Dual Concentric 1MEG Pots!

[The Ballzz]

Hi All,
I don't post here often, as it is hard to converse due to not having a good way to draw schematics/layouts. I have searched low and high for these pots and finally found a source for having them made at a reasonable price in semi reasonable quantity. Does anyone besides me see a use for this pot, in audio taper? The reason I ask is that I want to see if any folks have an interest in sharing an order before I place one. This is not intended as a for sale thread, but instead an offer to cut people in as a sort of "group buy at cost" before the fact. I'm not looking/asking for any $$ up front, simply a friendly commitment for ballpark quantities. In other words, I'm trying to avoid sitting on 80 or so pots that I don't need! They should come in at about $8-$10 each plus whatever it costs to get them from Las Vegas to you. I'm also wondering if anyone wants to venture a guess as to my intended use?
Specs Would Be:
1 meg Audio taper for both pots
Solder lugs for wire
20mm pot body diameter
8mm bushing with a 9mm bushing depth
Smooth spindles for set screw knobs
4mm upper/inner spindle
6mm lower/outer spindle
Spindle lengths yet to be determined

Anyone who wants them "after" I shell out $$ for them and get them in hand will see a markup.
All Thoughts/Opinions Welcomed,
Gene

[Kagliostro]

Does anyone besides me see a use for this pot, in audio taper?

I don't need it but I can see use for those pots

a LarMar PPIMV with the ability to use only a pair of tubes in a PPP of 4 tube

or

a PPIMV that swap from PP to SE (do you remember the Soma amp ?)

K

[The Ballzz]

Well,
My intention is to have one dual for gain and one dual for master and be able to switch from one end of the dual to the other for preset levels. Basically, for my purposes, it would provide one gain/master balance for my hum bucker guitars and a slightly different gain/master balance for my single coil Strats. I plan to control the switching with a relay. Does anyone here see an issue with this?
TIA,
Gene

[Firestorm]

What I've always done is get the Fender concentric pots made for the Jazz Bass and swap the resistive elements for whatever values/tapers I needed. The pot is about $7.50, plus the cost of cannibalizing two other pots. Not cheaper, but you can make any values you want on the fly.

[Meat&Beer]

As an aesthetic aside, where would you source the knobs for these dual concentrics? I've had more than just a really hard time finding more than one or two styles for this type of pot. Specifically, for the round/smooth shaft. Anyone know where to get these that aren't for a guitar/bass? Other than that, I've found one other style, and I don't find it to be very flattering.

[The Ballzz]

Yessir,
Knobs are definitely a concern. It's important that they are overall short enough to not extend past the edge/lip of the amp cabinet. It would also be nice for them to look nice. There are a few options and I am waiting for replies from a few buddies who are machinists in the Hot Rod world who should be able to knock off a small pile of custom specced aluminum knobs fairly quickly and easily. If doing a Marshall style amp, I don't see a gold version of the Knurled Telecaster style looking too bad. I have also found some all black plastic units. I did run across a company who could make some injection molded units to look a lot like Marshall knobs for only $7-$8 per set, however there is a minimum order of 500 pieces! Another option would be, instead of trying to find dual concentric knobs to match existing amp knobs (looking for a Unicorn) simply switch the rest of the knobs out to match an existing dual concentric style. By the way, Meat & Beer are two of my favorite things!
Gene

[Kagliostro]

I plan to control the switching with a relay. Does anyone here see an issue with this?

NO

[Gaz]

Sounds like a lot trouble and expense for your purposes. What's wrong with just using two small pots next to each other? I know it's not quite as streamlined or fancy, but still classy and simple if laid out right in the face plate.

[The Ballzz]

Sounds like a lot trouble and expense for your purposes. What's wrong with just using two small pots next to each other? I know it's not quite as streamlined or fancy, but still classy and simple if laid out right in the face plate.

While you sir, are correct, especially for a new build, lets compare how invasive each approach is for an existing amp, bearing in mind also that an owner of a fairly nice, almost vintage, mid 80's, 2203/2204 may be hesitant to have his chassis drilled and a new, non-stock faceplate made/installed.

Separate Pots:

A - Dismantle amp far enough to remove faceplate, including wiring to switches, pilot light, etc.
B - Precisely drill new holes for pots.
C - Precisely measure for new faceplate and order it.
D - Install relay board, etc.
E - Decide where to put 2 holes in the rear panel, one each for foot switch jack and toggle switch to use in lieu of the foot switch. Drill the holes and install the jack & switch.
F - Wait ?? weeks for faceplate to arrive
G - Ream/adjust holes in faceplate to make up for less than precise measuring on your part or the faceplate maker.
H - Install extra pots & wire them up
I - Re-install all parts and test.
J - End up with an amp with somewhat irreversible modifications!

Dual Concentric Pots

1 - Remove existing gain and master volume pots
2 - Install relay board, etc.
3 - Decide where to put 2 holes in the rear panel, one each for foot switch jack and toggle switch to use in lieu of the foot switch. Drill the holes and install the jack & switch.
4 -Install dual concentric pots & wire them up
5 - Test
6 - End up with an amp that has a mostly reversible mod, except for the 2 extra hole s in the rear panel.

One could also make the operation less invasive and avoid drilling holes in the chassis by eliminating the Low input jack on the front and replacing it with a toggle switch and replacing one of the speaker jacks with a jack for the foot switch! Everything in this scenario is totally reversible, except possibly whatever mounting means were used for the relay board. Not to mention, when drilling a chassis (especially a steel one) that chassis really should be gutted to avoid steel chips, etc, from the drilling process, getting into somewhere that you don't want them!

Thanks to Kagliostro for posting an exact diagram of what I had in mind!

thanks All,
Gene

[The Ballzz]

I'm really surprised that with all the amp builders and modders on this site, there are so few interested. The cost to cannibalize/modify an existing pot (at least if using good quality, "new" parts) is easily more than $20. These should be in the ballpark of $10 each, which is considerably less than other dual concentric pots of other values. Except for this situation, the 1meg is generally not available anywhere! Unless, of course there is a better way to skin the cat I am trying to skin. If that is the case, please let me know, I'm all ears!
Confused,
Gene

[matt h]

(deleted)

[Kagliostro]

One option may be to use a composable pot

you can stack more than one unit and add the shaft

http://it.rs-online.com/web/p/potenziom ... PSF_433048

http://it.rs-online.com/web/p/potenziometri/0393863/?

[img:244:356]http://img-europe.electrocomponents.com ... 784-01.jpg[/img]

[img:233:242]http://img-europe.electrocomponents.com ... 778-01.jpg[/img]

K

[pops]

I have built two champs in a tweed deluxe cab and used dual pots for volume and tone for each amp and it works great, i can see no reason not to use them for some things.

[The Ballzz]

One option may be to use a composable pot

you can stack more than one unit and add the shaft

http://it.rs-online.com/web/p/potenziom ... PSF_433048

http://it.rs-online.com/web/p/potenziometri/0393863/?

[img:244:356]http://img-europe.electrocomponents.com ... 784-01.jpg[/img]

[img:233:242]http://img-europe.electrocomponents.com ... 778-01.jpg[/img]

K

Uhhh, Yeah,
But how would that give me separate control of each pot as with a dual concentric style? It would just be a dual pot controlled by one shaft/knob.
Gene

[Kagliostro]

Sorry, my fault

those composable pots can have only a single shaft


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K