Capacitor Question ???

[METAL Rulez 4ever]

Hello all,

Happy New Year. I hope everyone and families had a safe and wonderful Christmas.

Just wondering, with Bass capacitors, if i want to modify my bass tone / sound, do i add a capacitor to a pot to turn the pot into a tone pot instead of a volume pot ? So any pot that has a capacitor is a tone control and without a capacitor is a volume control ?

Also too, which number capacitor should i use ? What do the numbers and color of a capacitor represent please ?

Regards,
Naim.

[Simon Barden]

A volume pot has all three of its connection tags used as it's being used as a potential divider. A tone pot has just two of its tags used as it's being used as a variable resistor and is used in series with a capacitor.

Capacitors normally have the value marked on them, so you just need to be able to understand what part of the writing is the value and what is the manufacturers' code. Occasionally capacitors do have values written in coloured bands like resistors do and here's a web site explaining those. http://www.electronics-tutorials.ws/capacitor/cap_5.html

If you are referring to 'orange drop' capacitors, then these are just a range of good quality, reasonably high tolerance capacitors made by Sprague, that just happen to be bright orange and generally about the size of a small sweet. They have the capacitance values printed on them.

The value of capacitor you use partly depends on the pickups you are using and partly on how bright the pickups are. The higher the capacitance value, the more treble is taken from the signal at full tone reduction. Brighter pickups like jazz bass single coils might have a tone capacitor of between 0.047uF and 0.1uF (micro-Farads). A slightly duller pickup like a P-bass probably would stick with a 0.047uF capacitor. A passive MM type humbucker might be between 0.033uF and 0.047uF.

It's easy enough to Google what the standard capacitor value is for a particular type of bass, or look up wiring diagrams for them on say the Seymour Duncan site.

If you switch to active pickups/circuits, then the tone controls are generally active and it's all built-in. If not active tone controls, then again, look at the pickup manufacturer's wiring diagrams and they will give you their recommended values.

[METAL Rulez 4ever]

A volume pot has all three of its connection tags used as it's being used as a potential divider. A tone pot has just two of its tags used as it's being used as a variable resistor and is used in series with a capacitor.

Capacitors normally have the value marked on them, so you just need to be able to understand what part of the writing is the value and what is the manufacturers' code. Occasionally capacitors do have values written in coloured bands like resistors do and here's a web site explaining those. http://www.electronics-tutorials.ws/capacitor/cap_5.html

If you are referring to 'orange drop' capacitors, then these are just a range of good quality, reasonably high tolerance capacitors made by Sprague, that just happen to be bright orange and generally about the size of a small sweet. They have the capacitance values printed on them.

The value of capacitor you use partly depends on the pickups you are using and partly on how bright the pickups are. The higher the capacitance value, the more treble is taken from the signal at full tone reduction. Brighter pickups like jazz bass single coils might have a tone capacitor of between 0.047uF and 0.1uF (micro-Farads). A slightly duller pickup like a P-bass probably would stick with a 0.047uF capacitor. A passive MM type humbucker might be between 0.033uF and 0.047uF.

It's easy enough to Google what the standard capacitor value is for a particular type of bass, or look up wiring diagrams for them on say the Seymour Duncan site.

If you switch to active pickups/circuits, then the tone controls are generally active and it's all built-in. If not active tone controls, then again, look at the pickup manufacturer's wiring diagrams and they will give you their recommended values.

Thank you Simon for all your info. Very helpful indeed. I will get onto this research and do my homework.

I just purchased this bass with a P style passives on Ebay and it sounds terrible. Gotta crank the amp to hear it, no bass, all treble and heaps of amp noise. Not even the tuner is picking up the strings to tune it. So its either the pick ups or the tone pot with the cap. This bass is supposed to have 1 volume and 1 tone, but the tone pot cuts out the volume instead ! So i reckon thats my problem. I wanna replace the pot and cap and replace it with my own combination of A500K pot and .33 cap.

[WeirdBits]

Post some photos of the current wiring and we may be able to spot the issue(s). It sounds more like mis-wiring than just a tone pot problem, but it could be a couple of things.

[Simon Barden]

Yes, sounds very much like a wiring problem or a faulty pickup. If there's hardly any output from the pickup, then the tone control will knock off most of the mid and treble from it, and it will certainly reduce the volume to almost nothing.

[METAL Rulez 4ever]

Post some photos of the current wiring and we may be able to spot the issue(s). It sounds more like mis-wiring than just a tone pot problem, but it could be a couple of things.

16454

Here are the pics WeirdBits and Simon. Thank you for your help so far, much appreciated.

[METAL Rulez 4ever]

Yes, sounds very much like a wiring problem or a faulty pickup. If there's hardly any output from the pickup, then the tone control will knock off most of the mid and treble from it, and it will certainly reduce the volume to almost nothing.

16455

Here are the pics WeirdBits and Simon. Thank you for your help so far, much appreciated

[Simon Barden]

Is it possible to take another picture (maybe more from the side) with the wiring moved so that it's easier to follow what's connected to what? With several black cables sitting on top of one another, it's not easy to follow the wiring with 100% confidence.

Also, if you can take a photo of the wiring on to the jack socket, that would be helpful.

Cheers.

[METAL Rulez 4ever]

I finally fixed the problem Simon. It was the pick ups that were faulty. I first replaced the cap, but that did not fix the problem, so i changed the pot, still not fixed, so i replaced the pick ups with a spare i had and now the bass plays beautifully. I replaced the original pot and cap, and still works fine. I wanted to know the exact problem, wasnt sure if it was the pot or / and cap or / and pick up. so it was just a faulty pick up. So i learnt a lot from this experience, helped me to finally study on different pots and caps. But i am confused...How can the pick ups still work thru the volume pot but not the tone pot ? Pick ups still gave sound, even though they were faulty ???

[Simon Barden]

With the volume control, the full-range of the signal is being attenuated as you would expect.

If you look at the wiring, the connection to the tone pot is made from the connection on the volume pot that also connects to the pickup output. So if you use the tone pot, some of that signal is going down to earth via the tone capacitor. Because it's the resistance of the pickup that forms the actual R part of the RC tone circuit, and there's obviously something wrong with the pickup, the low-pass circuit cut-off frequency is affected and probably all (not just the high frequency part) of the signal is passing to ground through the tone circuit. Because the tone pot is normally selected as a linear pot, then unlike the log/audio taper volume pot, it doesn't take much turning to significantly lower the pot resistance.

[METAL Rulez 4ever]

With the volume control, the full-range of the signal is being attenuated as you would expect.

If you look at the wiring, the connection to the tone pot is made from the connection on the volume pot that also connects to the pickup output. So if you use the tone pot, some of that signal is going down to earth via the tone capacitor. Because it's the resistance of the pickup that forms the actual R part of the RC tone circuit, and there's obviously something wrong with the pickup, the low-pass circuit cut-off frequency is affected and probably all (not just the high frequency part) of the signal is passing to ground through the tone circuit. Because the tone pot is normally selected as a linear pot, then unlike the log/audio taper volume pot, it doesn't take much turning to significantly lower the pot resistance.

Thank you for your info Simon. I have a lot to learn about pots and caps. I am still trying to understand the difference between linear and taper in pots and values and volts in capacitors.

[Simon Barden]

The 'volts' in capacitor ratings is easy to understand. The rating is the maximum voltage the insulation between the different layers that make up a capacitor can withstand before breaking down and allowing current to pass across them (basically destroying the capacitor). This is normally a DC voltage rating, though if it has AC in front of the value, then it will be a capacitor normally designed to go in AC power circuits. Sometimes a capacitor will have both AC and DC voltage ratings.

As AC voltages are normally given as RMS values (root mean square), this gives the average voltage level of the AC voltage, but the peak voltage (the one that affects the insulation levels) is 1.41 times higher than the RMS value (assuming a mains style sine-wave). So a 240v AC RMS mains voltage actually has a peak voltage level of 240 x 1.41 = 338.4v. So anything designed for mains voltages would need to have an insulation rating of at least 350v DC, preferably higher, to allow for normal variations in mains voltages.

But in capacitors, this is not the only consideration. As the voltage present nears the insulation rating, the actual capacitance value starts to reduce. At 95% of the rated insulation value, the value of the capacitor decreases significantly to around 20% of its nominal value e.g. with an applied voltage of 19v DC across it, a 10uF 20v DC capacitor would have an actual capacitance of around 2uF.

This isn't a linear effect, and only happens when the voltage reaches a significant percentage of the insulation rating. But it is standard practice to use a capacitor that's got an insulation rating of at least 200% of the highest voltage expected in that part of the circuit.

The higher the insulation rating, the more costly the capacitor, so it's natural for mass produced goods to have capacitors selected on a circuit board exactly for the maximum design voltages present.

On a guitar/bass, it's not really a problem as the highest voltages likely to be generated by even the highest output passive pickups is around 1v AC, with 0.1v AC being a more standard pickup peak value, so any capacitor rated above 3v DC should be fine. If it's a higher insulation rated capacitor (a lot of the Sprague Orange Drop capacitors sold are between 100v to 600v rated), it doesn't really matter because you are only buying one of two of them for your own guitar. If you were a factory making 20,000 guitars a year, you'd certainly fit something cheaper to your lower-end models and maybe fit Orange Drops to the more expensive models as a selling point.