Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: jordan86 on May 20, 2021, 09:46:44 am
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Trying to finish up a unique dual concentric setup on a homebrew. It's a Marshall super lead style preamp. Like a 4 hole but the Normal and Bright channels share an input and a dual concentric pot. Ideally I'd like the front knob to match the rest of the controls with a back knob that's low profile and sort of blends in. Attached a couple examples of the look I'd like. I just have had NO luck trying to find something like this on amp retailers sites and even electronics places like digikey and mouser. Maybe I am searching the wrong sites with the wrong search terms?
I attached two ideas. One a low profile stack, and one thats just a Fender indicator sleeve. I'd almost prefer something that's not a true stacked knob, more like the indicator. Just a knob/sleeve with a tab on it that I can see sticking up behind the front knob. I feel like I have seen these kind of things on radios and other pro audio gear so I imagine they exist. Usually they are like a treble on front, bass on back kind thing.
I think the easiest path forward may just be to make something myself out of hardwood and drill it for a tightening screw. The last resort I thought of would be to just 3D print something. My neighbor has a 3D printer and could probably help me figure it out.
Figured I'd ask here before throwing in the towel.
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If it were me, I'd cut and finish some hardwood dowel material that I have lying around for the concentric knobs. Very easy to do.
But jeez, if your neighbor would print up some knobs, that would be also work I am sure.
Whatever method you have tools for would be best.
I keep thinking I need one of those printers, and/or a CNC machine -- but then I look at my (crowded and messy) shop space and say "maybe later."
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You might try searching for jazz bass concentric knobs. Antique Electronic Supply has these.
https://www.tubesandmore.com/products/knob-fender-dual-concentric-jazz-bass (https://www.tubesandmore.com/products/knob-fender-dual-concentric-jazz-bass)
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I had to search high and low for that item recently. I found a good source:
https://www.thompsonguitarandthrift.com/collections/potentiometers/products/alpha-potentiometer-a250k-concentric-stacked-dime-size-pot
Not the cheapest pot, but good quality and a range around the 250k-1M region.
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Plenty of choices for dual concentric knobs on eBay. Here's the one in your first pic. BTW, your second and third pic are not knobs. They are just position indicators that are locked in place by the nut on the pot.
https://www.ebay.com/itm/294040492487?chn=ps&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&itemid=294040492487&targetid=1266996027031&device=c&mktype=pla&googleloc=9012987&poi=&campaignid=11617013650&mkgroupid=125071512689&rlsatarget=pla-1266996027031&abcId=9300455&merchantid=111920146&gclid=EAIaIQobChMIn5n-9Z7d8AIVsW5vBB0Jkg6pEAQYEiABEgKKGfD_BwE
PS... You need to know the shaft diameters when shopping for these. Most, but not all fit a 1/4" outer shaft, but you may find 3/16, 1/8, or who knows what for the inner shaft.
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Warmoth stocks a concentric CTS guitar pot and a small assortment of different knobs. It looks like the knobs use set screws, so if you're using pots with plastic shafts, I'm not sure how well that will work out for you.
https://www.warmoth.com/Concentric-Pot-C825.aspx (https://www.warmoth.com/Concentric-Pot-C825.aspx)
Presumably they stock them for use with these pots:
https://www.warmoth.com/Concentric-Pot-500k-By-CTS-P720C74.aspx (https://www.warmoth.com/Concentric-Pot-500k-By-CTS-P720C74.aspx)
Obviously, YMMV.
Best of luck with your search.
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Thanks all. Yes, I’ve measured the shaft diameter on my pots. Will make sure I get the right fit.
For clarification, I am not looking for that exact Danelectro knob and I am aware that the other options are not actually knobs. Trying to find more options in that sort of look/style.
Appreciate the links. I’ll keep looking. 3D print may be the way to go.
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I’ll keep looking.
I'm curious what you found! I gutted my pandemic project 5F1 Champ kit and decided that a stacked concentric pot setup was the best use of space in that tiny chassis, but finding a disc-shaped knob to go under a chicken-head knob is no easy task. I admit that it's already a weird aesthetic decision!
FYI this thread comes up in a "stacked dual concentric pot 1m" Google search under images, so I had to investigate!
As I plan the rebuild, I have to decide whether to make the volume knob more functional by stacking it or utilize the second input for master volume and/or tone or a switch for a cathode bypass cap. Or do nothing at all.
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I'm curious what you found! I gutted my pandemic project 5F1 Champ kit and decided that a stacked concentric pot setup was the best use of space in that tiny chassis, but finding a disc-shaped knob to go under a chicken-head knob is no easy task. I admit that it's already a weird aesthetic decision!
FYI this thread comes up in a "stacked dual concentric pot 1m" Google search under images, so I had to investigate!
As I plan the rebuild, I have to decide whether to make the volume knob more functional by stacking it or utilize the second input for master volume and/or tone or a switch for a cathode bypass cap. Or do nothing at all.
Take a look at my post from 11/13/22
https://el34world.com/Forum/index.php?topic=29661.msg326464#msg326464 (https://el34world.com/Forum/index.php?topic=29661.msg326464#msg326464)
Look at the set up for the JTM45 volumes, is that what you're trying to do?
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Look at the set up for the JTM45 volumes, is that what you're trying to do?
:w2: I'm not sure I understand the question. Are you asking me if I know what stacked concentric pots are?
Yes. I know what they are.
Or are you asking me to look at the volume knobs on your amp and see if I want to do something similar?
Your amp has no volume knobs. No knobs at all!
I suspect that since that post is from December 2022, and not November, maybe you linked to the wrong post and there's a pic of that amp with knobs somewhere.
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Or are you asking me to look at the volume knobs on your amp and see if I want to do something similar?
Your amp has no volume knobs. No knobs at all!
I suspect that since that post is from December 2022, and not November, maybe you linked to the wrong post and there's a pic of that amp with knobs somewhere.
Sorry, pic of knobs attached.
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Sorry, pic of knobs attached.
This isn't really the aesthetic I'm going for, but it's obviously the same idea. This knurled knob set is commercially available and all over the internet search results when looking for such a thing. I still want to keep the chickenhead volume knob on top, but use a disc underneath that looks like a thick washer but is really a knob for whatever the second pot's function is, similar to Danelectro plastic stacked knobs. For now, I'm just investigating what other people have done, and it looks like either I'm the first to think of it or it's obviously a bad idea but I don't know enough to know that yet.