need schematic for hum cancelling jazz bass pickups

[odyyiannis]

Hello everybody,
new in town,
I need a schematic for hum canselling vintage style jazz bass pickups, I am planing to use it as input stage (buffer) to an existing 3band eq.
I was looking for info in old posts with no lack.
Thank you in advance,

Yiannis Ioannides.

[David Schwab]

You want a schematic for a pickup? Pickups don't have schematics.

[odyyiannis]

Hi David,
thank you for answering in my thread and I know that you have the answer to my question,as you mention about it at list two times in your older posts. You see I have spend many hours during last 4 years reading the pickup forum.All the infos I got from all of you help me a lot in my work (I am bass builder since 1992).
I am very grateful to all of you for that knowledges.
I have setup a winding machine and make many tests and came with the results that pickup building its very simple-complicated !!! no final product till now but I like it.
You write that active hum canselling pickups color the sound but I want to give it a try and if I have good results I will post it (I have 6 years experience with on board preamps).

Thank you for your time,
All the best to you and ours,
Yiannis Ioannides.

[David King]

Welcome to the pickup-maker's ghetto Yiannis,

A buffer schematic with balanced input?

If you don't need the balanced input I'd think just a J-fet stratoblaster might work.

Undoubtedly there are dozens of dual input buffer chips with very low noise, low current draw. The datasheets will supply all the schematics you'll probably ever need.

[David King]

THAT 1510 and 1512 seem like they might be of interest if you are looking for an opamp that's still available in a DIP8. The specs are all pretty good until you get to current draw which is a whopping 6ma, about 10 times more than your typical LM442 etc.

[odyyiannis]

Hi David,
thank you for your replay,
stratoblaster will amplify hum to from a jazz bass single coil, so it's not work for me,
THAT 1510 seems to be nice but 6ma current draw is to high for on board preamp (ideal will be under 1ma).
The devise it's not necessary to be DIP8 package, can be surface mount ether (I can soldered at the back side of pcb board).
Well that's all for now,lets hear a nice song,
dedicated to all forum members.
Johnny Cash - I've Been Everywhere - YouTube

[David King]

Try this then: LS204

[odyyiannis]

Thank you David,
need to do a research and I'll come back.

[Mike Sulzer]

stratoblaster will amplify hum to from a jazz bass single coil, so it's not work for me,

As will any preamp. They all amplify the signal and magnetic hum together. The problem with a sc pickup is that it does not cancel hum from magnetic fields as a humbucker does. No preamp, not even differential input can do that. Magnetic hum must be canceled using two or more coils

[odyyiannis]

Hi Mike,
transformer maybe?

[Mike Sulzer]

Hi Mike,
transformer maybe?

No, same problem as a differential amp. The pickup uses the law of magnetic induction to sense the string and hum fields. You need to use the same law to cancel it.

[David King]

All those "noiseless" J pickups are either stacked coils or split coils or single string coils with equalized turns*areas.

[David Schwab]

All those "noiseless" J pickups are either stacked coils or split coils or single string coils with equalized turns*areas.

Not all of them. Both the Joe Barden and my Neo Jazzbuckers are dual rail humbuckers. I also make sidewinders in a J case. But stacks and splits are the most common.

[David King]

Oops! sorry I forgot about the rails and hbs! I'll go taste a 9v battery and repent for my inattention.

[odyyiannis]

Hi guess,
interesting, so options are:stacked coils (not so good alternatives for me),split coils (sound's good, but not 100% hum free particularly 5 strings),single string coils (not familiar with them),rails (as I hear David's Schwab's sidewinders they worth a check),hbs (?).
According to your opinion witch ones are the best alternatives ?

[odyyiannis]

I think we have to rename the post to "JB noiseless alternatives"

[David Schwab]

Hi guess,
interesting, so options are:stacked coils (not so good alternatives for me),split coils (sound's good, but not 100% hum free particularly 5 strings),single string coils (not familiar with them),rails (as I hear David's Schwab's sidewinders they worth a check),hbs (?).
According to your opinion witch ones are the best alternatives ?

Stacks are OK. EMG Js are stacks. They are a little lower in volume, and tend to be very bright unless you over wind them. Split coils are very quiet. Listen to a P bass. There are a lot of Jazz pickups made that way. There's different ways to handle five strings, but for that reason I avoided split coils.

The one thing that is missing in most Jazz pickups is shielding, and the magnets are not grounded. We don't have to slavishly copy somewhat flawed designs from the past. You can improve upon them.

[odyyiannis]

stacks EMG are ok, most of bass players I know agree with that, but they don't want them in there basses.Split coils are ok to, but recently I send a 5string bass with Bart's split coils to a friend in Boston and he have a bud noise at his home (bud home electrics) without heaving the same noise with is fretless (Bart's humbuckers) at gig was all ok.

[odyyiannis]

The one thing that is missing in most Jazz pickups is shielding, and the magnets are not grounded. We don't have to slavishly copy somewhat flawed designs from the past. You can improve upon them.

an easy and effective way to ground mag's in jazz pickups is:before inserting magnets in forbon holes (bottom side),I use a reamer on each hole at half thickness of forbon,then I stick copper foil to the bottom, and I insert the magnets into the forbon.This way the copper foil goes into the holes with the magnets providing contact.Works always.
I have attached a photo witch I hope will appear.

[David King]

The 5 string splits aren't that hard to do, you just have to wind some extra turns on the 2 string segment and then make the magnets a little less powerful, probably the easiest way to do that is to make them a bit shorter. It probably makes sense to use a AWG 43 on that 2 string segment while you are at it just to have room for those extra turns. Id say the biggest problem with the splits is the phase shift of the strings on either side of the split which tends to knock the amplitude of those wrings down a bit. I'm pretty sure this is why Bartolini decided to go with 5 individual coils. You can't mix and match with other types of pickups however.

[David Schwab]

The 5 string splits aren't that hard to do, you just have to wind some extra turns on the 2 string segment and then make the magnets a little less powerful, probably the easiest way to do that is to make them a bit shorter. It probably makes sense to use a AWG 43 on that 2 string segment while you are at it just to have room for those extra turns.

I think that would make the 2 string part sound very different from the 3 string part. UNless that's what you want I wouldn't wind each half with different gauges of wire. As far as weaker magnets, I wouldn't do that either.

Id say the biggest problem with the splits is the phase shift of the strings on either side of the split which tends to knock the amplitude of those wrings down a bit.

Works fine on P basses and on split Jazz pickups. The two coils are out of phase, and have opposite magnetic polarity, so they are in phase with the strings.

I'm pretty sure this is why Bartolini decided to go with 5 individual coils. You can't mix and match with other types of pickups however.

Actually if you read the patent, he made smaller coils for two reasons. One was because the first Hi-A pickups had separate outputs for each string. The main reason is because smaller coils are clearer sounding.

From patent 3983778:

Since both the inductance and capacitance of a sensing coil vary linearly with its mean radius, replacing one coil by multiple small coils can reduce the impedance of the pickup system by a factor equal to the number of coils and raise the self-resonant frequency by a factor equal to the square root of the number of coils.

[odyyiannis]

Last weekend I make some tests with split coils and seems that David King have right.
In two identical coils,were inner leads are connected and outers goes to hot and ground, the ground side coil was brighter sounding than the hot side coil ?
I try to unwound some turns to get same treble respond but I've got different output.
I check Nordy's split-5, in Bridge p-up the difference was not so noticeable but in neck p-up it was,the 2 bass strings was far dark sounding.
I didn't try David's suggestion yet (shorter mags with more turns in dark sounding coil) but I am afraid that some other problem will appear like output or different sound character.

[David King]

Winding is the easy part but getting everything to match up is going to take a lot of experimentation as there don't seem to be any straightforward rules. Again the problem with split J 5s is that unless you limit your turns or go with much taller coils you won't have room for 42 wire between the 2 halves of your splits.
Others have managed to do splits that sound OK so it's possible. It may be that the 43 will actually brighten the tone, especially if it's a heavy insulation.

David Schwab, -alternating magnetic and wind polarities all the way across will also eliminate the unevenness of some adjacent strings being in or out of magnetic phase as found on typical split coils, this is less a problem on bass where the strings are further apart but definitely a problem on guitar. Bill Bartolini doesn't mention it in the patent but that doesn't make it less of a problem...

[Mike Sulzer]

Actually if you read the patent, he made smaller coils for two reasons. One was because the first Hi-A pickups had separate outputs for each string. The main reason is because smaller coils are clearer sounding.

From patent 3983778:

Since both the inductance and capacitance of a sensing coil vary linearly with its mean radius, replacing one coil by multiple small coils can reduce the impedance of the pickup system by a factor equal to the number of coils and raise the self-resonant frequency by a factor equal to the square root of the number of coils.

Right on part of it, but if you put the coils back in series in order to get a single output, then the inductance is back nearly to where it would be with a single coil. So you have not gained anything there. So it is not going to sound more clear.

[David Schwab]

So it is not going to sound more clear.

Have you tried it? It actually does. A perfect example is the Wal pickup. Each coil has 10,000 turns of 42, and reads about 2.5k. On the model I have here, there are eight coils, with each row of four in series. So each row is 10k. You would think it would be a dark sounding pickup, but even with all the coils in series it's thick yet bright sounding.

If you wound a two coil humbucker up to 20k with 42 AWG it wound be mud, as in the case of the Gibson EB-0 pickup.

So the only difference between these two are the multiple coils.

You can also hear it in the Bartolini pickups that use multiple coils.

[Mike Sulzer]

If the best you can do is to compare to a different pickup made by Gibson, I will stick with the obvious: if winding four small coils makes the inductance one quarter of a larger coil, then the inductance goes back up when you put them in series.

You quoted the Bartolini patent. This means that you believe what he wrote; that is, that four small coils, used individually, each have one quarter of the inductance of the larger coil (at least approximately), and you deduce that this makes the sound clearer. Then to be consistent, you have to believe that putting the coils back in series makes the inductance the same as the original larger coil, and that this is the less clear sound. You do believe that things have to be consistent, right?

By the way, while I have your attention, have you made any progress in understanding how the guitar string changes the reluctance of the magnetic pickup circuit without becoming magnetized? As far as physics is concerned, the only interaction is the alignment of the atomic currents, which is magnetization. If there is another form of interaction, the world wants to know!

Have you tried it? It actually does. A perfect example is the Wal pickup. Each coil has 10,000 turns of 42, and reads about 2.5k. On the model I have here, there are eight coils, with each row of four in series. So each row is 10k. You would think it would be a dark sounding pickup, but even with all the coils in series it's thick yet bright sounding.

If you wound a two coil humbucker up to 20k with 42 AWG it wound be mud, as in the case of the Gibson EB-0 pickup.

So the only difference between these two are the multiple coils.

You can also hear it in the Bartolini pickups that use multiple coils.

[David Schwab]

If the best you can do is to compare to a different pickup made by Gibson, I will stick with the obvious: if winding four small coils makes the inductance one quarter of a larger coil, then the inductance goes back up when you put them in series.

But it doesn't sound like two large coils. Does it? Oh wait, I will stick to the obvious too. You never tried it.

You said: "So it is not going to sound more clear." But that's not true. Explain why that is. As I pointed out in the example of the Wal pickup. It has eight coils wound with 10,000 turns of wire each. In series it's 20k, but does not sound like a pickup with two coils wound to 20k with the same gauge wire. This isn't conjecture on my part. I have the example pickups right here.

I asked if you tried it. Have you? If not, why are you commenting on it?

Mike, you like to state that the Bartolini patent is wrong, yet he's actually making pickups based on that, and they do what he said they do. So his goal was successful. If you care to build some pickups to demonstrate why he's wrong, be my guest.

Regarding the string being magnetized; as I have have said before, of course the string becomes temporarily magnetized. But that's swamped by the permanent magnet's field. You can see this by removing the permanent magnet and hearing that the pickup does not work very well. So the variable reluctance model makes more sense. Without the main magnet in the pickup, the magnetized string barely creates a signal. The fact that the string is magnetized is secondary to the string disturbing the permanent magnet's field.

[Mike Sulzer]

Single sgtring coils are one of the things I do. If you check back several (well, maybe, many) years in the MIMF archives, you will find a discussion where I described alternating the magnetic and electrical polarities and connecting the coils in series to make a strat bridge pickup, The inductances do add up, as they must. In this case, the total inductance was still below what most Strat bridge pickups have, and so it was a sort of clean sounding pickup (unless you added some capacitance in parallel). In every case I have tried, the sound of the series combination is exactly what you would expect from the total inductance. I think you need to make more careful A-B tests.

The steel used for strings retains very little magnetization. When you remove the magnet, it drops to a very small value immediately. That shows that the string magnetization is an essential feature of the pickup.

You are treating "reluctance" as if it is an independent property of the interaction of a magnetic material with a magnetic field, independent, that is, of the magnetization. It is not. It is a quantity that is defined as a matter of convenience in order ta allow a convenient analogy between electric and magnetic circuits.

So, do you see why I am asking you to show where reluctance comes from if not from the magnetization? If it is an independent property, it must have some physical basis. What is this?

But it doesn't sound like two large coils. Does it? Oh wait, I will stick to the obvious too. You never tried it.

You said: "So it is not going to sound more clear." But that's not true. Explain why that is. As I pointed out in the example of the Wal pickup. It has eight coils wound with 10,000 turns of wire each. In series it's 20k, but does not sound like a pickup with two coils wound to 20k with the same gauge wire. This isn't conjecture on my part. I have the example pickups right here.

I asked if you tried it. Have you? If not, why are you commenting on it?

Mike, you like to state that the Bartolini patent is wrong, yet he's actually making pickups based on that, and they do what he said they do. So his goal was successful. If you care to build some pickups to demonstrate why he's wrong, be my guest.

Regarding the string being magnetized; as I have have said before, of course the string becomes temporarily magnetized. But that's swamped by the permanent magnet's field. You can see this by removing the permanent magnet and hearing that the pickup does not work very well. So the variable reluctance model makes more sense. Without the main magnet in the pickup, the magnetized string barely creates a signal. The fact that the string is magnetized is secondary to the string disturbing the permanent magnet's field.

[David King]

My thinking is that the Barts sound cleaner because:
1) He's using Ceramic 8 magnets (at least on the bass pickups)
2) More of the wrap wire is closer to the magnets than on a single longer coil.
I don't know why having more wire closer to the iron poles increases brightness but it seems to.

I'd also argue with anyone who wants to argue that the single string coils have less DCR resistance (less wire length) overall per number of strings for a given number or turns than a traditional coil. Not sure what effect this will have, most likely just less overall capacitance, hence brighter.

[Mike Sulzer]

Less overall resistance, if it is significant, raises the Q of the resonance, giving a brighter sound.

If winding for the same number of turns gives a lower resistance, then winding for the same resistance could give more inductance and a less bright sound. So I think you need to know exactly what A and B are.

My thinking is that the Barts sound cleaner because:
1) He's using Ceramic 8 magnets (at least on the bass pickups)
2) More of the wrap wire is closer to the magnets than on a single longer coil.
I don't know why having more wire closer to the iron poles increases brightness but it seems to.

I'd also argue with anyone who wants to argue that the single string coils have less DCR resistance (less wire length) overall per number of strings for a given number or turns than a traditional coil. Not sure what effect this will have, most likely just less overall capacitance, hence brighter.

[Marko Ursin]

David & Mike; I have an 10-coil pickup on my bass. Each coil is 1,75kOhm, 10 000 turns of 42AWG on each coil. It sure has thick low end and still sounds clear. How does wiring those coils 5 in series, then 2 rows parallel compare to 2 coils in series and 5 pairs in parallel? I find 5s 2p has more output and slightly more bass, when 2s 5p has a bit less output and a bit clearer sound. Why is that? I don't understand even half of what you are talking but I sure can hear what the pickup sounds like.
Marko

[Mike Sulzer]

David & Mike; I have an 10-coil pickup on my bass. Each coil is 1,75kOhm, 10 000 turns of 42AWG on each coil. It sure has thick low end and still sounds clear. How does wiring those coils 5 in series, then 2 rows parallel compare to 2 coils in series and 5 pairs in parallel? I find 5s 2p has more output and slightly more bass, when 2s 5p has a bit less output and a bit clearer sound. Why is that? I don't understand even half of what you are talking but I sure can hear what the pickup sounds like.
Marko

Yes, those two configurations should be significantly different. First, let's look at the inductance; Assume each coil has an inductance of x Henries. Make two sets with 5 in series. Each set has an inductance of 5x since inductances in series add. Now put the two sets in parallel; this makes the total inductance 5x/2. For 2s 5p case, each set of five has an inductance of x/5, and two in series have 2x/5. The ratio of the 2s 5p to 5p 2s is 4/25. When you combine this with the cable capacitance, the resonant frequency is increased by sqrt(25/4) = 5/2. This is more than a factor of 2 and should make quite a difference, the exact audible difference depending on how these frequencies relate to the useful range of the instrument.

For the output, assume that each each coil puts out y volts, and the impedance of a single coil is Z. Five coils in series have an impedance of 5Z. You can think of the 5s 2p case as a voltage divider where the top and bottom legs each have an impedance of 5Z. y volts coming from one coil is feeding the top leg, and the bottom leg then attenuates this to y/2. For the 2s 5p case, the five in parallel act like a voltage divider where the top leg has an impedance of Z, and the bottom leg has Z/4. This gives a voltage of y/5. So the 5p 2s has a voltage 2/5 as great. This is about 4 db down.

I am ignoring any loading effect of the following electronics, which could alter these results somewhat, but you can see approximately what is happening.

If you did 10s, you would get more output, but the inductance would be 10x, and the resonant frequency would be low, giving a less clear sound.

[Mike Sulzer]

Although I have not tried this, it seems likely string sampling effects are important in a bass as well as a guitar. (Sampling the string: differences between single coil and) This should be more of a problem when playing with a bright tone and not using flat wound strings. With a four string bass, it is easy to get hum canceling without using a humbucker like pickup where each string is sampled in two places, but it is harder with five strings.

The results of the discussion referenced above suggest a solution. One of the results of the discussion was that the filtering applied to a string by the two point sampling is a big effect on the no. 6 E string, but a small effect on the highest frequency strings. I would expect the effect to extend more across the strings on a bass, but still, the effect should be least on the highest frequency string.

The suggested solution is to use an individual coil on the four lowest frequency strings, alternating the magnetic and electric polarities in the usual way to get hum canceling. Then the fifth string would use a pair of coils, each about half the number of turns of the others, arranged along the string in the usual way and polarized for humbucking. All coils would go in series, wound with the number of turns necessary to give the required total inductance,

[David Schwab]

Mike, the pickup in question, which is also the same pickup Marko is speaking of, has two coils per string. So it is a conventional humbucker.



Each row measures 10k. In parallel with the next row would of course be 5k. But it still sounds very different from a pickup with two coils wound the same, and wired the same.

It even sounds very clear if you wire the two rows in series. I've tried this. What I said earlier, which you didn't think was relevant, was that in series at 20K it was very clear, which a thick sounding low end, and bright top end. In comparison a two coil sidewinder wound to 20K, e.g., the Gibson mudbucker, has very little high end and a very pronounced midrange. I'd speculate that the mudbucker has more wire on it, but I don't know that for sure. The Wal pickup has 10,000 turns on each of it's small coils, so it's still not small amount of wire. Both pickups are wound with 42AWG.

[David Schwab]

I'd also argue with anyone who wants to argue that the single string coils have less DCR resistance (less wire length) overall per number of strings for a given number or turns than a traditional coil. Not sure what effect this will have, most likely just less overall capacitance, hence brighter.

They clearly have a higher resistance than a single similar size coil, and more turns as well. But they don't sound like a single coil wound to the same resistance.