Nigel Skeels & Robin Hall, Psychedelic Wah, Maplin Electronics, October 1994

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modman
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Full article in PDF:
Maplin-Electronics-1994-10 Psychedelic Wah Wah.pdf
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I built one of these back in, err! can't remember, but I do remember I couldn't set it up as per the instructions. 30+ years on I recently rediscovered the pedal and thought I would take another look. I found a teeny weeny spike of a solder splash bridging a couple of pins that I cleared and now the pots seem to do what the instructions say so it looks like the circuit works but how can I test it to know everything is up to spec. I don't have a fancy spectrum analyser or frequency sweeping equipment to check my output against the graph in the article but I do have a digital oscilloscope. One of the pots, the high frequency one I think, is almost impossible to adjust if the circuit is working as designed. I would put multi turn trimmers or a range reducing resistor to allow easy setting because the existing pot causes a ten fold change in the output level with the slightest touch. :shock: I set the low and high frequency pots as best I can by feeding 80 Hz and 1500 Hz in that gave voltages of 0.9V and 2.11V. Perhaps I should have used E7 frequency of 2637 Hz instead of 1500 Hz. The article instructions are good for the electronics but very vague for the set up. :(
The pedal doesn't seem to give much of a Wah Wah to me but I have nothing to compare it to so any test ideas to check each part of the circuit would be useful.

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Thanks for your feedback, RuptorGB!

I posted most of these articles out of documentary interest... this world of electronic magazines died about the time this article was published. 1994 was year I discovered the internet. Anytime anybody built any of these projects, errors turn up... Pre-internet, the quality of information wasn't better -- because much was the work of one person.

Any project on this forum, you can read the feedback and build reports from other users...
Thanks for providing some feedback on this project! hopefully, somebody else chimes in.
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Post by RuptorGB »

modman wrote: 05 Jul 2024, 10:08I posted most of these articles out of documentary interest... this world of electronic magazines died about the time this article was published. 1994 was year I discovered the internet. Anytime anybody built any of these projects, errors turn up... Pre-internet, the quality of information wasn't better -- because much was the work of one person.
Yes every time I built something out of a magazine it always had an error that prevented it from working. The electronics magazines were the only things available when I started knocking up things in the Glamrock days of the 1970's. 8) I think this unit was designed by electronics engineers not musicians because the compander idea is good in theory but not for music in practice if you want dynamic sound in my opinion although maybe it doesn't matter to people on a wah unit. Having made it work as intended it needs to be set up in a very narrow range of pot movements other wise weird things start to happen like motor boating of hum without any guitar signal going in. :shock: It does a Wah but the top frequencies don't get much it is mainly the mid range. The biggest problem is it limits the output level that to me seems to be happens at a much too lower signal input level. It is like an auto volume control it doesn't produce clipping or distortion it just holds the output signal within the output operating range which is where the dynamics is lost. A low level input gets amplified and wah but high inputs get the same output. I guess it is a distortion preventing volume limiting box with a wah. That's my tuppence worth.

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