Are these linear or audio taper pots?

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Mbira

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(Thanks PRR!!)

Are the 5K pots above linear or Log taper?  And how did you know the answer?  I'm thinking they'd be log since they are responding to a mic capsule input and audio is heard in a log way, but I'm totally just guessing...In fact I hope they are linear because Mouser has those in stock and the log taper are not due back in for a few weeks...
 
They're log, just passing audio to the summing stage.

How did I know the answer? Simple voltage dividers like this have most natural control range for audio in some log-like shape. You can use linear, it won't break. Just that your pot will only have about 1/10th of meaningful control range this way. It'll stay "too loud" most of its range.

Also, mouser will have thousands - if not tens of thousands - of these in stock, both lin and log. If you ever see 5k in a fader or pot, just read 4k7. Or else the designer did something very wrong.
 
Thanks for the info...

I'm wanting the 12mm ones, and sadly, the audio taper are out of stock with 470 on order and due back in a few weeks. Edit-those were for the solderlug ones-I'll just get the PC mount...
 
Thanks guys-yeah, I'll want to be able to adjust....so then is the rule of thumb-if audio is passing through the pot then use an audio taper?
 
A linear taper will drop the signal level linearly... so 50% rotation is -6dB, 25% =-12dB. 10% = -20dB

Audio taper will generally be -10 to -20 dB at 50% rotation so the perceived loudness changes (in dB) are more spread out across the entire rotation.  A linear taper pot will be faster at the bottom and slower at the top..

JR

PS: I've seen consumers confused by a product using linear pots that was louder at 12 o'clock, thinking that it had more output, while it was just a different (wrong) taper.
 
Hi JR-I know what they do, I was wondering how to know which to use...is the rule of thumb if audio is passing through the pot then use an audio taper?
 
We perceive loudness on a logarithmic scale (think dB) not linear...

So an audio taper pot will more closely mimic how we perceive loudness, and give better adjustability than linear especially near the bottom of the range.

JR
 
Hi guys-I'm sorry I'm not being clear-I understand how log taper and linear taper work.  I understand how that works in relationship to our ears...

What I'm wondering is how when looking at a circuit that does not indicate which taper to use, you know which to use...

Is it when that part of the circuit is carrying audio AC that the log taper would be used, and in other sections (power supply, etc) where audio is not running a linear taper would be used? 
 
Indeed you have to look at the function of the potentiometer.

However, it can still carry audio and does not have to be log as John already mentioned.

Take a volume pot. The electrical relation is linear as it is just a voltage divider, and the circuit is oblivious to what type of pot it is. All it does is to amplify the voltage level thrown at its input. If you are going to set a voltage level and leave it then it does not matter whether it is lin or log, but if you are going to audibly interact with the output of the amplifier then the relation will have to be logaritmic.

Take a feedback potentiometer on a servomotor. The input/output relation is linear as the full resistive value of the potentiometer represents the full angle of rotation of the motor shaft on the output. So the potentiometer has to be linear.
 
Mbira said:
I understand how that works in relationship to our ears...
What I'm wondering is how when looking at a circuit that does not indicate which taper to use, you know which to use...

You generally want a logarithmic taper for channel faders in a standard circuit like this but you need to look at a few other things to determine what pot is needed.
As John said, a linear pot will attenuate by 6dB @ the 50% rotation point, so most of the control will be in the top 75% (12dB) of the pot's travel, with the last area rapidly attenuating the signal as it approaches the "zero" point.  This is assuming there's negligible load on the wiper.

Here, we don't have a significant load but we do have "some" load on the wiper in the form of the 10K build-out resistors and, to a lesser extent, the pots and build-out resistors from the other channels in parallel

It's difficult to analyze exactly because of interaction but,  assuming a few channels are still connected (let's say they're turned off), for a simple thumb calculation: ... 
10K build-outs (plus a few other parallel channels worth of 10K build-out 's @ ground potential on the pot side) results in an attenuation of closer to 8dB @ 50% rotation of a 5K linear pot rather than the ideal 6dB. 
So the pot's linear taper has been changed (faked), albeit a little, and is leaning more towards a log taper. 
To get closer still we'd need to lower the value of the wiper load, and, a wiper load value of about half of the pot's value would give a pretty good approximation to a log taper.  However, the load on the source is now also lower so some number crunching of assumed levels and current would be in order.

In this circuit with these values: linear or log?  I don't know.  Depends how it's being used or where you want most of the control. 
Just a wee small caveat that, because of the wiper load, although it's not a drastic deviation, neither a linear nor a logarithmic pot. will quite behave as stated on the can. 




Edited for a mistake in thumb mathematics.
 
A good thing to remember is that if the level scale is one way, for example 0-10, it will want to be log for smoothness.

If the scale is two way, for example ±0-10, such as a cut or boost pot in an EQ, use linear for proper symmetry.

Don't confuse the two or your EQ 0dB points will be off.

 
If I understand your question, I thought I answered that in my first reply...

If it is set it and forget it, it doesn't matter (so much) it may be a little harder to adjust audio levels with a linear pot but trims are generally not used at their extremes. If it is a front panel control that you need to adjust audio output level over the full range with, the audio taper is more representative of what we hear.

JR
 
Got it guys. Thanks for the further clarifications!

JR-I know you did answer my question, I was just wanting to go deeper in my understanding.  Thanks for your help!
 
almost every audio circuit i have seen has log pots for volume,

one exception was the Ampeg Portaflex circuit,

but after building it, you will find that those 1  meg lin pots come on way too quick,

so that means that 100 percent of all circuits i have seen have a log pot,

go for the wafer switch if you want true log,

modern stuff is just 2 or maybe 3 (if your lucky) straight lines that get spliced together but this has been going on for years, so no biggy,,
 
They are trim-pots. They "can" be the little screwdriver-adjust pots, to save size and cost.  Trim-pots are always linear.

You have lost the context of the original question. Many-miked marimba.

All the sources are "nearly the same": the bars of one marimba. It isn't like a band where the drums are 30dB louder than the singer. In fact with 5 mikes in 5 feet, if one mike has to be set 6dB (half-turn) down, it probably can be turned all the way down. (Or moved away from a node.) You can easily set a trim-pot 12dB down, 20dB down without much care. You'd never need to set one of 5 close mikes 30dB down, it may as well be off (which a linear can do).

Also you have no gain between mike and pot. You do NOT want to take large loss here.

Also I would think you will wail in private, aim and balance low-mid-high, again at rehearsal then maybe once in concert, and leave it set more or less permanently.

The _whole_ marimba-mix _then_ gets mixed with/against your Moon-style drums and pinkie-piano. At that stage you probably need LOG-range controls to handle the large differences in levels. But that's your Mackie-mixer for the whole act. Not the marimba sub-mix.
 
I've been watching this thread out of interest, but did NOT realize the mixer circuit shown in the very first post was intended to mix a bunch of pickups/mics for a marimba down to one output.

Based on that, I'm 100% with PRR's comments....use something like 10 or 20 turn trimmers, which will almost always have a linear taper.  This is a specialized application.  Eons ago, a "crazy" guy I know wanted to put an electret mic in front of every singer in a 100+ piece church choir and mix them all down into sopranos, altos, tenors, and bass singer stems so the choir showed up on four pots on the FOH desk.

If this was a mixer for more generalized applications, the choice for the level adjustment pots would TYPICALLY use log/audio taper pots. 

But, that ASSumes that the impedance load on the wiper of the level control pot is much higher than the value of the pot itself.

I have seen circuits in some desks (certain Neve and ADM desks) which used a linear taper pot with a "slug"/load resistor from the wiper to ground to 'emulate' a log/audio taper response.  Typically, the 'slug' R was 1/3 or 1/4 the value of the R of the pot.

Best,

Bri

 
Well, I got my $23 bag of log taper pots today from Mouser...

We wail on stage with drums, monitors, PA, singers, etc, etc...since I've ordered the parts, and I don't want to spend the money on ordering new trim pots right now, the plan is to mount the six pots on a metal plate on the marimba-if the log pots suck and need to be replaced later, I can do that.  I'll let you guys know how it all pans out here in the real world an don various stages...That'll of course be the real test in all this. 

Thanks guys, and sorry I didn't provide enough info there...
 
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