Basic Bass Guts

Afternoon Folks…A question: My 68 Silvertone has the original 100K pots in it, one for volume and one for tone, along with a three way switch and the input for the cord to the amp. My question is should I stick with the 100K or could I go up to something like a 250K?

2 Likes

it’s totally possible to use 250k pots, you just have to know that higher value pots will give a bit more treble, so the bass will sound a bit brighter.

4 Likes

So if I want the same tone it has now I should stick with the 100’s?

1 Like

absolutly

1 Like

Ok…Thanks, Big Time!

2 Likes

I know a pot is a potentiometer. Does anybody want to explain what a 100K versus 250K pot is?

3 Likes

it is the resistance value of the pot, in ohm. in fact a potentiometer is exactly like 2 resistors in series wired in voltage divider, like this :

the outer legs of the pots are where you see “Vin” and the ground sign. the third leg, in the middle, is where you see “Vout” and what’s cool with a pot is that when you turn it, you make Z1 and Z2 vary (in fact you move the middle point between the two outer legs). But the total resistance of the pot always remains the same, it’s Z1+Z2. here Z1+Z2 equals 100k ohm or 250k ohm, in what we talked about.

in a high impedance circuitry like a passive bass, the signal has a very very low current, and is very much affected by the load. the load is the resistance the signal “sees” and the pot values are very important for this. A 100k pot will load the pickups more than a 250k pot, the signal will be affected and this will result as a loss in the detail (which is in fact the treble content of the audio spectrum) and that’s why 100k pots will sound darker than 250k pots. About the tone control it’s a little bit different, let’s say that a 100k pot won’t allow to really set the filter to “zero” and the tone control will always be a little bit active (so, less treble again).

there is another important thing with pots which is not related at all with its value : the progression curve when you rotate the pot. it can be linear but it can also be logarithmic (or even reverse log, but it’s way more rare). My advice would be using a linear pot for the volume and a log pot for the tone control.

6 Likes

@terb Man, thanks for posting this.

Is there a resource you could recommend for learning this stuff. Something like Electrical Engineering for Music Equipment or is this just considered general EE knowledge?

2 Likes

The first part of what he posted is basic electronics and is not that hard to learn - I was lucky enough to learn it in High School, back when good and worthwhile vocational classes were a thing.

The second part - about how these things relate to music and tone - that’s super interesting and I would love some good links for that too :slight_smile:

2 Likes

it’s hard to give a precise source, but I remember there are some bass-related basic electronic stuff in this book : http://www.ak-line.com/medium/Bassschaltungen.pdf

it’s in german but Google Translate can make some miracles :grin:

what I said is pretty basic electronic, I assume it’s pretty easy to find informations everywhere. even Wikipedia could be a nice starting point. keywords : voltage, current, resistance, voltage divider ; and for tone controls : capacitor, RC filter, low-pass filter

1 Like

I learned about the way the electronics basically work by searching in Youtube…you can find some very good videos on guitar and bass electronics…but I didn’t know, til the other day, thanks to @terb about how the rating of the pot affected the overall tone…gotta love this stuff!!

2 Likes

@terb . . . you’re the man! :+1:

Cheers, Joe :slight_smile:

1 Like