38AWG and me...

[bbsailor]

Joseph,

You are quite right that you can (and should) add capacitance to get the best sound for the particular application. This is an option that is often overlooked.

I partly disagree with you about the noise pickup. Low impedance pickups are much less sensitive to pickup from electric fields; there is no doubt about that. But for magnetic fields, I believe it works out to the same. Suppose you decrease the number of turns by some factor. The voltage pickup from both the strings and stray magnetic fields decreases by the same amount. The voltage gain in the transformer then amplifies both, and the signal/hum ratio is no different.

Mike,

One point to consider is that lower impedances are less succeptable to noise than higher impedances. If a low Z coil has 300 to 500 turns is has about one tenth the turns of a high impedance pickup and has 100 times lower impedance. Assume that the transformer is in a shielded can, which it is, then the transformer will pickup minimal additional noise mounted at the amp.

The noise induced in the 300 to 500 turns will be much less than 5000 or more turns of AWG 42 immersed in the same magnetic field. I can use a low impedance Alumitone pickup within 2 ft of my computer and monitor with no external noise. I can not do that with a high impedance humbucking pickup, as I must orient the guitar for minimal noise. Try it and see for yourself.

Joseph Rogowski

[Mark Hammer]

While minimal noise/hum, and decent level, are certainly design objectives, another design objective is also aiming for certain resonant peaks by means of coil properties.

As one who has spools of #36, 38, 39, and 40 wire, can I safely assume that I could wind myself coils of whatever gauge and however many turns and, provided I found myself a matching transformer with suitable primary and secondary properties to match the pickup to the milieu, it would "work"?

[bbsailor]

While minimal noise/hum, and decent level, are certainly design objectives, another design objective is also aiming for certain resonant peaks by means of coil properties.

As one who has spools of #36, 38, 39, and 40 wire, can I safely assume that I could wind myself coils of whatever gauge and however many turns and, provided I found myself a matching transformer with suitable primary and secondary properties to match the pickup to the milieu, it would "work"?

Mark,

Is there concensus about which resonant peaks are desireable or do people just go by trial and error until they find one they like or use one with known properties? The term "work" is where the subjective evaluation comes in.

I am only suggesting an alternative with easily obtainable off-the shelf parts (ShureA95U transformer) and pickup bobbins wound with 1/10 the number of turns to have a impedance range 100 times lower so that 2.5K to 5K pots can be used in a low Z design opening up a new palate of potential sounds and reduced noise pickup.

You only need one high quality Shure A95U transformer on the amp end to use with many guitars. I am only suggesting that there are alternatives to high impedance pickups where noise is a problem. I can make a pickup out of almost any magnet, any piece of wire and a low Z to high Z transformer.

You can even connect a piece of wire to a string beind the nut and loop it through a CST1005 current transformer, connect the other end behind the bridge and obtain sound from the current transformer when connected to an amp.

Output level, noise, tone and the environmental effects require some tradeoffs. Les Paul worked at the low Z microphone level with his recording guitar many years ago. Today, most commercial microphones are low impedance to minimize the effects of long cables but guitars have stayed high impedance because the amps and guitar pickups continue to be made high impedance.

I see no reason why guitar pickups cannot be made to have the noise advantage of low impedance and the tonal advantage of on-board tone shaping to replicate their favorite single coil or humbucking pickups.

I do not disagree with what you said.

Joseph Rogowski

[Mike Sulzer]

Mike,

One point to consider is that lower impedances are less succeptable to noise than higher impedances. If a low Z coil has 300 to 500 turns is has about one tenth the turns of a high impedance pickup and has 100 times lower impedance. Assume that the transformer is in a shielded can, which it is, then the transformer will pickup minimal additional noise mounted at the amp.

The noise induced in the 300 to 500 turns will be much less than 5000 or more turns of AWG 42 immersed in the same magnetic field. I can use a low impedance Alumitone pickup within 2 ft of my computer and monitor with no external noise. I can not do that with a high impedance humbucking pickup, as I must orient the guitar for minimal noise. Try it and see for yourself.

Joseph Rogowski

I believe the alumnitone is a humbucking design, right? Then the reason it rejects magnetic field interference is that it is carefully designed and constructed to get good cancelation. As for the interference from electric fields, you are quite right: the impedance of an inductor goes with the square of the number of turns, and so a single turn pickup is extraordinarily insensitive to electric fields even without shielding. Normal humbuckers do not reject all that well since the two coils in many designs do not have the same sensitivity to magnetic fields. And if run without the cover, they have some sensitivity to electric fields, although the base plate is partially effective as a shield.

You can cancel the magnetic hum in high impedance pickups very well. I prefer to use a buffered dummy coil. A single source follower serves as the buffer, and the canceling is injected at the bottom of the single coil pickups (that is, the connection that normally goes to ground) through an adjustment pot (low R value). The dummy coil needs to have 10 or 20 % more sensitivity than the pickup so that you have some adjustment range. And the resonant frequency of the dummy coil needs to be well above that of the pickup/cable system. This method keeps the single coil sound, and has very simple electronics.

[bbsailor]

I believe the alumnitone is a humbucking design, right? Then the reason it rejects magnetic field interference is that it is carefully designed and constructed to get good cancelation. As for the interference from electric fields, you are quite right: the impedance of an inductor goes with the square of the number of turns, and so a single turn pickup is extraordinarily insensitive to electric fields even without shielding. Normal humbuckers do not reject all that well since the two coils in many designs do not have the same sensitivity to magnetic fields. And if run without the cover, they have some sensitivity to electric fields, although the base plate is partially effective as a shield.

You can cancel the magnetic hum in high impedance pickups very well. I prefer to use a buffered dummy coil. A single source follower serves as the buffer, and the canceling is injected at the bottom of the single coil pickups (that is, the connection that normally goes to ground) through an adjustment pot (low R value). The dummy coil needs to have 10 or 20 % more sensitivity than the pickup so that you have some adjustment range. And the resonant frequency of the dummy coil needs to be well above that of the pickup/cable system. This method keeps the single coil sound, and has very simple electronics.

Mike,

Thanks for sharing that ingenious method of humbucking and adjusting the bucking of a pickup to external noise. This method should have been patented. However, this is an active method and requires a buffer transistor/FET and a battery.

Yes, the Alumitones are humbucking, both the narrow Fender style pickups as well as the wider humbucker style Alumitone pickups. Do a closer examination of the Alumitones and see that only one magnet is under the strings. This produces a humbucking effect for external hum but produces a single coil type sound because there is no cancellation of the string vibrating over two magnets and coils at the same time.

Low impedance pickups have not been given their fair opportunity to demonstrate the tonal possibilities that people have been historically accustomed to hearing with high impedance pickups. This is just my humble opinion from about 50 years of tinkering with magnets, coils and guitar pickups.

Engineers typically push the boundaries.

Joseph Rogowski

[Mike Sulzer]

Mike,

Low impedance pickups have not been given their fair opportunity to demonstrate the tonal possibilities that people have been historically accustomed to hearing with high impedance pickups. This is just my humble opinion from about 50 years of tinkering with magnets, coils and guitar pickups.

Engineers typically push the boundaries.

Joseph Rogowski

Thank you, this is very true. You are right that low impedance pickups are better. It is too bad that they did not become the standard!

[dBe]

Thank you, this is very true. You are right that low impedance pickups are better. It is too bad that they did not become the standard!

Guys,

I just wanted to say that this is a great discussion and has gotten my old brain working overtime.

Thanks,

Dave

[Béla]

bbsailor:

Could I possibly make a low-Z pickup by unwinding a few thousand turns off a cheap p-90 style pickup? How far would that get me into the world of lowZ pickups? Will it have the wide-bandwidth noiseless features of a Gibson Recording's pickup?

Also, since I have already made an active preamp into my guitar, could I use that instead of a transformer?
I know I asked this from you earlier, but that was about the single-loop pickup. Could a transistor input handle the lowZ pickup output without the need of a xformer?

[bbsailor]

bbsailor:

Could I possibly make a low-Z pickup by unwinding a few thousand turns off a cheap p-90 style pickup? How far would that get me into the world of lowZ pickups? Will it have the wide-bandwidth noiseless features of a Gibson Recording's pickup?

Also, since I have already made an active preamp into my guitar, could I use that instead of a transformer?
I know I asked this from you earlier, but that was about the single-loop pickup. Could a transistor input handle the lowZ pickup output without the need of a xformer?

Bela,

The simple answer is no. Take all the wire off and replace it as described below.

The reason is that low impedance pickups should have lower resistance, using wire in the AWG30 range. This is one of the main resons why low Z pickups have lower noise. The rule of thumb would be that if you reduced the total number of turns on the low Z pickup to 1/10 the number of turns on the high Z pickup, you will have an impedance difference of 100. 500K Pots become 5K and 250K pots become 2.5K. Then you look for a transformer with a turns ratio of a minimum of 1:10 to boost the voltage back up to close to what it would have been if you had alll the turns of AWG 42 on the bobbin. In reality you would look for a turns ratio of 1 to 12 or 15 to to make up for the transformer losses. If the transformer has a Center Tap (CT) you could get some additional tonal variations by switching between these two transformer inputs.

It is best to use the matching transformer off the guitar, right at the amplifier input using a Shure A95 series-like matching transformer. Then, the coax cable has minimal effect on attenuating high frequencies.

You could also use an active circuit to boost the gain of the low impedance pickup back to the level of the high Z pickup with a gain of about 10. You would enjoy a broad frequency response, and not have any high frequency attenuation due the the coax cable.

Go to an AWG wire table and look up the diameter of AWG30 and see how many turns will fit on one layer of the P90 bobbin (about.25" tall). Then see how many layers can fit on the P90 bobbin. If you have enough space for about 500 turns at about a 70% fill factor, you should have pretty good results. If obtaining enough turns with AWG30 is a problem, the try AWG32.

FETs are typically used on high Z circuits when you want minimal loading. Transistors typically work at the 10K ohms input range so they should work well with a low Z pickup.

One mod you can try for some more output and a little different sound is to bend a piece of thin steel in a "wide-U" shape to fit under the pickup. This plate will help focus the magnetic force on to the strings and in very noisy environments will help minimize noise as this plate should be grounded.

Joseph Rogowski
bbsailor

[David Schwab]

bbsailor:

Could I possibly make a low-Z pickup by unwinding a few thousand turns off a cheap p-90 style pickup? How far would that get me into the world of lowZ pickups? Will it have the wide-bandwidth noiseless features of a Gibson Recording's pickup?

Also, since I have already made an active preamp into my guitar, could I use that instead of a transformer?
I know I asked this from you earlier, but that was about the single-loop pickup. Could a transistor input handle the lowZ pickup output without the need of a xformer?

bbsailor is correct, however I have to slightly disagree with him as far as your question is concerned.

About 28 years ago I made my first low Z pickup by unwinding wire off of a P bass pickup. Well I might have removed all the wire first since it was lacquered, but I had been messing with unwinding pickups and I used that same 42 AWG wire to wind about 500 turns on each bobbin.

Back then I used an external Barcus Berry preamp designed for piezo pickups.

These days I've made a number of low Z pickups with 42 AWG wire and FET buffers. Technically you don't need a very high input impedance for a low Z pickup, as bbsailor pointed out. It could lead to extra noise. But in practice this is how it's often done, including pickup systems by Alembic. They use 40 AWG wire and the front end of their preamp uses FET's.

So yes, you can unwind a P-90 to about 1,000 turns or less and use a preamp to boost the signal back up. I use a very simple self biasing FET preamp.

I used 42 AWG because I had it available. Next I'm going to try some heavier wire like 38.

[bbsailor]

David said: bbsailor is correct, however I have to slightly disagree with him as far as your question is concerned.


David,

His initial question was in relation to the Gibson Recording pickup which I assumed to be the Les Paul Recording low Z pickup. This pickup uses between AWG28 and AWG32 wire.

Granted, you can use fewer turns of AWG 42 to experiment with a low Z pickup but to properly drive a low Z transformer you should have near the same DC resistance as the transformer. This means you need to use a thicker wire to develop enough drive current with 1/10 the turns of an AWG 42 coil winding.

Using different gauges of wire will definately affect to tonal balance between lows and highs. Ultimately, this depends on what sounds good to your ears. With added high frequencies of a good broadband match, they can always be removed passivly but cannot be added without some active circuitry or some high pass circuits with their attendant losses.

Working with 1/10th the number of turns is a good low Z range to work in. It changes the impedance range by a factor of 100 and is still in the range of commonly available pots, capacitors and matching transformers.

Joseph Rogowski

[David Schwab]

David,

His initial question was in relation to the Gibson Recording pickup which I assumed to be the Les Paul Recording low Z pickup. This pickup uses between AWG28 and AWG32 wire.

Granted, you can use fewer turns of AWG 42 to experiment with a low Z pickup but to properly drive a low Z transformer you should have near the same DC resistance as the transformer. This means you need to use a thicker wire to develop enough drive current with 1/10 the turns of an AWG 42 coil winding.

Using different gauges of wire will definately affect to tonal balance between lows and highs. Ultimately, this depends on what sounds good to your ears. With added high frequencies of a good broadband match, they can always be removed passivly but cannot be added without some active circuitry or some high pass circuits with their attendant losses.

Working with 1/10th the number of turns is a good low Z range to work in. It changes the impedance range by a factor of 100 and is still in the range of commonly available pots, capacitors and matching transformers.

Joseph Rogowski

I agree for a LP recording pickup, and for low z pickups in general, you should use the heavier wire.

I was just pointing that out as it's an easy way (unwinding a cheap P-90) to try out a low Z pickup.

[David Schwab]

Using different gauges of wire will definately affect to tonal balance between lows and highs. Ultimately, this depends on what sounds good to your ears. With added high frequencies of a good broadband match, they can always be removed passivly but cannot be added without some active circuitry or some high pass circuits with their attendant losses.

Joseph, what do you think the tonal different would be between a low Z pickup using like 38 and one using 42, assuming they are wound to the same resistance?

I tried out some 30 gauge I got from RadioShack, but it wasn't a very big roll, so I got maybe 200 turns, and it was hard to wind on my Schatten winder... which was too underpowered for that stuff. Needless to say I ended up with a loose coil and very little output.

[bbsailor]

Joseph, what do you think the tonal different would be between a low Z pickup using like 38 and one using 42, assuming they are wound to the same resistance?

I tried out some 30 gauge I got from RadioShack, but it wasn't a very big roll, so I got maybe 200 turns, and it was hard to wind on my Schatten winder... which was too underpowered for that stuff. Needless to say I ended up with a loose coil and very little output.

David,

200 turns of AWG30 was only about 100 ohms. You would need about 200 to 250 ohms to match better through a Shure A95U transformer.

Heavier wire tends to emphasize the lower frequencies. To do a comparison, matching resistance is not the way to compare them. Use the same number of turns. An AWG38 will have many more turns than the AWG42 when wound to the same resistance. Then, more turns always wins out as far as output goes until the wire gets so far from the magnets that each additional turn adds no additional voltage, but only adds to the high frequency attenuation due to the added capacitance.

The Ampeg/Burns Wild Dog low impedance pickups used matching transformers. One clever thing they did was to purposly mismatch the pickup coil to the transformer impedance to obtain a large tonal shift. I worked at Ampeg, Linden NJ one Summer and was fascinated by this pickup arrangement.

In transformer lingo, maximum power transfer between a coil and a transformer takes place when the impedances of the coil and transformer at the desired frequency are equal or close to equal. If the pickup coil has a much higher resistance/impedance than the transformer coil, there will be a loading mismatch that will result in less output and some tonal shift towards tonal range where the impedances of the coil and transformer are or would be a closer match.

Remember what you said about being able to tell the tonal differences between pickups wound with AWG42 vs AWG43?

Joseph Rogowski

[Béla]

Thank you for being so helpful Joseph!

Right now's not the best time for me to experiment with this, but I will do it some time soon. I'm sure I'll document the steps and get some sound bits from it.

One mod you can try for some more output and a little different sound is to bend a piece of thin steel in a "wide-U" shape to fit under the pickup. This plate will help focus the magnetic force on to the strings and in very noisy environments will help minimize noise as this plate should be grounded.

I wonder why this is not done with regular pickups