Here is the DIY instructions for our filter with a schematic and construction instructions
SCHEMATIC: C1 R1 ______ Pos ---------------| |--------------o-----------l______l----------------- Neg | o | Drain wire from shield ----------------
So that's pretty simple huh? A cap and resistor in series that is connected to your speaker or amp in parallel. A snubber, an R/C network call it what you like. The hard part is the construction. The cap could be a Wima metalized paper cap, a Vishay polypropelene or any other mid priced cap. Don't use a cheapy disc but I also haven't heard benefit from say a pricey Mundorf in this application. If you don't buy a good cap the sound will suffer. A minimum of 100 volt should be used. The Wima is X rated (250 volts)
For resistors I like the Vishay metalized film 1% tolerance 1/2 watt. Mills and other good resisitors work. Hand Made Electronics in Pa. has a nice carbon resistor for audio use.
Now to values: many use a .01 cap and a 10ohm resistor. You can use a higher value of resistor as well. I know others that use a .047 with a 100 ohm resistor. Look at Chris DeCostas pdf and look at his cascading values. Sorry it's hard to find now. You can make the filter with multiple R/C networks in parallel. DIY is nice cuz you get to decide!
Don't skimp on quality on either part. You should be able to get all four parts for a pair for under $10. Spend more if you like. You'll need a lot of other materials. Here is a list:
Spades or Bananas - get at least some decent ones $5-10 or more you need 4 Wire- use good solid wire 14 ga. copper or silver seems about right.Don't use stranded Filter Body - you can use hose, tubing or model rocket body at least .6" ID Heatshrink to fit over the tubing - 5" for two filters Copper foil sheet or tape with adhesive back - this can be a bit costly Silicone caulk that dries "rubbery" not hard Solder - silver is better! 2 inches of 24 gauge stranded wire (optional)
So you can see you can easily spend $30-40 or more in parts plus shipping to get them if you don't have some or all on hand.
Solder the cap and resistor together and the lead wires to the opposite ends. Add the small piece of 24 gauge wire to the resistor end. This is for the optional shield drain wire that connects to the copper shield. These solders must be VERY GOOD so the stress of use doesn't break them. Also remember to make the total length of the cap/resistor short as possible so it doesn't need a large tube body to cover it.
Cut your tubing in which you will insert the filter for proper length. You should have about 1/3rd of an inch of the heavy wire you will attach either a banana or spade inside the tube. Make sure your 24 gauge wire is sticking out, you'll need to adjust its position after the next step. After you have that situated fill the tube totally full with your silicone and let it dry. This dampens vibration and helps relieve strain when you put pressure on the hook wires. Before it dries position the drain wire as it will connect to the copper exterior.
After the tube has dried cut a piece of heat shrink for each filter that sticks over one half inch on each end of the filter body. Heat it and shrink it tight!
Attach your bananas or spades to the wire ends. Did you remember to make a polarity mark for positive and negative? Remember positive goes to the cap side, negative to the resistor side.Hold the wire as close to the body as you can with needle nose and bend the wire ends with the connectors to the spacing you need to mate with your speaker or amp. You'll need to measure them on center to know this.
Finally trim the heat shrink ends so you can bend your foil tape or sheet and make nice tight clean looking ends. Attach your foil tape/sheet carefully. It should be wider then the filter body so you can fold the ends over. Solder the drain wire to the copper at this point. Fold the ends over so they looks nice and you're done!
I hope I made this easy to understand. At some point I will have pictures to go with this. Feel free to email me with any questions.
And now the disclaimer. This info is for your own personal use. If you don't have experience with electronics you shouldn't try this or should do so knowing there is a risk on several levels which includes hurting yourself or your gear if improperly made. It's always good to test the filter and make sure it does NOT have continuity on a low range like r X 1, 10 or on a digital meters 2000 ohm range. If you don't understand this you shouldn't be doing this. Sorry.
DIY VERSION OF THE AC FILTER
This AC filter has been discussed at length at Audio Asylum in the "tweaks" area. Thanks to all those that posted on this. Audio Asylum has a great search tool if you want to see posts on the topic.
First a disclaimer YOU ARE WORKING WITH AC POWER IF YOU DON'T HAVE THE PROPER TOOLS AND KNOW HOW STOP NOW, THIS IS NOT FOR YOU! YOU MUST USE X OR Y RATED SAFETY CAPS AND FLAMEPROOF RESISTORS FOR SAFETY!!!
OK, that's done. The circuit is easy to build, it is simply four cascading resistor/cap/resistor values in series tied together in parallel. Here is the schematic:
Well that's it.Lets talk about the safety ground though, which is omitted from the above drawing but should be used. There are folks that build this filter both with and without using it. Most often the above parts are put on a little board that is then put in a small P-Box. I prefer the ABS boxes which I then line with copper or TI Shield for RFI/EMI rejection. These "shields" conduct so the board must be isolated from the conductive shield. You could cover the board and parts with silicone on all sides and then cover it with black tape to be SAFE! If the safety ground is utilized the shield should have a drain wire connected to that utilized safety ground. You can hard wire a 3 conductor AC cable to the circuit or get a chassis mount IEC connector to put on the P-Box that allow disconnection of the power cable.