11-21-2011, 01:24 PM
Location: Ontario, California
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DIY Bass Knob/RCA level Control
Taking from another forum. thread can be found here:
DIY bass knob/RCA level control, for just a few bucks.
This thing is great! it cost me exactly $4.35+gas so about 7 bucks for it compared to $20+
this is great for the guys out there that cant find a OEM bass knob for their amp.
Disclaimer: I take no credit for this! BUT ITS GREAT! Made one myself!
I made one of these for a buddy a while back, and figured I'd make another one and take pics along the way to share here.
Everyone probably knows what a PAC LC-1 is, but if not it's a simple RCA level control. People most often use them as a remote bass level knob up front, when their sub amplifier doesn't have its own remote level control, but it can also be used as an overall volume control or a separate level control for any amplifier- to change the level of rear fill in a setup without a fader for example. The PAC version is about $20, so it's not an expensive piece, but I made this for $2. Yes, two dollars.
To start with, you'll need a small dual gang potentiometer. These are available with two different sweep tapers, "audio taper" and "linear taper". For this you'll want a linear taper pot. They're available in a number of different resistance values, I chose 50 kilohms- mainly because that's the value of the PAC one. It'll usually be marked "B50K", the B designates linear taper (A is the designation for audio taper) and the 50K is obviously the resistance of the pot.
I purchased a quantity of 9 of these from an eBay seller in Hong Kong, they were $9.99 with free shipping for 9. They included a small washer and mounting nut.
Next you'll want a knob of some sort to attach to the potentiometer's shaft. There are a number of different options for a 6mm/.25" shaft, just get whatever type you don't mind looking at.
I purchased a quantity of 10 knobs from the Parts Express tent sale, they were 10 for a dollar but they were marked down 20% so I got 10 for about 85 cents including tax. These ones have 2 small setscrews to hold them in place on the shaft, a splined interior that grips on its own would be preferable but for 8.5 cents each I'll deal with it.
The last thing you'll need is a way to get signal in and out, via RCAs. You can cut an existing RCA cable and insert the pot inline, or you can make your own RCA ends on short pieces of wire, or whatever.
I chose to use some M/F/F RCA "Y" adapters simply because I had them already in a junk drawer, cutting the male end off gives you two color coded female ends which works out perfectly.
Closeup of potentiometer's markings:
Cutting the male end off of the Y adapters:
Stripping the wire, leaving about 5/8" exposed, and twisting the shielding:
Twisting both Right shields together and both Left shields together, and tinning the bare ends:
Soldering the Left channel wires directly to the potentiometer's terminals. In this pic the shield is on the left, Left output is in the center, and Left input is on the right.
Doing the same for the Right channel:
Pot soldered up with the knob attached:
Diagram for easier visualization:
You can heat shrink each individual wire connection if you want, but I personally have a hard time getting heat shrink that small and that close to not shrink up from the heat of the soldering iron while making the connections. Instead what I'll do with this is (after I test it) I'll squeeze a globber of hot glue around all of the terminals and then put a single piece of heat shrink around the whole thing.
After it's done you can either mount it in a dash panel through a .25" hole, or you can mount it in a project box, or just tuck it away if it's something you won't use very often.
This is a very simple project for anyone with basic tools, but it's one I haven't seen posted anywhere before. Hopefully this will help someone out.