EMG active pickups preamp circiut schematic.

[Mike Sulzer]

So is anyone who wants to make clone of them.

No way. This is not a circuit I would use when you have both coils available separately. You can put an op amp, non-inverting, on each coil and add the outputs through resistors. If the coils are the same, you can make the amplifier inputs truly identical, adjusting the input resistance and capacitance for the sound you want. If you want to use different coils, you have the most flexibility in adjusting the input impedance and gain to get the sound and good hum cancellation.

[ubaid88]

No way. This is not a circuit I would use when you have both coils available separately. You can put an op amp, non-inverting, on each coil and add the outputs through resistors. If the coils are the same, you can make the amplifier inputs truly identical, adjusting the input resistance and capacitance for the sound you want. If you want to use different coils, you have the most flexibility in adjusting the input impedance and gain to get the sound and good hum cancellation.

I just need clean sound. I heard one of the Emgs it was as clean as acoustic guitar with high gain.

[David Schwab]

I just need clean sound. I heard one of the Emgs it was as clean as acoustic guitar with high gain.

EMG's are not hi-fi clean. They sound like regular pickups with a buffer.

If you want clean wind a low impedance coil and use a preamp to boost the level up. Just wind a regular humbucker with about 1000 turns on each coil. That will be as clean as an acoustic guitar.

[David Schwab]

I'm curious about how the cage is wired - is that (and any other metal) connected to a drain wire or braided shield that's sent to ground, separate from the beginning and end of the coils?

As far as I could tell is was grounded at the same spot as the coils were, which is the common ground.

It totally enclosed the pickup.

[David Schwab]

So is anyone who wants to make clone of them.

Not me. I was just curious how they had their coils arranged. I like my pickups better.

[Joe Gwinn]

I think every EMG made has the coils in parallel. That's one thing I don't like about the EMG-P.

In the circuit diagram, the coils are not in parallel. They are each connected to their own input of a differential amplifier, and so are electrically isolated from one another. Unlike a direct-wired electrical parallel connection, the coils do not load one another.

I have an old Bartolini Hi-A pickup with one coil being intentionally 1K different from the other, and it's dead quiet. I had it installed in one of my '74 Ric basses, and along with total copper foil shielding of the bass, I was able to remove the string ground with no noise whatsoever.

I make some bass pickups with similarly large offsets with no hum problems.

Perfect matching is not required to obtain adequate hum cancellation. Here is a simple numerical example:

Consider each coil as two voltage sources in series, the music source (Vm) and the hum source (Vh). The coils also differ in that they don't have the same number of turns and thus induced voltages, the ratio being called k, where k=1 if the coils are identical. All of k will be allocated to coil 2. The coils differ in that the algebraic signs of Vm and Vh are the same in coil 1, and opposite in coil 2, so:

Vc1=Vh+Vm but Vc2=k(Vh-Vm), the difference being the sign and the factor k.

A differential amplifier amplifies the difference between the two inputs, so (assuming a gain of one for now) we get

Vout= Vc1-Vc2= Vh+Vm-k(Vh-Vm)= Vh(1-k)+(1+k)Vm

If k=1, we get double the music voltage and complete cancellation of the hum voltage. But k is never exactly unity, so what is the effect of mismatch?

The cancellation ratio is (1-k)/(1+k). How large can k be to achieve 20 dB cancellation? For 20 dB, the cancellation ratio is one tenth, so 0.1=(1-k)/(1+k), and k= 0.8181, and 1-k=0.182. This means that if the coils are geometrically similar and differ in turns count by 18% or less, 20 dB or better cancellation will be achieved.

For 30 dB cancellation, 1-k= 6%.

Either way, take a look at the photo I posted of the circuit board inside the 81. That's where that schematic came from. The IC and one surface mount part is missing, but you could probably trace the circuit assuming they didn't use a double sided board. I've been meaning to do it but haven't had the time.

The usual with surface mount cards is to use two-sided boards, perhaps with components on both sides, unless the circuit is so simple that it's cheaper to implement crossovers with wire bridges and drilled holes. So, I'd photograph both sides of the circuit board, and be sure to identify one corner with a magic marker such that it's visible in both photos.

[Stan H]

If you want clean wind a low impedance coil and use a preamp to boost the level up. Just wind a regular humbucker with about 1000 turns on each coil. That will be as clean as an acoustic guitar.

Hi David, what size wire would you use for such a pickup, would 42 work or would you recommend something larger?

[David Schwab]

In the circuit diagram, the coils are not in parallel. They are each connected to their own input of a differential amplifier, and so are electrically isolated from one another. Unlike a direct-wired electrical parallel connection, the coils do not load one another.

I knew that! That's what happens if you haven't thought through what you are going to type ...

The EMG-P is in parallel, but not the humbuckers. But I meant to say they aren't in series as you would expect.

The usual with surface mount cards is to use two-sided boards, perhaps with components on both sides, unless the circuit is so simple that it's cheaper to implement crossovers with wire bridges and drilled holes. So, I'd photograph both sides of the circuit board, and be sure to identify one corner with a magic marker such that it's visible in both photos.

Now that I think about it, the other side of the board is the back of the pickup, so there are no parts...

[David Schwab]

Hi David, what size wire would you use for such a pickup, would 42 work or would you recommend something larger?

I did a bunch of bass pickups using 42 and 43. Generally you want heavier wire for a low Z pickup, but 42 worked fine.

I used a simple JFET preamp.

[Stan H]

Thanks for the info, David!

[Mike Sulzer]

Perfect matching is not required to obtain adequate hum cancellation.

Yes, I agree with your numbers. Another way of saying it is that you can approach 6 db better than implied by 1-k. That is, 1-k = .1 gives 25.58 db rather than 20 db, and 1-k = .01 gives 45.98 db rather than 40 db, while k-1=.31622 gives 14.53 db rather than 10 db, but only 4.53 db better than implied by 1-k.

But how much is good enough? Do you plan for the average environment, or the really bad one that might not be too common, but is still out there?

[David Schwab]

But how much is good enough? Do you plan for the average environment, or the really bad one that might not be too common, but is still out there?

It's very common to mismatch PAF coils, and look at all the people who play Strats and Teles!

So how good is enough? Some people don't seem to mind the hum at all.

[Mike Sulzer]

It's very common to mismatch PAF coils, and look at all the people who play Strats and Teles!

So how good is enough? Some people don't seem to mind the hum at all.

And look at how much effort there is to make strat pickups that sound like the original and have no hum.

[David Schwab]

And look at how much effort there is to make strat pickups that sound like the original and have no hum.

Oh I agree. I don't use single coils. You can get away with it in a club, but I do a lot of recording, so I need quiet pickups.

[Joe Gwinn]

Yes, I agree with your numbers. Another way of saying it is that you can approach 6 db better than implied by 1-k. That is, 1-k = 0.1 gives 25.58 db rather than 20 db, and 1-k = 0.01 gives 45.98 db rather than 40 db, while k-1=0.31622 gives 14.53 db rather than 10 db, but only 4.53 db better than implied by 1-k.

Yes. The music voltage Vm is doubled when the coils are exactly matched, and doubling voltage causes a 20 Log10[2]= 6 dB increase. As the coils become increasingly mismatched, the 6 dB will decline, but the effect isn't that strong.

But how much is good enough? Do you plan for the average environment, or the really bad one that might not be too common, but is still out there?

As a rule of thumb, 10 dB is quite noticable, 20 dB is pretty good (and would probably make the hum inaudible in a noisy venue), 30 dB is almost perfect, and 40 dB isn't any better than 30 dB in practice.

When people intentionally mismatch coils, the difference in turns count seems to be of order 10%, which would allow for very good cancellation: 20 Log10[(1-0.90)/(1+0.90)]= -25.6 dB.


This assumes that the electrostatic shielding is adequate. Perfectly matched coils are still susceptible to electrostatic pickup if not shielded.