P 90 " Dummy Coil " ..... a few very quick questions please ....

[ben ifin]

Hey all

I have put together a good working P 90 Dummy Coil setup using two identical P 90's ..... each P 90 is around 9 k.

Wired the Dummy P 90 in series and the hum cancel is basically perfect ie: %99.99 gone .... even with very high gain sounds at very high volumes there is virtually no 60 cycle hum.

Haven't really lost much top-end [ just a touch ] but I seem to have lost a bit of the P90 "oomph" / "grunt" / "output".

So ..... a few [hopefully] simple questions please:-

1 -> does the Dummy Coil Pickup *have* to be the same model and same " k " as the main pickup ?

2 -> can you use a Strat Dummy Coil with a P 90 ?

3 -> does it matter if the Strat Dummy Coil is only around 5 k and the P 90 around 9 k ?

4 -> is it correct that if I use a lower " k " Strat Dummy coil [ say 5 k ] with a higher " k " P 90 [ say 9 k ] main pickup, that the tone loss will be less but that the hum will higher ?

5 -> when installing a Dummy Coil, is it normal / expected that you will lose a bit of the "output" / "oomph" of the main pickup ?

And lastly ..... I have read that the dummy coil should be wired such that the winding direction of the dummy coil is opposite of the winding direction of the pickup to cancel the noise signal .... in my 2 x P90 example above, each P 90 has a ground, a white [hot] and a black .... so .....

6 -> as my main [live] P90 has the white [hot] wired to lug 1 on the Vol Pot and the Ground and Black both "grounded" ...... should the Dummy P90 actually have the black wired to lug 1 on the Vol Post and the White and Ground " grounded " ?

My sincere thanks in advance.

Ben

 

[Funkfingers]

Re: P 90 " Dummy Coil " ..... a few very quick questions please ....

The hum cancellation depends upon the coils used being (as near as possible) equal and opposite.

Pairing a P90 and a Stratocaster type can only be expected to provide partial cancellation.

If anybody ever produces a hum-cancelling replacement for the P90 that retains the tonal and dynamic qualities of the original, I shall buy it in bulk.

*

Knowing that we are only weeks away from the launch of the Fishman Fluence replacement pickups for Telecaster, I reckon that we cannot be too far away from a Fluence P90 style unit. (Frank Falbo probably already knows the situation but is subject to a confidentiality agreement.)

 

[uOpt]

Re: P 90 " Dummy Coil " ..... a few very quick questions please ....

There isn't a "tone loss". The frequency of the resonance peak is shifted as the capacitance, inductance and resistance of the combined coils change.

The change is different depending on whether you put the dummy coil in series or in parallel. Series has a lower resonance frequency, parallel has higher.

It is generally worth experimenting with putting them in parallel, upping the frequency of the resonance peak, and then using a carefully picked load capacitor to get the frequency back down. That will come closest to the original EQ, potentially at the same resonance frequency. There are still losses from having the dead coil float around of course.

An alternative is to use one preamp each for the coils, so that impedance is changed before you "join" the coils. That way the resonance peak never changes, except of course you now need a carefully picked load capacitor in front of the seeing (non-blind) coil to replace the guitar-to-amp cable capacitance that you just cut out of the picture.

 

[namklak]

Re: P 90 " Dummy Coil " ..... a few very quick questions please ....

The SD P-Rails uses two unmatched coils, and it hum cancels very well.

 

[Gibson 1964]

Re: P 90 " Dummy Coil " ..... a few very quick questions please ....

The Gibson H-90 does pretty well with partial cancellation. It is not fully humbucking, and they are hard to get as they only came on a custom shop guitar. But I got one and they work pretty well.