getting assy about it, I think it deserved to be in the physical exhibit with all the installation mechanics we had built for its display in the real world..we could’ve even bought a bunch of Palm m505’s off of EBay and given them out with PDPal on them, those things are so cheap nowadays.

*shrug.

There’s no figuring the mind of the institutional curator. Plus, they over at MoMA have their perennial favorites that they shove into every show.

It’s on the list of @2011 Goals that I keep here to re-do in something like iOS — anything modern. I remember squirreling away in the depths of Metrowerks Code Warrior writing Palm PDA code to get this thing working. Seeking support from some dodgy Russian software company that made a little library I needed to use. Being up until the crack of dawn in an artist’s panic thinking — “This is it..This’ll be the end of me.”

At the end of it all — it was fine. It’s a lovely little bit of futuristic serendipity-y mobile app-y application. I don’t mean to get all, like..”back in my day”-y on you but, like — all the iPhone app kiddies? You have little idea what it was to program a PDA — that awful industry term that some knot head in the business unit came up with to describe these things. It was ugly. Thoroughly barely fun. There were no APIs for anything. You wrote to the metal and built things up from there. Really nasty. I reckon, even with my squeaky iOS skills that I could have an iOS edition of PDPal written in a week..couple of weeks if I work just at night.

Anyway — enough reminiscing. I’m just glad this one still has a little life left in ‘er.

Check out the main PDPal page here for more data points and to download the emulator, if you want. It’ll be wonderfully baffling.

Continue reading PDPal in Talk To Me

Design Fiction Workshop at UX Week 2011

So — enough yammering. Time for some hammering. It’ll be workshops from here to fore. Getting to work. Shirtsleeves. Lab coats. Smocks. Aprons. Hammers.

I’ll be doing a workshop later this summer — August 24 from 2-5:30, to be precise — at the UX Week week-ish long conference in San Francisco brought to you by the fine folks at Adaptive Path. It’s got the didactic title: How the Practice of Design Can Use Fiction to Create New Things. We’re done with fancy, clever, snarky titles for workshops.

It looks like a swell line-up. Old friends. New ones. Fun sounding workshops and methoducation sessions.

Sign up. It’ll be fun.

====

From Dick Fosbury to the guy who put wheels on luggage, creating disruptions to convention in positive ways has often meant looking at the world differently. Fiction, especially science fiction, is a way of telling a story about and then forcing one to think about the world by looking at it with a different lens.

Design can approach its creative and conceptual challenges to make things better, or to think differently or to disrupt convention by combining its practice with that of fiction.

In this workshop we will look at the practical ways of employing the rhetorical, creative and cinematic aspects of fiction to help think, act upon, design and create new things.

The principle is simple. If cinematic and literary fiction is able to help imagine and communicate things that may not be possible, how can these same forms of story telling help design practices create disruptive visions of the near future?

In the workshop will share a number of relevant case studies where design and fiction were brought together. The process and outcomes of these case studies will be discussed. Through these case studies we’ll discover approaches, techniques and principles for a pragmatic designing-with-fiction process.

Prerequisites:
An open mind, notebook, pen. Familiarity with science-fiction film, optional.

Outcomes:
A set of tools, approaches and processes for initiating practical design fiction in the studio.

Continue reading Design Fiction Workshop at UX Week 2011