EUB Project

[David King]

To cancel hum you need to reverse the magnets on one coil obviously but you also need to reverse the direction of wind or a least switch the leads if the two armatures are wound identically. I don't really have a good idea of the DCR but I'd try something around 8000-9000 turns to start with and see how that sounds. You have a tall magnet so no problem fitting lots of turns on there.

[Bruce Johnson]

Just for reference, those M-pickups for my Scroll Basses that I showed above on this thread are 5000 turns each around 3 magnets; about 1.90K each and 7.60K total. On the Scroll Basses, I wire them all together in series, non-humbucker, all of the magnets and coils the same direction.

I did experiment with wiring up the four alternating the winding, to make the group a humbucker. As a group, it did reduce outside hum a little bit, but not a whole lot. I got much more effective hum reduction by adding shielding, the brass shells, around each pickup.

The big problem with wiring up modular pickups like these as humbuckers comes if you also have another pickup onboard the instrument. When you blend the group in with the other pickup, two of the coils end up in phase with the other pickup, and the other two are out of phase. So, as you bring up the blend, two of the strings on the bass go soft and muffled!

The best way to make a humbucker out of a modular pickup group like this is to add a fifth larger "dummy" coil down under the four pickups. This coil is wound or wired in the opposite direction, has no magnets, and should have a resistance about equal to the total of the four pickups. I may eventually add a dummy coil like this to my Scroll Basses. I've left a space for it under the M-pickup group. But, for now, these instruments don't really have much of a noise problem.

[scojack]

Thanks Again

Thanks guys much appreciated.
I think i have enough to get something together.
Thanks for the detailed spec on the M-pickups Bruce, you are a gentleman.
Im just waiting for the tech guys from work to russle up a wee coil winder, i work for a Japanese company that makes servos and drive controllers and they promise me they can do it...failing that...i have a strong wrist

[scojack]

Hello fellows,
Well I got the pickup done after rattling up a winder from an old HP printer and a counter from an akai tape deck.
Went for a 4 coil job with 3*20mm alnico rods and 5000 winds each, built into an indian ebony cover. I built brass shielding into the design as well. It works a treat !
I'd say if anything it sounds a bit like a precision. You can see it mounted of the finished bass. I was so chuffed it all worked so well im doing a humbucker now with 1 inch magnets and Cocobolo, dont know if i'll use it on this bass or keep it for EUB#2 with cocobolo facings.
Thanks again for all your help, this is a fantastic forum i couldnt have done it without you. Fancy doing a humbucker with blades now.

[David King]

Nice job scojack,
That cocobolo bucker looks very pretty -as one would expect.
I'll bet the P bass sound is a funtion of the distance to the bridge. Try a sliding pickup next time and you'll open up a few additional sounds.

[scojack]

I tried the new humbucker (coco-bucker)in the bass today sounds really really good, problem is i prefer it to the first one but it wasnt made to fit this bass, its a little smaller so going to build another.

I do have a slight problem though and im hoping somedody can help...

Im getting a hum when i take my fingers off the strings, theres also a definate 'click' when you tap a string too.
This happens with both pickups.
I thought it was maybe a shielding thing but pickup 1 is well shielded with brass which is grounded. I also have shielded cable from pickup to pots.
I have tested all the wiring and its all showing good connections.
The strings are grounded too, theres a wire runs up to them and connects to a brass plate that the strings sit on.
The control cavity is not shielded.

Any ideas anybody?
Is more shielding required or is it a grounding problem?
I dont understand why the hum goes away when im touching the strings.