Blade pickup for a cello????

[Peter Ormonde]

G'day.

I'm wanting to do something odd - not unusual for me.

I'm wanting to build a humbucking blade/rail pickup on a cello. Trouble is these gadgets have a 70mm radius or so over the fingerboard and bridge. That's 2 3/4" in old money.

What I'd like some advice - hunches will do - on is how evenly the charge from the magnet carries over the blade - that is, does the field "drop off" over distance or will it be evenly spread despite the middle being a good half inch or more further away than it is at the ends?

I'm thinking of using a decent lump of neodymium under each blade. Not sure about that either. I'm trying for warm soft tones rather than twang - I get enough twang from the bridge piezos.

The idea is then to hook them together through a blender/eq circuit - piezos for bowing, magnetics for plucking.

All ideas suggestions hunches and scornful dismissals welcome. Well, less so the last one.

[soundguruman]

The middle pole pieces can be raised by screw adjustments, not blades. Yes, you will loose a lot of signal 1/2" away.
The piezo idea is fading, because of hum and feedback from the peizo pickup.
A humbucking PU would work much better...but you still have to use a preamp and EQ...preferably a parametric EQ.

[big_teee]

Welcome to the Forum.
This sounds like a project that will require a lot of trial and errror.
Blade pickups sound like they would work OK.
Don't know what you will mount the pickup to.
It would help if you could give us some pictures of the area from the neck to the bridge.
Also some String spacing dimensions would help.
As far as warmth of pickup sound, You might consider Alnico magnets.
Also where you place the pickup will determine the tone of the pickup.
I too would go with some form of humbucking pickup.
Maybe some of the other winders that cruze through here will have some ideas!
Good Luck,
T

[rjb]

... 70mm radius or so over the fingerboard and bridge.
... will it be evenly spread despite the middle being a good half inch or more further away than it is at the ends?

What if you make the blades with curved tops?

...neodymium under each blade....warm soft tones rather than twang

Why not a standard HB magnet?

...scornful dismissals welcome. Well, less so the last one.

Just mic it like a stand up bass and be done with it!

[Bruce Johnson]

Another approach that you might consider is using four separate coils, one for each string. For example, use four Strat-like coils turned to be in line with the strings. Mount them on a bracket, so that each has the right distance from the string, and wire them together as a humbucking group.

Attached is a picture of one of my Series IV model Scroll Basses, from a few years back. That model uses a 4" radius fingerboard, so I used the four individual narrow coil configuration for that center pickup. Those aren't actual Strat coils; I made those up myself to my own design, but you get the idea. It's an interesting pickup combination, because it has a long aperture along the length of the string and a relatively narrow aperture across the string. It's a clear, but warm sound. They are built and wired as a humbucking group, with alternating magnets and alternating coils. Each coil has three 1/4" Alnico 5 rod magnets.

A couple of years ago I sold a set of 5 of those coil units to a guy who plays crazy music on an electrified 5 string full size upright bass. He mounted them on a bracket down at the end of the fingerboard, and they work great. The individual coils allowed him to fine tune the levels of each string.

You didn't mention the strings, but I assume that you know that you'll have to use strings with significant iron content, in order for them to work with magnetic pickups?

[soundguruman]

What if you make the blades with curved tops?



Why not a standard HB magnet?



Just mic it like a stand up bass and be done with it!

You could curve the blade but I think you would get much better out of a humbucking PU.
There is a PU called a Rebow
Rebo - new magnetic pickup for bowed strings - Gearslutz.com
You will get more out of it with a preamp and EQ. The need for the EQ is to tune out feedback. A parametric EQ will be handy for eliminating resonant frequencies.
Once the resonant frequencies are tuned out, the volume can be much louder, without ringing or squealing

This resonant frequency is what you are up against when you amplify a hollow body instrument.
Granted the peizo is easy to attach, but plenty resonance. Even that would be improved with a parametric EQ.

[big_teee]

You could curve the blade but I think you would get much better out of a humbucking PU.
There is a PU called a Rebow
Rebo - new magnetic pickup for bowed strings - Gearslutz.com
You will get more out of it with a preamp and EQ. The need for the EQ is to tune out feedback. A parametric EQ will be handy for eliminating resonant frequencies.
Once the resonant frequencies are tuned out, the volume can be much louder, without ringing or squealing

This resonant frequency is what you are up against when you amplify a hollow body instrument.
Granted the peizo is easy to attach, but plenty resonance. Even that would be improved with a parametric EQ.

If You put two blades together, and wire in series correctly, you would a humbucking pickup.
The four independant coils like Bruce said would probably work best.
T

[Peter Ormonde]

If You put two blades together, and wire in series correctly, you would a humbucking pickup.
The four independant coils like Bruce said would probably work best.
T

Many thanks for these suggestions folks.

Definitely attracted towards humbucker set up. So yep two coils one reversed.

What I'm toying with is actually a standard(ish) blade humbucker (bit smaller and taller than usual) - except the blades (mild steel plate) will be curved at a 70mm (2 3/4") radius or so - so the height of the blade will be standing about 12mm (1/2") taller in the centre than the blade under the outer strings. 42 awg wire wound to 10k Ohms. That seems the simplest - if it works at all.

I have thought about a single pair of humbucking coils under each string - and there are some nice possible advantages out of that - like being able to adjust the volume and position of each pickup individually. If this doesn't work I'll definitely have a go at that. But so far I've been completely unable to get any information on how the field would be affected by having a steeply curved blade ... no one seems to know. So I guess I'll just have to build one and see.

While the strings are spaced closely (12mm - 1/2") and they are set over a steep radius - there is one redeeming feature - quite a lot of height between the body and strings - all up about 65mm (2 1/2") ... so I can build whatever it is quite tall. If I end up going with the single string pickup idea I'll probably mount them on a arched timber block with some capacity for indiovidual height and volume adjustment.

Schaller make a shocking looking gadget that attaches to the end of the fingerboard - apparently a bit rattly. Imagine a couple of short precision pickups set up on an angle ... all chrome and ugly as a bat.

Oh yes - these cellos are pretty radical - small, headless, solid bodied from very dense Australian hardwood but essentially identical to a cello to play - the actual "working measurements" are identical with a 17th century cello. Sustain goes on forever. Run the thing through an octaver and you have a very very playable double bass that doesn't need its own truck.

I'll keep you posted on my adventure... meanwhile keep the suggestions pumping folks - muchly appreciated. And oh yeah if you know anyone who'd be up to winding me a set of 8 X 2.5k Ohm single string bobbins (for money) let me know. I've tried ordering a few from folks I've tracked down on the interweb but no luck so far.

[big_teee]

Many thanks for these suggestions folks.

Definitely attracted towards humbucker set up. So yep two coils one reversed.

What I'm toying with is actually a standard(ish) blade humbucker (bit smaller and taller than usual) - except the blades (mild steel plate) will be curved at a 70mm (2 3/4") radius or so - so the height of the blade will be standing about 12mm (1/2") taller in the centre than the blade under the outer strings. 42 awg wire wound to 10k Ohms. That seems the simplest - if it works at all.

I have thought about a single pair of humbucking coils under each string - and there are some nice possible advantages out of that - like being able to adjust the volume and position of each pickup individually. If this doesn't work I'll definitely have a go at that. But so far I've been completely unable to get any information on how the field would be affected by having a steeply curved blade ... no one seems to know. So I guess I'll just have to build one and see.

While the strings are spaced closely (12mm - 1/2") and they are set over a steep radius - there is one redeeming feature - quite a lot of height between the body and strings - all up about 65mm (2 1/2") ... so I can build whatever it is quite tall. If I end up going with the single string pickup idea I'll probably mount them on a arched timber block with some capacity for indiovidual height and volume adjustment.

Schaller make a shocking looking gadget that attaches to the end of the fingerboard - apparently a bit rattly. Imagine a couple of short precision pickups set up on an angle ... all chrome and ugly as a bat.

Oh yes - these cellos are pretty radical - small, headless, solid bodied from very dense Australian hardwood but essentially identical to a cello to play - the actual "working measurements" are identical with a 17th century cello. Sustain goes on forever. Run the thing through an octaver and you have a very very playable double bass that doesn't need its own truck.

I'll keep you posted on my adventure... meanwhile keep the suggestions pumping folks - muchly appreciated. And oh yeah if you know anyone who'd be up to winding me a set of 8 X 2.5k Ohm single string bobbins (for money) let me know. I've tried ordering a few from folks I've tracked down on the interweb but no luck so far.

We would all love to see some pictures of your cello. Maybe inspire us, with some more ideas.
Hope it all works out!
T

[Bruce Johnson]

Just to clarify:

The setup on my Series IV bass is only 4 coils total, not 8. You don't have to put a humbucking pair on each string. The four coils are wired up in series, with alternating winding directions and magnet polarities. As long as the whole group is alternating pairs, it will buck the hum.

[big_teee]

Just to clarify:

The setup on my Series IV bass is only 4 coils total, not 8. You don't have to put a humbucking pair on each string. The four coils are wired up in series, with alternating winding directions and magnet polarities. As long as the whole group is alternating pairs, it will buck the hum.

So to clarify?
On a Bass, you would have the E, & A, a humbucking pair?
Have the D & G a humbucking pair?
Then what do you do with the two pairs?
Wire the two pairs in series, or parallel?
T

[Bruce Johnson]

The E and D coils are North/clockwise, the A and G are South/counterclockwise, and all four coils are in series. It works fine, very quiet, and the total DCR is where I wanted it.

[Peter Ormonde]

That's very clever. Cuts the work (and bits) in half. I even understand that. Gotta be something I'm getting wrong! But that gives the single coils another 25% advantage I reckon! Stumbled across this fella this morning: Peter MalinoskiArt Guitars ... makes a cute little single string stacked coil which looks like the bees' knees but from what you are saying isn't really necessary for my kinda contraption.

My god there's a lot of confused and confusing stuff online about these magical gadgets isn't there? People talk about things being in and out of "phase" when they mean something else entirely. Spend half the time falling about trying to actually explain and describe what they really meant! Very confusing for a rookie.

I've been reading up on stacked humbuckers - still exploring the high arched blade notion - because like I said I've got a fair bit of height to play with. Now about half the wisdom says the bottom coil is essentially a dummy - no pole pieces required just wound (or wired up) in reverse - the other half disagrees... and the (unstacked - side by side) ones I've seen made by professionals all have two matching blades. Which is it? First remotely expert sounding opinion wins! I'm starting to bump into walls and fall about. I think it's concussion.

If the bottom coil is essentially a dummy can I stick the bar magnet between the two coils and just slot the blade down onto it, leaving the bottom coil totally insulated?

But there has been some progress... of a sort... I've built myself a gadget to wind wire - using a 6:1 eggbeater fishing reel ... Not really an option for making a lot of these contraptions - about 1200 turns a coil - but seems to give a nice scatter wound result from this morning's trial run. Looks very pretty and shiny.

I'm looking for a bartolini "hollowed out" sort of tone ... mellow and smooth.... any recommendations on wire size and coating also gratefully received.

Many thanks for your help. Like aspirin and a hot bath.

[Bruce Johnson]

Peter, I think that you are making the design more complicated than necessary. If you don't want to try the four-coil approach like mine (one per string, along the string), then just make a conventional two-coil blade humbucker. The two coils each go across all four strings, one behind the other. Don't stack them. The two coils are identical: the same size, the same number of turns, same wire, wound the same direction. You wire them together in series so that the current goes around in opposite directions on them. That is, connect the "Finish" wire of one to the "Finish" wire of the other. Then each coil gets an arched steel blade with a big magnet stuck on the bottom. The blades and magnets are identical, except that one is flipped over. One blade should read North and the other should be South. There's your basic simple humbucker pickup. A pair of identical but opposite pickups.

The only tricky part in your application will be shaping the contour of the blades to get an even level output from the four strings. You are going to have to do that by trial and error, pulling the blades out and grinding the shape. The blades will need to be closer to the center strings than they will to the outer strings, because the coils will be farther away from the center strings. You'll have to experiment to see how much. Or, you can use blades to get the main shape, and then put adjustable screws in it under each string to do the fine tuning.

That's the big advantage of the four-coil arrangement. I can balance out the levels of the four strings with an Allen wrench, by raising and lowering individual coils.

[Peter Ormonde]

Yep you've convinced me Bruce. Simple as always better when it comes to any sort of design. I also had a closer look at your rather sexy bass above and dips my lid ... that's a very nice piece of work.

I'll have a crack at knocking up some single string coils next week and see how we go. I'll snap some pix.

Many thanks