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Discussion in 'Luthier's Corner' started by B_E_A_D_G, Aug 16, 2012.
Would 6 aa batteries work the same as one 9 volt in a bass? Something different
Wired in series, yes. And as near as I can tell from looking up generic battery performance statistics, 6x AA batteries should last longer than 1x 9V battery.
Your average AA battery gives ~2000 mAh of life with a constant 500mA draw, while the average 9V gives about 550mAh.
Of course, 6x AA batteries are considerably more expensive than a single 9V.
Interesting note: a single 9V battery actually contains 6 very small 1.5v batteries.
would last longer and be heavier
And take up much more room in the cavity. A 9v will last at least 6 months, so I would say its not worth it.
do the batteries in an 18v (two 9v) system last longer than a 9v system?
Also, do the batteries last longer if the treble and bass pots are set to "no gain)?
All else equal, yes.
It's kind of like gas in your car. If you don't drive much, or don't drive aggressively, then your gas lasts longer. Boosting the bands on your preamp requires energy, and that energy comes from the energy source (battery).
Edit: I should also point out that the above is purely academic. For all practical purposes, you should just play your ass off, and not worry about the batteries. Or go passive.
Nice. It looks like both guitar players are playing Mosrites. Back to regularly scheduled programming.
Not necessarily true. If wired in series then no they will not last any longer, they will be the same as a single battery, theoretically. If wired in parallel then they will produce 9V and they will last longer than a single 9V, but I'm nt exactly sure how much longer.
The hard bit would be mounting it into the guitar, small 9 volt battery holders can be easily blended into an existing finish
I recently contacted Walter at Cafe Walter about purchasing a PZP-1 piezo buffer for use in an upcoming build. I asked him about running the PZP-1 at 18V, and I'd like to take the liberty of including his response here - within the context of active circuitry, battery life, and at what point the battery voltage becomes insufficient, I feel his words are illuminating:
"Re transients: yeah, this is a real issue. The way to understand it
is: under percussive playing, a pickup can put out a brief voltage
spike of as much as 2 volts. Now, that doesn't sound like it should
be a problem for a 9V system, but that 9V has to power both positive
and negative signals; so effectively it is a +/-4.5V system. Still
not a problem, right? Well, if the battery is not fresh, it might be
more like 7V; so effectively +/-3.5V. Still no problem, right? Well,
the circuitry itself consumes some of that: most circuits (whether
discrete or opamp) can't swing all the way to the power rails, and
even if they can they usually can't do so very quickly. Generally you
can only get within about 1.5V of the rails, depending on the circuit.
So now, you're right up against that 2V spike; if there is any
voltage gain (such as what active EQ will do), you exceed the limits
of the amp.
Basically, an 18V system is massive overkill; even a consistent 10V
would be fine. But the 7 to 9V that a battery puts out is just...
not... quite... enough for all signals. The end result is that those
short transients get cut off. Now, that doesn't sound like distortion
as such, because the waveform really doesn't change much. But our
ears are sensitive to short sharp sounds, and when they go missing,
the whole thing just sounds a bit blurrier, warmer, less crisp. Fine
for some styles of playing - Jamerson sure didn't need transient
headroom - but not for others. If your playing style is percussive,
you will cut through the mix better if you can preserve those
The obvious corollary is that the amount of time it takes an 18V system to drop below "sufficient voltage" will be significantly longer than for a 9V system.
When you put it that way, yes. I was referring to completely dying, not dropping below sufficiency. My Carvin runs 18V, and has lasted me 10 months so far with no signs of dying anytime soon. I keep my treble gain high and my bass flat, not boosted nor cut. I have not ever used a 9V circuit so I cannot speak to the battery efficiency in such, I was just referring to the overall battery life differences between 9V battery circuits - series vs. parallel vs. single - from what I know of DC circuits from grade 9 science.
I'm fairly sure that internally, a 9v battery IS 6 smaller batteries.
It is, 6 1.5V cells.
DC power is DC power. Batteries all produce clean DC power with no ripple. The only thing you need to worry about is how the power source supplies for transient current demands, and how long it will supply a high current before the voltage drops. When you consider that most bass preamps draw somewhere between 85uA for the lowest power opamps, to a few milliAmps for higher current discrete FET based circuits, you really don't need to be worried about current consumption. You just need to make sure the supply voltage remains high enough that there are no headroom issues with the signal. Depending on the preamp, some find 9V sufficient, while others prefer 18V for improved headroom. In any case, if a preamp will run on either, keep in mind that the current consumption of Ohmic devices increases with supply voltage, so you have to weigh that against the change in battery capacity with combinations of multiple batteries versus one battery.
So... In a properly designed circuit, when a 9V battery outputs only 7V, the battery is pretty much dead. Voltage will remain relatively constant until the current drain becomes "too much", leading to a voltage drop. There are two reasons for a voltage drain becoming "too much". First, there is too little resistance to the circuit, but as I said, a properly designed(and built, actually) circuit should not have this problem. Second, the battery attempts to supply the proper amount of current, but is unable because it is almost literally "out of juice". It just can't supply the current at the proper voltage so the voltage falls off a cliff. had he said 8V, rather than 7, I probably wouldn't have said anything. But 7V is, for all practical purposes, dead.
The real benefit of an 18V system is that you can get essentially a +9V, -9V, and a neutral. This gives increased headroom(even a "dead" 7V battery will be plenty), the circuit doesn't have to "artificially" divide the single supply voltage.
So, now I'm just being picky, but batteries don't always produce clean power. I'd estimate that 99.999% of the time, it's not worth worrying about, but sometimes, in very sensitive systems it is necessary think about. This does not include audio.