Magnets & Copper Wire: A Pickup Building Thread

[Verne Andru]

The best way to get a pure signal is to do as Bruce suggests; design the pickup to be powerful enough to not need additional help.

All preamps create an "image" of the incoming signal using opamps, transistors, tubes, whatever as a form of translator between input and output. The conversion process pre-supposes the output will be whatever the translator device imparts; all components have their own sonic signature. This necessitates the addition of circuitry to adjust the signal into a form the engineers consider correct with mixed results.

I have a Godin Multiac with RMC piezo saddles and preamp. Best of the best in my experience. While it sounds very good there is a considerable amount of "noise" added to the signal by the components, particularly the opamp. When I got a hold of Richard (the R in RMC) about it he explained the choice of opamp was a balance between signal quality and battery life; the noisy opamp provides significantly longer battery use.

Since I rely on power from a pedal and don't use the battery it didn't matter other than the noise problem. He graciously sold me a replacement preamp board with a socket where the opamp goes so I could populate it with whatever I chose. I put in a high end Excalibur from the same family and all the noise problems went away.

So while it's doable to get a clean signal using preamps, off-the-shelf often doesn't cut it in my experience.

 

[Bruce Johnson]

A well-designed preamp can have a flat response from dc to way above the range of human hearing.

Oh, I agree, a well designed pre-amp can have a nice flat EQ curve. When set neutral. But most of them are designed specifically to mess around with the EQ curve by turning the knobs. Because that's what people want: knobs to turn that change the sound.

The "filtering" I was referring to is more about dynamics and clarity. When you make a weak pickup and boost its output level with a pre-amp, you generally lose dynamic range and clarity.

 

[Bruce Johnson]

The best way to get a pure signal is to do as Bruce suggests; design the pickup to be powerful enough to not need additional help.

All preamps create an "image" of the incoming signal using opamps, transistors, tubes, whatever as a form of translator between input and output. The conversion process pre-supposes the output will be whatever the translator device imparts; all components have their own sonic signature. This necessitates the addition of circuitry to adjust the signal into a form the engineers consider correct with mixed results.

I have a Godin Multiac with RMC piezo saddles and preamp. Best of the best in my experience. While it sounds very good there is a considerable amount of "noise" added to the signal by the components, particularly the opamp. When I got a hold of Richard (the R in RMC) about it he explained the choice of opamp was a balance between signal quality and battery life; the noisy opamp provides significantly longer battery use.

Since I rely on power from a pedal and don't use the battery it didn't matter other than the noise problem. He graciously sold me a replacement preamp board with a socket where the opamp goes so I could populate it with whatever I chose. I put in a high end Excalibur from the same family and all the noise problems went away.

So while it's doable to get a clean signal using preamps, off-the-shelf often doesn't cut it in my experience.

Almost 25 years ago, I worked with Rick Turner developing a piezo/magnetic pickup system for one of my early model Scroll Basses. We intentionally worked out an installation of piezo chips in the bridge saddles which had enough output level that they could operate passive. For exactly the reason you describe. We didn't want the Op-Amps modifying the sound. The magnetic pickup (made by Rick) also was strong enough to operate passive. He built a pre-amp for that system, but it was there to allow nice blending and EQ adjustment. In neutral setting, it was operating at unity gain.

 

[Bruce Johnson]

Yes, how you define "improve" is a matter of opinion.

And whatever you plug your instrument in to is going to have a preamp, and the best place to have one is as close to the pickup as possible.

Yeah, that's true, but I still prefer to have the preamp off-board the instrument. That gives you the choice of what preamp you use with it. If you are jamming with your friends in a garage, you can plug into a nasty amp and pedals, and you don't really care much about the fine points of the bass' sound. The sound works for that environment, and you may want some of the effects of the preamp. But in a high-end studio recording, you may not want to put in any preamp at all. Most of my Scroll Bass customers do their studio work plugging straight into the console, passive. Using the console's internal preamps, if any. And listening to themselves through headphones. That's the best way to record the full sound of one of my basses. And that's the reason why I build my basses single-pickup, all passive.

And I realize this isn't for everybody. Many bassists depend on electronic manipulation to get their sound. And they want the control on the bass or on pedals. Not my style*.

*A funny side note: My AMB-2 Scroll Bass has actually turned out to be excellent for....Doom Metal !! I never expected that, because I designed the AMB-2 to sound more like an upright bass; percussive attack curve and mid-range coloration, etc. But one of my customers has two of my AMB-2's and uses them for serious Doom Metal. He's found that the single pickup, passive, with extra clear sub-lows is a great base signal into his distortion chain. It makes the distortion really bad-ass. The distortion is clearer, if that makes sense. I've heard his albums; the bass tones make your chest rattle! Which is hilarious to me, thinking that's my sweet, elegant Scroll Bass doing that!

 

[slowburnaz]

Yeah, that's true, but I still prefer to have the preamp off-board the instrument. That gives you the choice of what preamp you use with it. If you are jamming with your friends in a garage, you can plug into a nasty amp and pedals, and you don't really care much about the fine points of the bass' sound. The sound works for that environment, and you may want some of the effects of the preamp. But in a high-end studio recording, you may not want to put in any preamp at all. Most of my Scroll Bass customers do their studio work plugging straight into the console, passive. Using the console's internal preamps, if any. And listening to themselves through headphones. That's the best way to record the full sound of one of my basses. And that's the reason why I build my basses single-pickup, all passive.

And I realize this isn't for everybody. Many bassists depend on electronic manipulation to get their sound. And they want the control on the bass or on pedals. Not my style*.

*A funny side note: My AMB-2 Scroll Bass has actually turned out to be excellent for....Doom Metal !! I never expected that, because I designed the AMB-2 to sound more like an upright bass; percussive attack curve and mid-range coloration, etc. But one of my customers has two of my AMB-2's and uses them for serious Doom Metal. He's found that the single pickup, passive, with extra clear sub-lows is a great base signal into his distortion chain. It makes the distortion really bad-ass. The distortion is clearer, if that makes sense. I've heard his albums; the bass tones make your chest rattle! Which is hilarious to me, thinking that's my sweet, elegant Scroll Bass doing that!

So you could say it's a... Doom Scroll bass?

 

[Bruce Johnson]

So you could say it's a... Doom Scroll bass?

Yeah, I guess.....To me, it's like seeing your daughter for the first time, on stage, as the lead singer of a metal band! Shocking! Sweetheart, is that really you???

My customer, Rob Morffit, is the leader of the LA based band Witches Of Hell. Some serious Doom Metal. Album artwork NSFW. He has two of my AMB-2's, #009 and #017. #009 is fairly nasty looking, in classic red/black sunburst. But #017 is one of my walnut models, made to look like a bass from the 1940's, that your Grandpa would have played. It's amazing to me to think of Rob playing it in live Doom Metal shows, rattling chests of screaming audiences.....But he loves them, sound, look and feel. They are his two favorite basses. I think he has #017 set up BEAD.

Some years back, while Rob was waiting for me to build #009, I loaned him my prototype AMB-2 #001. He took it on a short tour and recorded one of their albums with it. That same bass, #001, has also been loaned out to several other musicians, who have recorded all kinds of other music with it. Movie sound tracks, light jazz, salsa, rock, etc. I've personally done a couple of years of electric blues gigs with it. It's done it all. With one pickup, passive.

 

[Fred Miller]

That's my Secret Formula. Which I've been publicly explaining on this thread from the beginning.

Greight, you've found a formula that works and I thank you for your input. Others, like myself and RichterScale like to explore and experiment. Maybe we'll find a formula that works for us, maybe we'll use active electronics. There's an infinity of possibilities out there!

 

[Fred Miller]

Oh, I agree, a well designed pre-amp can have a nice flat EQ curve. When set neutral. But most of them are designed specifically to mess around with the EQ curve by turning the knobs. Because that's what people want: knobs to turn that change the sound.

Personally, as a performer, I like the bare minimum of knobs on a bass, just a volume control. I change the tone by playing differently.

 

[Flamingo21]

@Bruce Johnson I have taken the liberty of quoting that interesting story in the Doom Bassists Club.

 

[deff]

@Bruce Johnson I have taken the liberty of quoting that interesting story in the Doom Bassists Club.

I'm curious. Do you have a link? My Google fu is lacking

 

[ardgedee]

I'm curious. Do you have a link? My Google fu is lacking

#60260

 

[smart51]

For those who make wooden pickup covers - how thick do you make the top? I've just made my first one and I've made it 3mm thick. I wonder if I could go thinner without the risk of it cracking. What do you do?

 

[Fred Miller]

Depending on the wood, 1mm shouldn't be a problem if the wood is sealed.

 

[Jeff Siddall]

I make mine 1.56 mm (1/16")

 

[Bruce Johnson]

For those who make wooden pickup covers - how thick do you make the top? I've just made my first one and I've made it 3mm thick. I wonder if I could go thinner without the risk of it cracking. What do you do?

The answer is: As thin as you dare. You'd like it to be less than 1/16" (1.5mm) thick if you can, to allow the magnets to get close enough to the strings. To make the wood that thin, and prevent it from cracking, you should reinforce it from the inside. Brush in a coat of marine epoxy.

Better yet, brush in some epoxy, lay in a rectangle of cloth, brush in some more epoxy over the cloth. The cloth doesn't have to be fiberglass or carbon fiber, any old cloth will do. A scrap cut from a T-shirt. The fibers embedded in epoxy will hold the wood stable and prevent it from cracking.

 

[smart51]

I suppose the magnets and bobbins would support veneer thin wood from behind. More so if they were potted in place



I've routed my test piece down to 2mm and it seems quite strong still. I'll try being a bit braver tomorrow and take it further.

 

[smart51]

I suppose the magnets and bobbins would support veneer thin wood from behind. More so if they were potted in place



I've routed my test piece down to 2mm and it seems quite strong still. I'll try being a bit braver tomorrow and take it further.

An update to say I took the wood thickness down to just under 1mm. It was strong enough to support itself but sounded very thin when touched. My coils are now potted into the wooden casing and all is completely solid. The wooden shells work brilliantly.

What doesn't work so well is a remote preamp. Previously I've put the preamp into the shell with the coil. A single coil pickup, shielded in copper tape and earthed was completely silent. With a remote preamp it hums unless the other coil is turned up to make it buck hum, even using screened cable. It seems the short hook up wires were an essential part of making it hum free.

 

[Jeff Siddall]

An update to say I took the wood thickness down to just under 1mm. It was strong enough to support itself but sounded very thin when touched. My coils are now potted into the wooden casing and all is completely solid. The wooden shells work brilliantly.

What doesn't work so well is a remote preamp. Previously I've put the preamp into the shell with the coil. A single coil pickup, shielded in copper tape and earthed was completely silent. With a remote preamp it hums unless the other coil is turned up to make it buck hum, even using screened cable. It seems the short hook up wires were an essential part of making it hum free.

This is hard to understand. Shielded cable, especially in lengths that might exist inside a bass, should be pretty effective at blocking RFI. Consider that lots of people use something like 20 feet of the stuff to go from the bass to an amplifier, and don't normally complain about the noise picked up by long vs. short cables.

 

[smart51]

It doesn't hum loudly, it's just that the difference between a single coil mode and humbucker mode is obvious.

 

[Fred Miller]

It doesn't hum loudly, it's just that the difference between a single coil mode and humbucker mode is obvious.

Has to be something else I think. Maybe the few millimetres where the signal wire is exposed at the connection points? Would lining the control cavity with copper tape help?