Saturday, May 16, 2015

Monumental absence on the blog-front, my apologies. I like to have something of an orderly line of thinking in this format, and frankly it seems as if I've been ensconced in avalanches of R&D or convoluted puzzles to the point that settling on a single train of thought would be detrimental to the process. Since there has in fact been physical realization of something, I can just shut up and talk about that! Haha, thanks for understanding.

Pictured above is the preliminary assembly of the first two sections of a three section noise generator. The initial prototype is essentially a lifted collector white noise section cascading into a low pass section which in turn feeds a malformed state variable filter (not yet stuffed, obviously). I can't really call it that, because while it began life as a state variable it became mangled. I'm not going to elaborate further, because with the second generation prototype that section is facing a deep revision. The sonic goal of stage 3 is a pop-corn type crackle with adjustable intensity, please stand by.

Let's fast forward the initial build and actually listen to it:

Something of an acquired taste, perhaps. Seems also to have aggravated the youtube compression algorithms, I can provide a clean recording on request (but seriously, the second generation is shaping up to be improved, so why bother!)

Guts! Nothing much more to add here. I have slapped a primitive voltage regulation into it because I built it with a spot on 9 volts supplied by my bench supply, and every single wall wart I tried once built made it go haywire. Here's the believed to be accurate schematic of the initial prototype:

If you're a lunatic and want to build one yourself, I would advise contacting me instead of going off this schematic - unless you want to be saddled with all the issues that are under resolution with the current build. Amongst design flaws that are resolved at this point: the loading down of the low passed crumble output control when other stages are turned up got cleaned up with a common collector buffer.

Layout on the proto-board is also taking a more direct path.

With the exception of the initial noise source stages, I identified gain stages and buffers - then settled on a uniform configuration of values to simplify assembly. This created additional problems with the triac, but since the operating characteristics of each and every one seems different (I'm pulling from a really old bag, so it's anyone's guess if this is due to my circuit conditions or age/sloppy manufacturing tolerances) I needed to allow for calibration anyway. Now I can dial the triac up to the point where it's *not quite* stuttering and cutting out, which has improved the crumble of stage two substantially.

So there you have it, I may update on stage three once I get it sorted (lower right knob needs more travel/interaction), or we might take a look at something else. I'll try and touch base before another season goes by...

Tuesday, December 16, 2014

After a long while (10+ years) of periodically checking for 2.75"/70mm throw sliders to fill the gaps on the Langevin AM301, I finally stumbled across an auction for unused Duncan Slidelines and decided to procure one for every channel.

Granted, these are 100K lin as opposed to 50K log, but this gives me an excuse to fumble around with changing the law via external resistor AND to finally dive into this unit.

Off with its face!

This explains some of the non-functional channels, some others have fader assemblies that are breaking apart (not pictured, yet).

Better oust these old electrolytics while I'm at it.

Here's a shot of the stock wiring.

Here's someone's mod, I guess. Dual gang to unify two channels across one fader? It does explain why there has been an empty slot staring back at me as long as I have owned this thing. Mind you, I don't think this "fix" is still functional. Was it ever?

The stems on these faders are slightly smaller than the stock Slidelines, meaning I will be going with another sort of cap (I know I mentioned seeking some red Rollo looking caps last time). Onward & upward.

Monday, November 17, 2014

Here I am, working around the inherent constraints of SMT componentry for use in your garden variety free form "rat's nest" point to point build.

Saturday, November 15, 2014

Found out what was rattling around in my old Pioneer SR-101, something sheared the top of a 6BM8.

More inspiration to stop gigging the antiques.

Saturday, November 08, 2014

Whew! So I have to remind myself how HTML works every time I post. Clearly I'm not being active enough, but rest assured, the wheels have been turning in the background. I've got a couple "filler" angles I can exploit, and while I detest the notion of coughing up fluff, if I have to stop and think about how to break a new paragraph something has to give.

Anyway, been tearing down some organs lately and have wound up (literally) wading through piles of interesting parts.

Low tech switch design. Left depicts an open condition, right depicts an operational failure. Easy fix, of course; sort of like brushing the bugs out of an early computer.

Lots of gritty potential.

More 1970s analog drum machine guts!

Daughterboard sounds as follows: #5 = BASS, #3 = SNARE, #4 = CLAVE, #6 = CONGA. Presumably the BRUSH, CYMBAL & SANDBLOCK (?) are handled on the inductor laden side of the main board. I'm a bit apprehensive about snare being built around the same circuit topology as bass & conga (the daughterboards are identical PCBs stuffed with different values), but whatever the sounds I have to thank the good people at Gulbransen for clearly labelling voltage supply points, etc.

I guess I should mention that the lowest daughterboard in that picture is a signal amplifier, not a one shot oscillator. I'm too fond of individual outputs to leave that section alone, but I'm certain it will see use in some capacity.

Once I scrape the dust off this it'll be a snap to try out.