Resistor in parallel w/ pot

[FSFX]

As can be seen from using the spreadsheet here, the use of any resistors across the terminals of a linear potentiometer will change the taper to a non-linear one.

http://www.fleetingspider.com/files/CustomPots.xlsx

BTW, this is not my spreadsheet and I don't actually know who created it, I just have it here to allow people to access it.

Here is the resultant taper you will get (in red) with two 1.2k resistors and a 10k potentiometer.

[GibsonGM]

I'm of the opinion that ain't nothin' like the real thing - but if you can't wait, or just can't get one, then trying this might work ok, depending on what you're building. Or try one close in value instead. 

I would rather use, say, a 50k volume pot in a Fuzzrite than TRYING to make a "33k" that was only available in the 60s (AFAIK).  Same goes for using a 500k (instead of 350k) for the dirt pot.  Every time I've done the 'trick', the control feels odd - evidenced by the curves above.

[Phend]

Unfortunately my 10K hack to make a 1K odd ball is necessary.
Since the 1K pot is not available in the form I need for my next build.
An Axis Face with Attack and Smooth control.
(Built and tested but not boxed)
Fortunately I built the same effect a few years ago with a 1K.
(It used a "Standard" 16mm pot)
The hack works as well.
Thanks for the comments and graph.
The graph shows what to listen for in its rotation.
Posted comments on this Attack control mention that it really "kicks" in at 1 to 3.
That is what I hear in both cases.

[ElectricDruid]

Here is the resultant taper you will get (in red) with two 1.2k resistors and a 10k potentiometer.

Now that would be quite handy to avoid needing the stupid pot taper used in the TubeScreamer tone control. Can't think of of much else to do with it, but if it fixes the poor control response of gyrator tone controls, that's actually a pretty big plus. Compare with this:



(From https://www.electrosmash.com/tube-screamer-analysis)

Please note I'm not claiming this as an original thought! I'm quite sure it's been done a load of times already. Only that I haven't see it or thought about it till now, so I'm playing my usual game of catch-up

[Rob Strand]

Now that would be quite handy to avoid needing the stupid pot taper used in the TubeScreamer tone control. Can't think of of much else to do with it, but if it fixes the poor control response of gyrator tone controls, that's actually a pretty big plus

Putting two parallel resistors across a 10k pot creates the wrong taper for a tube screamer, it has an ever larger deadband in the center.   Near the ends the resistance change speeds up.

The G taper used on the Tube screamer has the inverse tape.  It creates an S shaped which slows down the resistance change towards the ends.   There's simple no way to get that with external resistors.

The only way to improve the adjustment of the tube screamer near the ends of adjustment with a linear pot is to use a lower pot value, but that changes the response slightly.  A 5k pot is nice to use, a 10k is on the edge of improvement but affects the response less.

The main idea behind adding parallel resistors is to shift the voltage divider ratio of the pot in the center.  However the taper itself (ie adjustment per degree of rotation) isn't a good match with a real pot with the correct taper.

[Phend]

Difficult to know the difference in tone sound / control of said tone using G20K , B25K , A20K or modified  // resistor pot .
Hard knowing not witnessing Tube Screamer with these different pot setups.
What is the biggest difference? 

[Rob Strand]

Difficult to know the difference in tone sound / control of said tone using G20K , B25K , A20K or modified  // resistor pot .
Hard knowing not witnessing Tube Screamer with these different pot setups.
What is the biggest difference

As far as tone goes:
- 25K vs 20k is a small change.
- taper changes don't affect tone. 

Tapers affects usability of the control.
(For TS9 and Gyrator EQ's) With a linear pot nothing happens in the center then everything is cramped up in the last 10% of rotation. If you set everything to 12 O'Clock you won't notice anything.  If you like to fine tune around 2 to 3 O'Clock on G pot the linear pot will be a pain because it will require very fine adjustment around 4 to 5 O'clock.

[ElectricDruid]

Now that would be quite handy to avoid needing the stupid pot taper used in the TubeScreamer tone control. Can't think of of much else to do with it, but if it fixes the poor control response of gyrator tone controls, that's actually a pretty big plus

Putting two parallel resistors across a 10k pot creates the wrong taper for a tube screamer, it has an ever larger deadband in the center.   Near the ends the resistance change speeds up.

The G taper used on the Tube screamer has the inverse tape.  It creates an S shaped which slows down the resistance change towards the ends.   There's simple no way to get that with external resistors.

Ok, so that diagram on Electrosmash is misleading? It should be the other way round? More S, not Z?

[Rob Strand]

Ok, so that diagram on Electrosmash is misleading? It should be the other way round? More S, not Z?

I see the bigger problem now.   I actually thought the plot was for a funky taper pot but marked G.  It just looks wrong.

Should be like this, (just change word slider to % pot rotation)



The wiper to end resistance is a low fraction of the total but changes slowly.

[Dormammu]

Ok so using this calculator here...

http://www.diystompboxes.com/analogalchemy/emh/emh.html


I am told I will need two 83k Ohm resistors. Where do I place them tho?

It will be good for the task at hand.

[Phend]

^ According to my BB test, to make 10k into 1K you need two 1.2K .
Lugs 1 to 2 and 2 to 3.
With those Pot measures 1.2R to 1039.
That calculator tells me to use two 555R ?
I trust my DMM.

[FSFX]

^ According to my BB test, to make 10k into 1K you need two 1.2K .
Lugs 1 to 2 and 2 to 3.
With those Pot measures 1.2R to 1039.
That calculator tells me to use two 555R ?

If you were to have used the spreadsheet that I posted a link to then you would have got more accurate results.

Using a 10k pot and values of -0.92 for the A/R factor and B/R factor produces resistor values of 1.202k for A and B and a resultant resistance across the pot of 1.073k.

[Phend]

Unfortunately in my current electronics bag there is no accuracy.
I usually if not always measure the component and try to find the one closest to what is specified.
Mostly never find an "accurate" one.
Hence these guitar effect circuits are like "rubber".
To a degree, values can deviate quit a bit from the specification. 
Which can often make an even better circuit than the original.
Because everything is out of spec and your lucky.
When I first started making simple effects, I mentioned that I "Blue Printed" the circuit I was building.
At that time I had a stash of stuff so as I could measure and find close or "~exact" values.
I heard the word "Blue Printed" when I was a teen and some guy had a muscle car that was BPed. 
Meaning that the parts in the engine were all selected to be dead nuts tolerance.
Of course there are times when transistors need to be matched...etc..
So in this effect business 1K can be 950 or 1090, and still work, just don't turn the knob as far.!!
I have never seen any tolerance call out on an effect circuit except the Phase 45.
But nothing wrong with all that,  effects sound good built with what they are built with. !

[Phend]

An Axis Face with Attack and Smooth control.
Posted comments on this Attack control mention that it really "kicks" in at 1 to 3.
 

Need a pot  lesson (again)
So the B1K Attack Control "kicks" in at 1 to 3 o'clock.
Would changing this to a C1K pot solve this and make it more "useful" (or work better thru its range) ?

[PRR]

I don't know my ABCs.

The emitter is like 30 Ohms. So 100 ohms in the pot is a significant drop from max. Taking habitual CW=more, you want a Reverse Audio, or even more extreme.

Or wire an Audio backward. You will learn. People who "pick up" pedals won't like it and may leave it behind some day.

[Baran Ismen]

Is it possible to make a C taper pot from a B taper?

[Phend]

I found an answer...

The following is from General Guitar Gadgets in their Fuzz Face instructions:

"Our kits include a 1k C (reverse log taper) for the Fuzz control instead of the
1k B that the originals have. It is a known fact that the reverse log taper gives
a much better rotation for the fuzz control. We wouldn't have made this
upgrade if we weren't absolutely sure this is a worthwhile improvement. You
can use a 1k B and it will work fine, but we like the 1k C better. We have left
the schematics and diagrams to show a 1k B since that is the original value."

[antonis]

Is it possible to make a C taper pot from a B taper?

As possible as is to make a A taper from a B taper..

The Secret Life of Pots

[Baran Ismen]

Am I too stupid to comprehend this matter or my pots are just weird?

https://www.elby-designs.com/webtek/documents/tailoringpotentionometers.pdf

According to this PDF file's 5th Figure, I need to solder a 100k resistor between 2 active lugs of my 1m linear pot and it becomes logarithmic, right?

Mine becomes however something completely different, it reads around 80k or something. For Rev.Log, what shall I do? Add a resistor of 10m?

Thing is, the circuit I deal with right now is Small Stone and there are only 2 lugs connected. 3rd one is empty, or shorted to 2nd.

[Dormammu]

Am I too stupid to comprehend this matter or my pots are just weird?

https://www.elby-designs.com/webtek/documents/tailoringpotentionometers.pdf

According to this PDF file's 5th Figure, I need to solder a 100k resistor between 2 active lugs of my 1m linear pot and it becomes logarithmic, right?

Mine becomes however something completely different, it reads around 80k or something. For Rev.Log, what shall I do? Add a resistor of 10m?

Thing is, the circuit I deal with right now is Small Stone and there are only 2 lugs connected. 3rd one is empty, or shorted to 2nd.

May be (you're dumby,a little).   
It is not clear what value of the pot you want to get.
PDF link is not work.
Post the circuit with the pot marked, if it's not too much trouble.