making a face plate and need some advice

[versuviusx]

i'm trying to make a mic pre face plate and i need to know
1. what is the typical type of potentiometers used for gain.
i need to know the standard diameter so i can get the right hole punched for it.
please let me know. thanks
if anyone has any spares they could easily throw out i'd love to get some.

 

[soundguy]

what are you building?

You generally make a faceplate after you've built the unit and are satisfied with the components youve selected. If you drill a hole first, then you are stuck having to deal with it.

If you use a pot with a 1/4" shaft, most bushings will mount in a 3/8" hole. If you use a pot with an 1/8" shaft, most bushings will mount in a 1/4" hole. If you use a gain switch it can be any size under the sun.

dave

 

[versuviusx]

ok here is my problem i looked in the mouser book and they have pots. they have many manufacturers. but i do not know what kind of pot i'm looking for. is it a precision? could someone let me know the technical kind of pot i'm looking for in mouser? i'm looking for a manufacturer who makes good but cheap pots. this manufacturer has to make different types such has 500k, 100k etc, but make them all the same length and diameter. please help. i'd like to be able to find what i'm looking for.

 

[soundguy]

dude, what are you using them for...

dave

 

[Scodiddly]

You can buy a hand-held reamer at a lot of hardware stores. I've done astonishing amounts of metalwork with just a hand-held "nibbler" and a reamer. Then you can get the smallest likely hole, say 1/4" (the little pots from Mouser fit 1/4"), and then later ream out as needed.

But I'd take soundguy's advice - do something easy and disposable until you've got a working unit, then spring for the nice panel.

 

[fum]

To state Dave's points slightly differently, building a box is a very mechanical thing.

I don't ever attempt it without the parts in hand. Unless you are the ultimate in seeing things in your head, you'll screw it up if you don't put everything in the box roughly, and then work out where you really want stuff. (And even then, you'll still screw up here and there :green: ).

So the steps I normally take are:

1. Figure out what I'm building

2. Source the parts.

3. Do the electronics, test, and get it working.

4. Mount it in the box, and layout/drill the front panel.

Based on the above steps, I will state that I don't remember what size holes to drill for the different pot shafts. I eyeball it everytime, and haven't bothered to write it down yet :roll:

Hope this helps.

ju

 

[NewYorkDave]

Get a set of calipers (inexpensive, found at most hardware stores), measure the diameter of the mounting collar of the pot, switch or jack, and drill or punch the hole just slightly bigger than that.

I find it very helpful to do a full-sized paper layout of the chassis before touching any tools to metal. If you're really careful to line it up correctly, you can even tape a 1:1 scale copy of your paper layout to the chassis and use it for a guide for your center punch. (Always use a center punch to locate holes before drilling). I write the necessary hole diameters on my paper layout for reference when I do the drilling later on.

I would LOVE to get my hands on a 3/8" knockout punch, if such a thing exists. I do all holes 1/2" and up with punches and the contrast between the super-clean punched holes and the ******-looking-by-comparison drilled holes is pretty stark :roll: At least it all gets covered up by components in the end.

Oh, here's a handy tip: if you have enough room to maneuver, you can deburr a drilled hole pretty well by using a drill bit a couple of sizes larger than the one used to drill the hole.

For what it's worth, I've been drilling/punching chassis for my projects for several years and my results still don't look nearly as professional as some of the projects I see presented here. So don't be discouraged if your early results are less than perfect.

 

[AnalogPackrat]

I wish I could justify the cost of a nice set of Greenlee punches, but I'd rather spend the $$ on the guts of the device. I used to drill cases with standard twist bits and they always were wonky--not round and not exactly where I wanted them. I started using a unibit stepped bit recently and that thing is really cool.

I mark the center using a spring loaded center punch (got it from Rockler for woodworking--works great on Al), drill a small pilot hole (3/32" or so) and then have at it with the unibit. Deburring can be done with a reamer or by gently applying the unibit since the "steps" are actually tapered.

Unibits come in several sizes--mine goes from 1/8" to 1/2" in 1/32" steps. They aren't cheap ($25-40), but they are a lot less expensive than a set of small punches. Oh, and you can drill all of your small holes without changing bits. :thumb:

Analog Packrat

 

[soundguy]

when I lay out my panels I dont even bother with paper anymore as Dave suggests, I just get some of that low tack blue painters mask tape and cover the front and back of my front panel with it. Draw everything out with a pen on the tape and then use one of those spring sets for my center holes and drill out the panel with the tape right on there, works like a dream. Makes it a lot easier for me to visualize everything with the panel in front of me. I always keep making the same measurements over and over and over and over, once you do a few boxes you'll get a hang of parts you like and make a cheat sheet of hole sizes and centering dimensions for standard boxes, makes the work flow go quite a bit faster. I used to DREAD doing the boxes, not Ive got it sorted to where its just annoying. Hopefully onf ot thse days it will be fun...

dave

 

[versuviusx]

thanks for all the replies, but no one answered my questions.
first i'm looking for pots for gain knobs. i was told that i would need log taper pots and that the only place i could get them was from state-elec.com
what i'm trying to do is make faceplate that can be standardized for the most part. i'm not talking about usinga 50K pot for every mic pre application. i'm talking about finding a manufacturer who makes all their pots with the same length and diameter. then as soon as i find that manufacturer i can just order 1 pot and use the dimensions based on that one for my pot holes that i'm going to drill.
i'm using masterCAD and i'd like to make available standardized face plates so people can just buy these and hook up their guts and get the job done really quick. the pots at state-elec.com are really expensive. like 19-30/piece. that's really expensive to me. i was thinking like a dollar at the most for each pot.

so to recap i'm looking 1. manufacturer who makes all their pots the same dimensions 2. i'm looking for name of the pot that i will need. so far i know that there is a log taper pot used for gain it is also called audio pot, but i was wondering if their is a different kind i can use that would be cheaper. i'm looking in mouser and they have tons of pots but i do not know which one to get. i understand totally that you guys are saying the pot that you will get will be determined upon the application and that there is no one pot that will work for every application. i understand that. i'm looking for a series of pots that have different ranges but same dimensions that way if someone has a mic pre project that that requires a 50k pot they can use my faceplate and if someone needs a mic pre that uses a 100k pot they can use my face plate as well. please let me know

 

[versuviusx]

hi ok i come to learn that there are linear taper pots and Log taper pots. can i use linear taper pots for my gain knobs?

 

[pstamler]

Some thoughts for the original poster, and one for NY Dave:

Most manufacturers have several lines of pots, which will have different dimensions. Within each line, though, different values will have the same dimensions; a 50k pot will be the same size as a 500k, as long as it's the same series.

Log pots are pretty much universal for level and gain controls in mic preamps; both log and linear pots are used in EQ circuits, depending on the design. Find a manufacturer's line that includes both -- Bourns 91 series is an example. Clarostat makes one also. Most lines are linear only, if you'll pardon the expression.

Log pots are available from other places besides state-electronics: Mouser, for one; also Allied Electronics and even a few from Digi-Key. Some of the ones from Mouser are very cheap; however, often the builder will prefer a $20 pot to a $1 one, because the more expensive pot will probably last longer and may also sound better.

Finally, New York Dave asked about finding a 3/8" punch: I got mine from www.sescom.com -- they also sell a 7/16". The cost is $15.75. They have no minimum order, a change from previous years.

Peace,
Paul

 

[soundguy]

[quote author="versuviusx"]thanks for all the replies, but no one answered my questions.[/quote]

OMG. WTF are you building... There's no way anyone is gonna be able to give you any decent advice as to the type of pot you need with the wholly general info you have provided.

Are you actually building something or just going into the faceplate business, which is an entirely different discussion.

Virtually every potentiometer manufacturer makes different series which come in standard sizes with different values and different taper. The specific specs will come down to what each manufacturer offers and you can source this information for yourself at the honeywell/clarostat, bourns, PEC, etc. websites.

Sure you can use a linear pot for a gain pot, it depends on the circuit you are building. You can also use a log taper, or a reverse log taper, it depends on what the circuit needs, not what you want to mount on the front panel. If you are building something you are going about the process exactly backwards. If you are offering a faceplate service again, you are going about it backwards as each project is going to have a slightly different faceplate depending on what is inside the box. Ive built many many many boxes and have never drilled a faceplate the same. ALL of this stuff is project to project dependent. If you provide some info as to what you are either a)building or b)trying to provide a faceplate service for Im sure you will get some responses that you will consider to be more helpful. The responses you are getting are general because your questions are general.

dave

 

[EZ81]

[quote author="NewYorkDave"]
[...] I would LOVE to get my hands on a 3/8" knockout punch, if such a thing exists. I do all holes 1/2" and up with punches and the contrast between the super-clean punched holes and the ******-looking-by-comparison drilled holes is pretty stark. [...]
[/quote]

Hi Dave,
These produce very clean holes even when used in a cordless drill:

I have a 10.2mm (or similar) one for pot shafts etc. and love it.

 

[WJS]

Most of the projects I've built have used pots of about 2 or 3 sizes but most are about 3/8 inch(about, I dont remember exatly). usually, unless you are gettting mini pots or something non standard, they will all be the same size. being log or lin is internal, it has to do with how the resistant stuff is applyed to the inside tracks (I know this is not very technical). also the resistance of the pot (50k, 500k etc) does not (generaly) effect the hole size. the value of the pot is 90% dependent on the schematic, there is usually some play but it will need to be within a range (deturmined by the builders needs, the part interactions, etc) if you would show us a plan or schematic someone might be able to help more.

ps I just checked radioshack, their pots mound in 5/16 inch holes with a 1/4 inch shaft although I believe they work fine in 3/8

pps I use a tapered or stepped bit for drilling big holes, they done leave burs and dont bend the metal like most bits. they also make ones which dont need a pilot hole and easily cut holes big enough to mount octal tube bases.

 

[kiira]

There's a set of fake greenlee punches made which sells for $50. I've been using mine for 5 years and they still work ok. Ned at triodeelectronics sells them I think. They work on Fender chasses which are pretty tough.

If you just get a Mouser catalog and look inside the dimensions of components is listed on the helpful little pictures. They have Clarastat and Bourns and Alpha which are commom pots you would use in audio and most other components, all with pictures usually, you would need too.

Sourcing parts is a basic DIY skill like soldering or reading schematics - ya just have to learn what's in the catalogs. The meta faqs have TONS of info.
Have you built anything before? Maybe a project with a parts list or even a kit, like the green pre here would be the thing to get you goin? Or the JLM 99v kit.


tra,
Kiira