How to seat knobs (concentric) without wobble

chinjazz

chinjazz

Sep 11, 2002
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Atlantic Beach, FL
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#1
Hey Folks,

Something that has bugged me for a while but never looked for an answer.

I find whenever I put the smaller knobs on dual concentric pots, the top knob always looks and turns wobbly looking or "catty wompus". I try and fiddle with trying to make it flat/level, tighten and still always looks weird when turning it.

There's got to be some easy step I'm missing.

He's an example:

IMG_2112.JPG


Thanks!
 
#6
They came with optional inner brass sleeves that work for thiner rods
Click to expand...

If your knobs came with those sleeves, then (obviously) they are 1/4inch knobs.

Those brass sleeves are really for using a 6mm splined shaft with a 1/4 inch knob. There are pots around with solid 6mm shafts, and I doubt that those sleeves would fit over them easily.

Perhaps that's what's going on here. Try measuring with digital calipers.

You may actually have 1/4inch shafts as well, but just have a loose fit. Perhaps the knobs have 6.5mm holes. It does happen. In which case, you'll need to use a little tape I guess. Perhaps try a single wrap of copper shielding tape.

Or you can also get a 6mm or 4mm knob and drill it out. A 1/4inch drill may be too big and you'd be back to square one. So you may need a 6.3mm or 6.2mm from an engineering supply. You don't need a drill press for this, you are simply skimming the hole. Wrap it with masking tape, then put it firmly in a vice.

When I was doing a lot of custom tech work, matching pots to knobs was a constant headache.

FWIW, it looks like you need to mount the pots a bit lower too. If there's not enough thread for a second nut on the inside of the cavity, then a second (or third) shakeproof washer will lower the pot so there's only just enough thread poking through to get a flat washer and a nut on. This will make the knobs as low profile as possible. Stacked pots are the highest thing poking out from you bass. Believe me, they get knocked about, especially if you only use a light gig bag. (Ask any tech.)

Also, FWIW, you also have the lower knob mounted upside-down.
 
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#7
RobbieK said:
If your knobs came with those sleeves, then (obviously) they are 1/4inch knobs.

Those brass sleeves are really for using a 6mm splined shaft with a 1/4 inch knob. There are pots around with solid 6mm shafts, and I doubt that those sleeves would fit over them easily.

Perhaps that's what's going on here. Try measuring with digital calipers.

You may actually have 1/4inch shafts as well, but just have a loose fit. Perhaps the knobs have 6.5mm holes. It does happen. In which case, you'll need to use a little tape I guess. Perhaps try a single wrap of copper shielding tape.

Or you can also get a 6mm or 4mm knob and drill it out. A 1/4inch drill may be too big and you'd be back to square one. So you may need a 6.3mm or 6.2mm from an engineering supply. You don't need a drill press for this, you are simply skimming the hole. Wrap it with masking tape, then put it firmly in a vice.

When I was doing a lot of custom tech work, matching pots to knobs was a constant headache.

FWIW, it looks like you need to mount the pots a bit lower too. If there's not enough thread for a second nut on the inside of the cavity, then a second (or third) shakeproof washer will lower the pot so there's only just enough thread poking through to get a flat washer and a nut on. This will make the knobs as low profile as possible. Stacked pots are the highest thing poking out from you bass. Believe me, they get knocked about, especially if you only use a light gig bag. (Ask any tech.)

Also, FWIW, you also have the lower knob mounted upside-down.
Click to expand...


Thanks RobbieK!

It was just seeming counter intuitive to be spending so much time getting the knob to sit right :)

I did get it to sit better by taking the shaft which was split and widening it with a small flat head. In fact, I realize that it's split and moves when
tightening the knobs allen punch screw. Maybe putting some shielding tape in between there would help.

I'll definitely lower the knobs some more with those shake proof washers. On the Stacked pot, I think it's as low as I can get it, but I'll work
them all again. Thanks for pointing out the lower knob being upside-down :).

Cheers!
 
#10
I had a similar issue with a then new MV4. The Volume pot knob would encounter a physical resistance midway through it's range, the bottom of the knob coming into contact with the lock nut...

IMAG1575.jpg


... it was a splined shaft (sans brass sleeve) and I'm thinking the set screw(s) had been over tightened, damaging the splines to the point that the knob no longer sat straight.

Of course, Sadowsky has excellent costumer service, as Pete sent me a new volume pot (smooth shaft) and knob... less play when new, or old knob mates with new shaft, now.

In the mean time, I positioned a black plastic washer under pots that weren't stacked, raising them all the same height... my OCD wouldn't have it any other way.
 
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#12
Spidey2112 said:
I had a similar issue with a then new MV4. The Volume pot knob would encounter a physical resistance midway through it's range, the bottom of the knob coming into contact with the lock nut...

View attachment 1143432

... it was a splined shaft (sans brass sleeve) and I'm thinking the set screw(s) had been over tightened, damaging the splines to the point that the knob no longer sat straight.

Of course, Sadowsky has excellent costumer service, as Pete sent me a new volume pot (smooth shaft) and knob... less play when new, or old knob mates with new shaft, now.

In the mean time, I positioned a black plastic washer under pots that weren't stacked, raising them all the same height... my OCD wouldn't have it any other way.
Click to expand...

I hear you.. It's just right, and nothing wrong with that. I say to myself I'm OCD about most things when it comes to adjusting, tweaking, setups, and dabbling with building basses,
but it's probably not a real OCD, even though my wife says it is :).
 
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#14
chinjazz said:
Yeah, I should have mentioned that. It's probably the root cause of this wonky-ness...
Click to expand...

Yep. IMHO the best solution is to just get knobs that match the pot shafts, or vice versa. I'm really not a fan of concentric pots on basses to begin with, personally. But sometimes you gotta do what you gotta do.
 
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#15
Passinwind said:
Yep. IMHO the best solution is to just get knobs that match the pot shafts, or vice versa. I'm really not a fan of concentric pots on basses to begin with, personally. But sometimes you gotta do what you gotta do.
Click to expand...

Yeah, I agree and for my next build I'll have a much larger rear route cavity so I can do whatever I need to with more knobs and cow bells.
 
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#16
chinjazz said:
Yeah, I agree and for my next build I'll have a much larger rear route cavity so I can do whatever I need to with more knobs and cow bells.
Click to expand...

I've been running into this issue all the time lately as I try to work up a few of my own onboard preamps designs. I eventually bought some custom concentric knobs for way too much money and then finally decided I'd rather have less features rather than the potential durability issues RobbieK alluded to.
 
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