CTS pots are fitted as standard to most top end guitars on the market, with Fender® and Gibson® using them almost exclusively in various guises, with PRS®, ESP® and Gretsch® using them on most their higher end models. Primarily used as volume and tone controls on electric guitars, CTS have been the market leader since the 1950s as near as we can figure.
There are quite a few different versions of CTS pots truth be known, but they can be pretty easily split into “groups” based on their post type.
You normally get “split shaft” pots – which are these ones - pretty easy to identify really - they almost always have a brass threaded collar (3/8” in diameter (about 9.8mm)), with a 24 spline (teeth), brass "turning post" where you'll affix the knob and usually, any pot made by CTS will usually have CTS stamped somewhere on a metal part of the pot.
You also get Solid shaft pots, which are almost identical, but don’t have the teeth or split in the turning post – for simplicities sake, we treat those separately to split shafts. They’re available here.
And, a fairly new addition to the game – you also get “metric” split shaft pots too – almost identical to a standard split shaft, but rather than having a 3/8” thread on them, they have an M8 thread – again, to keep it simple, they’re a separate product too. Available Here.
Pots come in different resistance (or impedances – more on that in a second) – and as a general rule of thumb, the “rules” run as follows.
- Single coils run best on 250k pots
- Humbuckers work best on 500k pots.
Easy right? There are no other guitars then a Stratocaster® and a Les Paul®, the worlds a simple place, let’s have the rest of todays lesson outside!.. if only eh?
I joke, but as a rough guide, that’ll treat you absolutely fine though – but there’s a bit more to it than that.
Why does resistance matter?
The reason we have the 250k=singles/500k=humbuckers is because of the way pots actually work. In a very basic (and completely wrong) sense – pots act as low pass filters (even when on 10, seemingly doing nothing) – they allow a certain range of frequencies to pass through unscathed, but anything above that range, is shunted to ground, and lost.
So, the bigger the resistance, the wider the range of the low pass filter, and as such, the more top end you allow to get through to the amp. So, all things being equal – it’s that simple – you want your guitar to sound brighter? You can fit bigger pots – you’ll open up the low pass filter, and you’re away.
And that’s pretty much why we have this 250k/500k rule – a Strat® sounds like a Strat® (or at least has the best chance of sounding like a Strat®!) if you stick 250ks after a set of single coils – your losing just the right amount of top end to make it work as it should. (And the same goes for a humbuckers on 500ks – that’s what has always been used, that loss of frequency vs. the signal being created is in perfect balance, it does what we expect, and everyone’s happy about it)
So what we’re actually looking at with when we speak about a pots resistance is essentially, “how much top end do I actually want to lose here?” – Nothing more nothing less.
So – as a slightly expanding “rough and ready” rule set – lets work to this.
- Single coils and Telecaster, P Bass and Jazz Bass– 250k
- Humbuckers, Mini Humbuckers, Filtertrons and P90s – 500k
- Jazzmaster and Jaguar – 1 Meg
If you live your life working to those guides, you won’t go far wrong – but – there’s a little more to it than that too.
At this point, we’re getting more into “how pickups work” rather than “how pots work” – so I’ll try and keep this fairly sensible.
Pickups, as well as having a resistance, also have an inductance (that’s why we never use “impedance” when we’re speaking about guitar bits – too easy to misread) – and its actually the inductance that dictates the pot value more than number of coils – BUT – only to a certain point.
In short – if you’ve got a pickup that’s inducing 2-3.5 Henrys, chances are it’s going to sound absolutely perfect on a 250k pot (and it’ll maybe be a little over bright on a 500k) – and equally, if you’ve got a pickup that’s inducing 5-10 Henrys? Probably going to be great on 500ks.
But – this does raise the interesting point that you can’t treat all pickups the same doesn’t it?
I know for a fact, that most Telecaster® bridge pickups run between 4 and 7 Henrys – so they should all be on 500k pots right? Not quite. Same goes for Bass – a Precision bass is usually ticking along around 5-8 Henrys – but again – 250k pots would be the order of the day. Or a Jazzmaster®? That’s almost always 3.5 Henrys – but it’s running on 1 meg pots!
Its important with this, if you’re starting to really think about this, is to remember what the guitars actually meant to be doing – the Jazzmaster® is meant to be very bright, very jangly – so those 1 meg pots and lower inductance is helping retain a lot of the twang – the opposite is true on the bass – they’re actually want to remove quite a lot of the top end from that, so a smaller resistance works a treat.
The Telecaster® is a bit of a weird one in all this – because even though its pumping out 5+ Henrys in most cases, in most cases, we do want to tame it slightly – so 250ks are “the norm” – but remember, in the 1970s, Fender® were fitting 1 meg pots to all Telecaster® models in an effort to revitalise the thing.
So in closing on resistances – it’s all a game of balancing what frequencies the pickup is actually producing (and inductance is a good guide line for that – lower the inductance, the brighter the pickup) and managing what the guitars actually meant to be doing (want it brighter? Go bigger pots)
And that pretty much rounds it out really – resistance in a slightly confusing nutshell!
A few points of note here too before we move on though
- All these rules and guide lines are great, but you will, one day, come up against a guitar that just doesn’t behave how you think it should – they’ll always be the weird specs – forewarned is forearmed!
- This is only true with “passive” guitars – guitars without a battery in them. “Active guitars” will always have a very low value pot (25k or 50k usually) – this is simply to stop the batteries potentially hitting a high resistance, and draining down. Active pickups and EQ systems (where you’ll most commonly find batteries) are built to compensate for this, and don’t rely on the pots to filter the frequencies.
- This is all only true in “real world” conditions – guitar, pedals, and amps – if you’re using an audio interface into a computer, it doesn’t make a blind bit of difference (the resistance on the input of the interface will be so low, the pots dont act as “accidental” filters. (not to say you should be following the rules – but be aware it does behave differently)
Taper - Modern Audio vs. Vintage Audio vs. Linear?
An alternative would be to use a linear taper pot rather than the standard Log version – this will give you much more accurate control over the tone of your pickups.
Taper is simply a technical term for how a pot moves from 1-10, or from 0-100%, depending on how you think of it. Different tapers have different roles within the guitar, and in most cases, they’re interchangeable to give varying results.
Linear pots give a true representation of the output, (so 1 on the dial is 10% of the output, 5 is 50% and 10 is 100%). For this reason you’ll find them used all over the place, (rightly or wrongly) doing a variety of jobs,
Logarithmic (what most people call Audio Taper) come in a few different styles (we carry "Modern" and "Vintage") and they're a little bit more specialised. They offer very narrow control range. Electrically speaking, by running though 0 – 5 on the dial, you cover a very small range on the output, then tracking from 6 – 10 covers a much larger range,
The difference between modern and Vintage is pretty simple really. Vintage pots are at 20% of their total resistance at 5 on the dial, whilst a modern pot is at 15%.
Probably the easiest way to explain the whys and what for’s, is to break down the pots into real life situations you’ll find in your guitar.
As a volume control, you’ll mostly find linear pots on Import guitars. In this case, a true representation of output lends itself really well to bedroom playing. It’s purely aimed at a target market looking to keep the guitar quiet and controllable, hitting low volumes during practise. They also turn up fairly often on bass guitars with 2 pickups, but no switching – giving the player a fairly easy to follow blending system.
You’ll mostly find logarithmic pots on higher end instruments acting as the volume – in these cases the guitar is obviously targeted at gigging musicians. The guitars never going to be played quiet for extended periods so a log pot actually gives a nice “sweep” at the top end which lends itself to moving through different volumes whilst playing (moving from 10 to 8 on the dial will pretty much half the volume). This gives a great effect when used in combination with true amp overdrive.
Relation to our hearing
Obviously if you play on 10 constantly, it’s not going to make much difference; the arguments only really start when you’re changing volume.
The main point to take into consideration is that the human ear works on a logarithmic scale. So whilst moving through volumes during playing, it pays to try to match the way the ear works. The problems start when you consider that our hearing is far superior to anything electrical, so the “curve” of a log pots output never really matches up perfectly, so although the sweep feels more natural, it’s still not perfect. Speaking personally, I try not to think of the curve as matching our hearing, instead I think of it as a “sensitive” control that allows better control at high volumes through less movement.
The downfall of this “theory” is that it flags up the log pots main cause of concern. Most of the numbers on the dial (1-6) only give access to a very low output. This leads us back to the way the ear works – you can hear a pin drop just as well as you can hear a jet engine, the ear should be able to pick out the lower volume sound the same way it picks the higher volume, and your brain should tell you it’s quieter.
Unfortunately, it’s not that clear cut, and this isn’t a perfect world, and although some people can either live with this feature (even use it to their advantage), others find the lower volume settings next to useless and the sudden drop off (usually between 6 and 7) quite annoying (some describe it as acting as a kill switch – basically muting the guitar)
So linear volume?
On the back of this – the linear pot seems the natural solution, but as with most things, it just isn’t that simple. Although the linear pot is great for low volume playing, and it’s easy to see where you are etc – they sweep in a way that isn’t conducive to human hearing. It sounds like its jumps from one setting to the next, and the ear finds it rather unnatural.
But not all is lost
Fortunately, “sweeping” from low volume to high volume still sounds perfectly fine on a log pot, but moving around at low volumes is still something that’s never been quite perfected as yet. Luckily, it’s not something most of us do.
In closing on the volume topic – if you like making use of volume control whilst playing, then logarithmic control is probably your best bet thanks to the more natural curve of the output, but if you’re looking for a straight forward control solution at set volumes, where dial position represents the output, then linear pots are a great solution.
The tone pot on most guitars is a fairly neglected control nowadays sadly. The tone of any given pickup at anything less than 9 seems somewhat muddy and woolly, so more often than not the tone pot is stuck on 10 and left there.
In our experience, most complaints with pots come purely from the control that the stock tone pot is offering to the player.
The reason seems to be that most tone pots (contrary to popular belief oddly) in any production guitar will in fact be a Logarithmic taper. This will make it behave exactly the same as the volume control (at least to our ears).
As we discovered earlier, a Log pot will have most of its control at the higher end of its sweep – which works absolutely fine for volume control – however, with a tone control, when you’re making a “selection” – it leaves a little to be desired, purely because each setting is not equal to the ear.
Some people are absolutely fine with this setup, and will use the tone pot to make minute tweaks in the higher numbers.