The basic flaw in the p-bass

[GeorgeBerlin]

Anybody have L and R values of a typical series connected P pickup pair? Then I can do a detail sim with the typical 47nF of P tone control later. Otherwise I'll just use my measured values of a G&L MFD. At any rate the hump will be moderate (low Q from the series connection) and rather high in freq, in the mids or lower mids at best.

they're typically:
DC resistance: 10.5k -11k ohms
Inductance: 6.4 henries

Thanks, John.

OK, here we go :

I've been using 47nF for the tone cap, and 250k pots for tone and volume (volume fully up and not loaded down by amp input, assuming a 1Meg or greater input impedance).

Tone pot was step logarythmically 300 Ohms to 300kOhms.

We can see, in the first three steps (300R to 3k) that basically the Q of the resonant circuit is changing, while the final rolloff is the same. Peaking frequency is 220Hz, this is upper bass or lower midrange, for bass instruments.

The 10k, and notably 30k (pot at midway position) curves show an interesting effect, the rolloff gets flatter but also the section below the resonance shows a falling slope. This is from the resistor loading down the inductive (high) impedance

100k and 300k curves then look more like expected, the pup is unloaded again.

So I stand corrected (the resonance is lower and the inductance is higher than I had expected).

At 200Hz there is a 3dB difference, and at 100Hz a 1.5dB difference, between tone blend fully closed and halfway up, and this is audible and could be declared as a loss of upper bass. In the very low bass (<40Hz) curves get closer and there is no effective decrease in level, but this is outside the range of the instrument.

 

[Hopkins]

Oh get real. Maybe it's just that some of us don't consider that Entwistle thing a flaw.

+1

 

[taurus1]

You mean every Fender fan boy comes flying into the thread to act irrationally? Wouldn't say that was "to the rescue". As soon as you point out the flaws in a P bass you get "omgzzz!!!! well _____ plays with one so he must suck!!!! *rolleyes* *rolleyes* p bass is all i need. I've played every single bass on the market and p bass is the greatest! james jamerson only used a p bass lulz!!!!"
Yet, the moment a virtuoso or one of the greats says something like Entwisle did here and suddenly the fan boys turn on him. I don't get brand loyalty, especially the fanatics for P basses. They are worse than iphone fan boys.


Waits for the comprehensive list of musicians who use P basses, that contains several musicians who don't use p basses.

I don't perceive any fanboyisms at all in this thread.
Entwistle and the op said something seemingly ridiculous and
got called out for it.

 

[Ric5]

I exited this thread for all of the hate directed at me. Saying the p-bass had a flaw on this site is like telling a religious zealot that there is no God.

But I see the thread has evolved into a useful discussion.

I have owned and played many p-basses. I have gigged with p-basses. I don't play 4 string basses or flats any more. About half of my basses are passive and half are active. I am not a purist. I modify pretty much everything I own.

I like a full frequency sound on bass. I like the fundamental and the overtones. I like bass, mids, and treble.

The p-bass seems to excel when the tone control is rolled off and it emphasizes the low mid frequencies.

Those of us who like to open up the treble will notice that the p-bass tone is no longer dominated by low mids and it seems to not have that "full" tone. That is why in 1973 Entwistle switched to the Thunderbird, and Fenderbird basses so he could get more low end. Also Billy Sheehan added the neck pickup to his p-bass and biamped it so he get the high mid snarl and the full bottom from the neck pickup.

I think this characteristic of the p-bass to have the low mid growl with the tone rolled off is why recording engineers like the p-bass in the studio.

I like the like low mid growl of a p-bass, but I also like the high mid bite of Ricks, and the treble bite of a jazz bass opened up and the full bottom of an active bass. The p-bass doesn't excell at all of those tones. Which is why quite often the p pickup is paired with a jazz, or stingray pickup.

 

[dkelley]

Thanks, John.

OK, here we go :

I've been using 47nF for the tone cap, and 250k pots for tone and volume (volume fully up and not loaded down by amp input, assuming a 1Meg or greater input impedance).

Tone pot was step logarythmically 300 Ohms to 300kOhms.

We can see, in the first three steps (300R to 3k) that basically the Q of the resonant circuit is changing, while the final rolloff is the same. Peaking frequency is 220Hz, this is upper bass or lower midrange, for bass instruments.

The 10k, and notably 30k (pot at midway position) curves show an interesting effect, the rolloff gets flatter but also the section below the resonance shows a falling slope. This is from the resistor loading down the inductive (high) impedance

100k and 300k curves then look more like expected, the pup is unloaded again.

So I stand corrected (the resonance is lower and the inductance is higher than I had expected).

At 200Hz there is a 3dB difference, and at 100Hz a 1.5dB difference, between tone blend fully closed and halfway up, and this is audible and could be declared as a loss of upper bass. In the very low bass (<40Hz) curves get closer and there is no effective decrease in level, but this is outside the range of the instrument.

very impressive! I'm happy someone else is doing this stuff these days... I don't have it in me any more.

much appreciated

 

[taurus1]

Thanks, John.

OK, here we go :

I've been using 47nF for the tone cap, and 250k pots for tone and volume (volume fully up and not loaded down by amp input, assuming a 1Meg or greater input impedance).

Tone pot was step logarythmically 300 Ohms to 300kOhms.

We can see, in the first three steps (300R to 3k) that basically the Q of the resonant circuit is changing, while the final rolloff is the same. Peaking frequency is 220Hz, this is upper bass or lower midrange, for bass instruments.

The 10k, and notably 30k (pot at midway position) curves show an interesting effect, the rolloff gets flatter but also the section below the resonance shows a falling slope. This is from the resistor loading down the inductive (high) impedance

100k and 300k curves then look more like expected, the pup is unloaded again.

So I stand corrected (the resonance is lower and the inductance is higher than I had expected).

At 200Hz there is a 3dB difference, and at 100Hz a 1.5dB difference, between tone blend fully closed and halfway up, and this is audible and could be declared as a loss of upper bass. In the very low bass (<40Hz) curves get closer and there is no effective decrease in level, but this is outside the range of the instrument.

very cool, 200Hz or so is right around where I hear it on my bass.

 

[huckleberry1]

p bass was my first bass, I thought it sucked. Looking back it was me that sucked but I still hate the take it or leave it tone set up.

 

[kevteop]

Just here to give props to the science guy.

I don't get why people are so territorial about this stuff. If you like P basses then just be content in liking P basses. Hell my main bass is a Thumb bass and practically nobody likes them except me and every producer I've ever recorded with.

 

[Ric5]

Thanks, John.

OK, here we go :

I've been using 47nF for the tone cap, and 250k pots for tone and volume (volume fully up and not loaded down by amp input, assuming a 1Meg or greater input impedance).

Tone pot was step logarythmically 300 Ohms to 300kOhms.

We can see, in the first three steps (300R to 3k) that basically the Q of the resonant circuit is changing, while the final rolloff is the same. Peaking frequency is 220Hz, this is upper bass or lower midrange, for bass instruments.

The 10k, and notably 30k (pot at midway position) curves show an interesting effect, the rolloff gets flatter but also the section below the resonance shows a falling slope. This is from the resistor loading down the inductive (high) impedance

100k and 300k curves then look more like expected, the pup is unloaded again.

So I stand corrected (the resonance is lower and the inductance is higher than I had expected).

At 200Hz there is a 3dB difference, and at 100Hz a 1.5dB difference, between tone blend fully closed and halfway up, and this is audible and could be declared as a loss of upper bass. In the very low bass (<40Hz) curves get closer and there is no effective decrease in level, but this is outside the range of the instrument.

If I read that correctly then with the treble rolled off the pbass seems to empahsize 300hz (low Mids) and with the treble opened up it seems to empahsize 1000hz (high mids)

Remember I am not an electrical engineer, I am an Architectural designer who knows a little about electronics.

This would seems to back up Entwistle's perception of "the bottom dropping out" ... perhaps he should have said low mids dropped out?

 

[GeorgeBerlin]

If I read that correctly then with the treble rolled off the pbass seems to empahsize 300hz (low Mids) and with the treble opened up it seems to empahsize 1000hz (high mids)[...]

Yep, that sums it up, especially for the 300Hz point. The interesting find is that pot half-way up does both a gentle, not peaking rolloff of the treble as well as a true loss of level of effective bass, while (low) bass response is at max level with the pot either fully up or fully down.

If the two coils were wired in parallel rather than series, the resonance peak would be much more severe and about twice as high in frequency but the loss of bass at mid position would be much less.

As usual, Leo had it right the way he designed it, the bass loss was a compromise he had to make to get a musically useful (for most users at least) yet simple to implement tone control.

 

[MegaSwing]

No P bass player wants to admit there is a flaw. Too many people get their egos invested in their equipment, and saying that it isn't the best, is like saying they are less of a man

Wanna fight?

 

[MegaSwing]

I exited this thread for all of the hate directed at me. Saying the p-bass had a flaw on this site is like telling a religious zealot that there is no God.

But I see the thread has evolved into a useful discussion. <snip>

You can bet that's just a momentary aberration.

 

[DanBass81]

This is probably the thing right here. When a P bass Tone control is rolled back a certain amount, (a bit more than half way back usually) a relatively large resonant hump appears somewhere in the low midrange response. Depending on the particular pickup/cap/pot this may fatten up the tone considerably. This will often be interpreted/felt/heard as increased 'low end.' This additional 'low end' of course goes away as you roll the Tone pot back toward open, and Bob's your uncle.

This post is from page 7. I'm glad the thread has finally gotten back to the crux of the issue. The amount of misinformation in this thread is hard amazing.

 

[Kukulkan61]

Your right Edward G. and if God played bass it would be a 61 Fender P

 

[thiocyclist]

I think we are on the same page. I think a frequency shift may be the best way to describe what is happening. I think with an audio taper pot on the tone control. The shift would be smoother and you wouldnt have such a drastic like in your sound clip. As one frequency increases one rolls off and it would happen seamlesly.

I'm sure you are right that a lin pot would totally change the sweep pattern. Doesn't isher use lin? Think I caught that...

 

[BuffaloBass]

She wouldnt need no bass to make it thunder man.

 

[ggunn]

Is there a graph that shows a certain frequency at a higher output with a tone control rolled off vs a pickup wired with no tone control at all? If the level of that frequency never gets higher than the straight pickup output then it is not a boost.

It's that semantic thing again. It's not a boost; a passive filter cannot add energy to a circuit. It's conservation of energy, no perpetual motion machines, etc. No boost without a battery.

But (and I provisionally stand corrected on this) passive circuits can move energy around. I'm a long time out of engineering school (a very long time; I graduated with my BSEE before many of you were born) and my analog filter days, but my error in thinking was to disregard the considerable inductor in the circuit that is the pickup. An RC filter doesn't have a resonance peak, but an RLC filter does. Extreme ones are sometimes called "tank" circuits because they ring like an empty tank when they are excited. Think of a bass where no matter what note you play, its a Bb.

I have not heard the effect that touched off this branch of the discussion, and I cannot speak to how subtle or pronounced it is. A lot of what is or isn't there in a sound spectrum is in the ear of the listener and no one's ears are an objective measurement of anything. Beyond that, there are a lot of capacitor/inductor ratios out there in instruments, and resonance is a highly variable attribute of a circuit.

So who knows if it's real, i.e., audible? I dunno from firsthand experience, but what I do know is that I was incorrect to have assumed out of hand that it had to be solely psychoacoustical in nature. As Mythbusters would say, it's not busted.

 

[taurus1]

It's that semantic thing again. It's not a boost; a passive filter cannot add energy to a circuit. It's conservation of energy, no perpetual motion machines, etc. No boost without a battery.

But (and I provisionally stand corrected on this) passive circuits can move energy around. I'm a long time out of engineering school (a very long time; I graduated with my BSEE before many of you were born) and my analog filter days, but my error in thinking was to disregard the considerable inductor in the circuit that is the pickup. An RC filter doesn't have a resonance peak, but an RLC filter does. Extreme ones are sometimes called "tank" circuits because they ring like an empty tank when they are excited.

I have not heard the effect that touched off this branch of the discussion, and I cannot speak to how subtle or pronounced it is. A lot of what is or isn't there in a sound spectrum is in the ear of the listener and no one's ears are an objective measurement of anything. Beyond that, there are a lot of capacitor/inductor ratios out there in instruments, and resonance is a highly variable attribute of a circuit.

So who knows if it's real, i.e., audible? I dunno, but what I do know is that I was incorrect to have assumed out of hand that it had to be solely psychoacoustical in nature. As Mythbusters would say, it's not busted.

it's very subtle, I can hear it if I hold a note on the G string, it's not perceivable (to me) on the E, A or D string.
I hear absolutely no bottom end attenuation with the tone knob rolled back.

 

[Hopkins]

It's that semantic thing again. It's not a boost; a passive filter cannot add energy to a circuit. It's conservation of energy, no perpetual motion machines, etc. No boost without a battery.

But (and I provisionally stand corrected on this) passive circuits can move energy around. I'm a long time out of engineering school (a very long time; I graduated with my BSEE before many of you were born) and my analog filter days, but my error in thinking was to disregard the considerable inductor in the circuit that is the pickup. An RC filter doesn't have a resonance peak, but an RLC filter does. Extreme ones are sometimes called "tank" circuits because they ring like an empty tank when they are excited.

I have not heard the effect that touched off this branch of the discussion, and I cannot speak to how subtle or pronounced it is. A lot of what is or isn't there in a sound spectrum is in the ear of the listener and no one's ears are an objective measurement of anything. Beyond that, there are a lot of capacitor/inductor ratios out there in instruments, and resonance is a highly variable attribute of a circuit.

So who knows if it's real, i.e., audible? I dunno from firsthand experience, but what I do know is that I was incorrect to have assumed out of hand that it had to be solely psychoacoustical in nature. As Mythbusters would say, it's not busted.

That post you quoted was from a few pages back. I think I have it figured out. Its more of a frequency shift than a boost.

 

[SolarMan]

You can bet that's just a momentary aberration.

Yeah, we can't figure out if this is a flaw, a bonus, voodoo, or carrots.

I think someone needs to come up with a good car analogy.