What the difference between 250k and 500k Pots and then audio or linear

[Gavin1393]

What is the difference between 250K & 500K pots?
The first thing to establish is that we are talking about passive pickups as opposed to active pickups in this thread. Either 250K or 500K pots can be used with any passive pickups however the values of the pot used will affect tone slightly. The rule is: Using higher value pots (500K) will give the guitar a brighter sound and lower value pots (250K) will give the guitar a slightly warmer sound. This is because higher value pots put less of a load on the pickups which prevents treble frequencies from "bleeding" to ground through the pot and being lost.
This is why you will find that guitars with humbuckers like Les Pauls will opt to use 500K pots to retain more highs for a slightly brighter tone and guitars with single coils like Stratocasters and Adam's extensive collection of Telecasters will use 250K pots to add some warmth by slightly reducing the highs. You can also fine tune the sound by changing the pot values regardless of what pot value the guitar originally had. It is also worth noting that most pots have a 20% tolerance so that 500k pot may actually be anywhere from 400 - 600k!!

What is the difference between Audio and Linear taper pots?
Audio and Linear taper pots have the same total resistance but they differ in which position of rotation the pot will reach the 25%, 50% and 75% value as well as every other value between 0 and 100% . . Linear pots are usually marked with a B (examples 250KB, B250K and will reach 50% of its total resistance in the 50% rotation point. Audio taper pots are usually marked with an A (examples 500KA, A500K) and will decrease most of the resistance in the last 50% of the rotation. This can give a more gradual audio reduction is some cases. Some manufactures like Fender use Audio taper pots for both volume and tone controls. Gibson on the other hand uses linear taper pots for both volume and tone. And still others use Linear taper pots for volume and Audio taper pots for tone. However, if a problem of exists where a volume or tone pot has no effect on the sound, try changing the taper.

How to check the taper with an ohm meter: Set the pot to the center position (50% rotation) and measure the resistance between the center pin and each of the outer pins. If the the resistance is equal (50% of the pots value) the pot is linear. If the values are not equal, the pot is an Audio taper.

[robin]

Gav, thanks so much for posting this. As you know I struggle with understanding the electronics of guitars and anything I can learn will help when I finally gain enough confidence to start modding guitars.

Can I be a total pain and ask you to briefly explain about different Cap values and their affect on tone, and anything else you think might be of value.

It will be great to have this info in one thread to help those of us who are challenged by electrickery.

Thanks mate
rob

[keloooe]

Hey Gav, Gibson use linear 300k for volume and audio 500k for tone normally!!!

[Gavin1393]

/<\\/p>[]<\\/p>/Quote from keloooe on July 13, 2013, 18:42
Hey Gav, Gibson use linear 300k for volume and audio 500k for tone normally!!!

Pest, this is only true of the newer Gibson models. PBG only use 250k and 500k on all our kits.

[WeirdBits]

Rob, these StewMac wiring articles would be a great place to start.

Caps work as filters by blocking low frequencies while allowing high frequencies to pass through them. Basically, the higher the value of the cap the lower its cut-off frequency, thus a greater range of high frequencies can pass through it. So, in a basic guitar tone circuit, the cap determines what range of high freqencies can be sent to ground and the tone pot determines how much those freqs are attenuated. Strats and Teles (single coil) want to cut back on the brightness so they use 0.047 caps to tame the shrill, while LP's (humbuckers) are warmer and want to retain some brightness so they use the lower value 0.022 caps.

In context with Gav's post:
Big pot (500K) = more bright, small pot (250K) = less bright
Big cap (0.047) = less bright, small cap (0.022) = more bright

Treble bleed circuits use low value 0.001 caps to allow the ultra high freqs to bypass the volume pot and go straight to output, thus retaining those highs at any volume setting etc.

(I hope I haven't trampled on Gav's toes)

[robin]

Thanks Scott for the Link AND the lesson. I am finding that the more I learn, the more I realize I don't know.

But this whole journey of making guitars has been a learning experience for me. Thoroughly fulfilling, exciting, frustrating and enjoyable. Sometimes in equal measure sometimes not. But I'm just glad that I started, wish I had done it years ago.

Cheers guys,
rob

[Brendan]

Robin - if you'd have done it years ago, PBG wouldn't have existed! You'd then be a pro by now and we may not have had the pleasure of your company here! Therefore, I for one am happy you didn't start years ago .

[robin]

Aww, thanks Brendan.

Even if I had started earlier I doubt that I would be a pro. But if I was I would like to think that instead of just asking questions, I could contribute something to this community in the same generous spirit as DB, Gav, et al.

Cheers mate,
rob