Is it possible to wire my p/j bass with 2 volumes in series? I couldn't find diagram. Only v/v/t with a series/parallel switch. Can someone help, please?
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P/J wired V/V in series
- Thread starter BassFace13
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LoveThatBass
Supporting Member
If
I tried a P and J in series once and it did not turn out well tonally. 2 J pickups in series works well
I wouldn't expect good results. That's a lot of wire, so it is likely to sound hot and midrangey.
LoveThatBass
Supporting Member
That was what I expected but what I found surprised me. Probably because of the impedance mismatch and maybe other factors it lost it picked up more noise and sounded kinda flat to me.
You guys are probably right, but I'm hoping it solves the issue of the bridge pickup (that I had laying around) having much less output than the neck pickup.
LoveThatBass
Supporting Member
Try reversing the leads from the J pickup first. I had weak output of the jazz pickup on my P/J bass until I did that. Maybe it will help
LoveThatBass
Supporting Member
If that does not help, put the wires back as they were and then physically turn the J pickup around. This helped on one Jazz bass I had. It may or may not help but it is free to try before spending money.
Why would you want this? Wouldn't one volume control shut down both pickups? You wouldn't be able to solo either pickup.
Unless I'm missing something.
Nope. The way that the scheme works is that the two pickups are placed in series, and then a pot is placed across each pickup. When you turn a volume down, a load is placed across a pickup, simultaneously decreasing the output of that pickup, and allowing the signal from the other pickup to flow through the resistance of the pot. For example, if you were to solo the bridge pickup by turning the neck pickup's volume all the way down, then the pot would present a 0 Ohm load on the neck pickup, completely shorting it out. The bridge pickup's signal would then have a direct connection to the output, through that 0 Ohm path of the volume pot.
So the pickups are in series, and the pots are effectively in parallel with the pickups? And if I'm understanding it correctly, the normal configuration is to have the pickups in parallel, with the volume controls in series with each pickup, right?
Yes, the pickups are in series, with a pot parallel to each pickup.
In a standard parallel pickup configuration, the volume pots have both series and parallel resistances. The series resistances are between the pickups and the output, while the parallel resistances are between the pickups and ground. It helps to think of what the pots actually do in the circuit. If you look at the circuit for one pickup and its volume pot, what you have is a resistance across the output jack, with the pot varying the point at which the pickup "taps into" that resistance. If you have a 500k pot, there will be some point in the rotation where the pickup has a 100k path to the jack and a 400k path to ground. And another point where the pickup has a 200k path to the jack and a 300k path to ground. And so on.
With the series wiring, the volume pots don't work that way. Rather, each volume pot simply varies the resistance of a path across (parallel to) each pickup. If a volume pot is turned all the way down, the result is that one pickup is completely shorted out, and the other sees a direct connection to either the jack or ground.
OK, so I did understand the standard configuration correctly, including the pots being in parallel to ground part.
It seems like doing it the other way opens a can of worms. What happens if you turn down both pickups? Are you shorting across each pickup simultaneously? If so, from the amp's perspective, how is that any different than just shorting the end of a guitar cable?
It seems like doing it the other way opens a can of worms. What happens if you turn down both pickups? Are you shorting across each pickup simultaneously? If so, from the amp's perspective, how is that any different than just shorting the end of a guitar cable?
When you turn both pickups down, there is no output. It is exactly the same as just shorting the end of a guitar cable.
I must be missing something. Any time the end of a guitar cable is shorted, the amp doesn't like it at all -- pops, loud hums, things like that, certainly nothing musical.
In the standard configuration, turning the pickups down to zero means that at the end of the cable there's several hundred thousand ohms, not zero ohms.
In the standard configuration, turning the pickups down to zero means that at the end of the cable there's several hundred thousand ohms, not zero ohms.
When you turn the volume pot all the way down on a single pickup passive bass, a Precision for example, the volume pot is shorting the end of the amp cable to ground. There is no issue with this. When you unplug your amp cable and touch it to various bits of metal or touch it with your fingers you get all kinds of pops and hums and etc. That doesn't happen when you turn a volume pot down because the circuit is always connected and the ground that you are shorting the tip of the amp cable to is the ground that the amplifier considers to be a good ground.
Are we using the word "short" the same way?
Lin6eman's explanation makes sense to me. The idea that there is no resistance across the output jack, when the pickups are turned all the way down, does not make sense to me.
I understand what you are saying about transient pops and hums when touching a cable with fingers or metal (plugging, unplugging, etc.), but in my experience, the hum continues when the contact is steady.
The embarrassing thing for me here is that I have had some training in electronics. But it was over 30 years ago, and most of it has leaked out, so here I am asking questions and trying to wrap my head around concepts.
This is 100% incorrect. When you short the input of an amp, what you get is complete silence. There is nothing for the input gain stage to conduct. This is the opposite of having hum or pops or whatnot. If you look at any bass with a master volume pot, the typical wiring is for the wiper terminal to be the output, rather than the input. This is the preferred way of wiring a volume pot, and it reduces output impedance to zero, when the volume is turned all the way down. (The reason you can't do it with dual volume configurations is that the volume pots can't function independently, so the wiper terminals get used as inputs, instead.) Additionally, if you look at instruments with killswitches, the quietest way to wire them is to let them directly short the output jack. Not only is it very common to let your output jack totally short out, it is the most preferable thing you can possibly do to make an instrument quiet when you want it to be.
