20k audio pot not available?

[formerMember1]

Anybody know if mouser does sell 16mm 20k audio taper pots for a boost pot in a RM.  i can't find them anywhere.

thanks

[ninoman123]

Get a 100k pot. Whip out ye old calculator. All you need to do to get a 20k pot is put a 25k resistor across lugs 1 and 3 of the pot. Now you will have a variable resistance of 20k. This should work. Ive done it this way before and it works well. If this isnt a good enough taper...Get two 13 k resistors. Or 10k or 15k whichever u can find thats close to 13k. Put one resistor from lug 3 to 2, and another from lug 2 to 1. That will simulate a 20k pot too.

[TheBigMan]

It's mentioned in several projects at generalguitargadgets.com that 20K pots are almost impossible to find anywhere.  I've certainly never found any in the UK.

[formerMember1]

ninoman123

Cool, sounds good to me, i'll try it.   i never thought about doing that.

TheBigMan
yeah i didn't come across it in the GGG projects, but thanks for the reply,

:wink:

[Paul Marossy]

You could also get a 50K pot and connect a 47K-50K resistor in parallel with it. I have done that sort of thing many times, it works well - a trick I learned from Mark Hammer.  

[Fret Wire]

The 20k "G" taper (for TS tone control) Small Bear is carrying might work real nice, and progress better to the ear. Who says they all have to used as 808 tone pots?
http://www.smallbearelec.com/Search.bok?category=Potentiometers+and+Trimpots&searchpath=421d832e1055960376b54&start=9&total=12

For the rest, no need to struggle with math, Joe Davisson did it for you.
http://www.diystompboxes.com/analogalchemy/emh/emh.html

Go down to tapered pot. To make a 20k log out of a 50k lin., it's a 64k between lugs 1 & 2, and a 2.2k between lugs 2 & 3. For a reverse log, switch around the resistors. Joe and Pete Snowberg put a lot of effort into it, we might as well use it.

[formerMember1]

cool, ill try it,

hey speaking of the ts9 tone control, did you ever try it in your tubescreamer?

[ninoman123]

Fret Wire-

I did use that  

[Fret Wire]

Cool  I use that alot, sure beats doing the math...thanks Joe and Pete!

[MartyMart]

It's mentioned in several projects at generalguitargadgets.com that 20K pots are almost impossible to find anywhere.  I've certainly never found any in the UK.

I got some 22k alpha pots from "Maplin"   !!!!! I know, hard to believe  :shock:
That's close enough.

Marty.

[TheBigMan]

It's mentioned in several projects at generalguitargadgets.com that 20K pots are almost impossible to find anywhere.  I've certainly never found any in the UK.

I got some 22k alpha pots from "Maplin"   !!!!! I know, hard to believe  :shock:
That's close enough.

Marty.

The plastic shaft ones or the minis?  I usually try to use the minis but Maplin have got such a crappy range of them.  :roll:

BTW at GGG the parts lists text files contain substitute parts if the originals aren't available.  E.g. the Tube Screamer and SOnic Distortion both used 20K pots originally.

[Fret Wire]

For you guys in the UK, how available are Omeg pots? They don't seem too bad, Roger Mayer and Dunlop are using them. They have slightly different values, ie. 470k, 2.2k, no big deal.
http://www.omeg.co.uk/index.html

Looks like the OW16BU and OW20BU are the type most DIY'ers would use.
http://www.omeg.co.uk/p20typ1.htm

http://www.omeg.co.uk/p16typ1.htm

[Paul Marossy]

Hey, I didn't know about that EMH thing... very cool!

[jimbob]

That is awsome! Im not sure how to use it though. I have a 100kb and want to make it a 50kb- what do i put in the taper box? Its linear is all I know. Also , r1 and r2. I assume that means resistor..Those are the boxes that recommend which value of resistor to connect to the lugs? But whick lugs?
Sometimes I swear everyone here is about a million times smarter than I.

[Mark Hammer]

Probably overkill, but you CAN get 20k pots...... in the form of 10k dual-ganged pots.  Just wire up two lugs in common to be the wiper.  Ironically, if you use a log pot and wire them up this way, you now have log/antilog in the same pot.

[Fret Wire]

For linear to linear, it's easy. Go to the Math Helper and click on Linear Pot.
http://www.diystompboxes.com/analogalchemy/emh/emh.html

On the site, there's a pot diagram, Joe's using the standard pot symbol.


So what ever value the calculator shows for R1, is the resistor you put between lugs 1 & 2 on the pot. Whatever value the calculator shows for R2, is the resistor that goes between lugs 2 & 3 of the pot.

For you, enter 100 for actual value, then enter 50 for desired value. Hit calculate.... it shows that a 50k is needed for R1 & R2. Lin to Lin will always be equal values for R1 & R2.

For tapered pots (made from lin pots), Joe has a separate calculator. He's already set the taper value (90% log) for you. Just enter the value of the lin pot you have, then enter the value of the log pot you desire. The values may seem odd, but it's correct. For reverse log, switch the resistor values for R1 & R2 around. You could make the 20k G taper pots with this, but I don't know the "G" taper % off hand. Neither calculator will convert log pots to smaller log pots, however.

Did that make sense?

[jimbob]

Fret Wire - it did make sense! thanks!

[formerMember1]

i soldered a 18k resistor in series with the wire going to the first lug in my
RM boost Pot.  It seems to of worked.  It increased the gain, but the treble is reduced.

can i do it that way?

thanks

[Fret Wire]

Cool  The easiest way to test it, is to use alligator leads to hook resistors up to the pot lugs. Then measure with a DMM. Nice thing about the calculator is that pots have a lot of tolerance, so you can measure the pot's exact value with the DMM and then use Joe's Calculator to make pots that come out exactly the value you want.

[formerMember1]

yeah good idea fret wire. i forgot about that, man i forget everything lately.   :?

in my last post ,i meant to write 8.2K resistor in series not 18k. :oops:

thanks :wink: