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Pots'n'caps...

M

manchild

Jan 30, 2008
512
2
#1
Been doing a lot of research on here and the ret of the net about how passive pots and caps effect tone.

Think i am just about understanding it...

If you wire your pups straight to the jack with no pots, you get an increase in high frequenceies because even turned up pots still dampen a little of the highs?

So without them on both volume and tone, your signal will be louder and brighter?

If you wire straight to the jack, would you still use caps, and if so what effect would they have or if not in the case?

Also if your pots are like 1M or higher, is it the same as having none when it is turned all the way up?

Soz if this a drag for you experts but a lot of people (like me)dont get the physics or the understanding of how it effects your sound.

Cheers ;)
 
#2
manchild said:
If you wire your pups straight to the jack with no pots, you get an increase in high frequencies because even turned up pots still dampen a little of the highs?

So without them on both volume and tone, your signal will be louder and brighter?
Click to expand...

Your signal will be full volume and all the highs will be there.

manchild said:
If you wire straight to the jack, would you still use caps, and if so what effect would they have or if not in the case?
Click to expand...

If you used a capacitor it would send all the frequencies above the shoulder frequency the ground at 3db per octave. So a .047uF cap would roll your highs off above 300Hz.

manchild said:
Also if your pots are like 1M or higher, is it the same as having none when it is turned all the way up?
Click to expand...

The idea is the higher resistance pots bleed fewer high frequencies to ground so the sound would approach the straight run.

The problem is the higher the value of the pot, the faster the resistance changes while you turn it.

Think of it as two identical dials except one is labeled from 1 to 10 and the other is labeled from 1 to 100. If you turn the dials at the same rate, the second dial will move through the numbers 10 times faster than the first.

So lower value pots are smoother to tune than higher valued ones. 500K is a nice compromise.
 
#3
Hi, thanks SnakeKappele,

Thats some good info there...

A .047uF cap would roll off highs starting with and above 300Hz? Is that not quite low in the frequency range if you have no pot and run at full?

As i type this i think i have not understood what you mean?
 
#5
manchild said:
How much more treble would you get with no caps or pots?
Click to expand...

This graph is an example of what a tone control does:
Tone graph.JPG

The top line is the straight connection to the jack or tone off. You get your highs out to 20000Hz (if you have them).

The leftmost line is the tone full on or the straight connection to the jack with a capacitor. As I understand it, a .047uF cap would cut the power at 1200Hz by 75%.

Here are the frequencies where the cutoff begins for some different capacitors:

.100uF - 200Hz
.047uF - 300Hz
.022uF - 400Hz
.010uF - 600Hz

Here is a good video where you can hear different capacitors in use:
http://www.youtube.com/watch?v=3I62Xfhts9k
 
#6
You seem very concerned about losing highs, so why not use Fender no-load pots for volume and tone?

The no-load pot is a 250K pot that is 250K full counter clockwise and sweeps toward 0 as you turn it clockwise. At full clockwise it clicks and disconnects the pot from the circuit.

When you use it as a volume control it is wired so the active lug is connected to the pickup + and jack out + and the center lug is connected to ground. This lets you have a volume control that gets louder as you turn it clockwise and then clicks and removes the volume pot from the circuit.

With no-load volume and tone controls you can have volume and tone control when you want and go straight out when you want.

Invalid Link Removed
 
#7
Nice one mate, thats great - not so much losing them, i just dont want it to be too 'tinny' sounding, as im planning a no controls straight through mod ;)

Thanks again, thats some great stuff to go on.
 
#8
if you want no controls but not too much brittleness, you can wire up resistors to simulate the pots on "10". 250ks for vintage fender, or 500k for a little more edge.

one resistor goes from hot to ground to "be" the volume pot on "10", and the other goes from hot into a cap, and then the other end of the cap goes to ground, to be a tone pot on "10".
 
#11
SnakeKappele said:
If you used a capacitor it would send all the frequencies above the shoulder frequency the ground at 3db per octave. So a .047uF cap would roll your highs off above 300Hz.
Click to expand...

Also depends on the impedance of the pickup. Tone controls have more of an affect on hotter pickups.

The problem is the higher the value of the pot, the faster the resistance changes while you turn it.

Think of it as two identical dials except one is labeled from 1 to 10 and the other is labeled from 1 to 100. If you turn the dials at the same rate, the second dial will move through the numbers 10 times faster than the first.

So lower value pots are smoother to tune than higher valued ones. 500K is a nice compromise.
Click to expand...

+1 This is often overlooked!

A pot is a voltage divider, so larger value pots put more resistance in series with the pickup when you turn it down.

1 Meg pots are brighter on 10, but often duller on 5.
 
#13
manchild said:
Is it possible to simulate a .047 with 250k pot sound on full (standard jazz set up) using only caps and no resistor?

I want to take out any unnecessary components for a no controls set up...
Click to expand...

If you want to simulate the controls on 10, just wire a 250K resistor between hot and ground. The effects of the tone control on 10 are negligible, so I wouldn't bother.
 
#15
Yeah i get what you mean, but im getting custom scratch plates etc for my jazz and only play with everything on 10, so im going with no controls...

I have read in other threads that the less you have in the way of your signal the 'cleaner' your sound will be, you was wondering if my thinking is right, that if i wire straight to the output using only a .01uf cap or something would be the same as .047uf with 250/500k? Or 1m?
 
#16
manchild said:
Yeah i get what you mean, but im getting custom scratch plates etc for my jazz and only play with everything on 10, so im going with no controls...

I have read in other threads that the less you have in the way of your signal the 'cleaner' your sound will be, you was wondering if my thinking is right, that if i wire straight to the output using only a .01uf cap or something would be the same as .047uf with 250/500k? Or 1m?
Click to expand...

The .01 cap will roll top end off. Just wire everything to the jack.
 
#17
I don't get it. If you want a cleaner sound why don't you just wire the pickups straight to the jack?

If you put the .01uF cap in you're rolling off the highs above 600Hz. You should have about half volume at 1200Hz.

Send it all out the jack and deal with it offboard.
 
#18
I mean cleaner in the sense that that there are less components in the system to disturb the signal...

Thanks for all the advice, think il try the various options you have given and see which i like before patching it up.

Cheers
 
#19
I was under the impression that no load pots could only be used for tone; NOT volume. I had thought that a no load pot used for volume would go from 1-9 and then click 'off' which for a volume pot would be '0' (no sound).

If this is wrong, I'd be happy, because I really like the no load idea.

-JV
 
#20
PS - I think some of this idea might appeal to you:

http://www.talkbass.com/forum/showthread.php?t=701011&highlight=

Basically, I'm wiring it so that the 'normal' state of my bass is both pickups straight to the output jack (with both pots in the 'down' position. If I pull up on the volume pot then I can control the volume and tone with the 500k pots, and if I pull up on the tone pot I get the bridge pickup solo. This gives me all the flexibility I want, none that I don't need, and all but eliminates the chance of finding that my knobs have gotten bumped mid-song, etc...

-JV
 

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