Wiring diagram for a passive neck/active bridge setup?

[quoricsant]

I'm modding a guitar (2 stock passive pickups, single tone, single volume, 3-way switch) by replacing the bridge with an EMG81 (active) pickup. I really want to preserve the passive neck pup because -unlike the stock bridge-, it sounds really good (for cleans at least).
I actually already took the guitar -along with the pickup- to a luthier in hopes he would sort it out.
I asked him not to put a third pot (second vol) as to avoid drilling +holes on the gtr.
So he decided to try and have the same circuitry for both the active and the passive pups.
He left the original volume pot (500kohm) and the tone pot, but now the guitar has some problems:

1. The middle switch position is dead (only active bridge is on).
The luthier says it's because the 81 simply 'eats up' the passive neck. I really don´t believe that.

2. The gain on the bridge is noticeably higher
(Do I absolutely have to install a separate vol pot for each pup?
And if so, do I have to get an EMG PA2 on the passive neck pup to match the impedance/gains?
I read some about this on this site).

3. The TONE knob does NOT work for the 81 bridge pup (only works for the passive neck).

Can you point me to the correct diagram?
PLease help me I want to have a fully functional axe!

[quoricsant]

What's the value on the capacitor in that diagram?

[Mark Le Comte]

The cap tone pot will only work for the passive pup so use a value of cap for passive pups. Generally something like 0.042uF depending on what you like.

If you want to stick with only two pots, you should consider getting concentric pots. 500k/500k pots are pretty easy to find so you could have passive vol and tone. If you can find a 25k/25k pot you can also have vol and tone for the active. The both pups on position is still going to be screwed up though.

Look at the emg website support section. There is a FAQ section, I think the one wiring deals with options for combining active and passive pups.

[quoricsant]

What are the advantages -if any- of using separate vol pots -like in the diagram-, as oppossed to the 250/500k (not sure which) vol pot that the guitar originally came with for both the passive AND the active pickup?
Will this even out the differences in volume?

From the 'Wiring questions FAQ' of your site I found the following:

Can I mix EMG’s with passive pickups?
It is possible to mix EMG’s with passive pickups. There are three possible wiring
confi gurations; one is better than the other two.
Use the high impedance (250K-500K) volume and tone controls. The problem is that
the high impedance controls act more like a switch to the EMG’s. The passive pickups,
however, will work fi ne. If you have a guitar with two pickups and two volume pots, with
a three-way switch, there is another alternative. Use the 25K pots for the EMG, and the
250K pots for the passive pickup. This way you can use one or the other with no adverse
affects, but with the switch in the middle position the passive pickup will have reduced
3
gain and response.
Use the low-impedance (25K) volume and tone controls provided with the EMG’s. The
problem here is that the passive pickups will suffer a reduction in gain and loss of highfrequency
response.
This is the best alternative. Install an EMG-PA-2 on the passive pickups. There are
two benefi ts to doing this. With the trimpot on the PA-2, you can adjust the gain of the
passive pickups to match the EMG’s. The PA-2 acts as an impedance matching device
so you can use the low-impedance EMG controls (25K) without affecting the tone of the
passive pickups. You will also be able to use other EMG accessory circuits such as the
SPC, RPC, EXB, EXG, etc. For this application, we recommend ordering the PA-2 without
the switch for easy installation on the inside of a guitar.

Should I use a PA-2 -or maybe an EMG AB AfterBurner- to even out the volume of the pickups?

btw even though in the diagram the ground is connected to all three pots, the tone pot will only work for the passive neck, right?
..

[morkin]

1. The middle switch position is dead (only active bridge is on).
The luthier says it's because the 81 simply 'eats up' the passive neck. I really don´t believe that.

I have an Ibanez with the S/S/H setup, I rewired it and I have the same issue with position 4 (same as middle on a 3-way switch). It doesn't so much 'eat up' the passive as it just simply drowns it out because the active is putting out much more power.

I'm working on a theory for my guitar that might work on yours too. Added resistance on the output of the active pickup (before reaching the switch). It should be able to dampen the output power of the active pickup to the same level of the passive. I just can't figure out what value to use and if it will affect the sound adversely.

btw even though in the diagram the ground is connected to all three pots, the tone pot will only work for the passive neck, right?

Yeah, in order for the tone pot to work for the active there would have to be a separate capacitor connected to the active volume. In essence, when the active is 'active' its output bypasses the tone pot while the passive goes through it.

[quoricsant]

I have one other question

Is it ok to use the 500k volume pot for both pups instead of separate volumes? (500k for the passive neck and 25k vol pot for the 81)

[ryaniomitch]

i have a question

does anyone have an actual diagram for this because i bought alnico pro IIs and 81TWs with out realising how hard this is to do.


please give me a link to a diagram