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Step 6Review the plans and solder the circuit.
I researched how others have wired their speaker microphones and schematics of various direct injection (DI) boxes to figure out how I wanted to build this one.
I've provided a PDF file (below) of my hand drawn schematics so you can print them off and have them at your workbench.
Warm up your soldering iron and follow the schematic. Lines that meet in a dot are connected. Lines crossing in a little "jump" are not connected.
Point to point wiring is actually simpler in this case. This is when components are soldered directly to each other without using a circuit board.
It may help to highlight different sections (paths that are connected together) of the circuit with different colors of ink, then wire one section at a time.
Solder leads to the transformer, and insulate the connections with electrical tape or heat shrink tubing. Then put the transformer into the container and run the leads through a hole drilled in the side. You may want to pad the transformer inside the container with a scrap of foam, cotton balls, or a plastic shopping bag so it doesn't rattle around inside. The connections on the transformer will be less likely to come loose if the transformer does not move.
Solder in the leads for the speaker and label them. Wait to solder them to the speaker terminals until after you have mounted the speaker in step 7.
The filtered ground can be lifted by opening S4.
I've provided a PDF file (below) of my hand drawn schematics so you can print them off and have them at your workbench.
Warm up your soldering iron and follow the schematic. Lines that meet in a dot are connected. Lines crossing in a little "jump" are not connected.
Point to point wiring is actually simpler in this case. This is when components are soldered directly to each other without using a circuit board.
It may help to highlight different sections (paths that are connected together) of the circuit with different colors of ink, then wire one section at a time.
Solder leads to the transformer, and insulate the connections with electrical tape or heat shrink tubing. Then put the transformer into the container and run the leads through a hole drilled in the side. You may want to pad the transformer inside the container with a scrap of foam, cotton balls, or a plastic shopping bag so it doesn't rattle around inside. The connections on the transformer will be less likely to come loose if the transformer does not move.
Solder in the leads for the speaker and label them. Wait to solder them to the speaker terminals until after you have mounted the speaker in step 7.
Circuit Explanation
The configuration of the coils can be changed by the rotary switch (S1).- Position 1 Single: A single coil of the speaker is used (4ohms), both 1/4" jacks are wired in parallel with the coil.
- Position 2 Series: Two coils are wired in series(8ohms), with the two 1/4" jacks wired in parallel.
- Position 3 Parallel: Two coils are wired in parallel (2ohms), with the two 1/4" jacks wired in parallel.
- Position 4 Damping: Coil A is normalled to the 100ohm potentiometer, which will electromagnetially dampen coil B. When a 1/4" plug is plugged in, the potentiometer is disconnected, and the input directly drives coil A. Coil B is wired in parallel with the 1/4" output jack.
The filtered ground can be lifted by opening S4.
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I hope this answers some questions. If not, just reply to this comment, and I'll do my best to help.
Here I have quoted from my original text, in italic, and added notes in between in normal text:
Circuit ExplanationThe configuration of the coils can be changed by the rotary switch (S1).
Position 1 Single: A single coil of the speaker is used (Coil B) (4ohms), both 1/4" jacks are wired in parallel with the coil. Coil A is disconnected. Any input will drive both Coil B and the DI's input.
Position 2 Series: Two coils are wired in series(8ohms), with the two 1/4" jacks wired in parallel. either input will drive the coils (a 8 ohm load) and the DI input
Position 3 Parallel: Two coils are wired in parallel (2ohms), with the two 1/4" jacks wired in parallel. Either input will drive the speaker coils (now a 2 ohm load) and the DI input
Position 4 Damping:
Coil A is normalled to the 100ohm potentiometer, which will electromagnetially (and perhaps inductively) dampen coil B. When a 1/4" plug is plugged into CN1, the potentiometer is disconnected, and the input (CN1) directly drives coil A only.
Coil B is wired in parallel with the 1/4" output jack CN2. A signal input here will drive coil B (at 4ohms) and the DI input.
In all positions, the output then passes through the phase flip switch, through a -20db pad, to one side of the transformer. The transformer's secondary outputs through the XLR jack. (The pins on the XLR jack are labeled.)
There's always some coil connected with the DI side. You can use either input in any position of the rotary switch and get sound out of the DI. Since there are different coils, loads etc. (that I haven't experimented with) each will affect the sound differently.
If you want a straight DI, disconnected from any speaker coils, you can install a switch to disconnect the coils from the input jacks. Or use a normalling jack for CN2, and the coil side connects to the normalling contact. (I just built myself a couple of regular DI boxes as separate units)
This page also helped me figure out what I was doing:
http://www.ethanwiner.com/gadgets.html