Should/Can I combine capacitors in a P bass?

[krispn]

Hey there tech heads

So I got some big old Russian caps and I'm thinking of trying them out in a P Bass - Im gonna install a recently acquired Nordstrand NP4, and a re-wire, into a VM Squire. While I have the guts exposed I was gonna mess about with some caps to alter the tone a little and was thinking of adding the .1uF to really bring out the low end but fear it might be too much.


As I await the arrival of the new pots etc my question is has anyone tried a .1uF in their P bass and more importantly would I be able to combine a Sprague Orange Drop .047 with the .1uF to retain some high but add more bass to the tone or would it not be worth the hassle? If I had all the bits I'd just do it but hopefully someones experience could save me the hassle.

Any views great appreciated as alway.

I've added a pic of the caps along with a penny for size reference just to make the post look pretty

[Al Heeley]

If you connect them in parallel then you get 0.147uF capactiance.
If you connect them in series you get 0.032uF.
Are you thinking you could use one for highs and one for lows? Electricity is not able to understand this.

I would think 0.1uF or greater is way too high to give your tone knob any usable sweep. That's fundamentally all the cap really influences.

Edited September 3, 2010 by Al Heeley

[krispn]

Hi Al

Yeah I was thinking the .1uF would be too much and result in pure mud. Im no physic's major so my basic understanding is all I have to go on. I'll be using them in a p bass so only one output so if I understand you correctly Im not using two outputs- high and low- just one single output.

Basically my understanding of what you're saying is that in series it's .032uF (and I could just find a cap rated at this and save me the extra soldering) while in parallel it would be pointless as it would render the tone knob pointless.

In conclusion I'd be safe sticking with the .47uF in your view? I guess I'll se what other feedback I get but I'd be inclined to agree with you unless the 0.1uF added anyhting when the tone knob was at 10 (but I guess it wont)

Cheers for the feedback

G

[hoiho]

A passive tone control doesn't [i]add[/i] anything; all it does is progressively remove higher frequencies.

[Al Heeley]

Don't get confused with high or low outputs, we're only talking about a single signal here.
You are correct, sticking with a single cap 0.047 or 0.033uF is best way to go.
For a passive bass, the smaller the cap, the higher the treble frequency cut-off as the tone knob turns from 10 to 0. The resistance of the pot also affects this ramp or 'sweep' as tone is turned down.
At 10, (tone pot = no resistance) to all intents and purposes, the signal goes straight through bypassing the cap, so it doesn't matter what value it is.
At zero, (tone pot at max resistance) a lot of the the signal will take the path of least resistance through the tone cap. This filters out the higher frequencies like a shock absorber soaks up the vibrations of a road surface - you still feel the pot holes. Bigger value caps retain more of the lower frequencies so only the lowest will get through. Tiny caps will just take off the top end sparkle. But only when the tone pot diverts enough of the signal (ie. it's turned down enough). I find it easiest to visualise the shock absorber image.

I would think that a 0.1 uF cap in the circuit would just give a muffled decrease in output when you turn the tone knob down. Now you won't be wanting that will you?

Edited September 3, 2010 by Al Heeley

[krispn]

Thanks Hoiho that bit I understand - and Thanks Al for your comprehensive explanation.

I guess the mud will kick in quicker with the .1uF and I think i'd like a bit more range with the tone pot so I'll stick to the less extreme. Saved me some extra work for sure

Thanks again

[nick]

[quote name='krispn' post='944379' date='Sep 3 2010, 11:30 AM']....my question is has anyone tried a .1uF in their P bass[/quote]
[quote name='Al Heeley' post='944520' date='Sep 3 2010, 01:35 PM']I would think that a 0.1 uF cap in the circuit would just give a muffled decrease in output when you turn the tone knob down. Now you won't be wanting that will you?[/quote]

I have a 0.1uF paper-in-oil cap in my P-Bass. Don't hear it as muffled myself, find it gives plenty of thump, but still defined. Great for Motown or dub.
Admittedly can be too much sometimes. I've got the usual .047uF in another precision. Love PIO caps.

[flyfisher]

The good thing about a passive bass is that you can't really break anything by experimenting (assuming you're OK with soldering and don't cook the components!).

But, as hoiho has pointed out, the circuitry in question is just a fairly crude low-pass filter and changing the components will really only change the frequency where the roll-off begins. If you really want to experiment, you could try multi-pole filters to roll things off more quickly, but if you really get into detailed frquency shaping then you might as well keep the bass output as flat as possible and feed the signal into a graphic equaliser to really play around with the tone.

[Delberthot]

I have those same caps and generally put them in all my basses - call it snake oil, call it good old Ruskie workmanship but I like them.

[BB2000]

[quote name='Al Heeley' post='944520' date='Sep 3 2010, 01:35 PM']Don't get confused with high or low outputs, we're only talking about a single signal here.
You are correct, sticking with a single cap 0.047 or 0.033uF is best way to go.
For a passive bass, the smaller the cap, the higher the treble frequency cut-off as the tone knob turns from 10 to 0. The resistance of the pot also affects this ramp or 'sweep' as tone is turned down.[/quote]

The larger the cap, the greater the HF attenuation.

[quote]At 10, (tone pot = no resistance) to all intents and purposes, the signal goes straight through bypassing the cap, so it doesn't matter what value it is.[/quote]

At 10 (fully CW) the resistance of the tone potentiometer is at a maximum. A lager capacitance will result in a larger HF attenuation.

[quote]At zero, (tone pot at max resistance) a lot of the the signal will take the path of least resistance through the tone cap. This filters[/quote]

At 0 (fully CCW) the resistance of the tone potentiometer is at a minimum. The capacitor value still determines HF cutoff due to interaction with vilume control and PUP impedance.