Page 1 of 2 12 LastLast
Results 1 to 10 of 16

Thread: DIY bass knob/RCA level control, for just a few bucks.

  1. #1
    Founding Member TREETOP's Avatar
    Join Date
    Aug 2010
    Posts
    326

    DIY bass knob/RCA level control, for just a few bucks.

    [Hopefully this is the right section to post this in, as it's a low cost audio solution. If it belongs in a different section, mods please feel free to move it.]


    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.

    Parts:


    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.

  2. #2
    Devil's Advocate Adam_MSS's Avatar
    Join Date
    Aug 2010
    Posts
    1,578
    Real Name
    Adam
    This stuff is great. Exactly the sort of simple, cost effective, and extremely useful project that demonstrates the benefits of doing it yourself. With tutorials like this, the forum is off to a great start.
    You don't use science to show that you're right, you use science to become right. - R.Munroe

    The important thing in science is not so much to obtain new facts as to discover new ways of thinking about them. - W.L.Bragg



  3. #3
    Big Daddy Chad's Avatar
    Join Date
    Aug 2010
    Location
    East-Central Illinois
    Posts
    1,570
    Does the 50K have a nice feel to it in linearity or is way touchy on one end or the other?

    Reason I ask is that you can't just use any old pot, if the resistance is too low you begin to load the output of the sending device too much since it's indeed driving the carbon path of the pot and at WFO ALSO the receiving device.

    it's barely seeing 50K though so it's fine.

  4. #4
    Founding Member TREETOP's Avatar
    Join Date
    Aug 2010
    Posts
    326
    Chad, it has a nice smooth sweep- all the way counterclockwise is full attenuation (or close enough that I can't tell the difference) and WFO it's just like the pot isn't inline at all. Neither extreme seems to be touchy at all. Maybe that's the difference with a linear taper and an audio taper?

  5. #5
    Big Daddy Chad's Avatar
    Join Date
    Aug 2010
    Location
    East-Central Illinois
    Posts
    1,570
    Well the linear taper helps, it's just that sometimes they can get touchy at the bottom end if their resistance is too low.

  6. #6
    That diagram's the shizzle.

  7. #7
    Founding Member TREETOP's Avatar
    Join Date
    Aug 2010
    Posts
    326
    Quote Originally Posted by bassfromspace View Post
    That diagram's the shizzle.
    I used to be pretty good at Pictionary. LOL.

  8. #8
    Founding Member
    Join Date
    Aug 2010
    Posts
    324
    This is really nice! I will have to whip one of these up here in the near future.

  9. #9
    Member mellephants's Avatar
    Join Date
    Oct 2010
    Location
    Urbana, IL
    Posts
    66
    This is definitely neat. I could see adding this to my setup, at least for the subwoofer, and possibly even one for each preout, just to have on-the-fly adjustment without having to use the head unit's controls.

    Also, if I ever add rear fill, I will be already using my head unit's three available outputs for high/mid/sub... so I could just throw one of these on a set of "mid" preouts for rear fill adjustment...

  10. #10
    Junior Member
    Join Date
    Oct 2010
    Posts
    6
    Thanks. That's kinda what I was looking for. Do all remote bass level knobs (that plug into the telephone style jack on the amp) work the same way ? Or are there significant differences in the end result by lowering the input signal Vs by changing the gain?

    How do we adapt this so that it can plug into the remote bass connector on the amp? Is it as simple as connecting the potentiometer at the correct pins on the telephone style jack or is there more to it?

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •