Linear vs Audio Pots for Idiots (well, one idiot...)

[Timfever]

So just so that I'm sure, if I absolutely can't ____ing stand how the volume pot on my SG does that thing where backing it off acts like a crappy tone control (which, incidentally, I also loathe 99% of the time and almost never use), then I should get...

AUDIO TAPER POTS for my volume controls!!!! 

(right...?) 

If I'm happy with the Tone controls as they exist (them capacitors with the real big-like numbers sure do sound purty though...), then I ought to get...

LINEAR TAPER POTS FOR MY TONE CONTROLS!!! 

Please let me know how I did on my test when you have the time. I'll be scouring eBay and dive bars for the Moby Dick that is a "VARIETY PACK" of 500K long shaft pots, with two being the audio type and two being the linear type...

[isaac42]

That's not how I understand it. The taper affects how quickly the value changes. For instance, I have some amps with linear taper volume controls, so at 2 they're almost full volume, and from 2-10 there isn't a lot of change. I don't see how changing the taper on your potentiometers will affect the issues you have.

To prevent or at least minimize the volume control acting as a crappy tone control, put a capacitor between the two ungrounded contacts of the volume control. The cap will pass the highs across the pot's resistance when you back off the volume.

Edit: add link to treble bleed mod
http://vintagevibeguitars.com/dox/trebleBleed_tip.pdf

[Timfever]

Huh. I'll look into that treble bleed, thanks. Re the different pots, I read (either on her the SD forum) that @5, audio pots will be at 25% volume and the linear will be at 50% volume. Considering my volume knob stays around 80% until its near zero, I figured it was a linear pot.

[WRGKMC]

Considering my volume knob stays around 80\% until its near zero, I figured it was a linear pot.

Might be but it may also have a trebble bleed, a higher ohm pot, or a vintage wireing. All three can change how the pot works, especially a 1 meg pot which often needs a full tirn to crank it down.

 

Take a look at the pot. It should have a letter on it next to the ohms.

In USA

• A - Audio or Log taper
• B - Linear taper
• C - Reverse Log taper
• G - Graphic taper

In Europe

• A - Linear taper
• B - Audio or Log taper
• C - Reverse Log taper
• G - Graphic taper

 

The difference in pots deals with how they attenuate the signal vs how the final results may sound natural to your ears. Ears arent linear so pots arent nessasarily linear. What you hear as being half the volume is not a linear change, its exponential change.

From a physical change turning a pot half way down to where it sounds like its half volume, its more likely 10X less volume based on electrical and spl/db's coming from an amp. Different amps also have different sensitivities and gains and some pots will taper differently depending on the pickup strength, amp type gain boxes etc.

Personally I like having a quick taper vs a long taper. When I'm playing live on say a Gibson, I can tweak one pot down 2 notches and the guitar cleans up "and" it cuts the trebble making for a crunchier chord tone. When I crank it up, the leads cut through the mix of other instruments.

The key is adjusting your amp for the attenuated sound. Then when you turn it up its right up there in your face for leads. I like the short turn becaise I often dont have the time between switching between lead and ruthum to do a full turn on a knob. I loose too much time doing that. In fact, I dont even use volumes for anything but adjusting tone and balance and dont use tone pots at all, except on some fenders which have too mich bite with new strings.

You can change how a pot tapers by swapping the hot wire and pickup wire on the pots. This makes the pot work and sound differently. It wont attenuate a second pickup like it does on a Gibson with both pups selected. You can turn one pot off and the other pickup will still be full volume. I've noticed the tone remains brighter as well. They used to use this on  vintage gibsons before switc hing to the modern wiring commonly used now. They still use it on guitars like Rickenbackers that remain chimey when turned down.

If thats what you want, its a simple mod to try.

If you want a longer tape that still sounds natural try a higher ohm pot. If you have a 500K try a 1 Meg. You'll get a little more brightness with those because less high frequency is drained to ground.

Or you can switch to a linear pot that drops the gain on a flat scale. Like I said, the only thing with those are you have to do an entire turn to get the pot to turn off and instead of the bump jump being at the beginning of the turn, it winds up being at the end of the turn.

Some people like that, and some dont. I use a volume pedal so like I said I use volumes for tone balancing and initial gain setting and use the volume pedal for overall volume. Its a cheap mod to try in any case and only requires basic soldering skills to do.

Heres a pot chart of the three main types. There are others.

[Maveric Manic]

And then there is the 'Digital Pot'. A binary digital code to control resistance. This is an idea I have about using it in Musical Applications for precise control of any parameter.

[WRGKMC]

^^^ I'm guessing you're talking about DSP, the kind of volume circuits you have in TV's and audio gear that uses a remote control to step the volume up and down is small steps.

I have this in my rack units and foot pedals cameras, and DAW programs that have digital circuits where you adjust the gain up and down. You usually have setting on these from 0~100 in steps or half steps. You can also have DSP control of of recording interfaces through their Drivers on computers and within virtual mixers in DAW programs.

Some of these can be very high quality and you have the benefit of maintaining the frequency response so the loudness changes sound natural to the ears. You would need an onboard digital circuit in a guitar to do this which would also involve having input and output preamps. I'm sure it can be done fairly well. Many guitar footpedals have it. I'm not sure it would appeal to many purists who use the direct inductance from a pickup to distort say a tube amp because the circuit would place preamps between their pickups and the amp plus it wont mimics a guitars RLC circuit on an amps input the same.

Most Guitarists rely on the non linear amplification curve of a guitar amplifiers preamp circuit when they vary the guitars input impedance with their volume knob. When a transistor or tube runs between 50~75% they get the maximum fidelity and when they turn it up it flattens the signal, and when turned down it reduces the presence of the signal. The guitarist uses these preamplifier characteristics to get his unique tones through manipulating his input gain.

Its not just the guitar circuit that changes the tone of the guitar, its what the guitar is plugged into that changes its tonal and gain characteristics. In a High Fidelity application like a Stereo, PA, Mixer, Microphone preamp, Recording Console or any other playback system, you'd likely want a linear volume curve so the fidelity is remained at all volume levels. Even bass guitar since its usually run clean will benefit from a linear change in volume.

Guitar is a unique instrument because many of its sounds come from the abuse an amps fidelity. Leo Fender designed his amps to provide good clean tones for players who played clean guitar back in his day. Some player who likely had an underpowered amp playing in a band, cranked the amp all the way up to be heard discovered he could get some unique tones with that saturation and it started the revolution of distorted guitar. Since then this kind of drive has been refined in unlimited ways.

There are two ways of passively attenuating volume that haven't been mentioned yet. A pot is simply a carbon resistor. They can be noisy because carbon in contact with a hard piece of metal like the contact slider that rides on the carbon can act like a diode. (Google up Crystal/Foxhole radio. You can use pencil lead and a razor blase as a primitive diode.) Diodes convert AC to DC and can be part of the reason pots shape the signal and can be noisy.

You can use a multi position rotary switch connected multiple resistors to attenuate the volume in steps. Instead of it acting like a varitone that uses caps and a coil to filter tones you can use resistance to change gains. I've had rotaries like this before that had like 20 steps and done some experiments using such circuits. You could even add add high/low pass caps that retain treble or remove bass on various resistors to change the frequency response curve as you attenuate the pickup.

Much of that would require some mathematics to figure out. I'd likely use a meter on a regular pot and measure the resistance at various steps I wanted resistors to substitute the volume pot. IOr I'd use a resistance and capacitor decade box to find the values so I could purchase the parts I needed.

The other way you can vary volume is something Neil Young uses on his old Fender amp. It's a gizmo involving motors connected to pedal switches that turn his amp up and down to change his volume. It fits on the face of the amp and small motors turn his volume and tone controls up and down. This would be an ideal way of changing your volume because your input impedance from the guitar remains the same.

You can buy motorized pots that can fit into a chassis. They are difficult to find and you'd need the space in the chassis to fit them in and additional wiring to run the motors. This would give you the analog response curves you'd want.

A modern version would be a digital volume circuit built inside the amp that could be controlled remotely like your TV's volume is controlled. Then you'd have the remote control built into or attached to the guitar so the player could manipulate the amp controls from his guitar without a wire. Or better yet done from a foot pedal either wirelessly or with a wire which frees your hands up to play. This kind of thing is done with rack units and midi control already, but I haven't seen it done allot on normal amps. Vox and Line 6 have midi pedals that control amp and effects parameters.I haven't seen any that control a tube amp circuit like a motorized pot would. I'm sure its been done but I guess manufactures went straight to digital control due to cost.

My Art preamp does it with midi but the expression pedals are a bit primitive and you can hear the steps occur when you use volume and wah settings for the pedals. Morley does it with light and photo sensors and it works very well. I prefer the Morley as a volume pedal over an actual pot because its smooth action and I don't have any pot issues or failures.

 

[Maveric Manic]

I have been looking into onboard (Guitar/Bass) Electronics using RISC uP and very low power Analog Op Amps to do DSP or similar processing. You can also do it in a pedal or Amp as well. These circuits are designed to run off of Coin cells 3.0V Lithium. RISC, as you probably know like Microchip, have a whole collection of circuit functions that can be used to process Audio. And no scratchy pots to clean.

[WRGKMC]

I use these with very good results. Super quiet, Low battery drain, and very good results. I've had some in guitars for 2 years and the battery is still good. http://artecsound.com/pickups/electronics/index.html

The VTC is a very good booster that adds allot of presence to pickups that are normally dead sounding. The BCU and EXP do some really neat things for dialing up tones like woman tone, flat tones, boosted mids etc.

I use the MT3 in my Electric Sitar and it really maked those Lipstick Pickups sound great when you can add or remove mids lows and highs.

I also have one of the QDD in a strat which is kind of neat. I can get a 5 step drive setting with a generic sounding overdrive happening. Mkes the strat have a Joe Walsh type drive to it.

The good part are they are cheap and have small footprings so you can mont them in fairly small cavities.

I'm not a huge fan of active electronics because I really dont need them with the gear I own, but they can do some neat things if you want them. You can stick several of them them in pedals too.

[Mr.scary96]

Yeah a treble bleed is what you need

 

[Maveric Manic]

Hey good to talk with a Technical guy WR and thanks for your help. Mav

[Timfever]

Oh wow...this was a bad time for me to have online burnout...! But its cool to have all this knowledge dropped on me.

 

I was exaggerating a bit about my volume knobs...and I've had that SG since 94 (it's a 93...) & its always done that barely noticeable change in volume until almost to 0 when played with psycho high gain. It seemed real odd since I was used to a 70s Strats volume taper...to be more specific, if I wanna be a dork at a party and do the Foxy Lady Volume swell (not that I'd ever do that...), it wouldn't sound right with my SG. I've noticed the same issue with other guitars and to me it sounds like every description of a linear pot I've read.

 

After reading around it seems like just about all production model Gibsons have 300k linear pots for the volume and 500k audio taper pots...unless I got that backwards.

 

Oh and WRGKMC, the massive wads of solder Gibson uses to connect everything PERFECTLY OBSCURE the info you mentioned.

[WRGKMC]

Gibson uses many different pots over the years. They often use 300K on with P90's and 500K with  Humbuckers or Mini Humbuckers but its going to depend on the model and the year. All of my Gibsons Les Pauls, Vintage SG's, Firebirds, The Paul and others had 500K.

I've never found Humbuckers to sound very good with treble bleed caps. You can try them of course. A Gibson's have a Gibson tone and a Fender's a Fender tone and much of that is in the pickup type and woods used. When it comes to guitars I like having different guitars giving me different signature tones. I've pretty much abandoned the idea of making one guitar sound like many others. I don't need to make a Gibson sound like a half assed Fender. I just make the Gibson sound like the best Gibson it can be and pick up a Fender If I want that tone.

On my old Les Paul I had in the 70's/80's, I tried every possible wiring scheme in that one including wiring it for stereo and active electronics. Some were neat for awhile. I even split the coils which didn't have 4 wire conductors. When I bought my 40th Anniversary addition new in 1991 I decided to leave it stock. I've been tempted to mod it but the guitars value has gone up so much I know its worth allot more untouched.

I instead build my own and put whatever mods I need in them to give me the tones I want. New pickups have multi connectors so its as easy as it gets to wire them series, parallel, split etc to get different tones.

If you want to try the 50's wiring there's plenty of schematics. Here's one that goes overboard a bit but its got some photo views that may make it easier for a beginner who doesn't read schematics.  http://www.solodallas.com/the-infamous-50s-wiring-d-i-y-tutorial/

I believe Gibson has a archive on all the different wiring schemes and components used as well. If you ever buy a guitar that's been modded and want to restore it to factory specs its a good site to bookmark. http://www.gibson.com/service/tech/schematics/ You can dig through and compare all the wiring types they've used over the years. Many are similar and some get a bit complex especially the designer models used by major artists.

Here's a better resource for vintage vs. modern wirings. The one I mentioned in my previous post are the last two on this page. http://www.dominocs.com/AshBassGuitar/WireLibrary-Gibson.html

 

You have to figure Gibson has been building designing and building electrics for a very long time and if there was a unique way of wiring a guitar that made it sound better than it does, they would have tried it.

I believe the move to modern wiring types was mainly to reduce hum. When guitars were used with clean amps at lower volumes, hum was lower too. When you gain them up hum becomes a factor so they mostly use the modern wiring which provides the best hum prevention. Of course now you can shield the cavity using conductive paint of copper foil and get all kinds of wiring schemes to work.

Like I said, I've kinda move on from rewiring guitars to do many things poorly and find the best wiring for the best tone and leave it that way and focus on playing it. I know my wiring schemes by heart and how they affect the sound and playability and usually wire them for the standard wiring types. I can predict what they'll do when I plug them in and I don't have to retweak all my pedals and amps to make them sound right. I have collected and built enough guitars where I can just grab the one that has the tones I want and keep a few over the top modders around for a change of pace.