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Topics - rockola

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Build Reports / SMD Echoplex preamp
« on: November 22, 2020, 09:15:42 AM »
Here's my latest build, all-SMD Echoplex preamp in a box that's slightly smaller than a 1590LB. KiCAD files & Gerbers @

Top in glorious British Racing Green. No LED for now, might be a good idea to put one in later though.


Gutshot. Sorry about the blurriness, it was tricky to get the phone camera to focus.

Build Reports / Swah
« on: June 27, 2020, 12:51:10 PM »
Just when you thought it was safe to go back in the water... This would have been my entry in the most recent MBP competition, except I couldn't get it to work in time for the deadline. Pulled it from the shelf of shame today and whaddayaknow, had inserted one of the ICs backwards. Should really stop doing that. In case it's not obvious, it's a Mad Professor Snow White Autowah clone on a GuitarPCB Swah board.

Had a number of accidents with the graphic, some happier than others. I've got another Swah PCB somewhere so may do another with less deranged graphics. I sprayed the laser decal with nitro that was apparently way too thick as the decal pretty much melted up immediately. Learned to do a mist coat first next time. However, the result was kind of interesting, as you can see.


Build Reports / Bloodstone Phaser (with extra fairies)
« on: June 03, 2020, 12:07:14 PM »
Here's my build of the Bloodstone phaser by Lectric-FX.

Front. Illustration shamelessly cribbed from the "Never Never Land" album cover by Pink Fairies. Redrawn with Inkscape. Laser decal and a touch of spray can lacquer.


Couldn't get it to fire up at first (what else is new), was getting weird voltages, so decided to swap all the opamps. Wouldn't you know it, that did the trick.

Here's the original quartet of what I presume to be fake 4558s. Probably bought from some Chinese eBay seller some years ago when I didn't know any better. The good ones that you can see in the gutshot are from Tayda.

Here's a sound demo. Dimed Rate knob makes the Phaser mode sound almost like a ring modulator.
0:00-0:43 Vibe mode, 5 different Rate settings
0:43-1:42 Phaser, min feedback, 6 different Rate settings
1:43-2:37 Phaser, max feedback, 6 different Rate settings
2:38-3:25 Something resembling a tune with sane settings

General Questions / Dr. Quack and Mr. Chirp
« on: January 25, 2019, 01:29:52 AM »
I would have entered this in the Creative Audio contest, if I'd had the foresight to grab a longer video. It's a Dr. Quack on vero behaving quite strangely, making chirping noises, and not passing any audio through. I had two solder bridges in there, removed those and the problem went away. Unfortunately I didn't make notes and don't remember where the solder bridges were, which brings us to my question:

How would I go about designing a circuit that does these chirping noises on purpose? Preferably using a similar set of parts as Dr. Quack (i.e. a few transistors and an opamp or two, not looking for a video game effect IC or a digital sample playing solution here).

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