Yet another Low Z pickup thread

[cnb77]

Hey I'm new to winding, and I have an interest in low impedance pickups. I made a post on Talkbass to get some basics down, but I'm coming here to have my idea scrutinized a little better. I'm aiming for a pretty "hifi" sounding pickup. That way I don't have to EQ around the inherent sound of the pickup, I get essentially what my bass sounds like unamplified, but louder (I hope!).

For starters I'll be dissecting a pickup from a dead bass I have to try out first. It's this bass: Ibanez GARTB20 Gio GARTB Electric Bass Guitar | Musician's Friend
As you can see, the pickups are fairly large, so that gives me some room to work. I'll be doing just a single coil at first. I will likely use 38 awg wire (Enameled Copper Magnet Wire - 38 AWG - 1.0 lbs Solderable 155C MW-79-C Natural | eBay)

Here's my idea for polepieces: Order Mild Steel 1018 Round in Small Quantities at OnlineMetals.com
I can get those cut to size

Then I'd like to use neo disc magnets stuck underneath: MAGCRAFT® - Rare Earth Magnet - Disc, 0.25 in. Diameter x 0.1 in. Thick, 50-Count

I'm curious as to what DC resistance I should wind to. Any ideas for starters? I'm sure I'll have to tweak it and experiment a bit.

The remaining info I need is about transformers, what kind to use and how to wire em up, and pots. I'd like the transformer inside the bass to be inside the bass. Can I just wire a regular volume and tone circuit with different pot/cap values?

Any ideas on how well this will work? Suggestions?

[David Schwab]

You shouldn't worry about DC resistance when winding. It's the number of turns that's more important.

With heavy wire like that you might only get 1000 turns or so, depending on the size of your bobbins. So try winding them until they are full.

[cnb77]

So is number of turns always a more is better proposition?

[Mike Sulzer]

The remaining info I need is about transformers, what kind to use and how to wire em up, and pots. I'd like the transformer inside the bass to be inside the bass. Can I just wire a regular volume and tone circuit with different pot/cap values?

Any ideas on how well this will work? Suggestions?

What is the transformer in the bass for? If you raise the impedance back up to what it would have been with a regular pickup, the cable will have a similar affect on the sound. If you want a net lower impedance to get flatter response, you just put somewhat less wire on than a normal pickup and accept a somewhat lower output level; no transformer needed. Experiment until you get what you want.

50K pots should be adequate. The resistance will help flatten the frequency response.

[cnb77]

What is the transformer in the bass for? If you raise the impedance back up to what it would have been with a regular pickup, the cable will have a similar affect on the sound. If you want a net lower impedance to get flatter response, you just put somewhat less wire on than a normal pickup and accept a somewhat lower output level; no transformer needed. Experiment until you get what you want.

50K pots should be adequate. The resistance will help flatten the frequency response.

Oh, I'd hoped that bringing the impedance up outside of the pickup would change matters...

I guess low output is the way to go then.

[cnb77]

Getting the custom cut pieces was a bit expensive, so I just grabbed a few standard humbucker polepieces to use for now. I guess this first wind will be shorter and fatter like a P90. Got two sizes of magnets to play with different strengths. Now we just play the waiting game til the pieces come

[David Schwab]

What is the transformer in the bass for? If you raise the impedance back up to what it would have been with a regular pickup, the cable will have a similar affect on the sound.

Not really. The basses with low Z pickups and a transformer still sound very different from hi Z pickups.

A perfect example is the Epiphone Jack Casady model, or the old Les Paul Triumph bass.

They aren't low impedance to overcome cable loading. But ideally the transformer should be at the amp and not in the bass. That's how the first Les Paul Personal guitar was set up.

I prefer to use a preamp instead of a transformer.

[cnb77]

Not really. The basses with low Z pickups and a transformer still sound very different from hi Z pickups.

A perfect example is the Epiphone Jack Casady model, or the old Les Paul Triumph bass.

They aren't low impedance to overcome cable loading. But ideally the transformer should be at the amp and not in the bass. That's how the first Les Paul Personal guitar was set up.

I prefer to use a preamp instead of a transformer.

Will any preamp circuit do? Or does it need to be optimized for this usage?

[David Schwab]

Will any preamp circuit do? Or does it need to be optimized for this usage?

Google "Stratoblaster." It's simple JFET preamp made by Alembic. The schematic is all over the place. It has variable gain, so you can get your level up pretty high if you want.

I used to make low Z pickups and with that preamp I was actually able to get the bass up to line level and drive a power amp!

It's very clean and quiet too.

[cnb77]

Google "Stratoblaster." It's simple JFET preamp made by Alembic. The schematic is all over the place. It has variable gain, so you can get your level up pretty high if you want.

I used to make low Z pickups and with that preamp I was actually able to get the bass up to line level and drive a power amp!

It's very clean and quiet too.

Thanks! That looks simple enough, nice and small too.

[Mike Sulzer]

Not really. The basses with low Z pickups and a transformer still sound very different from hi Z pickups.

A perfect example is the Epiphone Jack Casady model, or the old Les Paul Triumph bass.

They aren't low impedance to overcome cable loading. But ideally the transformer should be at the amp and not in the bass. That's how the first Les Paul Personal guitar was set up.

I prefer to use a preamp instead of a transformer.

No, really. Many things go into the sound of an instrument, and one of them can be the fact that transformers are not ideal, especially a really light one that supposedly has good bass response and a wide bandwidth, and does not cost a significant fraction of the other components of the instrument. Unless for some reason you want the sound of a non-ideal transformer (and there is nothing wrong with that if that is what does it for you) then you are better off not using a transformer. You do not have to take off that many turns to get flat response or whatever you want. A preamp is not necessary unless you really want the same output level as s standard pickup. Beware of that mental phenom:"It is not as loud as the other pickup with the same settings, and it does not sound as good." Gains must always be adjusted for the same levels, and where relevant, the same amount of distortion.

Remember, when removing a few turns, the inductance goes with the square of the number of turns, while the output voltage level is only linearly proportional. You can move the resonance out beyond the range of the system (and flatten it) without losing too much signal.

[David Schwab]

A preamp is not necessary unless you really want the same output level as s standard pickup. Beware of that mental phenom:"It is not as loud as the other pickup with the same settings, and it does not sound as good." Gains must always be adjusted for the same levels, and where relevant, the same amount of distortion.

Wind a pickup with 1000 turns of wire and see if you don't need a preamp or a step up transformer. You most certainly will.

You also will not get that tone by winding a high Z pickup with fewer turns of wire. It will be flatter and brighter, but you wont get the same tone.

[Mike Sulzer]

Wind a pickup with 1000 turns of wire and see if you don't need a preamp or a step up transformer. You most certainly will.

You also will not get that tone by winding a high Z pickup with fewer turns of wire. It will be flatter and brighter, but you wont get the same tone.

There is no need to go as low as 1000 turns to get a response that is flat over the useful range of the amplification system. You simply move the resonance up and then decrease the load resister to damp the peak enough to give the "Hi Fi" sound that you want.

"flatter and brighter" Seriously? Flat and bright do not go together. You make a pickup bright by putting a resonant peak somewhere in the 4 point something to 5 or 6 KHz range (with the cable) and damping it lightly enough to get the sound you want. Flat or "Hi Fi" sound is achieved as I described above.

There is nothing significantly different about the sound of a low impedance pickup of otherwise conventional design. In fact, you can get a very conventional sound by resonating it where a normal Hi Z pickup would (with the cable) by putting a fairly large capacitor in parallel and selecting the load resistor. With my individual string pickups, capacitors in the range .022 to .047 microf are needed to do the job.

[David Schwab]

Mike, listen to this, and then tell me you can get that tone from a high Z pickup. You can't.

Back when Stanley showed up on the scene that tone was very different from what you were getting from basses. Alembic uses the low pass filters to put the resonant peak in, but I used to make low Z pickups, and the extended top end is very different from pickup wound more.

Here's a clip I recorded back in 2006. These are conventional humbuckers, unlike the Alembic pickups which are single coils.

http://www.sgd-lutherie.com/media/sg...05-23-06_3.mp3

That clip was recorded direct into the board with no EQ.

Same pickups:

http://www.sgd-lutherie.com/media/Bass_Head.mp3

[cnb77]

Is it the number of actual turns that matters or the overall length of wire used? Like say you have two differently sized bobbins and you want to get similar tone from both, do you want the same number of turns or the same overall amount of wire?