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Thread: electronics for kit

  1. #1

    electronics for kit

    If i want to upgrade some electronics for MBM-1 kit - which opts do i need to buy?
    what shaft length? what thread length?
    can i know if push-pull pots will fit there before i get the kit?

  2. #2
    GAStronomist Simon Barden's Avatar
    Join Date
    Oct 2016
    Reading, UK
    The pots normally recommended for upgrading are either CTS, Bourns (both USA) or Alpha (S Korean).

    There are a few things to consider.

    1. Pot value. 250k is the normal standard for Fender-style single coils and 500k for P90s normal to medium powered humbuckers. High output humbuckers can sound muddy when played clean, so 1Meg volume pots are sometimes used here.

    2. Log/audio or linear taper? Volume pots should always be selected as log or audio taper if you want a smooth reduction in output volume (at least with clean sounds) as the logarithmic taper matches the way the ear responds to sound levels. Tone pots can be either log or linear, depending on preference. Log tone pots will give a smoother tone roll off. whilst linear pots you get less roll off to start with and then a lot in a short amount of movement. I tried both linear and log tone on one guitar and there wasn't a huge amount of difference to my ears (which it must be said aren't the best). If you don't use the tone pot, then it doesn't really matter. I go log/audio for all my pots, which also avoids any chance of a mix up!

    3. Solid or split shaft? Solid shaft pots are normally used on Telecasters and other guitars where the knob is held in place with a grub screw. Split shaft are for push-on knobs, which are used on most guitars (and all the Pit Bull kits as far as I know).

    4. Number of splines? You have a choice between 18 or 24. The knobs and the shaft spline count needs to match or they won't fit. The kit knobs will have 18 splines, and many replacement knobs will be 18-spline as well. CTS normally use 24 splines for their pots, though you can get 18 spline CTS pots from some suppliers. Assume 24 for CTS unless stated otherwise. Bourns and Alpha use 18 splines. If you get 24-spline knobs, you'll need to get new knobs to match them.

    5. Shaft length? CTS do pots with 6mm, 9.5mm and 19mm threaded lengths. 6mm is for direct pickguard/scratchplate mounting, 9.5mm will normally do for most guitars with a rear routed control cavity, and 19mm is for anything else with a really thick top. Bourns do 9.5mm and 19mm (you normally need to add an extra nut and washer if fitting a 9.5mm pot to a scratchplate). Alpha are similar to CTS in their shaft length options.

    6. Threaded shaft diameter? Alpha pots use the thinner M8 thread like the kit pots do. CTS and Bourns pots use an imperial 3/8" thread, which is roughly 9.5mm in diameter, so is slightly wider than the metric thread pots and so you'll have to enlarge the pot holes in the kit slightly to fit them.

    7. Pot size? Standard pots have a 24mm diameter, mini pots are 16mm diameter. 24mm pots are normally the best choice as the longer track length means that the taper is a bit more accurate and there's more casing available to solder ground wires to. 16mm pots are useful for fitting in tight spaces or when a harness has to be fed through thin F-holes. They are normally used on kit and low-priced guitars just because they are cheaper.

    So I'd go for 24mm diameter pots with an audio/log taper and medium length/9.5-10mm threaded shaft length. You'd have to chose split-shaft 18 or 24 splines (or even solid shaft) based on your knob choice.

    I don't know what you have available to you locally, but you should be able to get some or all of the above.

    The kit pots won't sound any different to replacements, but replacement pots will almost always last longer without going scratchy or intermittent in operation.

    Push/pull pots tend to use mini/16mm diameter pots, though CTS do a 24mm switched pot that is normally a couple of mm shorter overall than the normal variety of switched pot. You can normally fit switched pots into most of the Pit Bull kits, but you'll need ones with the right threaded shaft lengths so that you don't have to fit nuts and washers behind (so that you don't get too much shaft poking out of the top), which will effectively make the length of the pot in the cavity longer. But there aren't any cavity dimensions on the PB website, so you may want to wait before ordering and check. It will be some time before the guitar is ready to have the electronics fitted.

    If you really need to know, then you can always email Pit Bull and ask if they can check for you (providing they have an MBM-1 kit in the stores).

  3. #3
    wow simon,
    thank you for the super-detailed reply!
    i know the electronics won't sound different, but the push-pull option is something i'm considering
    the other option would be an DPDT switch to split coils
    i want to think ahead as to not damage the finish by drilling

  4. #4
    Mentor fender3x's Avatar
    Join Date
    Jan 2016
    Miami, FL, USA
    Quote Originally Posted by arie_shapira View Post
    i know the electronics won't sound different, but the push-pull option is something i'm considering
    the other option would be an DPDT switch to split coils
    The push pulls might be a better option than mini-swtches. I don't think there's a lot of room in your control cavity...

    Sent from my ONEPLUS A3000 using Tapatalk

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