Hollow Earth

Build report: the "Nurse Quacky", an envelope controlled filter

alex | 07 July, 2012 21:08

My first project not built from a kit was the "Nurse Quacky", an envelope controlled filter (or auto-wah) derived from the EHXDoctor Q from the 1970s. I got the schematics and some more information about it from home-wrecker.com. This is my build report of all steps from scratch to the finished stomp box. 

My first step was to put the circuit on an experimental board to try out the sound of it and to decide if it's worth being build.

Nurse Quacky

The sound was ok for me, so I continued the project. I wanted to use the perfboard layout of the home-wrecker site, but then decided to draw my own perfboard circuit for two reasons: I wasn't sure if my parts would fit the layout and on the other hand I wanted to gain experience transfering a schematic to a perfboard. The software I used was the DIY Layout Creator, an open source java application. Unfortunately the application crashed randomly on my MacBook, but using it on Linux worked very well. [UPDATE] The current version 3.15.0 of DIYLC works very well on Mac OSX, I didnt' suffer from any crashes yet.

Here's the result:

Nurse QuackyNurse Quacky

I didn't know if I got everything right at this time - but I compared the circuit several times with the schematic and was pretty sure that it was ok. So I cut a stripboard to the right size and drawed the circuit with a permanent marker on the upper side.

Nurse Quacky

Next step was soldering the components onto the board, beginning with the lower components like resistors. Mostly I used the wires of the components for the circuit paths and silver wire to cover the rest.

Nurse QuackyNurse Quacky

I checked if everything worked well by means of my experimental board, before starting to do the final wiring:

Nurse Quacky

As it did work well, I designed the look of it and prepared the aluminium box by drilling the required holes into it.

Nurse Quacky

For the top label I printed the design on a white self-adhesive film, covered it with clear coat and put it on top of the case. Afterwards I put the mechanical components into place and soldered the wiring. And that's how it looks like in the end:

Angry Duck aka Nurse Quacky - interiorAngry Duck aka Nurse Quacky - top viewAngry Duck aka Nurse Quacky - back view

You can't see it well on the images, but the eyes of the duck are the two LED of the circuit. When turned on, the left eye is glowing permanently and the right eye is flickering depending on the attack of the signal ;-)

Here's my parts list for the project:

  • Resistors: 1 x 100R, 1 x 22R, 1 x 51R, 1 x 10K, 1 x 22K, 5 x 47K, 3 x 470K, 1 x 3.3M
  • Capacitors: 2 x Orange Drop 0.0047uF/600V, 1 x Orange Drop 0.001uF/600V, 1 x Orange Drop 0.01uF/600V, 1 x TEC Polyester 0.1uF, 1 x MKT 0.01uF
  • Transistor: 2N3904
  • IC: 1458N
  • Potis: 100K lin, 25K lin, 1K lin
  • Diodes: 2 red LED
  • Case: Hammond 1590BB
  • Other: 6.3mm stereo jack, 6.3mm mono jack, dc jack, 3PDT switch, 2 board fasteners, several coloured wires, 3 poti knobs

There is no particular reason I used Orange Drop capacitors, MKT film capacitors or ceramic capacitors with the same capacitance may work as well and require less space.  

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Disclaimer: all media on this page is my own work and licenced under CCL, if not elsewise stated.