EMG 9V to 18V with Push/Pull Switch and Battery Indicator Light

[alexreinhold]

Hi all, I am planning on wiring an 81/60 combo with a standard three-way switch. Instead of doing a full 18V-mod, I want to be able to switch from 9V to 18V by using a push/pull tone knob. I've read elsewhere that it's recommended to do this via series/parallel wiring (to drain batteries simultaneously I suppose?). I also want to install a PMT LoBat light indicator. Below you find the wiring diagram I prepared. I have three questions:

1. Is the wiring diagram correct?
2. Is there any risk to running batteries in series/parallel (note: it's the recommended way in another forum. But my physicist friend expressed doubts - though he wasn't sure)
3. Do you think the PMT LoBat will be able to account for the battery discharge correctly when wiring the batteries series/parallel?

[ArtieToo]

IMHO, parallel is what you want. (As you have it drawn.) The reason for this is that if your 9-volt option only uses one battery, then it can be at a level of discharge lower than the other. When you go to 18-volt, the stronger battery will try to recharge the weaker battery. Very bad, maybe even dangerous, with alkalines.

[PFDarkside]

Also, it looks like that device auto detects 9v/18v so I think it would work. It probably has several bands:
0-7.6v = low
7.7v-10v = good
10.1v - 15v = low
15.1v - 20v = good
etc.

[nexion218]

Whatever you do, double check the polarity of the current. I tried to do the same thing a while ago. Everything was fine except that accidentally I wired things up in a way that the setup supplied reverse current. Fried the EMG preamps in a heartbeat, turning my 81-85 set into passive PAFs....

[alexreinhold]

Given I'm an amateur, I am a tiny bit proud that I got that one right at first try :-)

@Nexion thanks for the advice. Will pay double attention.

[JB_From_Hell]

Before you go to the trouble of wiring this, have you tried them at 9 and 18 for a decent amount of time? 18 does make a difference, but IMHO, not enough to justify switching between the two on demand.

[Edgecrusher]

Before you go to the trouble of wiring this, have you tried them at 9 and 18 for a decent amount of time? 18 does make a difference, but IMHO, not enough to justify switching between the two on demand.

This was my thoughts too, It was never a sound that I felt i needed to switch between. Funny enough ive gone back to using just 9 volts, to me that is "THE" EMG sound.

[alexreinhold]

I've been very much in between the EMG 81/60 and 81x/60x. From what I understand, the x version is pretty much the sound of an 18V mod and comparing the two (in those Youtube shootout videos), I found the difference interesting (though you probably don't hear it in real life haha). But, here are some other reasons I will probably go ahead and do it:

1. I have no other use for a push-pull with EMGs and always wanted to try one
2. I have double battery life if I go for 18V
3. I will improve my wiring skills
4. I can brag to all my friends who understand what an 18V mod is (=no one)

[JB_From_Hell]

While we’re at it, at 9V, an EMG humbucker will go like 3000 hours. A battery life indicator isn’t necessary.

If you wire the batteries in series, you’ll be at 18V, but you will not double the battery life. The increased headroom you get from that scheme will use more juice than 9V. If you wire in parallel, you’ll double the battery life, but will not increase headroom for the “18V sound.”

[Mincer]

A few companies make proprietary systems that charge via USB like a phone. I wonder if aftermarket pickup companies are working on such a thing.

[Edgecrusher]

I've been very much in between the EMG 81/60 and 81x/60x. From what I understand, the x version is pretty much the sound of an 18V mod and comparing the two (in those Youtube shootout videos), I found the difference interesting (though you probably don't hear it in real life haha). But, here are some other reasons I will probably go ahead and do it:

1. I have no other use for a push-pull with EMGs and always wanted to try one
2. I have double battery life if I go for 18V
3. I will improve my wiring skills
4. I can brag to all my friends who understand what an 18V mod is (=no one)

Negative ghost rider. The EMG 81x's and 60x's are not the sound of the 18v mod. The EMG X's have a preamp that has 6db less output to get more headroom that way and they have an active tone control.

The function of both was to increase headroom but when you reduce the preamp gain it has a different effect from using 18 volts of power. Bascially a 81 at 18volts has the headroom AND the gain. If you think about whats happening, the 81's with less gain are basically allowing you to smash the strings 6db more before they start clipping. Where the 18v mod gives the preamp more reserve power when you hit the strings hard before it clips. They arent radically different sounding but they are different.
Coincidently 81x's at 18v's sound like pewp.

[ArtieToo]

While we’re at it, at 9V, an EMG humbucker will go like 3000 hours. A battery life indicator isn't necessary.

Not only that, but your average LED will draw 10 - 15 times more current than the pups themselves. It would be like having a gas powered gas gauge.

[alexreinhold]

While we’re at it, at 9V, an EMG humbucker will go like 3000 hours. A battery life indicator isn’t necessary.

If you wire the batteries in series, you’ll be at 18V, but you will not double the battery life. The increased headroom you get from that scheme will use more juice than 9V. If you wire in parallel, you’ll double the battery life, but will not increase headroom for the “18V sound.”

Regarding the battery life indicator - having been in the situation where batteries went dead, I just want to avoid the constant panic that it might happen again. It's a gimmick worth 15 bucks I think. Also it's kinda cool to have a tiny LED light up when you put in the plug.

Regarding the series/parallel. Yeah - but that's the whole point, isn't it? I expect to be in parallel (9V) most of the time because I prefer the classic 81/60 sound but might move to series (18V) for certain clean tones or when I want to increase headroom. So I stay flexible, and assuming, I will in fact be in parallel most of the time, increase battery life.

[alexreinhold]

Not only that, but your average LED will draw 10 - 15 times more current than the pups themselves. It would be like having a gas powered gas gauge.

From what I've read about that specific product (PMT LoBat-Active), it does not reduce battery life: "Super low current draw will not reduce battery life"

[ArtieToo]

From what I've read about that specific product (PMT LoBat-Active), it does not reduce battery life: "Super low current draw will not reduce battery life"

And they're probably right. I'm accustomed to "old-school" LED's that typically drew 10 - 15 ma's. Active pup sets generally draw less than 1 ma. I'm probably behind the times on technology.